Centre for Medical Image Computing, University College London, London, United Kingdom.
Magn Reson Med. 2012 Sep;68(3):783-93. doi: 10.1002/mrm.23298. Epub 2012 Jan 10.
Evaluation of small bowel motility from two-dimensional dynamic MRI is of increasing interest for the assessment of segmental diseases such as Crohn's disease. We propose to use nonrigid image registration for automated motility analysis. Registration is particularly difficult when localized intensity changes occur (e.g., due to intraluminal flow or through-plane motion). Therefore, displacements were extracted using a joint registration and modeling of intensity changes. Results were analyzed in 10 patients with known or suspected Crohn's disease. Bowel wall displacements were assessed by tracking bowel cross-sectional markers over time. Automated tracking with the proposed technique was in good agreement with manual tracking (similar bias, improved standard deviations). The ability to quantify different grades of bowel motility was investigated by comparing direct motion measures (i.e., changes in bowel cross-sectional diameter or area) and various parametric maps, e.g., based on the Jacobian of the measured displacements with expert grading. Among these measures, the standard deviation over time of the Jacobian was the best at predicting grades from 1 (moving normally) to 4 (not moving at all) in 50 bowel regions with normal and pathologically reduced motility, yielding 93% correct classification with a 1-class tolerance (i.e., same score as the expert ± 1).
从二维动态 MRI 评估小肠动力对于评估节段性疾病（如克罗恩病）越来越感兴趣。我们建议使用非刚性图像配准进行自动运动分析。当发生局部强度变化时（例如，由于腔内流动或平面内运动），配准特别困难。因此，使用强度变化的联合配准和建模来提取位移。在 10 名已知或疑似克罗恩病的患者中分析了结果。通过随时间跟踪肠壁的横截面标记来评估肠壁位移。提出的技术的自动跟踪与手动跟踪具有良好的一致性（相似的偏差，改进的标准偏差）。通过比较直接运动测量值（即肠横截面直径或面积的变化）和各种参数图，例如基于测量位移的雅可比行列式与专家分级，研究了量化不同程度的肠运动的能力。在这些措施中，雅可比行列式随时间的标准偏差在预测从 1（正常运动）到 4（根本不动）的 50 个正常和病理性运动减少的肠段的等级方面表现最佳，具有 1 类容差（即，与专家相同的分数±1）的 93%正确分类。
