多发性硬化患者的磁化传递及弥散张量成像特点

Characteristics of magnetization transfer and diffusion tensor imaging in multiple sclerosis

目的比较多发性硬化(MS)患者脑内病灶、表现正常脑白质(NAWM)及健康志愿者脑白质的磁化传递及弥散特性的差异,探讨MS患者的磁化传递率(MTR)与平均弥散率(MD)的相关性。方法分别对24例复发缓解型MS患者和24名健康志愿者行常规MRI、磁化传递成像(MTI)及弥散张量成像(DTI),经处理后得到相应的MTR、MD及各向异性分数(FA)图。测量MS病灶、对侧NAWM及健康志愿者相应脑白质区域的MTR、MD及FA值。结果MS患者病灶的平均MTR值(23.49%±5.16%)明显低于NAWM组(29.49%±3.38%)及健康对照组(32.78%±3.42%,F=101.44,P<0.01);病灶的平均FA值(0.32±0.09)也明显低于NAWM组(0.42±0.09)及对照组(0.51±0.09,F=95.41,P<0.01);而病灶的平均MD值[(1.10±0.17)×10-3mm2/s]明显高于NAWM组[(0.92±0.13)×10-3mm2/s]及对照组[(0.76±0.04)×10-3mm2/s,F=144.89,P<0.01]。与MS患者T1WI等信号病灶相比,低信号病灶的MTR值及FA值降低,而MD值升高。MS患者病灶的MTR值与MD值显著相关,而NAWM的MTR与MD值无明显相关性。结论MTI和DTI的指标可以反映MS患者脑内不同部位病理变化的不同,为常规MRI提供补充信息。

Objective To compare magnetization transfer and diffusion characteristics of multiple sclerosis （MS） lesions, normal-appearing white matter （NAWM） from patients, and normal white matter from control subjects, and to investigate the correlation between the magnetization transfer ratio （MTR） and mean diffusivity （MD） in MS patients. Methods Conventional MRI, magnetization transfer imaging （MTI） and diffusion tensor imaging （DTI） were performed in 24 relapsing remitting MS patients and 24 healthy volunteers. Based on these images, the MTR, MD and fractional anisotropy （FA） maps were obtained. Then the MTR, MD and FA values were measured in lesions and NAWM from patients, and in the relevant white matter regions from volunteers. Results Average MTR in lesions （ 23. 49% ± 5. 16% ） from MS patients was lower than those both in NAWM （29. 49% ± 3. 38% ） and in the counterparts of the controls （ 32.78% ± 3. 42% , F = 101.44, P 〈 0. 01 ）. The average FA in lesions （0. 32 ± 0. 09） was also lower than those in NAWM （0. 42 ±0. 09） in the controls （0. 51 ±0. 09, F =95.41, P 〈0. 01 ）. The average MD in lesions （ （ 1.10 ±0. 17） × 10^-3 mm^2/s） was higher than that in NAWM （ （0. 92 ±0. 13） × 10^-3 mm^2/s）, and that in controls （ （0. 76 ±0. 04） × 10^-3 mm^2/s, F= 144. 89, P 〈0. 01 ）. In MS patients, the average MTR and FA of the hypointense lesions on T1WI were lower and the average MD was higher than those in isointense lesions. There was a strong correlation between average MTR and MD in lesions, whereas no correlation was found between average MTR and MD in NAWM. Conclusion Indices derived from MTI and DTI can reflect the differences of the underlying pathological changes in different brain regions of MS patients, and may provide complementary information for conventional MRI.