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Cui W, Dai J. A leaf sequencing algorithm for an orthogonal dual-layer multileaf collimator. Biomed Phys Eng Express 2024; 10:065021. [PMID: 39111322 DOI: 10.1088/2057-1976/ad6c52] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2024] [Accepted: 08/07/2024] [Indexed: 09/19/2024]
Abstract
Purpose. Dual layer MLC (DMLC) has have been adopted in several commercial products and one major challenge in DMLC usage is leaf sequencing for intensity-modulated radiation therapy (IMRT). In this study we developed a leaf sequencing algorithm for IMRT with an orthogonal DMLC.Methods and Materials. This new algorithm is inspired by the algorithm proposed by Dai and Zhu for IMRT with single layer MLC (SMLC). It iterately determines a delivery segment intensity and corresponding segment shape for a given fluence matrix and leaves residual fluence matrix to following iterations. The segment intensity is determined according to complexities of residual fluence matrix when segment intensity varies from one to highest level in the matrix. The segment intensity and corresponding segment shape that result least complexity was selected. Although the algorithm framework is similar to Dai and Zhu's algorithm, this new algorithm develops complexity algorithms along with rules for determining segment leaf settings when delivered with orthogonal DMLC. This algorithm has been evaluated with 9 groups of randomly generated fluence matrices with various dimensions and intensity levels. Sixteen fluence matrices generated in Pinnacle system for two clinical IMRT examples were also used for evaluation. Statistical information of leaf sequences generated with this algorithm for both the random and clinical matrices were compared to the results of two typical algorithms for SMLC: that proposed by Dai and Zhu and that proposed by Bortfled.Results. Compared to the SMLC delivery sequences generated with Dai and Zhu's algorithm, the proposed algorithm for orthogonal DMLC delivery reduces the average number of segments by 27.7% ∼ 41.8% for 9 groups of randomly generated fluence matrices and 10.5% ∼ 41.7% for clinical ones. When comparing MU efficiency between different algorithms, it is observed that the proposed algorithm performs better than the optimal efficiency of SMLC delivery when dealing with simple fluence matrices, but slightly worse when handling complex ones.Conclusion. This new algorithm generates leaf sequences for orthogonal DMLC delivery with high delivery efficiency in terms of number of leaf segments. This algorithm has potential to work well with orthogonal DMLC for improving efficiency or quality of IMRT.
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Affiliation(s)
- Weijie Cui
- Department of Radiation Oncology, National Cancer Center/National Clinical Research Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100021, People's Republic of China
| | - Jianrong Dai
- Department of Radiation Oncology, National Cancer Center/National Clinical Research Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100021, People's Republic of China
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Samir F, Meaz TM, Hussiny FAE, Ahmed AA, Mahmoud AA, Refaat T, Gawish A, Abouegylah M. Analytical dosimetric study of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for prostate cancer. J Cancer Res Clin Oncol 2023; 149:6239-6246. [PMID: 36702973 PMCID: PMC10356637 DOI: 10.1007/s00432-023-04586-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 01/11/2023] [Indexed: 01/28/2023]
Abstract
PURPOSE The study aimed to compare the dosimetric results and treatment delivery efficiency among four techniques to explore the preferred technique in prostate treatment. MATERIALS AND METHODS 7 IMRT, 9 IMRT, 1 ARC, and 2 ARC plans were created for 30 prostate cancer patients using the Eclipse™ treatment planning system (Varian Medical Systems). All the plans were designed to deliver 80.0 Gy in 40 fractions to the prostate planning target volume (PTV). Target coverage, organs at risk (OARs), number of monitor units, homogeneity, and conformity were compared across the four techniques to assess the quality of the plans. RESULTS The study revealed better Planning Target Volume (PTV) dose coverage in the VMAT-2A than in the other plans. At the same time, VMAT-2A plans were found to be significantly lower in terms of Bladder and rectum doses than other techniques. In addition, VMAT has the advantage of considerably reducing the number of monitor units and treatment time. CONCLUSION For prostate cancer, VMAT may offer a favorable dose gradient profile, conformity, and MU and treatment time compared to IMRT.
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Affiliation(s)
- Fady Samir
- Alexandria Clinical Oncology Department, Alexandria University, Alexandria, Egypt
| | - Talaat M Meaz
- Physics Department Faculty of Science, Tanta University, Tanta, Egypt
| | - Fathi AEl Hussiny
- Physics Department Faculty of Science, Tanta University, Tanta, Egypt
| | - Ahmed A Ahmed
- Ayadi Almostakbal Oncology Center, Alexandria, Egypt
| | - Amr A Mahmoud
- Department of Clinical Oncology, Kafr Elsheikh University, Kafr El-Sheikh, Egypt
| | - Tamer Refaat
- Department of Radiation Oncology, Loyola University Chicago, Chicago, USA
| | - Ahmed Gawish
- Department of Radiation Oncology, University Hospital Magdeburg, Magdeburg, Germany.
| | - Mohamed Abouegylah
- Alexandria Clinical Oncology Department, Alexandria University, Alexandria, Egypt
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Moran JM, Bazan JG, Dawes SL, Kujundzic K, Napolitano B, Redmond KJ, Xiao Y, Yamada Y, Burmeister J. Quality and Safety Considerations in Intensity Modulated Radiation Therapy: An ASTRO Safety White Paper Update. Pract Radiat Oncol 2022; 13:203-216. [PMID: 36710210 DOI: 10.1016/j.prro.2022.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 11/11/2022] [Indexed: 12/14/2022]
Abstract
PURPOSE This updated report on intensity modulated radiation therapy (IMRT) is part of a series of consensus-based white papers previously published by the American Society for Radiation Oncology (ASTRO) addressing patient safety. Since the first white papers were published, IMRT went from widespread use to now being the main delivery technique for many treatment sites. IMRT enables higher radiation doses to be delivered to more precise targets while minimizing the dose to uninvolved normal tissue. Due to the associated complexity, IMRT requires additional planning and safety checks before treatment begins and, therefore, quality and safety considerations for this technique remain important areas of focus. METHODS AND MATERIALS ASTRO convened an interdisciplinary task force to assess the original IMRT white paper and update content where appropriate. Recommendations were created using a consensus-building methodology, and task force members indicated their level of agreement based on a 5-point Likert scale, from "strongly agree" to "strongly disagree." A prespecified threshold of ≥75% of raters who select "strongly agree" or "agree" indicated consensus. CONCLUSIONS This IMRT white paper primarily focuses on quality and safety processes in planning and delivery. Building on the prior version, this consensus paper incorporates revised and new guidance documents and technology updates. IMRT requires an interdisciplinary team-based approach, staffed by appropriately trained individuals as well as significant personnel resources, specialized technology, and implementation time. A comprehensive quality assurance program must be developed, using established guidance, to ensure IMRT is performed in a safe and effective manner. Patient safety in the delivery of IMRT is everyone's responsibility, and professional organizations, regulators, vendors, and end-users must work together to ensure the highest levels of safety.
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Affiliation(s)
- Jean M Moran
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Jose G Bazan
- Department of Radiation Oncology, Ohio State University, James Cancer Hospital and Solove Research Institute, Columbus, Ohio
| | | | | | - Brian Napolitano
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts
| | - Kristin J Redmond
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Ying Xiao
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Yoshiya Yamada
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Jay Burmeister
- Department of Oncology, Wayne State University School of Medicine, Karmanos Cancer Center, Detroit, Michigan
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Shimizu N, Myojin M, Tamura M, Nishiyama N, Yamashiro K, Yuyama Y, Okazaki Y, Suzuki Y, Takahashi M. Significance of boost radiotherapy in early invasive ductal breast cancer with ductal carcinoma in situ component under negative surgical margins. JOURNAL OF RADIATION RESEARCH 2022; 63:80-87. [PMID: 34718690 PMCID: PMC8776689 DOI: 10.1093/jrr/rrab103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Revised: 07/08/2021] [Indexed: 06/13/2023]
Abstract
We hypothesize that there is a risk of ipsilateral breast tumor recurrence (IBTR) in surgical margin-free invasive ductal carcinoma (IDC) in the presence of ductal carcinoma in situ (DCIS) component affecting surgical margins in early stage. From 1990 to 2014, 343 patients with IDC in which the DCIS component constitute have received radiotherapy (RT) following breast-conserving surgery (BCS). All patients received whole breast irradiation with a prescribed dose of 50 Gy in 20 fractions (four times a week). This one-arm cohort with boost RT (253 patients) was compared for IBTR with a non-cohort group receiving no boost RT because of freedom from positive margins (90 patients). Median observation months were 98 (boost group) vs 119 (no boost group), respectively. The 15-year local recurrence-free survival (LRFS) rates were 98.5% and 85.6% in the boost and no boost groups, respectively (Cox proportional hazards model univariate analysis; p = 0.013, HR 0.13). Similarly, for other background factors, there was a significant difference in the LRFS between age groups. The 15-year LRFS rate was 91.8% in patients aged 45 years or younger and 94.6% in patients older than 46 years (p = 0.031, HR 0.21), respectively. Only these two factors were independently significant in Cox proportional hazards model multivariate analysis. IBTR risk in margin-free IDC with DCIS component was independently decreased by boost RT in the cohort setting. Tumor size, extensive intraductal component (EIC), boost dose, the presence of lymph node (LN) metastasis and hormonal therapy were not IBTR risk factors in this study.
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Affiliation(s)
| | - Miyako Myojin
- Corresponding author. Department of Radiation Oncology, Keiyukai Sapporo Hospital, 14-kita1-1 Hondori Shiroishi-ku, Sapporo, Hokkaido 003-0027, Japan, Telephone: +81-11-863-2101,
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Estimation of monitor unit through analytical method for dynamic IMRT using control points as an effective parameter. JOURNAL OF RADIOTHERAPY IN PRACTICE 2021. [DOI: 10.1017/s1460396921000017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Abstract
Introduction:
The control points (CP) play a significant role in the delivery of segmented based Intensity-Modulated Radiation Therapy (IMRT) delivery, particularly in dynamic mode. The number of segments is determined by control points and these segments will transfer from one to the other either during beam ON called dynamic delivery or during beam OFF called static delivery or step and shoot. This study was aimed at indirect estimation of the total monitor units (MU) to be delivered per field by exploiting the control points and also to find the MUs at any nth segment.
Materials and methods:
This study was performed in the Eclipse treatment planning software version 13.8.0. The details of control points, metre set weight per segment, leaf positions for each segment, field size, etc. were taken into consideration.
Results:
TPS calculated MU value and analytically estimated MU value were compared and the percentage of difference was estimated. The overall mean percentage of deviation was 1·03% between the TPS calculated method and the analytical method. The paired sample t-test was performed and, p-value <0·05, no significant difference was found. The analytical relationship determined to estimate the total number of MU delivered for any nth control point was also evaluated.
Conclusion:
The control points are a potential parameter in the conventional IMRT delivery. Through this study, we have addressed the indirect method to estimate the monitor units delivered per segment.
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Medeiros H, Goldbarg EFG, Goldbarg MC. On the three-objective static unconstrained leaf sequencing in IMRT. Med Biol Eng Comput 2020; 58:2025-2037. [PMID: 32623643 DOI: 10.1007/s11517-020-02210-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 06/09/2020] [Indexed: 10/23/2022]
Abstract
Algorithms are an essential part of radiation therapy planning, which includes three optimizations problems: beam angle configuration, fluence map, and realization. This study addresses the third one, also called the leaf sequencing problem, which arises for each chosen irradiation angle, given the optimized fluence map. It consists in defining a sequence of configurations of a device (called multileaf collimator) that correctly delivers radiation to the patient. A usual model for this problem is the decomposition of a matrix into a weighted sum of (0,1)-matrices, called segments, in which the ones in each row appear consecutively. Each (0,1)-matrix corresponds to a configuration of the device. The realization problem has three objectives. The first one is to minimize the sum of weights assigned to the (0,1)-matrices. The second is to minimize the number of segments. Finally, the third one is to find the best order to apply those configurations. This study presents a greedy and randomized algorithm to this problem and compares it with other algorithms presented previously in the literature. Statistical tests show that our algorithm outperformed the previous ones regarding the quality indicators investigated. Graphical Abstract a Illustrates how the IMRT realization is modelled to a mathematical problem. b Shows a decomposition example of the IMRT realization. c The scheme of the algorithm that is proposed on this work, called GRA-SRA.
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Affiliation(s)
- Hudson Medeiros
- Graduate Program in Systems and Computing, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
| | | | - Marco Cesar Goldbarg
- Department of Informatics and Applied Mathematics, Federal University of Rio Grande do Norte, Natal, RN, Brazil
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Yaparpalvi R, Ohri N, Tomé WA, Kalnicki S. Trends in Physics Contributions to the 'Red Journal': A 30-year Journey and Comparison to Global Trends. Cureus 2018; 10:e3012. [PMID: 30254802 PMCID: PMC6150769 DOI: 10.7759/cureus.3012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
INTRODUCTION In this study, we catalogued physics contributions in the Red Journal over the past three decades and compared publication trends with global publication trends. METHODS We used the website of the Red Journal (International Journal of Radiation Oncology, Biology, and Physics) to access physics contributions published between 1988 and 2017. The contributions were catalogued following taxonomy guidelines endorsed by the American Association of Physicists in Medicine. From each issue, publications classified as "Physics Contributions" or as "Technical Innovations" or listed a physicist as one of the primary authors was indexed. Results are presented using descriptive statistics; chi-square [Formula: see text]2 testing were utilized to examine trends in contributions over 10-year time intervals. For global trend comparison of Red Journal physics contributions, we utilized PubMed database to obtain publication counts on the topics of interest. RESULTS A total of 2,852 physics contributions were indexed (86 volumes and 436 issues). Overall, 76% of contributions were photon-beam therapy applications, 15% brachytherapy, 7% particle-beam therapy, and 3% electron-beam therapy. [Formula: see text]2 analyses revealed significant changes in this distribution over time (p<0.001). Brachytherapy accounted for 23% of publications in the first decade, compared to 7% in the third decade. Particle beam therapy accounted for 4% of publications in the first decade and 12% in the third decade. Among treatment techniques, three-dimensional conformal radiation therapy (3D-CRT) accounted for 64% of contributions in the first decade, compared to 3% in the third decade. Intensity-modulated radiation therapy (IMRT)/volumetric modulated arc therapy (VMAT) accounted for 4% in the first decade, compared to 54% in the third decade. Significant increases in the proportions of studies focused on motion management, functional imaging for treatment planning, and radiation safety/quality assurance during the third decade were observed (p<0.001). CONCLUSION Trends of physics publications in the Red Journal and globally, in general, largely mirror technological advances in the field of radiation oncology. These changes reflect a technological transition in the field over three decades from beam's-eye-view designed static treatment ports to functional imaging and knowledge-based treatment planning with biological dose optimization and real-time tumor tracking.
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Affiliation(s)
- Ravindra Yaparpalvi
- Radiation Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, USA
| | - Nitin Ohri
- Radiation Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, USA
| | - Wolfgang A Tomé
- Radiation Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, USA
| | - Shalom Kalnicki
- Radiation Oncology, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, USA
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Njeh CF, Salmon HW, Schiller C. The Impact of Dose Rate on the Accuracy of Step-and-Shoot Intensity-modulated Radiation Therapy Quality Assurance Using Varian 2300CD. J Med Phys 2018; 42:206-212. [PMID: 29296034 PMCID: PMC5744448 DOI: 10.4103/jmp.jmp_18_17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Introduction Intensity-modulated radiation therapy (IMRT) delivery using "step-and-shoot" technique on Varian C-Series linear accelerator (linac) is influenced by the communication frequency between the multileaf collimator and linac controllers. Hence, the dose delivery accuracy is affected by the dose rate. Aim Our aim was to quantify the impact of using two dose rates on plan quality assurance (QA). Materials and Methods Twenty IMRT patients were selected for this study. The plan QA was measured at two different dose rates. A gamma analysis was performed, and the degree of plan modulation on the QA pass rate was also evaluated in terms of average monitor unit per segment (MU/segment) and the total number of segments. Results The mean percentage gamma pass rate of 94.9% and 93.5% for 300 MU/min and 600 MU/min dose rate, respectively, was observed. There was a significant (P = 0.001) decrease in percentage gamma pass rate when the dose rate was increased from 300 MU/min to 600 MU/min. There was a weak, but significant association between the percentage pass rate at both dose rate and total number of segments. The total number of MU was significantly correlated to the total number of segments (r = 0.59). We found a positive correlation between the percentage pass rate and mean MU/segment, r = 0.52 and r = 0.57 for 300 MU/min and 600 MU/min, respectively. Conclusion IMRT delivery using step-and-shoot technique on Varian 2300CD is impacted by the dose rate and the total amount of segments.
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Affiliation(s)
- Christopher F Njeh
- Diagnostic and Treatment Center, Marshfield Clinic, Weston, WI.,Department of Radiation Oncology, Franciscan St. Francis Health, Indianapolis, IN 46237, USA
| | - Howard W Salmon
- Department of Radiation Oncology, Franciscan St. Francis Health, Indianapolis, IN 46237, USA
| | - Claire Schiller
- Diagnostic and Treatment Center, Marshfield Clinic, Weston, WI
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Oelfke U, Bortfeld T. Optimization of Physical Dose Distributions with Hadron Beams: Comparing Photon IMRT with IMPT. Technol Cancer Res Treat 2016; 2:401-12. [PMID: 14529305 DOI: 10.1177/153303460300200505] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Intensity modulated radiotherapy with high enengy photons (IMRT) and with charged particles (IMPT) refer to the most advanced development in conformal radiation therapy. Their general aim is to increase local tumor control rates while keeping the radiation induced complications below desired thresholds. IMRT is currently widely introduced in clinical practice. However, the more complicated IMPT is still under development. Especially, spot-scanning techniques integrated in rotating gantries that can deliver proton or light ion-beams to a radiation target from any direction will be available in the near future. We describe the basic concepts of intensity modulated particle therapy (IMPT). Starting from the potential advantages of hadron therapy inverse treatment planning strategies are discussed for various dose delivery techniques of IMPT. Of special interest are the techniques of distal edge tracking (DET) and 3D-scanning. After the introduction of these concepts a study of comparative inverse treatment planning is presented. The study aims to identify the potential advantages of achievable physical dose distributions with proton and carbon beams, if different dose delivery techniques are employed. Moreover, a comparison to standard photon IMRT is performed. The results of the study are summarized as: i) IMRT with photon beams is a strong competitor to intensity modulated radiotherapy with charged particles. The most obvious benefit observed for charged particles is the reduction of medium and low doses in organs at risk. ii) The 3D-scanning technique could not improve the dosimetric results achieved with DET, although 10–15 times more beam spots were employed for 3D-scanning than for DET. However, concerns may arise about the application of DET, if positioning errors of the patient or organ movements have to be accounted for. iii) Replacing protons with carbon ions leads to further improvements of the physical dose distributions. However, the additional degree of improvement due to carbon ions is modest. The main clinical potential of heavy ion beams is probably related to their radiobiological properties.
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Affiliation(s)
- U Oelfke
- Department of Medical Physics, Deutsches Krebsforschungszentrum (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
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Chow JCL. Some computer graphical user interfaces in radiation therapy. World J Radiol 2016; 8:255-267. [PMID: 27027225 PMCID: PMC4807334 DOI: 10.4329/wjr.v8.i3.255] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 11/06/2015] [Accepted: 01/07/2016] [Indexed: 02/06/2023] Open
Abstract
In this review, five graphical user interfaces (GUIs) used in radiation therapy practices and researches are introduced. They are: (1) the treatment time calculator, superficial X-ray treatment time calculator (SUPCALC) used in the superficial X-ray radiation therapy; (2) the monitor unit calculator, electron monitor unit calculator (EMUC) used in the electron radiation therapy; (3) the multileaf collimator machine file creator, sliding window intensity modulated radiotherapy (SWIMRT) used in generating fluence map for research and quality assurance in intensity modulated radiation therapy; (4) the treatment planning system, DOSCTP used in the calculation of 3D dose distribution using Monte Carlo simulation; and (5) the monitor unit calculator, photon beam monitor unit calculator (PMUC) used in photon beam radiation therapy. One common issue of these GUIs is that all user-friendly interfaces are linked to complex formulas and algorithms based on various theories, which do not have to be understood and noted by the user. In that case, user only needs to input the required information with help from graphical elements in order to produce desired results. SUPCALC is a superficial radiation treatment time calculator using the GUI technique to provide a convenient way for radiation therapist to calculate the treatment time, and keep a record for the skin cancer patient. EMUC is an electron monitor unit calculator for electron radiation therapy. Instead of doing hand calculation according to pre-determined dosimetric tables, clinical user needs only to input the required drawing of electron field in computer graphical file format, prescription dose, and beam parameters to EMUC to calculate the required monitor unit for the electron beam treatment. EMUC is based on a semi-experimental theory of sector-integration algorithm. SWIMRT is a multileaf collimator machine file creator to generate a fluence map produced by a medical linear accelerator. This machine file controls the multileaf collimator to deliver intensity modulated beams for a specific fluence map used in quality assurance or research. DOSCTP is a treatment planning system using the computed tomography images. Radiation beams (photon or electron) with different energies and field sizes produced by a linear accelerator can be placed in different positions to irradiate the tumour in the patient. DOSCTP is linked to a Monte Carlo simulation engine using the EGSnrc-based code, so that 3D dose distribution can be determined accurately for radiation therapy. Moreover, DOSCTP can be used for treatment planning of patient or small animal. PMUC is a GUI for calculation of the monitor unit based on the prescription dose of patient in photon beam radiation therapy. The calculation is based on dose corrections in changes of photon beam energy, treatment depth, field size, jaw position, beam axis, treatment distance and beam modifiers. All GUIs mentioned in this review were written either by the Microsoft Visual Basic.net or a MATLAB GUI development tool called GUIDE. In addition, all GUIs were verified and tested using measurements to ensure their accuracies were up to clinical acceptable levels for implementations.
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Gang GJ, Stayman JW, Ehtiati T, Siewerdsen JH. Task-driven image acquisition and reconstruction in cone-beam CT. Phys Med Biol 2015; 60:3129-50. [PMID: 25803361 PMCID: PMC4539970 DOI: 10.1088/0031-9155/60/8/3129] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
This work introduces a task-driven imaging framework that incorporates a mathematical definition of the imaging task, a model of the imaging system, and a patient-specific anatomical model to prospectively design image acquisition and reconstruction techniques to optimize task performance. The framework is applied to joint optimization of tube current modulation, view-dependent reconstruction kernel, and orbital tilt in cone-beam CT. The system model considers a cone-beam CT system incorporating a flat-panel detector and 3D filtered backprojection and accurately describes the spatially varying noise and resolution over a wide range of imaging parameters in the presence of a realistic anatomical model. Task-based detectability index (d') is incorporated as the objective function in a task-driven optimization of image acquisition and reconstruction techniques. The orbital tilt was optimized through an exhaustive search across tilt angles ranging ± 30°. For each tilt angle, the view-dependent tube current and reconstruction kernel (i.e. the modulation profiles) that maximized detectability were identified via an alternating optimization. The task-driven approach was compared with conventional unmodulated and automatic exposure control (AEC) strategies for a variety of imaging tasks and anthropomorphic phantoms. The task-driven strategy outperformed the unmodulated and AEC cases for all tasks. For example, d' for a sphere detection task in a head phantom was improved by 30% compared to the unmodulated case by using smoother kernels for noisy views and distributing mAs across less noisy views (at fixed total mAs) in a manner that was beneficial to task performance. Similarly for detection of a line-pair pattern, the task-driven approach increased d' by 80% compared to no modulation by means of view-dependent mA and kernel selection that yields modulation transfer function and noise-power spectrum optimal to the task. Optimization of orbital tilt identified the tilt angle that reduced quantum noise in the region of the stimulus by avoiding highly attenuating anatomical structures. The task-driven imaging framework offers a potentially valuable paradigm for prospective definition of acquisition and reconstruction protocols that improve task performance without increase in dose.
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Affiliation(s)
- Grace J. Gang
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
| | - J. Webster Stayman
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Tina Ehtiati
- Siemens Healthcare AX Division, Erlangen, Germany
| | - Jeffrey H. Siewerdsen
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
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Gang GJ, Stayman JW, Ouadah S, Ehtiati T, Siewerdsen JH. Task-driven imaging in cone-beam computed tomography. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2015; 9412:941220. [PMID: 26052176 PMCID: PMC4457372 DOI: 10.1117/12.2082169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
PURPOSE Conventional workflow in interventional imaging often ignores a wealth of prior information of the patient anatomy and the imaging task. This work introduces a task-driven imaging framework that utilizes such information to prospectively design acquisition and reconstruction techniques for cone-beam CT (CBCT) in a manner that maximizes task-based performance in subsequent imaging procedures. METHODS The framework is employed in jointly optimizing tube current modulation, orbital tilt, and reconstruction parameters in filtered backprojection reconstruction for interventional imaging. Theoretical predictors of noise and resolution relates acquisition and reconstruction parameters to task-based detectability. Given a patient-specific prior image and specification of the imaging task, an optimization algorithm prospectively identifies the combination of imaging parameters that maximizes task-based detectability. Initial investigations were performed for a variety of imaging tasks in an elliptical phantom and an anthropomorphic head phantom. RESULTS Optimization of tube current modulation and view-dependent reconstruction kernel was shown to have greatest benefits for a directional task (e.g., identification of device or tissue orientation). The task-driven approach yielded techniques in which the dose and sharp kernels were concentrated in views contributing the most to the signal power associated with the imaging task. For example, detectability of a line pair detection task was improved by at least three fold compared to conventional approaches. For radially symmetric tasks, the task-driven strategy yielded results similar to a minimum variance strategy in the absence of kernel modulation. Optimization of the orbital tilt successfully avoided highly attenuating structures that can confound the imaging task by introducing noise correlations masquerading at spatial frequencies of interest. CONCLUSIONS This work demonstrated the potential of a task-driven imaging framework to improve image quality and reduce dose beyond that achievable with conventional imaging approaches.
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Affiliation(s)
- G J Gang
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore MD, USA 21205
| | - J W Stayman
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore MD, USA 21205
| | - S Ouadah
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore MD, USA 21205
| | - T Ehtiati
- Siemens Healthcare, Baltimore MD, USA 21205
| | - J H Siewerdsen
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore MD, USA 21205
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Gang GJ, Stayman JW, Zbijewski W, Siewerdsen JH. Task-based detectability in CT image reconstruction by filtered backprojection and penalized likelihood estimation. Med Phys 2014; 41:081902. [PMID: 25086533 PMCID: PMC4115652 DOI: 10.1118/1.4883816] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 05/28/2014] [Accepted: 06/03/2014] [Indexed: 12/17/2022] Open
Abstract
PURPOSE Nonstationarity is an important aspect of imaging performance in CT and cone-beam CT (CBCT), especially for systems employing iterative reconstruction. This work presents a theoretical framework for both filtered-backprojection (FBP) and penalized-likelihood (PL) reconstruction that includes explicit descriptions of nonstationary noise, spatial resolution, and task-based detectability index. Potential utility of the model was demonstrated in the optimal selection of regularization parameters in PL reconstruction. METHODS Analytical models for local modulation transfer function (MTF) and noise-power spectrum (NPS) were investigated for both FBP and PL reconstruction, including explicit dependence on the object and spatial location. For FBP, a cascaded systems analysis framework was adapted to account for nonstationarity by separately calculating fluence and system gains for each ray passing through any given voxel. For PL, the point-spread function and covariance were derived using the implicit function theorem and first-order Taylor expansion according to Fessler ["Mean and variance of implicitly defined biased estimators (such as penalized maximum likelihood): Applications to tomography," IEEE Trans. Image Process. 5(3), 493-506 (1996)]. Detectability index was calculated for a variety of simple tasks. The model for PL was used in selecting the regularization strength parameter to optimize task-based performance, with both a constant and a spatially varying regularization map. RESULTS Theoretical models of FBP and PL were validated in 2D simulated fan-beam data and found to yield accurate predictions of local MTF and NPS as a function of the object and the spatial location. The NPS for both FBP and PL exhibit similar anisotropic nature depending on the pathlength (and therefore, the object and spatial location within the object) traversed by each ray, with the PL NPS experiencing greater smoothing along directions with higher noise. The MTF of FBP is isotropic and independent of location to a first order approximation, whereas the MTF of PL is anisotropic in a manner complementary to the NPS. Task-based detectability demonstrates dependence on the task, object, spatial location, and smoothing parameters. A spatially varying regularization "map" designed from locally optimal regularization can improve overall detectability beyond that achievable with the commonly used constant regularization parameter. CONCLUSIONS Analytical models for task-based FBP and PL reconstruction are predictive of nonstationary noise and resolution characteristics, providing a valuable framework for understanding and optimizing system performance in CT and CBCT.
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Affiliation(s)
- Grace J Gang
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5G 2M9, Canada and Department of Biomedical Engineering, Johns Hopkins University, Baltimore Maryland 21205
| | - J Webster Stayman
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore Maryland 21205
| | - Wojciech Zbijewski
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore Maryland 21205
| | - Jeffrey H Siewerdsen
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5G 2M9, Canada and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205
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Bakiu E, Telhaj E, Kozma E, Ruçi F, Malkaj P. Comparison of 3D CRT and IMRT Tratment Plans. Acta Inform Med 2014; 21:211-2. [PMID: 24167395 PMCID: PMC3804479 DOI: 10.5455/aim.2013.21.211-212] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2013] [Accepted: 07/25/2013] [Indexed: 11/03/2022] Open
Abstract
Plans of patients with prostate tumor have been studied. These patients have been scanned in the CT simulator and the images have been sent to the Focal, the system where the doctor delineates the tumor and the organs at risk. After that in the treatment planning system XiO there are created for the same patients three dimensional conformal and intensity modulated radiotherapy treatment plans. The planes are compared according to the dose volume histograms. It is observed that the plans with IMRT technique conform better the isodoses to the planning target volume and protect more the organs at risk, but the time needed to create such plans and to control it is higher than 3D CRT. So it necessary to decide in which patients to do one or the other technique depending on the full dose given to PTV and time consuming in genereral.
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Affiliation(s)
- Erjona Bakiu
- Radiotherapy Department, Hygeia Hospital Tirana, Albania
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Liljegren A, Unukovych D, Gagliardi G, Bjöhle J, Wickman M, Johansson H, Sandelin K. No difference in dose distribution in organs at risk in postmastectomy radiotherapy with or without breast implant reconstruction. Radiat Oncol 2014; 9:14. [PMID: 24406085 PMCID: PMC3907145 DOI: 10.1186/1748-717x-9-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Accepted: 01/02/2014] [Indexed: 12/25/2022] Open
Abstract
The aim of this study was to quantify the variation in doses to organs at risk (ipsilateral lung and heart) and the clinical target volume (CTV) in the presence of breast implants. In this retrospective cohort study, patients were identified through the National Breast Cancer Register. Consecutive breast cancer patients undergoing mastectomy between 2009 and 2011 and completing a full course of postmastectomy radiotherapy (PMRT) were eligible. All included patients (n = 818) were identified in the ARIA© oncology information system and further stratified for immediate breast reconstruction (IBR+, n = 162) and no immediate breast reconstruction (IBR-, n = 656). Dose statistics for ipsilateral lung, heart and CTV were retrieved from the system. Radiation plans for patients with chest wall (CW) only (n = 242) and CW plus lymph nodes (n = 576) irradiation were studied separately. The outcome variables were dichotomized as follows: lung, V20Gy ≤ 30% vs. V20Gy > 30%; heart, Dmean ≤ 5 Gy vs. Dmean > 5 Gy; CTV, V95% ≥ median vs. V95% < median. In the univariate and multivariate regression models no correlation between potential confounders (i.e. breast reconstruction, side of PMRT, CW index) and the outcome variables was found. Multivariate analysis of CW plus lymph nodes radiation plans, for example, showed no association of breast reconstruction with dosimetric outcomes in neither lung nor heart- lung V20Gy (odds ratio [OR]: 0.6, 95%CI, 0.4 to 1.0, p = 0.07) or heart Dmean (OR: 1.2, 95%CI, 0.5 to 3.1, p = 0.72), respectively. CTV was statistically significantly larger in the IBR+ group (i.e. included breast implant), but no correlation between the implant type and dosimetric characteristics of the organs at risk was revealed. In the current study, the presence of breast implants during postmastectomy radiotherapy was not associated with increased doses to ipsilateral lung and heart, but CTV definition and its dosimetric characteristics urge further evaluation.
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Affiliation(s)
| | - Dmytro Unukovych
- Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden.
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16
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Jiang L, Xiong XP, Hu CS, Ou ZL, Zhu GP, Ying, HM. In vitro and in vivo studies on radiobiological effects of prolonged fraction delivery time in A549 cells. JOURNAL OF RADIATION RESEARCH 2013; 54:230-4. [PMID: 23090953 PMCID: PMC3589931 DOI: 10.1093/jrr/rrs093] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 09/07/2012] [Accepted: 09/19/2012] [Indexed: 05/20/2023]
Abstract
Intensity-modulated radiation therapy, when used in the clinic, prolongs fraction delivery time. Here we investigated both the in vivoand in vitroradiobiological effects on the A549 cell line, including the effect of different delivery times with the same dose on A549 tumor growth in nude mice. The in vitroeffects were studied with clonogenic assays, using linear-quadratic and incomplete repair models to fit the dose-survival curves. Fractionated irradiation of different doses was given at one fraction per day, simulating a clinical dose-time-fractionation pattern. The longer the interval between the exposures, the more cells survived. To investigate the in vivoeffect, we used sixty-four nude mice implanted with A549 cells in the back legs, randomly assigned into eight groups. A 15 Gy radiation dose was divided into different subfractions. The maximum and minimum tumor diameters were recorded to determine tumor growth. Tumor growth was delayed for groups with prolonged delivery time (40 min) compared to the group receiving a single dose of 15 Gy (P< 0.05), and tumors with a 20 min delivery time had delayed growth compared to those with a 40 min delivery time [20' (7.5 Gy × 2 F) vs 40' (7.5 Gy × 2 F), P= 0.035; 20' (3 Gy × 5 F) vs 40' (3 Gy × 5 F); P= 0.054; 20' (1.67 Gy × 9 F) vs 40' (1.67 Gy × 9 F), P= 0.028]. A prolonged delivery time decreased the radiobiological effects, so we strongly recommend keeping the delivery time as short as possible.
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Affiliation(s)
- Ling Jiang
- Department of Radiation Oncology, Fudan University Shanghai Cancer Center, No. 270, Dong-An Rd., Shanghai, China, 200032
- Department of Oncology, Shanghai Medical College, Fudan University, No. 270, Dong-An Rd., Shanghai, China, 200032
- Department of Medical Oncology, Xu-Hui Center Hospital, No. 966, Huai-Hai Middle Rd., Shanghai, China, 200031
| | - Xiao-Peng Xiong
- Department of Nuclear Medicine, Ren-Ji Hospital, Shanghai Jiaotong University, No.1630, Dong-Fang Rd., Shanghai, China, 200127
| | - Chao-Su Hu
- Department of Radiation Oncology, Fudan University Shanghai Cancer Center, No. 270, Dong-An Rd., Shanghai, China, 200032
- Department of Oncology, Shanghai Medical College, Fudan University, No. 270, Dong-An Rd., Shanghai, China, 200032
| | - Zhou-Luo Ou
- Department of Oncology, Shanghai Medical College, Fudan University, No. 270, Dong-An Rd., Shanghai, China, 200032
- Breast Cancer Center, Fudan University Shanghai Cancer Center, No. 270, Dong-An Rd., Shanghai, China, 200032
| | - Guo-Pei Zhu
- Department of Radiation Oncology, Fudan University Shanghai Cancer Center, No. 270, Dong-An Rd., Shanghai, China, 200032
- Department of Oncology, Shanghai Medical College, Fudan University, No. 270, Dong-An Rd., Shanghai, China, 200032
| | - Hong-Mei Ying,
- Department of Radiation Oncology, Fudan University Shanghai Cancer Center, No. 270, Dong-An Rd., Shanghai, China, 200032
- Department of Oncology, Shanghai Medical College, Fudan University, No. 270, Dong-An Rd., Shanghai, China, 200032
- Corresponding author. Tel: +86-21-6417-5590; Fax: +86-21-6417-5590;
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Shin JS, Shin E, Han Y, Ju SG, Kim JS, Ahn SH, Kim TG, Jeong BK, Park HC, Ahn YC, Choi DH. Analysis of changes in dose distribution due to respiration during IMRT. Radiat Oncol J 2011; 29:206-13. [PMID: 22984672 PMCID: PMC3429904 DOI: 10.3857/roj.2011.29.3.206] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 08/23/2011] [Accepted: 08/31/2011] [Indexed: 12/25/2022] Open
Abstract
Purpose Intensity modulated radiation therapy (IMRT) is a high precision therapy technique that can achieve a conformal dose distribution on a given target. However, organ motion induced by respiration can result in significant dosimetric error. Therefore, this study explores the dosimetric error that result from various patterns of respiration. Materials and Methods Experiments were designed to deliver a treatment plan made for a real patient to an in-house developed motion phantom. The motion pattern; the amplitude and period as well as inhale-exhale period, could be controlled by in-house developed software. Dose distribution was measured using EDR2 film and analysis was performed by RIT113 software. Three respiratory patterns were generated for the purpose of this study; first the 'even inhale-exhale pattern', second the slightly long exhale pattern (0.35 seconds longer than inhale period) named 'general signal pattern', and third a 'long exhale pattern' (0.7 seconds longer than inhale period). One dimensional dose profile comparisons and gamma index analysis on 2 dimensions were performed Results In one-dimensional dose profile comparisons, 5% in the target and 30% dose difference at the boundary were observed in the long exhale pattern. The center of high dose region in the profile was shifted 1 mm to inhale (caudal) direction for the 'even inhale-exhale pattern', 2 mm and 5 mm shifts to exhale (cranial) direction were observed for 'slightly long exhale pattern' and 'long exhale pattern', respectively. The areas of gamma index >1 were 11.88%, 15.11%, and 24.33% for 'even inhale-exhale pattern', 'general pattern', and 'long exhale pattern', respectively. The long exhale pattern showed largest errors. Conclusion To reduce the dosimetric error due to respiratory motions, controlling patient's breathing to be closer to even inhaleexhale period is helpful with minimizing the motion amplitude.
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Affiliation(s)
- Jung Suk Shin
- Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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Webb S. A 4-bank multileaf collimator provides a decomposition advantage for delivering intensity-modulated beams by step-and-shoot. Phys Med 2011; 28:1-6. [PMID: 21907604 DOI: 10.1016/j.ejmp.2011.08.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 08/10/2011] [Accepted: 08/24/2011] [Indexed: 11/28/2022] Open
Abstract
During the delivery of intensity-modulated radiation therapy (IMRT) by the multileaf collimator (MLC) step-and-shoot technique, it is required to sequence the two-dimensional intensity-modulated beams (2D IMBs) into a series of components that can be shaped with the MLC. In this paper it is shown that the use of an MLC that has four banks of leaves (in two orthogonal pairs) instead of two banks only is advantageous for this purpose.
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Affiliation(s)
- S Webb
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey, SM2 5PT, UK.
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19
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Mellado X, Artacho JM, Hernández M, Cruz S, Millán E. Fixed number of segments in unidirectional decompositions of fluence matrices for step-and-shoot IMRT. Phys Med Biol 2011; 56:2601-15. [PMID: 21444972 DOI: 10.1088/0031-9155/56/8/017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The decomposition of a fluence matrix in step-and-shoot mode for intensity-modulated radiation therapy (IMRT) usually yields a large number of segments (NS) and, consequently, treatment time is substantially increased. In this paper, we propose a method for reducing the original NS in multileaf collimator segmentations to a user-specified quantity. The proposed method clusters original segments into the same number of groups as desired NS, and computes for each group an equivalent segment and an associated weight. In order to avoid important changes in dose-volume histograms (DVHs), equivalent segments and weights are computed taking into account the original fluence matrix and preserving the highest fluence zones, thus staying as close as possible to the original planned radiation. The method is applicable to unidirectional segmentations, where there is no backtracking of leaves, since this property facilitates the grouping of segments. The experiments showed that treatment times can be considerably reduced, while maintaining similar DVHs and dosimetric indexes. Furthermore, the algorithm achieved an excellent reduction/dose-quality ratio since the final NS was close to that reported for direct step-and-shoot solutions.
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Affiliation(s)
- X Mellado
- Communications Technology Group (GTC), Aragón Institute for Engineering Research (I3A), Universidad de Zaragoza, C/María de Luna 1, 50018 Zaragoza, Spain.
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20
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Zheng XK, Chen LH, Wang WJ, Ye F, Liu JB, Li QS, Sun HW. Impact of prolonged fraction delivery times simulating IMRT on cultured nasopharyngeal carcinoma cell killing. Int J Radiat Oncol Biol Phys 2010; 78:1541-7. [PMID: 21092834 DOI: 10.1016/j.ijrobp.2010.07.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Revised: 06/28/2010] [Accepted: 07/03/2010] [Indexed: 02/06/2023]
Abstract
PURPOSE To determine the impact of prolonged fraction delivery times (FDTs) simulating intensity-modulated radiotherapy (IMRT) on cultured nasopharyngeal carcinoma (NPC) cell killing. METHODS AND MATERIAL Cultured NPC cell lines CNE1 and CNE2 were used in this study. The biological effectiveness of fractionated irradiation protocols simulating conventional external beam radiotherapy and IMRT (FDT of 15, 36, and 50 minutes) was estimated with standard colony assay, and the differences in cell surviving fractions after irradiation with different protocols were tested by use of the paired t test. The impact degree of prolonged FDTs (from 8 to 50 minutes) on cell killing was also assessed by the dose-modifying factors, which were estimated by comparing the effectiveness of intermittently delivered 2 Gy with that of continuously delivered 1.5 to 2 Gy. RESULTS The cell surviving fractions of both CNE1 and CNE2 after fractionated irradiation simulating IMRT were higher than those simulating conventional external beam radiotherapy (p < 0.05). The dose-modifying factors for a fraction dose of 2 Gy increased from 1.05 to 1.18 for CNE1 and from 1.05 to 1.11 for CNE2 with the FDT being prolonged from 15 to 50 minutes. CONCLUSIONS This study showed that the prolonged FDTs simulating IMRT significantly decreased the cell killing in both CNE1 and CNE2 cell lines, and these negative effects increased with the FDT being prolonged from 15 to 50 minutes. These effects, if confirmed by in vivo and clinical studies, need to be considered in designing IMRT treatments for NPC.
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Affiliation(s)
- Xiao-Kang Zheng
- Department of Radiation Oncology, Nanfang Hospital, Southern Medical University, Guangzhou, China.
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21
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Haute dose dans la prostate par radiothérapie guidée par l’image : apport de l’arcthérapie avec modulation d’intensité du faisceau. Cancer Radiother 2010; 14:679-89. [DOI: 10.1016/j.canrad.2010.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 01/27/2010] [Accepted: 03/08/2010] [Indexed: 11/20/2022]
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22
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Mellado X, Cruz S, Artacho JM, Canellas M. Reducing the number of segments in unidirectional MLC segmentations. Phys Med Biol 2010; 55:N75-85. [PMID: 20057009 DOI: 10.1088/0031-9155/55/3/n01] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In intensity-modulated radiation therapy (IMRT), fluence matrices obtained from a treatment planning system are usually delivered by a linear accelerator equipped with a multileaf collimator (MLC). A segmentation method is needed for decomposing these fluence matrices into segments suitable for the MLC, and the number of segments used is an important factor for treatment time. In this work, an algorithm for reduction of the number of segments (NS) is presented for unidirectional segmentations, where there is no backtracking of the MLC leaves. It uses a geometrical representation of the segmentation output for searching the key values in a fluence matrix that complicate its decomposition. The NS reduction is achieved by performing minor modifications in these values, under the conditions of avoiding substantial modifications of the dose-volume histogram, and does not increase in average the total number of monitor units delivered. The proposed method was tested using two clinical cases planned with the PCRT 3D treatment planning system.
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Affiliation(s)
- X Mellado
- Communications Technology Group, Aragón Institute for Engineering Research (I3A), Universidad de Zaragoza, C/María de Luna 1, 50018, Spain.
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23
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Dobler B, Koelbl O, Bogner L, Pohl F. Direct machine parameter optimization for intensity modulated radiation therapy (IMRT) of oropharyngeal cancer--a planning study. J Appl Clin Med Phys 2009; 10:4-15. [PMID: 19918235 PMCID: PMC5720568 DOI: 10.1120/jacmp.v10i4.3066] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 05/05/2009] [Accepted: 05/14/2009] [Indexed: 11/23/2022] Open
Abstract
The purpose of the study was to investigate the potential of direct machine parameter optimization (DMPO) to achieve parotid sparing without compromising target coverage in IMRT of oropharyngeal cancer as compared to fluence modulation with subsequent leaf sequencing (IM) and forward planned two‐step arc therapy (IMAT). IMRT plans were generated for 10 oropharyngeal cancer patients using DMPO and IM. The resulting dose volume histograms (DVH) were evaluated with regard to compliance with the dose volume objectives (DVO) and plan quality. DMPO met the DVO for the targets better than IM, but violated the DVO to the parotids in some cases. DMPO provided better target coverage and dose homogeneity than IM and was comparable to IMAT. Dose to the parotids (23Gy) was significantly lower than for IMAT (48Gy), but somewhat higher than for IM (20Gy). Parotid sparing with IM was, however, only achieved at the cost of target coverage and homogeneity. DMPO allows achieving parotid sparing in the treatment of oropharyngeal cancer without compromising target coverage and dose homogeneity in the target as compared to two‐step IMAT. Better overall plan quality can be delivered with less monitor units than with IM. PACS number: 87.50.Gi
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Affiliation(s)
- Barbara Dobler
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany
| | - Oliver Koelbl
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany
| | - Ludwig Bogner
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany
| | - Fabian Pohl
- Department of Radiotherapy, Regensburg University Medical Center, Regensburg, Germany
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Siochi RAC. Optimized removal of the tongue-and-groove underdose via constrained partial synchronization and variable depth recursion. Phys Med Biol 2009; 54:1369-81. [PMID: 19204387 DOI: 10.1088/0031-9155/54/5/017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Full synchronization (FS) leaf sequencing removes tongue-and-groove underdosages (TGU) but increases the number of segments. Constrained partial synchronization (CPS) uses a minimum tongue-and-groove ratio (TGR) to reduce the number of segments while achieving acceptable TGUs. TGR is the ratio of non-overlapping intensities that irradiate a common junction. For TGRs of 1, 1.5 and 2, the TGUs were measured as 18%, 4% and 0%, respectively, for a 6 MV beam and a Siemens 82 leaf MLC. The extraction and sweep processes of the variable depth recursion (VDR) leaf-sequencing algorithm were constrained to satisfy a minimum TGR. For a Siemens MLC and 15 clinical cases, VDR with a TGR = 1.5 produced 7% more segments than the unsynchronized VDR, while a fully synchronized sweeping window algorithm produces 62% more segments. For random intensity maps, VDR with CPS produced significantly fewer segments than an unsynchronized sweeping window. Similar results can be obtained for MLCs that interdigitate. This has implications for direct aperture optimization algorithms (DAO) that use the sweeping window as a starting point (Pinnacle), for which a significant TGU has been observed. The concept of CPS can be applied to DAO by choosing appropriate levels for each of the segments in DAO.
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Affiliation(s)
- R Alfredo C Siochi
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA.
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25
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Artacho JM, Mellado X, Tobías G, Cruz S, Hernández M. A novel unidirectional intensity map segmentation method for step-and-shoot IMRT delivery with segment shape control. Phys Med Biol 2009; 54:569-89. [DOI: 10.1088/0031-9155/54/3/007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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26
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Orton CG, Bortfeld TR, Niemierko A, Unkelbach J. The role of medical physicists and the AAPM in the development of treatment planning and optimization. Med Phys 2008; 35:4911-23. [DOI: 10.1118/1.2990777] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Flynn RT, Bowen SR, Bentzen SM, Rockwell Mackie T, Jeraj R. Intensity-modulated x-ray (IMXT) versus proton (IMPT) therapy for theragnostic hypoxia-based dose painting. Phys Med Biol 2008; 53:4153-67. [PMID: 18635895 PMCID: PMC2695924 DOI: 10.1088/0031-9155/53/15/010] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In this work the abilities of intensity-modulated x-ray therapy (IMXT) and intensity-modulated proton therapy (IMPT) to deliver boosts based on theragnostic imaging were assessed. Theragnostic imaging is the use of functional or molecular imaging data for prescribing radiation dose distributions. Distal gradient tracking, an IMPT method designed for the delivery of non-uniform dose distributions, was assessed. Dose prescriptions for a hypoxic region in a head and neck squamous cell carcinoma patient were designed to either uniformly boost the region or redistribute the dose based on positron emission tomography (PET) images of the (61)Cu(II)-diacetyl-bis(N(4)-methylthiosemicarbazone) ((61)Cu-ATSM) hypoxia surrogate. Treatment plans for the prescriptions were created for four different delivery methods: IMXT delivered with step-and-shoot and with helical tomotherapy, and IMPT delivered with spot scanning and distal gradient tracking. IMXT and IMPT delivered comparable dose distributions within the boost region for both uniform and redistributed theragnostic boosts. Normal tissue integral dose was lower by a factor of up to 3 for IMPT relative to the IMXT. For all delivery methods, the mean dose to the nearby organs at risk changed by less than 2 Gy for redistributed versus uniform boosts. The distal gradient tracking method resulted in comparable plans to the spot scanning method while reducing the number of proton beam spots by a factor of over 3.
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Affiliation(s)
- Ryan T Flynn
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI 53703, USA.
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Galvin JM, De Neve W. Intensity Modulating and Other Radiation Therapy Devices for Dose Painting. J Clin Oncol 2007; 25:924-30. [PMID: 17350940 DOI: 10.1200/jco.2007.10.6716] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The introduction of intensity-modulated radiation therapy (IMRT) in the early 1990s created the possibility of generating dramatically improved dose distributions that could be tailored to fit a complex geometric arrangement of targets that push against or even surround healthy critical structures. IMRT is a new treatment paradigm that goes beyond the capabilities of the earlier technology called three-dimensional radiation therapy (3DCRT). IMRT took the older approach of using fields that conformed to the silhouette of the target to deliver a relatively homogeneous intensity of radiation and separated the conformal fields into many subfields so that intensity could be varied to better control the final dose distribution. This technique makes it possible to generate radiation dose clouds that have indentations in their surface. Initially, this technology was mainly used to avoid and thus control the dose delivered to critical structures so that they are not seriously damaged in the process of irradiating nearby targets to an appropriately high dose. Avoidance of critical structures allowed homogeneous dose escalation that led to improved local control for small tumors. However, the normal tissue component of large tumors often prohibits homogeneous dose escalation. A newer concept of dose-painting IMRT is aimed at exploiting inhomogeneous dose distributions adapted to tumor heterogeneity. Tumor regions of increased radiation resistance receive escalated dose levels, whereas radiation-sensitive regions receive conventional or even de-escalated dose levels. Dose painting relies on biologic imaging such as positron emission tomography, functional magnetic resonance imaging, and magnetic resonance spectroscopy. This review will describe the competing techologies for dose painting with an emphasis on their commonalities.
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Affiliation(s)
- James M Galvin
- Department of Radiation Oncology, Thomas Jefferson University Hospital, Kimmel Cancer Center, Philadelphia, PA 19107, USA.
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Ahunbay EE, Chen GP, Thatcher S, Jursinic PA, White J, Albano K, Li XA. Direct aperture optimization–based intensity-modulated radiotherapy for whole breast irradiation. Int J Radiat Oncol Biol Phys 2007; 67:1248-58. [PMID: 17275205 DOI: 10.1016/j.ijrobp.2006.11.036] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Revised: 11/01/2006] [Accepted: 11/03/2006] [Indexed: 10/23/2022]
Abstract
PURPOSE To investigate the technical and dosimetric advantages and the efficacy of direct aperture optimized intensity-modulated radiation therapy (DAO-IMRT) over standard (e.g., beamlet optimized) IMRT and conventional three-dimensional conformal radiotherapy (3D-CRT) for whole breast irradiation in supine and prone positions. METHODS AND MATERIALS We retrospectively designed DAO-IMRT plans for 15 breast cancer patients in supine (10 patients) and prone (5 patients) positions with a goal of uniform dose coverage of the whole breast. These DAO-IMRT plans were compared with standard IMRT using beamlet optimization and conventional 3D-CRT plans using wedges. All plans used opposed tangential beam arrangements. RESULTS In all cases, the DAO-IMRT plans were equal to or better than those generated with 3D-CRT and standard beamlet-IMRT. For supine cases, DAO-IMRT provided higher uniformity index (UI, defined as the ratio of the dose to 95% of breast volume to the maximum dose) than either 3D-CRT (0.88 vs. 0.82; p = 0.026) or beamlet-IMRT (0.89 vs. 0.85; p = 0.003). Direct aperture optimized IMRT also gave lower lung doses than either 3D-CRT (V20 = 7.9% vs. 8.6%; p = 0.024) or beamlet-IMRT (V20 = 8.4% vs. 9.7%; p = 0.0008) for supine patients. For prone patients, DAO-IMRT provided higher UI than either 3D-CRT (0.89 vs. 0.83; p = 0.027) or beamlet-IMRT (0.89 vs. 0.85; p = 0.003). The planning time for DAO-IMRT was approximately 75% less than that of 3D-CRT. The monitor units for DAO-IMRT were approximately 60% less than those of beamlet-IMRT. CONCLUSION Direct aperture optimized IMRT improved the overall quality of dose distributions as well as the planning and delivery efficiency for treating whole breast in both supine and prone positions.
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Affiliation(s)
- Ergun E Ahunbay
- Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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Chow JCL, Grigorov GN, Jiang R. Intensity modulated radiation therapy with irregular multileaf collimated field: a dosimetric study on the penumbra region with different leaf stepping patterns. Med Phys 2007; 33:4606-13. [PMID: 17278813 DOI: 10.1118/1.2388571] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Using a Varian 21 EX linear accelerator with a multileaf collimator (MLC) of 120 leaves, the penumbra regions of beam profiles within an irregular multileaf collimated fields were studied. MLC fields with different leaf stepping angles from 21.8 degrees to 68.2 degrees were used. Beam profiles in different directions: (1) along the cross-line and in-line axis, (2) along the leaf stepping edges of the field, and (3) parallel to the stepping edges but in the middle of the field, were measured and calculated using Kodak XV radiographic film and Pinnacle3 treatment planning system version 7.4f. These beam profiles were measured and calculated at source to axis distance= 100 cm with 5 cm of solid water slab on top. On the one hand, for both cross-line and in-line beam profiles, the penumbra widths of 20%-80% did not vary with the leaf stepping angles and were about 0.4 cm. On the other hand, the penumbra widths of 10%-90% of the above two profiles varied with the stepping angles and had maximum widths of about 1.9 cm (cross-line) and 1.65 cm (in-line) for stepping angles of 38.7 degrees and 51.3 degrees , respectively. For profiles crossing the "rippled" stepping edges of the field, the penumbra widths (10%-90%) at the regions between two opposite leaves (i.e., profile end at the Y1/Y2 jaw position) decreased with the stepping angles. At the penumbra regions between two leaf edges with the tongue-and-groove structure of the same bank (i.e., profile end at the X1/X2 jaw position), the penumbra widths increased with the stepping angles. When the penumbra widths were measured between two opposite leaf edges and at corners between two leaves, the widths first decreased with the stepping angles and then increased beyond the minimum width point at stepping angle of 45 degrees. The penumbra width (10%-90%) measured at the leaf edge was larger than that at the corner. For the beam profiles calculated using Pinnacle3, it is found that the results agreed well with the measurements along the cross-line and in-line axis, while there was a deviation for the profiles along the leaf stepping edge of the field compared to the film measurements. The measured results in this study can help us to understand the dosimetric effect of the leaf stepping (due to finite leaf width), tongue-and-groove and rounded leaf end structure in the penumbra region of an irregular MLC field. A more dedicated penumbra model can be developed for the treatment planning system.
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Affiliation(s)
- James C L Chow
- Department of Radiation Oncology, University of Toronto and Radiation Medicine Program, Princess Margaret Hospital, University Health Network, 610 University Avenue, Toronto, ON N2G 1G3, Canada.
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Abstract
The processes of extraction and sweep are basic segmentation steps that are used in leaf sequencing algorithms. A modified version of a commercial leaf sequencer changed the way that the extracts are selected and expanded the search space, but the modification maintained the basic search paradigm of evaluating multiple solutions, each one consisting of up to 12 extracts and a sweep sequence. While it generated the best solutions compared to other published algorithms, it used more computation time. A new, faster algorithm selects one extract at a time but calls itself as an evaluation function a user-specified number of times, after which it uses the bidirectional sweeping window algorithm as the final evaluation function. To achieve a performance comparable to that of the modified commercial leaf sequencer, 2-3 calls were needed, and in all test cases, there were only slight improvements beyond two calls. For the 13 clinical test maps, computation speeds improved by a factor between 12 and 43, depending on the constraints, namely the ability to interdigitate and the avoidance of the tongue-and-groove under dose. The new algorithm was compared to the original and modified versions of the commercial leaf sequencer. It was also compared to other published algorithms for 1400, random, 15 X 15, test maps with 3-16 intensity levels. In every single case the new algorithm provided the best solution.
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Affiliation(s)
- R Alfredo C Siochi
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Street, Iowa City, Iowa 52240, USA.
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Galvin JM. Alternative Methods for Intensity-Modulated Radiation Therapy Inverse Planning and Dose Delivery. Semin Radiat Oncol 2006; 16:218-23. [PMID: 17010904 DOI: 10.1016/j.semradonc.2006.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A large number of IMRT systems are currently being marketed. Many of these systems appear to be unique, and manufacturers often emphasize design differences as they argue the merits of their particular approach. This paper focuses on highlighting the underlying feature that is intrinsically part of all IMRT systems. On the other hand, major differences often appear at the implementation stage for dose delivery. Such variations are evident because each manufacturer has a unique approach to balancing the issues of treatment time, leakage radiation reaching the patient's total body, aperture approximation of the ideal intensity maps, increasing the angles of approach for the treatment fields, integration of on-line imaging, selection of treatment distance, availability of different photon energies, and overall system complexity (i.e., cost). How these different issues are handled in the process of system design affects the relative advantages and disadvantages that appear in the final product. This paper takes the approach of dividing the various IMRT methods into categories that are divided roughly along the lines of the technique used during dose delivery to approximate the intensity patterns. Other features of each system are included under these sub-sections.
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Affiliation(s)
- James M Galvin
- Jefferson Medical College, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
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Abstract
The very first cornerstone paper on intensity-modulated radiation therapy (IMRT) was published in Physics in Medicine and Biology, and many seminal IMRT works have since appeared in this journal. Today IMRT is a widely used clinical treatment modality in many countries. This contribution to the 50th anniversary issue reviews the physical, mathematical, and technological milestones that have facilitated the clinical implementation and success of IMRT. In particular, the basic concepts and developments of both IMRT treatment planning ('inverse planning') and the delivery of cone-beam IMRT with a multileaf collimator from a fixed number of static beam directions are discussed. An outlook into the future of IMRT concludes the paper.
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Affiliation(s)
- Thomas Bortfeld
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
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Chow JCL, Grigorov GN, Yazdani N. SWIMRT: a graphical user interface using sliding window algorithm to construct a fluence map machine file. J Appl Clin Med Phys 2006; 7:69-85. [PMID: 17533330 PMCID: PMC5722447 DOI: 10.1120/jacmp.v7i2.2231] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Revised: 03/23/2006] [Accepted: 12/31/1969] [Indexed: 12/23/2022] Open
Abstract
A custom‐made computer program, SWIMRT, to construct “multileaf collimator (MLC) machine” file for intensity‐modulated radiotherapy (IMRT) fluence maps was developed using MATLAB® and the sliding window algorithm. The user can either import a fluence map with a graphical file format created by an external treatment‐planning system such as Pinnacle3 or create his or her own fluence map using the matrix editor in the program. Through comprehensive calibrations of the dose and the dimension of the imported fluence field, the user can use associated image‐processing tools such as field resizing and edge trimming to modify the imported map. When the processed fluence map is suitable, a “MLC machine” file is generated for our Varian 21 EX linear accelerator with a 120‐leaf Millennium MLC. This machine file is transferred to the MLC console of the LINAC to control the continuous motions of the leaves during beam irradiation. An IMRT field is then irradiated with the 2D intensity profiles, and the irradiated profiles are compared to the imported or modified fluence map. This program was verified and tested using film dosimetry to address the following uncertainties: (1) the mechanical limitation due to the leaf width and maximum traveling speed, and (2) the dosimetric limitation due to the leaf leakage/transmission and penumbra effect. Because the fluence map can be edited, resized, and processed according to the requirement of a study, SWIMRT is essential in studying and investigating the IMRT technique using the sliding window algorithm. Using this program, future work on the algorithm may include redistributing the time space between segmental fields to enhance the fluence resolution, and readjusting the timing of each leaf during delivery to avoid small fields. Possible clinical utilities and examples for SWIMRT are given in this paper. PACS numbers: 87.53.Kn, 87.53.St, 87.53.Uv
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Affiliation(s)
- James C L Chow
- Radiation Medicine Program and Department of Radiation Oncology, Princess Margaret Hospital, University Health Network, University of Toronto, 610 University Avenue, Toronto, ON, Canada.
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36
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Grigorov GN, Chow JCL, Barnett RB. Dosimetry limitations and a dose correction methodology for step-and-shoot IMRT. Phys Med Biol 2006; 51:637-52. [PMID: 16424586 DOI: 10.1088/0031-9155/51/3/011] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
For the step-and-shoot intensity-modulated radiation therapy (IMRT) technique, the combination of high dose rate, multiple beam segments and low dose per segment can lead to significant differences between the planned dose and the dose delivered to the patient. In this technique, a dose delivery inaccuracy known as the 'overshoot' effect is caused by the dose servo control system. This typically occurs in the first and last beam segments and causes an over- and underdose, respectively. Some dose positional error in the segment sequence is also possible there. Commercial ionization chambers (RK-type) and radiographic Kodak films were used for the measurements. The reported results were obtained using the Pinnacle(3)-V6.2 treatment planning system and a Varian Clinac 21 EX linear accelerator equipped with a 120-leaf Millennium MLC. The dose inaccuracy measurements were based on the comparison of the dose and profiles for reference fields and fields irradiated with the step-and-shoot technique. For our linear accelerators, an 'overshoot' effect ranging from 0.1 to 0.6 MU was found, corresponding to a dose rate from 100 to 600 MU min(-1), respectively. For segments with off-axis distances from 0 to 5.5 cm with >3.5 MU per segment and all dose rates, a MLC leaf-position error of <1 mm was measured. For segments with an off-axis distance of 9.5 cm, a positional error >2 mm was measured for 600 MU min(-1) and 1 MU per segment. The purpose of this study was to find a correction method for segmental dose errors caused by the 'overshoot' effect when small monitor unit and high dose rate are used. To better represent the fluctuation of the segment doses in the beam, a dose ratio between reference and step-and-shoot irradiated fields was defined. A method for the correction of segment dose inaccuracies and a quality assurance programme for the 'overshoot' effect were developed. The ordering of the biggest segment shape in the segment sequence was studied for ten randomly selected prostate patients planned for IMRT. The results of this work can be used to improve the agreement between the planned and delivered doses for IMRT.
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Affiliation(s)
- Grigor N Grigorov
- Medical Physics Department, Grand River Regional Cancer Center, 835 King Street West, Kitchener, ON N2G 1G3, Canada.
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Rangaraj D, Papiez L. Synchronized delivery of DMLC intensity modulated radiation therapy for stationary and moving targets. Med Phys 2005; 32:1802-17. [PMID: 16013738 DOI: 10.1118/1.1924348] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
When delivering intensity modulated treatments the "tongue-and-groove" underdosage effect is a concern that should not be ignored. Algorithms aimed at removing the tongue-and-groove underdosage have been investigated in the past for irradiation of stationary targets. This paper is devoted to algorithms that remove tongue and grove effect for stationary and moving targets. To this end this paper develops original mid-time based algorithms for leaf synchronization. These algorithms exhibit a few additional advantageous properties for DMLC IMRT delivery beyond the removal of tongue-and-grove underdosage. In particular, they safeguard the minimization of time of delivery (for mid-time synchronized algorithms). Moreover, they avoid iterative procedures for synchronization of delivery for multiple pairs of leaves.
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Affiliation(s)
- Dharanipathy Rangaraj
- Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Dai J, Que W. Simultaneous minimization of leaf travel distance and tongue-and-groove effect for segmental intensity-modulated radiation therapy. Phys Med Biol 2005; 49:5319-31. [PMID: 15656280 DOI: 10.1088/0031-9155/49/23/009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This paper introduces a method to simultaneously minimize the leaf travel distance and the tongue-and-groove effect for IMRT leaf sequences to be delivered in segmental mode. The basic idea is to add a large enough number of openings through cutting or splitting existing openings for those leaf pairs with openings fewer than the number of segments so that all leaf pairs have the same number of openings. The cutting positions are optimally determined with a simulated annealing technique called adaptive simulated annealing. The optimization goal is set to minimize the weighted summation of the leaf travel distance and tongue-and-groove effect. Its performance was evaluated with 19 beams from three clinical cases; one brain, one head-and-neck and one prostate case. The results show that it can reduce the leaf travel distance and (or) tongue-and-groove effect; the reduction of the leaf travel distance reaches its maximum of about 50% when minimized alone; the reduction of the tongue-and-groove reaches its maximum of about 70% when minimized alone. The maximum reduction in the leaf travel distance translates to a 1 to 2 min reduction in treatment delivery time per fraction, depending on leaf speed. If the method is implemented clinically, it could result in significant savings in treatment delivery time, and also result in significant reduction in the wear-and-tear of MLC mechanics.
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Affiliation(s)
- Jianrong Dai
- Department of Radiation Oncology, Cancer Institute (Hospital), Chinese Academy of Medical Sciences, Beijing 100021, People's Republic of China.
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40
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Abstract
In this study, we present a sequencer for delivering step-and-shoot IMRT using a six-bank multi-leaf system. Such a system was proposed earlier and combines a high-resolution field-shaping ability with a large field size. It consists of three layers of two opposing leaf banks with 1 cm leaves. The layers are rotated relative to each other at 60 degrees . A low-resolution mode of sequencing is achieved by using one layer of leaves as primary MLC, while the other two are used to improve back-up collimation. For high-resolution sequencing, an algorithm is presented that creates segments shaped by all six banks. Compared to a hypothetical mini-MLC with 0.4 cm leaves, a similar performance can be achieved, but a trade-off has to be made between accuracy and the number of segments.
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Affiliation(s)
- R Topolnjak
- Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
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41
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Zheng XK, Chen LH, Yan X, Wang HM. Impact of prolonged fraction dose-delivery time modeling intensity-modulated radiation therapy on hepatocellular carcinoma cell killing. World J Gastroenterol 2005; 11:1452-6. [PMID: 15770720 PMCID: PMC4305686 DOI: 10.3748/wjg.v11.i10.1452] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To explore the impact of prolonged fraction dose-delivery time modeling intensity-modulated radiation therapy (IMRT) on cell killing of human hepatocellular carcinoma (HCC) HepG2 and Hep3B cell lines.
METHODS: The radiobiological characteristics of human HCC HepG2 and Hep3b cell lines were studied with standard clonogenic assays, using standard linear-quadratic model and incomplete repair model to fit the dose-survival curves. The identical methods were also employed to investigate the biological effectiveness of irradiation protocols modeling clinical conventional fractionated external beam radiotherapy (EBRT, fraction delivery time 3 min) and IMRT with different prolonged fraction delivery time (15, 30, and 45 min). The differences of cell surviving fraction irradiated with different fraction delivery time were tested with paired t-test. Factors determining the impact of prolonged fraction delivery time on cell killing were analyzed.
RESULTS: The α/β and repair half-time (T1/2) of HepG2 and Hep3b were 3.1 and 7.4 Gy, and 22 and 19 min respectively. The surviving fraction of HepG2 irradiated modeling IMRT with different fraction delivery time was significantly higher than irradiated modeling EBRT and the cell survival increased more pronouncedly with the fraction delivery time prolonged from 15 to 45 min, while no significant differences of cell survival in Hep3b were found between different fraction delivery time protocols.
CONCLUSION: The prolonged fraction delivery time modeling IMRT significantly decreased the cell killing in HepG2 but not in Hep3b. The capability of sub-lethal damage repair was the predominant factor determining the cell killing decrease. These effects, if confirmed by clinical studies, should be considered in designing IMRT treatments for HCC.
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Affiliation(s)
- Xiao-Kang Zheng
- Department of Radiation Oncology, Nanfang Hospital, The Southern Medical University, Guangzhou 510515, Guangdong Province, China
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42
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Abstract
Multileaf collimators (MLCs) are the prevailing tool for the realization of radiation fields in intensity modulated radiation therapy (IMRT). One step in the treatment planning is to determine a set of leaf positions realizing a certain intensity modulated radiation field. In this paper we suggest two extensions in the use of the MLC that lead to considerable savings in terms of monitor units, thus potentially increasing the treatment quality. We test our method with random and with clinical sample matrices.
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Affiliation(s)
- Thomas Kalinowski
- Universität Rostock, Institut für Mathematik, D-18051 Rostock, Germany.
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43
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Abstract
The optimizing leaf sequencer IMFAST minimizes intensity modulated treatment times. However, algorithm modifications can yield improved results. Currently, during segment extraction, the largest extract for a given number of levels is chosen. The modification chooses an extract that yields the fewest segments and levels when the rod-pushing algorithm is applied to the difference between the original map and the extract. Also, successive optimization parameter values are now allowed to increase. These modifications reduced the number of segments and the relative fluence from the original algorithm by an average of 7%-11% and 8%-17%, respectively, depending on whether interdigitation and/or tongue-and-groove constraints were considered. The tests were done on two clinical head and neck intensity modulated radiation therapy cases. Compared to the sweeping window algorithm, a reduction of 35%-55% of the number of segments is possible with a change in the relative fluence of -9% - 16%, depending on the constraints. Compared to other previously published algorithms that deal with the constraints tested here, the modified IMFAST algorithm provides the greatest reduction in the number of segments with the minimum increase in the relative fluence.
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Affiliation(s)
- R Alfredo C Siochi
- Department of Radiation Oncology, St Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
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Kamath S, Sahni S, Ranka S, Li J, Palta J. A comparison of step-and-shoot leaf sequencing algorithms that eliminate tongue-and-groove effects. Phys Med Biol 2004; 49:3137-43. [PMID: 15357187 DOI: 10.1088/0031-9155/49/14/008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The performances of three recently published leaf sequencing algorithms for step-and-shoot intensity-modulated radiation therapy delivery that eliminates tongue-and-groove underdosage are evaluated. Proofs are given to show that the algorithm of Que et al (2004 Phys. Med. Biol. 49 399-405) generates leaf sequences free of tongue-and-groove underdosage and interdigitation. However, the total beam-on times could be up to n times those of the sequences generated by the algorithms of Kamath et al (2004 Phys. Med. Biol. 49 N7-N19), which are optimal in beam-on time for unidirectional leaf movement under the same constraints, where n is the total number of involved leaf pairs. Using 19 clinical fluence matrices and 100000 randomly generated 15 x 15 matrices, the average monitor units and number of segments of the leaf sequences generated using the algorithm of Que et al are about two to four times those generated by the algorithm of Kamath et al.
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Affiliation(s)
- Srijit Kamath
- Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL, USA.
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Chen Y, Hou Q, Galvin JM. A graph-searching method for MLC leaf sequencing under constraints. Med Phys 2004; 31:1504-11. [PMID: 15259654 DOI: 10.1118/1.1737512] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A new leaf-sequencing algorithm for step-and-shoot IMRT that is based on a graph-searching technique is described. An iterative process guided by a quantitative measure for the complexity of the initial or residual intensity pattern is used to identify the field segments shaped by a multileaf collimator (MLC). Given a user selected number of intensity levels, the algorithm searches deliverable segment candidates considering all intensity levels and two collimator positions separated by 90 degrees. The candidates for each intensity level are obtained as the least number of segments to cover the areas with equal or higher intensity. The shape of a deliverable segment is adjusted by leaving out certain beam elements for later delivery if this results in a simpler residual intensity pattern and the segment is still deliverable. For a MLC design that does not allow leaf interdigitation, it is initially assumed that a single segment cannot cover two disjoined areas. Among all candidates the segment with the greatest reduction of the complexity of the residual intensity distribution is chosen for the current step of iteration. The iterative process generates a set of deliverable segments of simply connected areas. These segments are combined later under specific MLC constraints. Different orders of segment combination are considered for minimizing the beam-on time. The final segments are sequenced to minimize the leaf travel. This algorithm has been tested using randomly generated intensity distributions and clinical cases for the Varian, Siemens, and Elekta MLC systems. The results show that as the number of intensity levels is increased, the numbers of segments and MUs increase only modestly. Using two collimator angles results in decreases in the required number of segments and the number of monitor units that can be as much as 20%.
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Affiliation(s)
- Yan Chen
- Department of Radiation Oncology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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46
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Wang D, Hill RW, Lam S. A new algorithm for determining collimator angles that favor efficiency in MLC based IMRT delivery. Med Phys 2004; 31:1249-53. [PMID: 15191316 DOI: 10.1118/1.1696708] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A new algorithm to determine collimator angles that favor delivery efficiency of intensity modulated radiotherapy plans was developed. It was found that the number of segments and monitor units (MUs) were largely reduced with the set of collimator angles determined with the new algorithm without compromising plan quality. The improvement of delivery efficiency using the new algorithm depends on the size and shape of the target(s), the number of modulation levels, and the type of leaf-sequencing algorithm. In a typical prostate case, when a sweeping leaf-sequencer is used for Varian 120 leaf (0.5 x 0.5 cm2 beamlet), 80 leaf (1 x 1 cm2 beamlet) and Elekta 40 leaf (1 x 1 cm2 beamlet), the number of segments was reduced by 42%, 29%, and 5%, respectively. The number of MUs was reduced by 41%, 35%, and 10%. For the Siemens MLC (IMFAST leaf sequencer, 1 x 1 cm2 beamlet) the segment reduction was 32% and the MU reduction was 14%. Comparison of the plans using the new and Brahme algorithms, in terms of target conformity index and dose volume histogram of the organs at risk, showed that the quality of the plans using the new algorithm was uncompromised. Similar results were obtained for a set of head and neck treatment plans.
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Affiliation(s)
- David Wang
- Cancer Care Group, PC, Medical Physics, 950 North Meridian Street, Suite 920, Indianapolis, Indiana 46204, USA
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47
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Galvin JM, Ezzell G, Eisbrauch A, Yu C, Butler B, Xiao Y, Rosen I, Rosenman J, Sharpe M, Xing L, Xia P, Lomax T, Low DA, Palta J. Implementing IMRT in clinical practice: a joint document of the American Society for Therapeutic Radiology and Oncology and the American Association of Physicists in Medicine. Int J Radiat Oncol Biol Phys 2004; 58:1616-34. [PMID: 15050343 DOI: 10.1016/j.ijrobp.2003.12.008] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2003] [Accepted: 12/04/2003] [Indexed: 11/16/2022]
Affiliation(s)
- James M Galvin
- American Association of Physicists in Medicine IMRT Subcommittee of the Radiation Therapy Committee, USA
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48
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Yang Y, Xing L. Quantitative measurement of MLC leaf displacements using an electronic portal image device. Phys Med Biol 2004; 49:1521-33. [PMID: 15152689 DOI: 10.1088/0031-9155/49/8/010] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The success of an IMRT treatment relies on the positioning accuracy of the MLC (multileaf collimator) leaves for both step-and-shoot and dynamic deliveries. In practice, however, there exists no effective and quantitative means for routine MLC QA and this has become one of the bottleneck problems in IMRT implementation. In this work we present an electronic portal image device (EPID) based method for fast and accurate measurement of MLC leaf positions at arbitrary locations within the 40 cm x 40 cm radiation field. The new technique utilizes the fact that the integral signal in a small region of interest (ROI) is a sensitive and reliable indicator of the leaf displacement. In this approach, the integral signal at a ROI was expressed as a weighted sum of the contributions from the displacements of the leaf above the point and the adjacent leaves. The weighting factors or linear coefficients of the system equations were determined by fitting the integral signal data for a group of pre-designed MLC leaf sequences to the known leaf displacements that were intentionally introduced during the creation of the leaf sequences. Once the calibration is done, the system can be used for routine MLC leaf positioning QA to detect possible leaf errors. A series of tests was carried out to examine the functionality and accuracy of the technique. Our results show that the proposed technique is potentially superior to the conventional edge-detecting approach in two aspects: (i) it deals with the problem in a systematic approach and allows us to take into account the influence of the adjacent MLC leaves effectively; and (ii) it may improve the signal-to-noise ratio and is thus capable of quantitatively measuring extremely small leaf positional displacements. Our results indicate that the technique can detect a leaf positional error as small as 0.1 mm at an arbitrary point within the field in the absence of EPID set-up error and 0.3 mm when the uncertainty is considered. Given its simplicity, efficiency and accuracy, we believe that the technique is ideally suitable for routine MLC leaf positioning QA.
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Affiliation(s)
- Yong Yang
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305-5304, USA
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Luan S, Wang C, Chen DZ, Hu XS, Naqvi SA, Yu CX, Lee CL. A new MLC segmentation algorithm/software for step-and-shoot IMRT delivery. Med Phys 2004; 31:695-707. [PMID: 15124986 DOI: 10.1118/1.1646471] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
We present a new MLC segmentation algorithm/software for step-and-shoot IMRT delivery. Our aim in this work is to shorten the treatment time by minimizing the number of segments. Our new segmentation algorithm, called SLS (an abbreviation for static leaf sequencing), is based on graph algorithmic techniques in computer science. It takes advantage of the geometry of intensity maps. In our SLS approach, intensity maps are viewed as three-dimensional (3-D) "mountains" made of unit-sized "cubes." Such a 3-D "mountain" is first partitioned into special-structured submountains using a new mixed partitioning scheme. Then the optimal leaf sequences for each submountain are computed by either a shortest-path algorithm or a maximum-flow algorithm based on graph models. The computations of SLS take only a few minutes. Our comparison studies of SLS with CORVUS (both the 4.0 and 5.0 versions) and with the Xia and Verhey segmentation methods on Elekta Linac systems showed substantial improvements. For instance, for a pancreatic case, SLS used only one-fifth of the number of segments required by CORVUS 4.0 to create the same intensity maps, and the SLS sequences took only 25 min to deliver on an Elekta SL 20 Linac system in contrast to the 72 min for the CORVUS 4.0 sequences (a three-fold improvement). To verify the accuracy of our new leaf sequences, we conducted film and ion-chamber measurements on phantom. The results showed that both the intensity distributions as well as dose distributions of the SLS delivery match well with those of CORVUS delivery. SLS can also be extended to other types of Linac systems.
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Affiliation(s)
- Shuang Luan
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
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Li K, Dai J, Ma L. Simultaneous minimizing monitor units and number of segments without leaf end abutment for segmental intensity modulated radiation therapy delivery. Med Phys 2004; 31:507-12. [PMID: 15070247 DOI: 10.1118/1.1644642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Leaf end abutment is seldom studied when delivering segmental intensity modulated radiation therapy (IMRT) fields. We developed an efficient leaf sequencing method to eliminate leaf end abutment for segmental IMRT delivery. Our method uses simple matrix and sorting operations to obtain a solution that simultaneously minimizes total monitor units and number of segments without leaf end abutment between segments. We implemented and demonstrated our method for multiple clinical cases. We compared the results of our method with the results from exhaustive search method. We found that our solution without leaf end abutment produced equivalent results to the unconstrained solutions in terms of minimum total monitor units and minimum number of leaf segments. We conclude that the leaf end abutment fields can be avoided without affecting the efficiency of segmental IMRT delivery. The major strength of our method is its simplicity and high computing speed. This potentially provides a useful means for generating segmental IMRT fields that require high spatial resolution or complex intensity distributions.
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Affiliation(s)
- Kaile Li
- Department of Radiation Oncology, University of Maryland, School of Medicine, Baltimore, Maryland 21201, USA
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