膝关节软骨成像的MRI技术探讨

目的　比较多个扫描序列在膝关节软骨成像中的优缺点 ,筛选出最佳扫描序列和最佳扫描参数。方法　选取健康成年志愿者 3 0名 ,分别计算并比较各序列关节软骨同生理盐水、骨髓和肌肉的对比度噪声比 (CNR )。扫描序列共 5种 :快速自旋回波 (FSE) :T1WI、T2 WI和PDWI双回波 ;短 TI反转恢复序列 (STIR)和三维脂肪抑制扰相梯度回波序列(3D FS SPGR)。其中后者分别选取激发角 3 0°、45°和 60°扫描。结果　 3D FS SPGR序列关节软骨同生理盐水、骨髓和肌肉的CNR值均较其他序列有显著性差异 ;当TE 6.9ms ,TR 3 8ms ,激发角 3 0°时 ,各组CNR值最大 ,与该序列传统扫描参数比较能明显缩短扫描时间。结论　优化的 3D FS SPGR序列较其他序列在关节软骨成像中有明显的优势 ,能使关节软骨显示更加清晰 ,结合三维重建技术能为临床诊断与治疗提供更多的信息。

Technique of MRI in Imaging of Articular Cartilage in the Knee

Objective To compare the advantage or shortage of several scan sequences in imaging of articular cartilage in knee and determine the optimal series and parameters. Methods The knees of 30 healthy volunteers were imaged with five different MR imaging sequences including T₁-weighted, proton density-weighted, T₂-weighted FSE, STIR and 3D-FS-SPGR. The flip angle of 3D-FS-SPGR were 30°,45° and 60°. The value of CNR was determined for cartilage versus a saline fluid phantom, marrow fat and muscle. Results The value of CNR of 3D-FS-SPGR for cartilage versus a saline fluid phantom, marrow fat, and muscle were compared with other sequences and were significantly different. The maximum value of CNR was acquaired in 3D-FS-SPGR sequences when TE was 6.9ms, TR was 38ms and the flip angle was 30°. Conclusion Compared with traditional parameters, Modified 3D-FS-SPGR series can shorten scan time obviously and have significant advantage in imaging normal articular cartilage of knee. It can show clearly the cartilage than other sequences and provide much information adding to 3D construction of cartilage.