Frank L R, Brossmann J, Buxton R B, Resnick D
Veterans Affairs Medical Center, San Diego, CA 92161, USA.
AJR Am J Roentgenol. 1997 Feb;168(2):547-54. doi: 10.2214/ajr.168.2.9016245.
The purpose of this study was to investigate the laminar appearance of cartilage on MR images.
Theoretical modeling of truncation artifacts was used to predict spatial patterns and associated intensity variations in MR imaging. A numerical simulation of a ring model was used to show truncation artifacts as a function of the angle in the image plane for unequal in-plane resolutions. MR imaging of 10 cadaveric human patellae at several resolutions used an imaging protocol that produced high-contrast images of cartilage. The high-resolution image of each MR imaging set was reduced in resolution by low-pass filtering and compared with the acquired images of equivalent resolution. Variable-resolution images of the patella of a healthy human volunteer were also acquired.
Truncation artifacts from opposing cartilage edges can create false laminae and artifactual intensities. The resulting geometric variations can alter the apparent width of the cartilage as well. The intensity variations produced by truncation artifacts can be as much as 22% of the actual intensity. The most pronounced artifactual trilaminar appearance occurs when cartilage thickness exceeds the image resolution by a factor of 4. Truncation artifacts vary as a function of the angle in the imaging plane for unequal resolutions in the two directions.
Truncation artifacts can produce an artifactual laminar appearance in cartilage and alter the apparent cartilage width.
本研究旨在探究磁共振成像（MR）图像上软骨的分层表现。
采用截断伪影的理论模型来预测MR成像中的空间模式及相关强度变化。使用环形模型的数值模拟来展示截断伪影与图像平面角度的函数关系，用于不同平面分辨率的情况。对10具尸体人类髌骨进行了多种分辨率的MR成像，成像方案能生成软骨的高对比度图像。通过低通滤波降低每个MR成像组的高分辨率图像分辨率，并与同等分辨率下采集的图像进行比较。还采集了一名健康人类志愿者髌骨的可变分辨率图像。
来自相对软骨边缘的截断伪影可产生假分层和伪强度。由此产生的几何变化也会改变软骨的表观宽度。截断伪影产生的强度变化可达实际强度的22%。当软骨厚度超过图像分辨率4倍时，最明显的伪三层表现出现。对于两个方向上不等分辨率的情况，截断伪影随成像平面角度而变化。
截断伪影可在软骨中产生伪分层表现并改变软骨的表观宽度。
