体素内非相干运动磁共振成像在眼眶内肿瘤对视神经损伤的研究

Intravoxel incoherent motion magnetic resonance imaging detecting alterations on optic nerve in the patients with orbital tumor

目的探讨体素内非相干运动(intravoxel incorherent motion,IVIM)磁共振成像在眶内肿瘤对视神经损伤程度评估方面的价值。材料与方法纳入眼眶内占位性病变25例患者,所有患者均在3.0 T磁共振上行眼眶常规和体素内非相干运动磁共振成像,纳入无视觉通路病变的对照组12例,比较患侧和健侧视神经表观扩散系数(apparent diffusion coefficient,ADC)、纯扩散系数(slow ADC,D)、伪扩散系数(fast ADC,D*)、灌注分数(fraction of fast ADC,f)的差异运用两配对样本t检验;比较患侧和对照组ADC、D、D*、f及ADC、D、D*、f不对称性指数的差异运用两独立样本t检验,采用国际标准视力图测量视力,患侧视力受损有11例,未受损14例。结果与健侧和对照组视神经f值相比[(46.4±3.0)%、(45.4±5.5)%],患侧视神经f值明显降低[(28.2±2.7)%],差异均有统计学意义(P=0.0015、0.002);与视力未下降组视神经D*值相比[(62.5±11.0)×10^-3 mm^2/s],视力下降组D*值降低[(26.6±7.0)×10^-3 mm^2/s],差异有统计学意义(P=0.023);与对照组视神经f值不对称指数相比(0.03±0.06),患者视神经f值不对称性指数显著升高(0.26±0.06),差异有统计学意义(P=0.033)。患侧视神经的D*值与视力成低相关(r=0.462,P=0.02)。结论体素内非相干运动参数D*、f在评估眶内肿瘤对视神经功能损伤方面优于传统单指数ADC,并且能够提供更加丰富的信息。

Objective:To investigate the value of intravoxel incoherent motion(IVIM)magnetic resonance imaging in evaluating the degree of optic nerve injury in orbital tumors.Materials and Methods:Twenty-five patients with space-occupying lesions confirmed by imaging examination and 12 volunteers were enrolled in this study,the difference of apparent diffusion coefficient(ADC),slow ADC(D),fast ADC(D*),fractional of fast ADC(f)of the affected side optic nerve and the contralateral side were compared by paired t test,parameters and the asymmetry index(AI)of parameters of optic nerve between the patient group and the control group were compared by independent sample t-test.International standard visual acuity chart was used to measure visual acuity,11 cases were impaired visual acuity,14 cases were not.Results:The affected side optic nerve presented significantly decreased f compared to the unaffected side[f=(28.2±2.7)%,(46.4±3.0)%respectively;P=0.0015],the affected side optic nerve presented significantly decreased f compared to the control group[f=(28.2±2.7)%,(45.4±5.5)%respectively;P=0.002],the visual impaired patients presented significantly decreased D*compared to the not visual impared[D*=(26.6±7.0)×10^-3 mm^2/s,(62.5±11.0)×10^-3 mm^2/s respectively;P=0.023];affected group optic nerve presented significantly increased AI of f compared to the control group(AI of f=0.26±0.06,0.03±0.06 respectively;P=0.033);there was a low correlation between visual acuity and D*of affected optic nerve(r=0.462,P=0.02).Conclusions:The voxel incoherent motion parameter D*was superior to the conventional single-exponential ADC in evaluating the optic nerve function damage caused by orbital tumors,and can provide more abundant information.