股骨头缺血坏死MRI动态增强的实验研究

Detection of acute avascular necrosis of the femoral head in dogs: Assessment of femoral perfusion with dynamic contrast enhanced magnetic resonance (MR) imaging

目的 :研究MRI动态增强对早期股骨头缺血坏死的诊断价值和病理基础。方法 :6只犬在术后 3h作MRI动态增强 ,其中 3只犬作墨汁灌注后处死 ;另 3只犬在第 7d作第二次MRI动态增强及墨汁灌注后处死。双侧股骨头标本作HE染色病理大切片。结果 :术后 3hMRI显示对照侧正常股骨头及双侧股骨干迅速增强 ,正常股骨头在 48s～ 144s增强达到高峰 ,平均峰值在 96s左右 ,增强率为 6 0 1% ;手术侧缺血股骨头持续未见增强 ,增强率为 1 5 %。HE染色切片证实缺血侧骨髓腔内毛细血管明显少于对侧。术后 7dMRI表现与术后 3h相似 ,但在缺血侧头颈交界处可见一增强率达 110 %的高信号带。HE染色切片显示此处有大量新生毛细血管 ,毛细血管密度为 13 8± 4 1,对照侧为6 8± 2 4。结论 :MRI动态增强可显示股骨头的血供状态 ,对ANFH早期诊断优于常规SE序列。

Objective:To evaluate the diagnostie valuc of dynamic contrast enhanced MR imaging for detecting early stage avascular necrosis of the femoral head(ANFH), and to study the correlation of MR imaging appearance with histologic findings. Methods:Six dogs were imaged 3 hours after devascularization. Thirty sequential gradient-recalled echo images (FLASH), 55/23(TR/TE) with a 40° flip angle, were obtained. Three of the six dogs were perfused ink through the abdominal aorta, and then were killed. Seven days later, the other three dogs were reimaged.Results:After injection of Gd-DTPA, normal marrow was characterized by rapid enhancement, with an average signal intensity increase of 60.1%, peaking at the 96th second. No measurable enhancement was seen in the marrow of ischemic femoral head. Histologic findings showed that capillaries in the marrow of ischemic femoral head were much poorer than that in the control side. Dynamic contrast enhanced MR images, obtained 7 days after devascularization, showed persistent lack of enhancement in the avascular marrow. The junction zone, characterized by rapid contrast enhancement in excess of 110% without early washout, was identified at the interface between normal and avascular marrow. Histologic findings revealed more capillaries in this area than that in control side. Conclusion:Dynamic contrast enhanced MR imaging is much more sensitive in the detection of early stage ANFH than conventional SE imaging.