Blatter D D, Bahr A L, Parker D L, Robison R O, Kimball J A, Perry D M, Horn S
Department of Radiology, LDS Hospital, Salt Lake City, UT 84143.
AJR Am J Roentgenol. 1993 Dec;161(6):1269-77. doi: 10.2214/ajr.161.6.8249741.
Multiple overlapping thin-slab acquisition (MOTSA) is a hybrid time-of-flight MR angiography technique that combines the advantages of two- and three-dimensional methods. A venetian blind-like artifact, resulting from variations in signal intensity at slab boundaries, is a potentially significant disadvantage. The objective of this study was to determine the accuracy of MOTSA MR angiography for the measurement of stenosis and to evaluate the effectiveness of modifications to reduce the venetian blind artifact.
Fifty-one consecutive patients undergoing conventional and MR angiography of the carotid arteries for suspected atherosclerotic disease were studied. Methods established in the North American Symptomatic Carotid Endarterectomy Trial (NASCET) were used to measure stenosis. Measurements from the conventional angiograms were compared with those from the MR angiograms. Modifications of the MR angiographic technique that were instituted after the initial 26 patients to reduce the venetian blind artifact included new acquisition parameters and the use of a postprocessing algorithm.
After modification, highly significant improvements in Spearman ranked correlation coefficients were observed for MR angiography interobserver comparison (.573 to .974, p < .001) and comparison of conventional and MR angiography (.774 to .949, p < .001). A corresponding reduction was observed in the standard deviation of the difference measurement for percent stenosis for both interobserver (34.5% to 11.7%, p < .001) and intertechnique (22.6% to 12.6%, p < .001) comparisons. In the postmodification group, the interobserver correlation coefficients for conventional and MR angiography were not significantly different (.969 vs .974). The areas under the receiver-operating-characteristic curves used to predict surgically significant disease for the premodification and postmodification groups were 0.79 and 0.98, respectively, for observer A and 0.85 and 0.95, respectively, for observer B.
Improved acquisition parameters and postprocessing significantly reduce the severity of the venetian blind artifact and increase the accuracy of MOTSA MR angiography in the measurement of percent stenosis. With these improvements, MOTSA MR angiography shows promise for noninvasive evaluation of stenosis of the carotid arteries.
多层重叠薄 slab 采集（MOTSA）是一种混合时间飞跃磁共振血管造影技术，它结合了二维和三维方法的优点。由于 slab 边界处信号强度变化导致的类似百叶窗的伪影是一个潜在的重大缺点。本研究的目的是确定 MOTSA 磁共振血管造影测量狭窄的准确性，并评估减少百叶窗伪影的改进措施的有效性。
对 51 例因疑似动脉粥样硬化疾病接受颈动脉传统血管造影和磁共振血管造影的连续患者进行研究。采用北美症状性颈动脉内膜切除术试验（NASCET）中确立的方法测量狭窄。将传统血管造影的测量结果与磁共振血管造影的测量结果进行比较。在最初的 26 例患者之后采用的磁共振血管造影技术改进措施包括新的采集参数和使用后处理算法。
改进后，磁共振血管造影观察者间比较的 Spearman 等级相关系数有高度显著改善（从 0.573 至 0.974，p < 0.001），传统血管造影与磁共振血管造影比较的 Spearman 等级相关系数也有高度显著改善（从 0.774 至 0.949，p < 0.001）。观察者间比较（从 34.5%至 11.7%，p < 0.001）和技术间比较（从 22.6%至 12.6%，p < 0.001）的狭窄百分比差异测量标准差均相应降低。在改进后组中，传统血管造影与磁共振血管造影的观察者间相关系数无显著差异（分别为 0.969 和 0.974）。用于预测手术相关疾病的改良前和改良后组的受试者操作特征曲线下面积，观察者 A 分别为 0.79 和 0.98，观察者 B 分别为 0.85 和 0.95。
改进的采集参数和后处理显著降低了百叶窗伪影的严重程度，并提高了 MOTSA 磁共振血管造影测量狭窄百分比的准确性。有了这些改进，MOTSA 磁共振血管造影在颈动脉狭窄的无创评估方面显示出前景。
