Gougoutas Alexander J, Wheaton Andrew J, Borthakur Arijitt, Shapiro Erik M, Kneeland J Bruce, Udupa Jayaram K, Reddy Ravinder
Metabolic Magnetic Resonance Research and Computing Center, Department of Radiology, University of Pennsylvania, B1 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104-2045, USA.
Acad Radiol. 2004 Dec;11(12):1389-95. doi: 10.1016/j.acra.2004.09.003.
A reduction in cartilage volume is characteristic of osteoarthritis and hence there exists a need for an accurate and reproducible method to measure in vivo cartilage volume. Quantification of cartilage volume from magnetic resonance (MR) images requires a segmentation technique such as the user-driven "Live Wire" strategy that can reliably delineate object volumes in a time-efficient manner. In the present work, the accuracy and reproducibility of the Live Wire method for the quantification of cartilage volume in MR images is evaluated.
The accuracy of the Live Wire method was assessed by comparing the MR-based volume measurement of a patellar cartilage-shaped phantom versus data calculated via water displacement. The inter- and intra-operator reproducibility of the technique was evaluated from Live Wire segmentation of the patellar cartilage volume from fat-suppressed 3-dimensional spoiled-gradient-echo images of five healthy human volunteers performed by three operators. To provide data for analysis of inter-scan reproducibility, the human scans were repeated five times with the aid of a leg-restraining jig to minimize repositioning error.
The volume of the patellar cartilage-shaped phantom measured via Live Wire segmentation of MR images was within 97.8% of its true volume. The average inter- and intra-operator coefficients of variation of three operators were 3.0% and 0.4%, respectively. The average inter-scan coefficient of variation of five repeated scans of each volunteer was 2.7%.
The data suggest that the Live Wire strategy is an accurate, reproducible, and efficient technique to measure cartilage volume in vivo in a feasible amount of operator time.
软骨体积减少是骨关节炎的特征，因此需要一种准确且可重复的方法来测量体内软骨体积。从磁共振（MR）图像定量软骨体积需要一种分割技术，如用户驱动的“活线”策略，该策略能够以高效的方式可靠地描绘物体体积。在本研究中，评估了活线法在MR图像中定量软骨体积的准确性和可重复性。
通过比较基于MR的髌软骨形状模型的体积测量结果与通过排水法计算的数据，评估活线法的准确性。由三名操作员对五名健康人类志愿者的脂肪抑制三维扰相梯度回波图像中的髌软骨体积进行活线分割，评估该技术在操作员间和操作员内的可重复性。为了提供用于分析扫描间可重复性的数据，借助腿部约束夹具对人体扫描进行了五次重复，以尽量减少重新定位误差。
通过MR图像的活线分割测量的髌软骨形状模型的体积在其真实体积的97.8%以内。三名操作员的平均操作员间和操作员内变异系数分别为3.0%和0.4%。每位志愿者五次重复扫描的平均扫描间变异系数为2.7%。
数据表明，活线策略是一种准确、可重复且高效的技术，能够在可行的操作员时间内测量体内软骨体积。
