Elster A D, Sobol W T, Hinson W H
Department of Radiology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27103.
Radiology. 1990 Feb;174(2):379-81. doi: 10.1148/radiology.174.2.2296649.
When excreted gadolinium diethylenetriaminepentaacetic acid (DTPA) collects in the bladder of a supine patient during magnetic resonance (MR) imaging, a puzzling pattern of signal intensities is noted. A gradual change in urine signal intensity with progressive addition of Gd-DTPA does not occur; instead, three sharply defined "layers" are seen both on T1- and T2-weighted images within the urine-Gd-DTPA mixture. The physical basis for this triple-layering phenomenon was investigated. A bladder phantom was constructed to reproduce the phenomenon. T1 and T2 relaxivities of urine doped with varying concentrations of Gd-DTPA were measured in vitro; measured signal intensities corresponded closely to predicted intensities. Early urine concentrations of excreted Gd-DTPA may be relatively high (10-40 mmol/L), resulting in extremely short T1 and T2 values (less than 30 msec). These extremely short relaxation times cause an artifactual pseudolayering of signal within the urine-Gd-DTPA mixture.
当排泄出的钆二乙三胺五乙酸（DTPA）在仰卧患者的膀胱中于磁共振（MR）成像期间聚集时，会观察到一种令人困惑的信号强度模式。随着钆-二乙三胺五乙酸（Gd-DTPA）的逐渐添加，尿液信号强度不会发生逐渐变化；相反，在尿液-Gd-DTPA混合物的T1加权和T2加权图像上均可见三个清晰界定的“层”。对这种三层现象的物理基础进行了研究。构建了一个膀胱模型来重现该现象。在体外测量了掺杂不同浓度Gd-DTPA的尿液的T1和T2弛豫率；测量的信号强度与预测强度密切对应。排泄出的Gd-DTPA的早期尿液浓度可能相对较高（10 - 40 mmol/L），导致T1和T2值极短（小于30毫秒）。这些极短的弛豫时间会在尿液-Gd-DTPA混合物中造成信号的人为假分层。
