Tsukamoto H, Kang Y S, Jones L C, Cova M, Herold C J, McVeigh E, Hungerford D S, Zerhouni E A
Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Invest Radiol. 1992 Apr;27(4):275-81. doi: 10.1097/00004424-199204000-00002.
There is a continuing need for a greater sensitivity of magnetic resonance imaging (MRI) in the diagnosis of avascular necrosis (AVN). Previously, it was demonstrated that a dynamic MRI method, with gadolinium-DTPA (Gd-DTPA) enhancement, can detect acute changes not seen on spin-echo images after arterial occlusion in a dog model. Because venous congestion appears to be a more directly relevant hemodynamic abnormality in a majority of clinical AVN cases, the authors extended the dynamic MRI technique to study changes in venous occlusion.
Dynamic MRI of the proximal femur was performed in five adult dogs before and after unilateral ligation of common iliac and lateral circumflex veins. Sixteen sequential gradient-recalled pulse sequence (GRASS) images (time resolution = 45 mseconds, echo time = 9 mseconds, flip angle = 65 degrees) were obtained immediately after a bolus intravenous injection of 0.2 mmol/kg of Gd-DTPA. Simultaneous measurements of regional blood flow were made using the radioactive microsphere method.
After venous ligation, there was a 25% to 45% decrease in the degree of enhancement compared with preligation values on the ligated side. The decrease in cumulative enhancement (integrated over the entire time course) was statistically significant. The occlusion technique was verified by confirming a statistically significant decrease in blood flow determined by the microsphere method.
Dynamic Gd-DTPA-enhanced fast MRI technique can detect acute changes in bone marrow perfusion due to venous occlusion. This technique may have applications in the early detection of nontraumatic AVN.
磁共振成像（MRI）在诊断缺血性坏死（AVN）方面仍需要更高的敏感性。此前，已证明一种动态MRI方法，即钆-二乙三胺五乙酸（Gd-DTPA）增强扫描，可在犬模型中检测到动脉闭塞后自旋回波图像上未显示的急性变化。由于在大多数临床AVN病例中，静脉充血似乎是一种更直接相关的血流动力学异常，作者扩展了动态MRI技术以研究静脉闭塞的变化。
对5只成年犬在单侧结扎髂总静脉和旋股外侧静脉前后进行股骨近端的动态MRI检查。在静脉推注0.2 mmol/kg的Gd-DTPA后，立即获取16个连续的梯度回波脉冲序列（GRASS）图像（时间分辨率 = 45毫秒，回波时间 = 9毫秒，翻转角 = 65度）。使用放射性微球法同时测量局部血流量。
静脉结扎后，结扎侧的增强程度与结扎前相比降低了25%至45%。累积增强的降低（在整个时间过程中积分）具有统计学意义。通过确认微球法测定的血流量有统计学意义的降低，验证了闭塞技术。
动态Gd-DTPA增强快速MRI技术可检测因静脉闭塞导致的骨髓灌注急性变化。该技术可能在非创伤性AVN的早期检测中具有应用价值。
