Department of Radiology, University of California, San Diego, La Jolla, California, USA.
Division of Biostatistics and Bioinformatics, Herbert Wertheim School of Public Health and Human Longevity Science, University of California, San Diego, La Jolla, California, USA.
J Magn Reson Imaging. 2021 May;53(5):1581-1591. doi: 10.1002/jmri.27566. Epub 2021 Mar 1.
Diffusion-weighted (DW) echo-planar imaging (EPI) is prone to geometric distortions due to B inhomogeneities. Both prospective and retrospective approaches have been developed to decrease and correct such distortions.
The purpose of this work was to evaluate the performance of reduced-field-of-view (FOV) acquisition and retrospective distortion correction methods in decreasing distortion artifacts for breast imaging. Coverage of the axilla in reduced-FOV DW magnetic resonance imaging (MRI) and residual distortion were also assessed.
Retrospective.
POPULATION/PHANTOM: Breast phantom and 169 women (52.4 ± 13.4 years old) undergoing clinical breast MRI.
FIELD STRENGTH/SEQUENCE: A 3.0 T/ full- and reduced-FOV DW gradient-echo EPI sequence.
Performance of reversed polarity gradient (RPG) and FSL topup in correcting breast full- and reduced-FOV EPI data was evaluated using the mutual information (MI) metric between EPI and anatomical images. Two independent breast radiologists determined if coverage on both EPI data sets was adequate to evaluate axillary nodes and identified residual nipple distortion artifacts.
Two-way repeated-measures analyses of variance and post hoc tests were used to identify differences between EPI modality and distortion correction method. Generalized linear mixed effects models were used to evaluate differences in axillary coverage and residual nipple distortion.
In a breast phantom, residual distortions were 0.16 ± 0.07 cm and 0.22 ± 0.13 cm in reduced- and full-FOV EPI with both methods, respectively. In patients, MI significantly increased after distortion correction of full-FOV (11 ± 5% and 18 ± 9%, RPG and topup) and reduced-FOV (8 ± 4% both) EPI data. Axillary nodes were observed in 99% and 69% of the cases in full- and reduced-FOV EPI images. Residual distortion was observed in 93% and 0% of the cases in full- and reduced-FOV images.
Minimal distortion was achieved with RPG applied to reduced-FOV EPI data. RPG improved distortions for full-FOV images but with more modest improvements and limited correction near the nipple.
3 TECHNICAL EFFICACY: Stage 1.
由于 B 不均匀性，扩散加权（DW）回波平面成像（EPI）容易产生几何变形。已经开发了前瞻性和回顾性方法来减少和校正这种变形。
本研究旨在评估小视野（FOV）采集和回顾性失真校正方法在减少乳腺成像失真伪影中的性能。还评估了在小视野 DW 磁共振成像（MRI）中腋窝的覆盖范围和残余失真。
回顾性。
人群/体模：乳腺体模和 169 名接受临床乳腺 MRI 的女性（52.4±13.4 岁）。
磁场强度/序列：3.0T/全视野和小视野 DW 梯度回波 EPI 序列。
使用互信息（MI）度量标准评估反转极性梯度（RPG）和 FSL topup 在校正乳腺全视野和小视野 EPI 数据中的性能。两名独立的乳腺放射科医生确定这两个 EPI 数据集的覆盖范围是否足以评估腋窝淋巴结，并确定残余乳头失真伪影。
使用双向重复测量方差分析和事后检验来识别 EPI 模式和失真校正方法之间的差异。使用广义线性混合效应模型来评估腋窝覆盖范围和残余乳头失真的差异。
在乳腺体模中，两种方法分别在小视野和全视野 EPI 中产生的残余变形分别为 0.16±0.07cm 和 0.22±0.13cm。在患者中，全视野（RPG 和 topup 分别为 11±5%和 18±9%）和小视野（8±4%）EPI 数据的失真校正后，MI 显著增加。腋窝淋巴结在全视野和小视野 EPI 图像中分别在 99%和 69%的病例中观察到。在全视野和小视野图像中，分别在 93%和 0%的病例中观察到残余失真。
应用于小视野 EPI 数据的 RPG 可实现最小变形。RPG 改善了全视野图像的失真，但改善程度较小，并且在乳头附近的校正有限。
3 技术功效：阶段 1。
