Teitelbaum G P, Ortega H V, Vinitski S, Clark R A, Watanabe A T, Matsumoto A H, Rifkin M D, Barth K H
Department of Radiology, Georgetown University Hospital, Washington, DC.
Radiology. 1990 Mar;174(3 Pt 2):1013-9. doi: 10.1148/radiology.174.3.174-3-1013.
Flow-phantom magnetic resonance (MR) gradient-echo (GRE) imaging at 1.5 T was performed on a titanium Greenfield filter containing trapped blood clots with a high concentration of either deoxyhemoglobin (DHb) or methemoglobin (MHb), simulating acute and older thromboemboli, respectively. Flip angle, repetition time (TR), and echo time (TE) were varied, and a contrast-to-noise ratio between trapped clots and flowing fluid (clot-flow contrast) was determined for each set of imaging parameters. Use of very low flip angles (less than or equal to 10 degrees) rendered MHb clots indistinguishable from flowing fluid. In general, DHb clots displayed greater clot-flow contrast than MHb clots regardless of flip angle. With increasing TE values, T2* effect was observed with MHb clots, and magnetic susceptibility artifacts increased. Overall, optimum clot-flow contrast for imaging of both DHb and MHb clots was achieved with a flip angle of 45 degrees-60 degrees, a TR of 50 msec, and the shortest TE possible. Using GRE parameters similar to the optimum parameters determined in vitro, the authors imaged four patients with nickel-titanium Simon filters and one dog with a titanium Greenfield filter. MR imaging was successful in demonstrating filter location, caval patency, and the presence and extent of intraluminal thrombus.
在1.5T条件下，对含有高浓度脱氧血红蛋白（DHb）或高铁血红蛋白（MHb）的血栓的钛制格林菲尔德滤器进行流动体模磁共振（MR）梯度回波（GRE）成像，分别模拟急性和陈旧性血栓栓塞。改变翻转角、重复时间（TR）和回波时间（TE），并针对每组成像参数确定血栓与流动液体之间的对比噪声比（血栓-血流对比）。使用非常低的翻转角（小于或等于10度）会使MHb血栓与流动液体无法区分。一般来说，无论翻转角如何，DHb血栓的血栓-血流对比都比MHb血栓更大。随着TE值增加，在MHb血栓中观察到T2*效应，并且磁敏感性伪影增加。总体而言，使用45度至60度的翻转角、50毫秒的TR以及尽可能短的TE可实现对DHb和MHb血栓成像的最佳血栓-血流对比。使用与体外确定的最佳参数相似的GRE参数，作者对4例使用镍钛西蒙滤器的患者和1只使用钛制格林菲尔德滤器的犬进行了成像。MR成像成功显示了滤器位置、腔静脉通畅情况以及腔内血栓的存在和范围。
