Neuroimaging with photon-counting computed tomography: A review of clinical applications

Abstract

Photon-counting computed tomography (PCCT) represents a transformative advancement in neuroimaging, offering superior spatial resolution, spectral imaging capabilities, reduced radiation dose, and enhanced contrast-to-noise ratios. This review explores the technical foundations of PCCT, its advantages over conventional CT, and its growing applications in neuroimaging. PCCT has shown promise in improving neurovascular imaging, detecting small vessels, and reducing artifacts near metallic implants. It also enhances the visualization of spontaneous intracranial hypotension and cerebrospinal fluid leaks and provides superior diagnostic accuracy in acute ischemic stroke imaging. However, current limitations, including protocol complexity, high data volume, and the absence of integrated artificial intelligence noise reduction algorithms, pose challenges to widespread adoption. Future research should address these limitations and refine PCCT’s applications to unlock its full clinical potential.

Key Words: Computed tomography; Photon-counting; Head; Neuroimaging; Neurovascular

Core Tip: Photon-counting computed tomography offers unprecedented spatial and spectral resolution in neuroimaging, enabling improved detection of subtle pathologies such as small vessels, cerebrospinal fluid leaks, and early ischemic changes, while reducing artifacts and radiation dose. Despite current challenges in protocol standardization, data handling, and integration of artificial intelligence-based noise reduction, photon-counting computed tomography holds strong potential to become a new standard in clinical neuroimaging.

INTRODUCTION

Computed tomography (CT) has become essential in diagnosing and evaluating numerous neurological conditions. Since its development in the 1970s, CT technology has advanced substantially, evolving from basic single-source systems to sophisticated scanners with larger detectors, faster helical scans, and multi-energy capabilities. In the 1990s, we witnessed the introduction of spiral CT, wide detector CT in 2004, dual-source CT in 2005, and dual-layer CT detectors in 2013. In the last two decades, dual-source CT systems have become widely used in clinical settings, especially in emergency neuroimaging[1,2]. The most recent innovation in CT technology is photon-counting detectors (PCDs). On September 29, 2021, the United States Food and Drug Administration approved the first photon-counting CT (PCCT) for clinical use, which has mainly been tested on models and adult patients. Other manufacturers are currently developing their system, but there is only scant information available on system design, capabilities, and, to our best knowledge, no use in humans[1,3,4]. Several manufacturers have now developed PCCT systems, including Siemens Healthineers (NAEOTOM Alpha), GE HealthCare (Revolution Aspire), Canon Medical (Aquilion PC CT), and United Imaging (uMI PCCT). While the core principle of direct photon conversion remains similar, these systems differ in detector materials (e.g., cadmium telluride vs cadmium zinc telluride), energy threshold design, count rate capability, and noise correction algorithms. Such variations lead to differences in achievable spatial resolution, spectral separation, and reconstruction efficiency, which can influence both image quality and dose performance across vendors. This review will explore PCCT based on our experience, outlining its technical foundations, highlighting its advantages over traditional CT, and discussing its established and potential applications in neuroimaging.

DETECTOR TECHNOLOGY

Energy-integrating detectors (EIDs) use a two-step process to convert X-ray photons into electronic signals. Incoming X-rays are first converted into visible light by a scintillator (e.g., gadolinium oxysulfide or cadmium tungstate), which emits light when exposed to ionizing radiation. This light is then absorbed by photodiodes, generating an electrical signal. EIDs output a signal proportional to the total X-ray energy deposited but lack the ability to distinguish photon energy levels, limiting their spectral information. Reflective components like septa are used to capture dispersing light photons but reduce geometric dose efficiency and spatial resolution[5,6]. In contrast, PCDs directly convert X-ray photons into electrical signals using semiconductors such as cadmium telluride, cadmium zinc telluride, or gallium arsenide. When photons interact with the semiconductor, they generate electron-hole pairs that are directed toward a pixelated anode under an applied voltage, creating an electrical pulse. Application-specific integrated circuits process these pulses, categorizing photons into 2-8 predefined energy levels. This allows PCDs to provide energy spectra for each photon, enhancing tissue characterization, electronic noise reduction, spatial resolution, and dose efficiency[5,6].

Furthermore, PCDs have the unique ability to register low-energy photons that are often discarded in EIDs due to electronic noise or inefficiencies in light conversion. This capability significantly enhances soft tissue contrast, enabling improved visualization of structures with subtle density differences, such as vessels or lesions in adipose tissue. Additionally, capturing low-energy photons contributes to dose efficiency by ensuring that a broader range of the X-ray spectrum contributes to image formation, thereby reducing unnecessary radiation exposure to the patient[5,6]. Unlike EIDs, PCDs eliminate the need for septa, enabling smaller pixel sizes and higher spatial resolution. However, technical challenges like charge sharing and pulse pile-up can occur. PCCT systems achieve improved image quality by enhancing the contrast-to-noise ratio (CNR) and offering advanced spectral imaging capabilities akin to color photography, where energy levels provide depth rather than relying solely on intensity[5,6] (Table 1; Figure 1).

Figure 1 A comparison of traditional energy integrating vs photon-counting detector systems. A: Energy integrating; B: Photon-counting detector.

Table 1 Comparison of energy integrating vs photon counting detector systems used in computed tomography.

	Energy integrating detectors	Photon counting detectors
Principle of operation	Measures the total energy deposited by all incoming photons, without distinguishing their individual energies	Detects and counts individual photons, measuring their energy levels to differentiate photon spectra
Energy conversion	X-rays, light energy, and electrical energy	X-rays, electrical energy
Detector material	Typically uses scintillators (e.g., cesium iodide) coupled with photodiodes	Utilizes semiconductors (e.g., cadmium telluride or silicon)
Energy resolution	Poor - cannot differentiate photon energies, resulting in a loss of spectral information	High - excellent energy resolution, enabling spectral imaging and material decomposition
Dose efficiency	Lower - loses information due to electronic noise and scatter	Higher - better noise performance and higher signal-to-noise ratio, enabling lower radiation dose
Spatial resolution	Moderate - limited by the size of the scintillator and optical coupling	High - smaller pixel sizes and direct detection improve spatial resolution
Spectral imaging capability	Limited - no ability to differentiate or quantify materials based on photon energy	Superior - enables spectral imaging by separating photons into energy bins for material characterization
Contrast Resolution	Limited - relies on iodine contrast enhancement but lacks the ability to differentiate materials based on energy spectra	High - can improve contrast resolution by distinguishing between materials using energy-specific information
Detector efficiency	Lower - efficiency decreases at higher photon energies due to scattering and light loss in the scintillator	Higher - direct photon-to-electron conversion results in greater efficiency across a wide energy range
Scatter sensitivity	Higher - more susceptible to scatter artifacts, reducing image quality	Lower - better scatter rejection due to energy discrimination
Temporal resolution	Limited - relies on integration over a specific time interval, which may result in temporal blurring	High - fast photon counting allows better temporal resolution for dynamic imaging
Artifacts	Susceptible to beam hardening and metal artifacts due to a lack of spectral differentiation	Reduces beam hardening and metal artifacts by using spectral information
Cost	Lower - widely used and cheaper due to mature technology and simpler design	Higher - emerging technology with more complex manufacturing processes and semiconductor materials
Power consumption	Lower - simpler electronics and integration processes result in reduced power needs	Higher - photon counting electronics and energy discrimination require more power
Longevity and robustness	High - well-established and reliable for routine use	Moderate - sensitive semiconductor materials may be prone to degradation over time or under high doses

APPLICATIONS

Vascular imaging

PCCT can offer enhanced visualization of stents and reduced blooming artifacts in head and neck angiographies. PCCT angiography provides precise lumen visualization and depiction of metallic stent meshes with higher accuracy than EID-CT angiography (CTA). PCCT reduces artifacts from metallic implants, such as intracranial clips and coils, by leveraging high-energy bins that suppress beam-hardening and electronic noise[7-9]. The reduced lateral spreading of secondary quanta in PCDs also relaxes the need for inter-pixel septa and enables the use of a much smaller pixel size (e.g., 0.1 mm) without sacrificing geometry efficiency. The inherent equal weighting of high and low energy photons in PCDs offers an improvement in the CNR of iodinated vessels. The energy resolving capability can also be used to generate virtual monoenergetic CT images that, upon optimization of the keV level, can improve the CNR of iodinated objects such as blood vessels[8]. Enhanced visualization with lower noise, superior signal-to-noise ratio (SNR), and reduced artifacts improves the evaluation of vascular anatomy, small arterial structures, tiny intracranial vessels, and diminutive vessels, and helps distinguish intracranial aneurysms from infundibula[7]. Blooming artifact reduction, through decreased voxel size and high-energy virtual monoenergetic imaging, reduces artifactual stenoses in calcified plaques and facilitates the characterization of structures near surgical clips[7]. PCCT allows improved evaluation of vascular stents, enabling better visualization of individual stent struts, enhanced evaluation of in-stent stenoses in small arteries, and improved assessment of aneurysms treated with occlusion systems like the Woven EndoBridge device[7].

Reduced beam hardening artifact benefits include better assessment of arterial segments near the skull base and cervical vertebrae, as well as superior evaluation of the petrous segment of the internal carotid artery, which is often obscured by beam hardening artifacts on EID-CT[10]. Spinal photon-counting CTA can be used for the characterization of spinal vascular malformations, including spinal dural arteriovenous fistulas, with high spatial resolution, helping to identify tiny vessels. Multi-energy acquisition allows for a virtual monoenergetic image to enhance iodine contrast, facilitating better vessel visualization with smaller or equal contrast doses[7].

While digital subtraction angiography remains the clinical gold standard for cerebrovascular evaluation, CTA is widely accepted as a non-invasive diagnostic alternative for imaging large cerebral arteries and veins. An important challenge that currently remains for CTA is its limited performance in imaging small perforating arteries with diameters below 0.5 mm[8]. PCCT can effectively improve the image quality of CTA maximum intensity projection (MIP) images, benefiting the visualization of perforating or small vessels for a given radiation exposure level, as evidenced by its ability to unveil structures not seen before, such as short and long posterior ciliary arteries. A recent work by Harvey et al[8] studied the potential benefits of using PCCT to improve the performance of CTA in imaging these small arteries. In particular, the study focused on an important component of the CTA image package known as the MIP image. PCDs lead to improved vessel SNR in MIP images since the SNR of PCCT MIP was found to be 5.8 ± 1.3 for PCCT, compared with 4.4 ± 0.9 for MDCT (P < 0.01)[8]. Further, the enhanced spatial resolution helps in identifying the arteriovenous malformation nidus and its reduction upon gamma-knife treatment.

SIH and CSF venous fistulas

Cerebrospinal fluid (CSF)-venous fistulas (CVFs), first identified in 2014, are a significant cause of spontaneous intracranial hypotension (SIH). Detecting CVFs using standard anatomical imaging can be difficult because, unlike other spinal CSF leaks, they do not typically result in fluid pooling in the epidural space, and the imaging signs are often subtle. To aid in CVF detection, specialized myelographic techniques have been developed[11]. Recently, PCCT myelography (PC-CTM) has been introduced as an effective method for identifying CSF-venous fistulas, demonstrating its potential for early diagnosis and targeted treatment of SIH. PC-CTM is likely to offer advantages in localizing dural tears, a different type of spontaneous spinal CSF leak that requires distinct myelographic techniques for accurate identification[7]. The high spatial resolution of PCCT allows for precise anatomical identification of leak sites with high sensitivity, without significant loss of specificity (Figure 2). This technique is capable of localizing subtle leaks and characterizing small osseous spicules. Additionally, it enables the creation of virtual monoenergetic images without dual-energy techniques and improves the visibility of nerve root sleeves, enhancing the detection and assessment of CVF leaks[12].

Figure 2 Cerebrospinal fluid-venous fistulas are challenging to detect using conventional computed tomography imaging. NAEOTOM Alpha makes Cerebrospinal fluid-venous fistulas visible (orange coloured arrow). Copyright ©Siemens Healthineers AG 2024. The authors have obtained the permission (Supplementary material).

The Bern score, which is based on brain magnetic resonance imaging findings in patients with suspected SIH, categorizes patients into high, intermediate, or low probabilities of having a spinal CSF leak or CVF, aiding in the selection of further investigations like digital subtraction myelography (DSM) or CT myelography[13-15]. These procedures, while necessary, are invasive, time-intensive, and involve significant radiation exposure. PCCT has shown potential for reducing radiation doses compared to EID-CT, making PC-CTM an appealing first-line imaging choice, particularly for younger patients. PC-CTM also offers enhanced visualization of venous abnormalities, including arteriovenous malformations and vascular shunts[13-15]. Works of Madhavan et al[16] found that decubitus PC-CTM for patients with intermediate and high Bern scores achieved diagnostic yields comparable to those reported for decubitus DSM and EID-CTM. Notably, PC-CTM showed higher yields in patients with low-probability Bern scores than other methods. However, the retrospective nature of this study calls for future prospective research to compare the sensitivity of PC-CTM with other modalities[17]. Another study by the same group confirmed the superiority of PC-CTM over DSM and EID-CTM for detecting CVFs, though limited by a small sample size, highlighting the need for studies involving larger patient groups[18]. PC-CTM offers further benefits, such as thinner axial section thicknesses (0.2-0.4 mm compared to 0.6 mm in EID-CT) for clearer visualization of small veins and improved temporal resolution. Faster scan speeds (average of 5.0 seconds) reduce motion artifacts and enable multiple time-point sampling within short intervals[18].

Acute ischemic stroke

PCCT images have 12.8%-20.6% less image noise and a 19%-20% higher signal-to-noise ratio than EID-CT for both grey and white matter, resulting in improved image quality and enhanced grey-white matter contrast, being about 15.7% higher compared to EID-CT[19,20]. As a result, it has the potential to significantly aid in the early detection and diagnosis of brain pathologies, including acute strokes, intracranial hemorrhage, and other soft-tissue abnormalities, by identifying subtle attenuation differences such as grey matter hypoattenuation changes, the insular ribbon sign, and other early ischemic changes[19,20]. In acute ischemic stroke patients, distinguishing between contrast pooling and hemorrhages (subarachnoid or parenchymal) is crucial for post-mechanical thrombectomy management. PCCT can accurately differentiate between hemorrhage and contrast media, preventing misdiagnosis and ensuring appropriate treatment decisions[19-21]. PCCT can potentially streamline acute stroke protocols by enabling multi-contrast imaging in a single scan, reducing time delays and improving diagnostic accuracy[22].

Imaging of atherosclerotic plaques

While traditional CT is commonly used for identifying calcium in atheromatous plaques, plaque rupture risk is influenced by several other factors beyond just calcium, such as intraplaque hemorrhage and lipid content. PCCT has the potential to go beyond calcium detection, making it highly valuable for evaluating the broader composition of atherosclerotic plaques. This could enhance our understanding of rupture-prone plaques, improving diagnosis, risk assessment, and the monitoring of treatments or preventive measures[23]. A recent study conducted using five carotid plaques from donations of patients with carotid stenosis undergoing endarterectomy showed that PCCT can distinguish several rupture-prone plaque features: Calcium and thrombus were shown to be distinguishable from intraplaque hemorrhage, fibrosis, fibrous cap, lipids, and necrosis. PCCT has the potential to detect photons in separate energy bins, reducing energy overlap and improving spectral separation. At high resolution, PCCT reduces calcium overestimation by minimizing blooming artifacts, a limitation of conventional CT. The study was, however, limited by the small number of carotid plaques and was conducted ex vivo without the use of contrast agents. The use of contrast agents would likely improve differentiation of plaque features[24].

Spectral PCCT faces technical challenges, including charge sharing, K-fluorescence escape, and photon count rate limitations, which affect spatial and energy resolution. Mitigations to these challenges include techniques like Charge summing, pixel masking, per-pixel calibration, and protocol optimizations, with anticipated future improvements as the technology evolves. Once adapted clinically, spectral PCCT could enable precise diagnosis and treatment planning, giving clinicians a detailed view of atheroma within arteries for better surgical intervention outcomes[25]. Experimental studies with apolipoprotein E knockout mice showed spectral PCCT’s ability to differentiate materials like gold, iodine, and bone, revealing macrophage accumulation in atherosclerotic models[26,27].

Post-treatment follow-up of treated aneurysms and intracranial stents

PCCT angiography can serve as an alternative to selective angiography, providing a less invasive and lower-radiation option for patients. This is especially valuable in cranial and spinal imaging, though detailed hemodynamic studies may still require conventional cerebral angiography[28]. PCCT angiography offers high precision in visualizing metallic stent structures, supporting its use in both stent and vascular imaging. Known for its enhanced spatial resolution, cone-beam CT with diluted contrast media is widely used for postoperative evaluations, particularly to assess stent adhesion and detect in-stent thrombosis. Given that PCCT angiography achieves comparable image quality to cone-beam CT, it presents a promising, less invasive alternative for detailed postoperative vascular assessments, allowing for effective monitoring of stent apposition, in-stent thrombosis (Figure 3), and intimal hyperplasia[28,29]. The PCCT angiography images captured the stent’s structure, and comparison of three-dimensional images from EID-CTA and PCCT angiography demonstrated that PCCT angiography offered superior resolution for evaluating stent shape and apposition. High kernels in PCCT enable detailed visualization of stent mesh and lumen, allowing clinicians to assess the stent’s integration with the vessel wall and detect issues like partial attachment (“fish-mouthing”). However, further research is needed to optimize kernel settings for evaluating in-stent intimal growth[29].

Figure 3 Image showing a conventional image of a head computed tomography angiogram (on the left) and its corresponding photon-counting computed tomography version (on the right), which clearly shows a middle cerebral artery stent with in-stent thrombosis. EID-CT: Energy-integrating detector-computed tomography; PCD-CT: Photon-counting detector-computed tomography; MCA: Middle cerebral artery. Image courtesy of Professor Cynthia H McCollough, Mayo Clinic, Rochester, MN, United States.

Assessment of DBS electrodes

Directional deep-brain stimulation (DBS) electrodes are increasingly used, but conventional CT is unable to directly image segmented contacts owing to physics-based resolution constraints. PCDs are a relatively novel technology that enables high-resolution imaging while addressing several limitations intrinsic to conventional CT[30] (Figure 4). Postoperative electrode segment orientation assessment is necessary because of the possibility of significant deviation during or immediately after insertion. PCCT can enable clear in vivo imaging of DBS electrodes, including segmented contacts and markers for all major lead manufacturers[31] (Figure 5). Manfield et al[30] describe postoperative imaging and reconstruction protocols developed to enable optimal lead visualization. High-fidelity images were obtained for 15 patients, clearly indicating the segmented contacts and directional markers both on CT alone and when fused to magnetic resonance imaging[30,32]. The highest resolution offered by PCCT is now 0.11 mm, some two to four times finer than that of contemporary conventional CT[33]. PCCT, including high-resolution lead tip imaging, delivered a statistically significant 13% dose reduction compared with their previously used combination of standard head CT plus fluoroscopy[30]. For most leads, the directly imaged lead orientations and depths corresponded closely to those predicted by CT artifact-based reconstructions. Indeed, conventional CT artifact-based methods can have a 180° error in orientation assessment, whereas PCCT provides direct and accurate imaging of lead orientation[30].

Figure 4 On the lumbar spine images acquired on the photon-counting computed tomography (on the left), the metallic artifacts are less evident when compared with conventional computed tomography (on the right).

Figure 5 Direct visualization of the DBS electrode with photon-counting computed tomography without having to rely on streak artifacts that overlap each other with multiple electrodes. CT: Computed tomography; EID-CT: Energy-integrating detector-computed tomography. Image courtesy of Professor Erik H Middlebrooks, Mayo Clinic, Jacksonville, FL, United States.

PCCT scans offer clearer imaging of electrode contacts and internal structures, which can aid in identifying faults in cases of suspected lead fractures. Variations in lead construction among manufacturers influence the ability to resolve internal structures[34-36]. PCCT can easily capture the directional segmentation of DBS electrodes for all major commercial systems, while also reducing radiation exposure compared to traditional imaging techniques. Its capability to discern fine details, such as the individual wires in certain DBS leads, provides valuable insights for diagnosing potential issues like lead fractures. Postoperative PCCT imaging is already a routine practice in many DBS centers for confirming target accuracy and excluding hematomas[30]. Using PCCT for DBS electrode imaging enables anatomically guided programming, which may streamline device setup and reduce time and complexity. Conventional methods, such as rotational fluoroscopy and CT artifact analysis, have limitations, including the need for orthogonal views and the potential for miscalculations in lead orientation[30].

Middle ear and internal ear

PCCT offers superior in-plane resolution and thinner section thickness compared to EID-CT. This enhanced resolution produces sharper images that consistently reveal fine details. Specifically, the microarchitecture of the ossicles, ossicular ligaments, tendons, and bony protuberances, which are crucial for accurate interpretation, is much more clearly visualized with PCCT. PCCT images offer detailed visualization of the complex anatomy of the epitympanum and hypotympanum, which are essential for diagnosing middle ear pathologies[37]. This enhanced clarity is especially relevant for assessing ossicular chain anomalies, including discontinuities, fibrous unions, congenital fusions, and fixations such as otosclerosis (Figure 6) and tympanosclerosis, thereby potentially improving clinical outcomes in ear pathology diagnostics[38]. Although ossicular chain dislocation is uncommon and often related to temporal bone trauma, its exact prevalence is not well defined. Approximately 50% of temporal bone fractures involve ossicular damage, but dislocations can occur even in the absence of fractures. Conventional imaging often struggles to detect dislocations, particularly in the incudomalleolar joint, whereas PCCT excels in identifying even minor dislocations with higher precision. The three-dimensional reconstruction capability further enhances the assessment of incudomalleolar and incudostapedial joints from various perspectives, improving diagnostic accuracy[37-39].

Figure 6 Axial high-resolution computed tomography image of the right temporal bone. On the photon-counting computed tomography image on the right is clearly evident a focus of otospongiosis that cannot be clearly identified on the traditional computed tomography image on the left. Visualized in the form of a hypodense demineralized otosclerotic plaque is noted in the fissula ante fenestram.

A study evaluating PCCT highlighted its potential for enhanced postoperative cochlear implantation imaging, which was shown by the fact that PCCT achieved higher interelectrode wire visibility (81.5%) compared to EID CT (EID-CT, 67.9%; P < 0.001)[40]. Additionally, PCCT provided more accurate measurements of electrode contact diameters, closer to the gold standard. No significant differences were observed in halo artifact diameters between the two modalities. While promising, the study’s small sample size and use of cadaveric specimens necessitate further research to validate these findings and optimize imaging settings[40].

TECHNICAL CHALLENGES

PCCT in neuroimaging faces several limitations that impact its clinical utility. Protocol optimization remains a challenge, as PCCT systems introduce additional complexity with adjustable bin thresholds, increasing the risk of errors that may necessitate rescans[41]. Unlike conventional CT, PCCT lacks integrated artificial intelligence-based noise reduction algorithms, which are critical for achieving both high resolution and low dose imaging[42]. Furthermore, PCCT generates significantly larger data volumes - estimated at 2-35 times higher than conventional CT - complicating storage, interpretation, and workflow management[3,43]. The quality of monoenergetic reformats in commercially available PCCT systems is inferior to dual-energy CT in key image quality parameters, and persistent artifacts below the calvarium and in the posterior fossa further diminish diagnostic reliability[44]. Additionally, PCCT systems currently offer fewer spectral outputs (four) compared to spectral CT systems (ten), limiting their analytical potential in applications such as proton therapy planning[3]. These challenges underscore the need for technological advancements to fully realize PCCT’s potential in neuroimaging.

FUTURE DIRECTIONS AND CLINICAL OUTLOOK

PCCT’s primary advantages - namely ultra-high spatial resolution, spectral quantification, and reduced radiation exposure - position it as a transformative modality for neurological imaging. Future development will likely focus on integrating artificial intelligence for noise suppression and automated spectral decomposition, expanding applications in perfusion and functional neuroimaging, and enhancing vendor interoperability. The next phase of PCCT adoption will depend on protocol standardization, cross-vendor calibration, and outcome-based validation in large patient cohorts.

CONCLUSION

PCCT marks a significant step forward in neuroimaging, delivering superior image quality, advanced spectral imaging, and reduced artifacts compared to traditional CT modalities. Its potential to improve the diagnosis of complex neurological conditions such as vascular abnormalities, CSF leaks, and acute ischemic strokes is evident from emerging studies (Table 2). Despite these advancements, technical challenges such as protocol optimization, data management, and noise reduction must be addressed to enable widespread clinical implementation. Future developments, including the integration of artificial intelligence algorithms and enhanced hardware designs, will be critical to overcoming current limitations. With continued innovation, PCCT is poised to become a cornerstone of neuroimaging, offering unparalleled diagnostic insights and patient care.

Table 2 Summary of established clinical neuroimaging applications of photon-counting computed tomography, along with the key properties of photon-counting computed tomography that provide benefits over conventional computed tomography.

Clinical application	Key properties of PCCT	Advantages in neurology
Neurovascular imaging	High spatial resolution, reduction of blooming artifacts, enhanced visualization of stents and metallic implants	Improved evaluation of tiny intracranial vessels, arterial stenoses, and vascular stents; reduced artifacts near the skull base
Acute ischemic stroke	Superior signal-to-noise ratio, enhanced grey-white matter contrast	Early detection of ischemic changes, differentiation of hemorrhage from contrast media
Spinal CSF leaks and fistulas	Enhanced resolution, virtual monoenergetic imaging	Precise detection of CSF leaks and venous fistulas, reduced radiation exposure
Deep brain stimulation electrode imaging	Ultra-high resolution, reduced noise, clear visualization of segmented contacts	Accurate postoperative assessment of electrode placement and orientation
Middle and internal ear pathologies	Superior in-plane resolution, thinner section thickness	Enhanced visualization of ossicular chains, dislocations, and cochlear implant positioning
Atherosclerotic plaque characterization	Material differentiation through spectral imaging	Improved detection of rupture-prone plaques and assessment of intraplaque hemorrhage and lipid content
Post-treatment monitoring (Aneurysms and stents)	High-resolution imaging, reduced blooming artifacts	Detailed visualization of stent apposition, in-stent stenoses, and aneurysm occlusion devices
Cranial and spinal tumors	Enhanced contrast-to-noise ratio, soft-tissue resolution	Better delineation of tumor margins and detection of smaller lesions

PCCT: Photon-counting computed tomography; CSF: Cerebrospinal fluid.