Multi-shot DWI with MUSE reconstruction improves image quality for the diagnostic evaluation of active Crohn’s disease

Diffusion-weighted imaging(DWI) can provide functional and quantitative information for the imaging assessment, and plays more and more important roles in the diagnostic evaluation of Crohn’s disease. Current DWI acquiring sequence is mainly based on single-shot method, such as single-shot diffusion-weighted echo planar imaging (ssDW-EPI). But single-shot method limits the spatial resolution and overall image quality of DWI. The conventional ssDW-EPI cannot effectively identify some penetrating complications or other active bowel inflammations, especially if the bowel is not well distended. Multi-shot diffusion-weighted echo planar image (msDW-EPI) sequence can produce high-resolution DWI images, but it is sensitive to motion-induced data inconsistency. A recently developed multiplexed sensitivity-encoding (MUSE) framework can deal with data inconsistency issue and produce msDW-EPI data with improved spatial resolution and reduced distortions. In this study, I proposed to improve the resolution and image quality of bowel DWI using two methods, one is using the MUSE framework with msDW-EPI, another is to use highly-accelerated SENSE (R=4) ssDW-EPI method, and evaluate their performance for diagnosing active Crohn’s disease. This study include eighty-six patients diagnosed with Crohn’s disease. Each patient underwent standard contrast-enhanced MRE protocol and three type of DWI sequences, conventional ssDW-EPI, SENSE(R=4) ssDW-EPI and msDW-EPI. Sixty-three patients were diagnosed with active bowel inflammation from contrast-enhanced MRE, which was regarded as the standard reference. The other 23 patients did not have radiological evidence of active inflammation on contrast-enhanced MRE and served as the control group. The raw data of SENSE(R=4) ssDW-EPI and msDW-EPI acquisition were transferred to a workstation for off-line image reconstruction. The reconstruction pipeline is identical to original MUSE framework, including Nyquist ghost correction and measurement of inter-shot phase variation. The SENSE and MUSE reconstructed images were exported to DICOM format for further analysis. For both patient groups, diagnostic evaluation of active bowel inflammation and evaluation of image quality were performed for conventional ssDW-EPI, SENSE(R=4) ssDW-EPI and msDW-EPI data. For assessment of the image quality, 1) image resolution, 2) degree of geometric distortion, 3) impact of artifacts on image quality and diagnostic evaluation, and 4) overall image quality were assessed with a 5-point Likert scale. Images were independently reviewed by two board-certified radiologists who were blinded to the type of DWI.The results showed that image resolution and overall image quality were rated higher for MUSE msDW-EPI compared with conventional ssDW-EPI and SENSE(R=4) ssDW-EPI by both raters. For geometric distortion, artifacts influence on image quality and artifacts influence on diagnostic evaluation, both raters rated MUSE msDW-EPI better than ssDW-EPI and SENSE(R=4) ssDW-EPI.The results of this study demonstrated that MUSE msDW-EPI produces superior image quality and resolution compared to conventional ssDW-EPI and SENSE(R=4) ssDW-EPI, and shows promise in improving the accuracy in diagnosing active bowel inflammation in Crohn’s disease.

扩散加权成像（Diffusion-weighted imaging, DWI）能够为影像评估提供功能性和定量信息，其在克罗恩病诊断评估中的作用日益凸显。当前DWI的采集序列主要基于单次采集方法，如单次扩散加权回波平面成像（single-shot diffusion-weighted echo planar imaging, ssDW-EPI）。然而，单次采集方法限制了DWI的空间分辨率和整体图像质量。传统的ssDW-EPI无法有效识别某些穿透性并发症或其他活跃肠道炎症，尤其是在肠道未充分扩张的情况下。多次数扩散加权回波平面成像（multi-shot diffusion-weighted echo planar image, msDW-EPI）序列能够产生高分辨率的DWI图像，但易受运动引起的数据不一致性影响。最近开发的复用敏感性编码（multiplexed sensitivity-encoding, MUSE）框架能够处理数据不一致性问题，并产生具有改进的空间分辨率和减少畸变的msDW-EPI数据。在本研究中，我提出了两种提高肠道DWI分辨率和图像质量的方法：一是使用MUSE框架与msDW-EPI相结合，二是采用高度加速的SENSE（R=4）ssDW-EPI方法，并评估它们在诊断活跃克罗恩病方面的性能。本研究纳入了八十六名被诊断为克罗恩病的患者。每位患者均接受了标准对比增强磁共振成像（MRE）方案和三种类型的DWI序列，包括传统的ssDW-EPI、SENSE（R=4）ssDW-EPI和msDW-EPI。其中六十三名患者经对比增强MRE诊断为活跃肠道炎症，被视为标准参照组。另外二十三名患者在对对比增强MRE的影像学检查中未发现活跃炎症的迹象，作为对照组。SENSE（R=4）ssDW-EPI和msDW-EPI采集的原始数据被传输至工作站进行离线图像重建。重建流程与原始MUSE框架相同，包括尼奎斯特鬼影校正和测量射击间相位变化。SENSE和MUSE重建的图像被导出为DICOM格式，以进行进一步分析。对于两组患者，对传统ssDW-EPI、SENSE（R=4）ssDW-EPI和msDW-EPI数据进行了活跃肠道炎症的诊断评估和图像质量评估。在图像质量评估中，包括1）图像分辨率，2）几何畸变程度，3）伪影对图像质量和诊断评估的影响，以及4）整体图像质量，均采用5点李克特量表进行评估。图像由两位经过认证的放射科医生独立审查，他们对DWI的类型保密。结果显示，两位评判者均认为MUSE msDW-EPI在图像分辨率和整体图像质量方面均优于传统的ssDW-EPI和SENSE（R=4）ssDW-EPI。在几何畸变、伪影对图像质量的影响以及伪影对诊断评估的影响方面，两位评判者均认为MUSE msDW-EPI优于ssDW-EPI和SENSE（R=4）ssDW-EPI。本研究结果表明，MUSE msDW-EPI相较于传统的ssDW-EPI和SENSE（R=4）ssDW-EPI，具有更优的图像质量和分辨率，并在提高克罗恩病活跃肠道炎症诊断的准确性方面展现出巨大潜力。