实验兔膝关节软骨的高场强磁共振成像

Study of High Field MRI of Knee Articular Cartilage of Experimental Rabbits

目的:探讨实验兔膝关节软骨的高场强MRI正常表现以及成像的最佳序列及参数。方法:应用飞利浦Intera 1.5T超导型磁共振扫描仪,分别采用PDW/SPAIR/D,T2W_3D_FFE及3D_WATSc序列对6只实验兔的膝关节行磁共振成像,观察不同序列关节软骨的信号特点,比较各序列的软骨信噪比(signal to noiseration,SNR)及软骨/软骨下骨对比噪声比CNR(contrast to noise ratio,CNR)。结果:兔膝关节软骨在三个序列中均表现为单层均匀的中等或高信号带;PDW/SPAIR/D、T2W_3D_FFE及3D_WATSc各序列的软骨SNR差异无显著性(P=3.840),而软骨/软骨下骨CNR差异有显著性(P=0.045);3D_WATSc序列的软骨/软骨下骨CNR高于PDW/SPAIR/D序列及T2W_3D_FFE序列(P<0.05),而PDW/SPAIR/D序列和T2W_3D_FFE序列间的软骨/软骨下骨CNR差异无显著性(P>0.05)。结论:高场强磁共振下,兔膝关节软骨表现为单层均一信号,三维扰相梯度回波结合水激励技术即3D_WATSc序列,可能是观察实验兔关节软骨的最佳成像序列。

Objective：To study the high field MRI appearances of normal rabbit knee articular cartilage, and evaluate the optimal sequences and parameters for imaging. Methods： a 1.5T Philip Intera MR system was used in the study, 6 experimental rabbits underwent knee MRI with PDW/SPAIR/D, T2W 3D FFE and 3D_WATSc sequences consecutively, the appearances of articular cartilage were reviewed, the cartilage signal to noise ration （SNR） and cartilage/subchondral bone contrast to noise ratio （CNR） of all MRI sequences were compared. Results： The rabbit knee articular cartilage presents as a homogeneous layer of intermediate or hyper intense signal in all 3 sequences. There was no significant difference of cartilage SNRs among PDW/SPAIR/D, T2W 3D FFE and 3D_WATSc（P = 3. 840） , but there was significant difference of artilage/subchondoral bone CNR among 3 sequences （ P =0. 045 ）. Furthermore, the CNR of 3D_WATSc was higher than those of PDW/SPAIR/D and T2W 3D FFE（P 〈0.05） ,while there was no difference of CNRs between PDW/SPAIR/D and T2W 3D FFE（P 〉0.05）. Conclusion： The articular cartilage of rabbit knee, imaged by a high filed MRI, was demonstrated as a single layer band with homogeneous signal. 3D-spoiled gradient echo with water excitation technique, viz. a 3D_WATSc sequence, was the optimal sequence for articular cartilage imaging.