Original Article
Copyright ©2013 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Radiol. Sep 28, 2013; 5(9): 334-344
Published online Sep 28, 2013. doi: 10.4329/wjr.v5.i9.334
Impact of field strength and RF excitation on abdominal diffusion-weighted magnetic resonance imaging
Philipp Riffel, Raghuram K Rao, Stefan Haneder, Mathias Meyer, Stefan O Schoenberg, Henrik J Michaely
Philipp Riffel, Raghuram K Rao, Stefan Haneder, Mathias Meyer, Stefan O Schoenberg, Henrik J Michaely, Department of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim-Heidelberg University, D-68167 Mannheim, Germany
Raghuram K Rao, the Russel H. Morgan Department of Radiology and Radiologic Science, the Johns Hopkins Hospital, Baltimore, MD 21287, United States
Author contributions: Riffel P, Rao RK and Haneder S performed the majority of the experiments; Rao RK wrote a majority of the manuscript draft; Riffel P organized the data into tables and created figures; Meyer M performed most of the statistical analysis; Schoenberg SO and Michaely HJ oversaw the project from initiation to completion, and helped to edit multiple revisions of the manuscript.
Correspondence to: Dr. Raghuram K Rao, MD, the Russel H. Morgan Department of Radiology and Radiologic Science, the Johns Hopkins Hospital, Musculoskeletal Radiology, 601 N. Caroline Street, Baltimore, MD 21287, United States. rrao2@jhmi.edu
Telephone: +1-443-2876032 Fax: +1-410-2876403
Received: April 30, 2013
Revised: July 17, 2013
Accepted: August 4, 2013
Published online: September 28, 2013
Processing time: 154 Days and 7.8 Hours
Abstract

AIM: To retrospectively and prospectively compare diffusion-weighted (DW) images in the abdomen in a 1.5T system and 3.0T systems with and without two-channel functionality for B1 shimming.

METHODS: DW images of the abdomen were obtained on 1.5T and 3.0T (with and without two-channel functionality for B1 shimming) scanners on 150 patients (retrospective study population) and 10 volunteers (prospective study population). Eight regions were selected for clinical significance or artifact susceptibility (at higher field strengths). Objective grading quantified signal-to-noise ratio (SNR), and subjective evaluation qualified image quality, ghosting artifacts, and diagnostic value. Statistical significance was calculated using χ2 tests (categorical variables) and independent two-sided t tests or Mann-Whitney U tests (continuous variables).

RESULTS: The 3.0T using dual-source parallel transmit (dpTX 3.0T) provided the significantly highest SNRs in nearly all regions. In regions susceptible to artifacts at higher field strengths (left lobe of liver, head of pancreas), the SNR was better or similar to the 1.5T system. Subjectively, both dpTX 3.0T and 1.5T systems provided higher image quality, diagnostic value, and less ghosting artifact (P < 0.01, most values) compared to the 3.0T system without dual-source parallel transmit (non-dpTX 3.0T).

CONCLUSION: The dpTX 3.0T scanner provided the highest SNR. Its image quality, lack of ghosting, and diagnostic value were equal to or outperformed most currently used systems.

Keywords: Abdominal imaging; Diffusion weighted; 3.0T; Radiofrequency excitation; Signal-to-noise ratio

Core tip: With the popularity of 3.0T imaging systems, radiologists have commonly found limitations in abdominal imaging with diffusion-weighted imaging (DWI) secondary to B1 in homogeneity artifacts at these higher magnet strengths. Because artifacts disturb diagnostic value of abdominal DWI, 1.5T systems have been mainly used for this particular purpose. However, newer techniques involving 3.0T using dual-source parallel radiofrequency (RF) excitation with parallel transmission and independent RF shimming have recently been developed which may succeed in addressing such limitations. Our study illustrates both the objective and subjective utility in the abdominal distribution while imaging under a 3.0T system which incorporates dual-source RF excitation.