Department of Radiology, Cumming School of Medicine, University of Calgary, Calgary AB3280 Hospital Dr NW, Calgary, Alberta, T2N 4Z6, Canada.
Biomedical Engineering Graduate Program, Schulich School of Engineering, University of Calgary, Calgary, AB, Canada.
BMC Med Imaging. 2020 Apr 7;20(1):36. doi: 10.1186/s12880-020-00437-8.
Medical imaging plays an important role in determining the progression of joint damage in rheumatoid arthritis (RA). High resolution peripheral quantitative computed tomography (HR-pQCT) is a sensitive tool capable of evaluating bone microarchitecture and erosions, and 3D rigid image registration can be used to visualize and quantify bone remodeling over time. However, patient motion during image acquisition can cause a "stack shift" artifact resulting in loss of information and reducing the number of erosions that can be analyzed using HR-pQCT. The purpose of this study was to use image registration to improve the number of useable HR-pQCT scans and to apply image-based bone remodeling assessment to the metacarpophalangeal (MCP) joints of RA patients.
Ten participants with RA completed HR-pQCT scans of the 2nd and 3rd MCP joints at enrolment to the study and at a 6-month follow-up interval. At 6-months, an additional repeat scan was acquired to evaluate reliability. HR-pQCT images were acquired in three individual 1 cm acquisitions (stacks) with a 25% overlap. We completed analysis first using standard evaluation methods, and second with multi-stack registration. We assessed whether additional erosions could be evaluated after multi-stack registration. Bone remodeling analysis was completed using registration and transformation of baseline and follow-up images. We calculated the bone formation and resorption volume fractions with 6-month follow-up, and same-day repositioning as a negative control.
13/57 (23%) of erosions could not be analyzed from raw images due to a stack shift artifact. All erosions could be volumetrically assessed after multi-stack registration. We observed that there was a median bone formation fraction of 2.1% and resorption fraction of 3.8% in RA patients over the course of 6 months. In contrast to the same-day rescan negative control, we observed median bone formation and resorption fractions of 0%.
Multi-stack image registration is a useful tool to improve the number of useable scans when analyzing erosions using HR-pQCT. Further, image registration can be used to longitudinally assess bone remodeling. These methods could be implemented in future studies to provide important pathophysiological information on the progression of bone damage.
医学影像学在确定类风湿关节炎（RA）关节损伤进展方面发挥着重要作用。高分辨率外周定量计算机断层扫描（HR-pQCT）是一种敏感的工具，能够评估骨微观结构和侵蚀，并且 3D 刚性图像配准可用于随时间可视化和量化骨重塑。然而，在图像采集过程中患者的运动可能会导致“堆栈移位”伪影，从而导致信息丢失，并减少可使用 HR-pQCT 分析的侵蚀数量。本研究的目的是使用图像配准来增加可使用的 HR-pQCT 扫描数量，并将基于图像的骨重塑评估应用于 RA 患者的掌指（MCP）关节。
10 名 RA 患者在研究入组时和 6 个月随访间隔完成第 2 和第 3 MCP 关节的 HR-pQCT 扫描。在 6 个月时，采集额外的重复扫描以评估可靠性。HR-pQCT 图像以三个单独的 1cm 采集（堆栈）进行采集，重叠 25%。我们首先使用标准评估方法进行分析，然后使用多堆栈配准进行分析。我们评估了在多堆栈配准后是否可以评估更多的侵蚀。使用基线和随访图像的配准和转换完成骨重塑分析。我们计算了 6 个月随访和同天重新定位的骨形成和吸收体积分数作为阴性对照。
由于堆栈移位伪影，13/57（23%）个侵蚀无法从原始图像进行分析。经过多堆栈配准后，可以对所有侵蚀进行体积评估。我们观察到，在 6 个月的时间内，RA 患者的骨形成分数中位数为 2.1%，吸收分数中位数为 3.8%。与同天重扫阴性对照相比，我们观察到骨形成和吸收分数中位数为 0%。
多堆栈图像配准是一种有用的工具，可在使用 HR-pQCT 分析侵蚀时增加可使用扫描的数量。此外，图像配准可用于纵向评估骨重塑。这些方法可在未来的研究中实施，以提供有关骨损伤进展的重要病理生理学信息。
