视网膜色素变性磁共振扩散张量成像研究及其与视野相关性分析

目的　使用磁共振扩散张量成像技术（DTI）研究视网膜色素变性（RP）患者的视神经改变及其与视野检查的相关性。方法　46例RP患者（RP组）和46例健康对照志愿者（对照组）进行了前瞻性研究。所有受试者进行3.0T MRI-DTI扫描检测，使用简化的小视野扩散张量成像（rFOV-DTI）序列推导出单个视神经的各向异性（FA）、平均弥散系数 （MD）、平行扩散系数（λ//）、垂直扩散系数（λ⊥），获得平均分数FA、平均扩散率和特征值图，用于定量分析。进一步分析视野平均偏差（MDVF）与患者的分数FA、平均扩散率、λ//及λ⊥的相关性。结果　RP组与对照组受试者间年龄和体质量等差异均无统计学意义（均为P>0.05），而两组之间最佳矫正视力和MDVF差异均具有统计学意义（均为P=0.000）。与对照组相比，RP组患者视神经FA降低，MD、λ//、λ⊥升高，两组之间差异有统计学意义（P<0.001）。RP组患者两侧视神经的FA、MD、λ//和λ⊥与MDVF行相关性分析，视神经FA及λ⊥与MDVF有显著相关性（右侧:r=-0.864、0.719,均为P<0.001；左侧:r=-0 .997、r=0.830,均为P<0.001）；MD与MDVF不相关（右侧:r=-0.026,P=0.866；左侧:r=-0.115,P=0.445）。结论　rFOV-DTI测量值可用于RP患者视神经轴突和髓鞘病变的早期诊断。

Magnetic resonance diffusion tensor imaging of retinal pigmentosa and its correlation with the visual field

Objective　To evaluate the optic nerve changes of retinitis pigmentosa (RP) patients and their correlation with visual field examination by magnetic resonance imaging-diffusion tensor imaging (MRI-DTI). Methods　A prospec-tive study was conducted on 46 RP patients and 46 healthy controls. The 3.0T MRI-DTI was performed for all subjects. The fractional anisotropy (FA), mean diffusivity (MD), parallel diffusion coefficient (λ//) and vertical diffusion coefficient (λ⊥) of a single optic nerve were deduced by using the simplified reduced field-of-view diffusion tensor imaging (rFOV-DTI) sequence, and the mean FA, MD, and eigenvalue graphs were obtained for quantitative analysis. The correlation of mean deviation of visual field (MDVF) with the FA, MD, λ// and λ⊥ were further evaluated. Results　The comparative analysis of age, body mass, MDVF and best corrected visual acuity (BCVA) of the two groups showed that there was no statistically significant difference in age and body mass (both P>0.05) between the two groups, but there was a statistically significant difference in the BCVA and MDVF (both P<0.001). The statistical analysis of DTI parameters and the degree of visual field defects in RP patients showed that the average FA of the optic nerve was decreased, while the MD, λ// and λ⊥ were increased, and the differences between the two groups were statistically significant (all P<0.001). In the RP group, the correction analysis of the mean FA, MD, λ// and λ⊥ of the optic nerves on both sides and the MDVF showed that the FA and λ⊥ of the optic nerves were significantly associated with the MDVF (right: r=-0.864, P<0.001; r=0.719, P<0.001; left: r=-0.997, P<0.001, r=0.830, P<0.001),while the MD was not correlated with the MDVF (right: r=-0.026, P=0.866; left: r=-0.115, P=0.445). Conclusion　The rFOV-DTI measurements can be used as an early diagnostic tool for optic nerve axon and myelin lesions in RP patients, making early intervention in RP patients possible.