The Study Of RFOV-DTI And MRI-IVIM In Evaluating Optic Nerve Injury Caused By Intraconal Orbital Tumor

Background and purposeOrbital tumor is one of the important factors of visual acuity decreases,especially those that root in intraconal or around the optic nerve,Routine Magnetic resonance imaging(MRI)plays a critical role in the diagnosis and differential diagnosis of orbital tumors,and it can display the morphology and signal characteristics of the lesion distinctly,but the conventional MRI cannot quantitatively analyze the pathological changes in the fibers of the optic nerve.Reduced field＿of＿view diffusion tensor imaging(rFOV-DTI)and intravoxel incoherent motion(IVIM)to quantitative measurement of nerve fibers and tissue microcirculation in vivo.Therefore,the purpose of this paper is to investigate value the of rFOV-DTI and IVIM in evaluating the optic nerve injury resulted from intraconal orbital tumor.Materials and methodsForty-four patients with unilateral intraconal orbital tumor confirmed by imaging examination and Forty-four healthy volunteers age and gender matched patients were enrolled in this study prospectively,patients and volunteers are the experimental group and control group respectively.Routine MR imaging of the orbits was performed to exclude optic nerve diseases on a 3T scanner,All subjects underwent rFOV-DTI and IVIM scan by GE Discovery MR750 3.0T equipment,respectively.Data of rFOV-DTI and IVIM were import into GE ADW4.6 workstation and were derived fractional anisotropy(FA),mean diffusion(MD),axial diffusion(AD),Radial diffusion(RD),apparent diffusion coefficient(ADC),true apparent diffusion coefficient(D),pseudo-apparent diffusion coefficient(D*),perfusion fraction(f)of individual optic nerves.FA,MD,and AD,RD,ADC,D,D*,f were obtained for quantitative analysis.All subjects underwent Ishihara and International standard eye chart test.For rFOV-DTI and IVIM measurement,Differences between patients and controls were evaluated by using two independent-samples t test,and differences between right and left eyes of patients were evaluated by paired samples t test.The comparison of rFOV-DTI and IVIM parameters between patients with benign tumors and patients with malignant tumors was performed using two independent samples t test.Meanwhile,spearman correlations of all rFOV-DTI and IVIM parameter values of optic nerves with the CVTS,as well as the VA,were calculated.P< 0.05 indicates that the difference was statistically significant.Receiver operating characteristics was analyzed for parameters with statistical differences,and P<0.05 indicates that the difference was statistically significant.Results1.There was no significant difference in the FA,MD,AD,RD values of the main parameters of rFOV-DTI of left and right optic nerve in the control group(P>0.05),ADC D D* f value of IVIM was not significantly different(P>0.05).2.The FA value of rFOV-DTI parameter of affected optic nerve in tumor patients was significantly lower than that of the healthy side and the control group,and the difference was statistically significant(P<0.001).MD,AD,RD value of rFOV-DTI parameter of affected optic nerve in tumor patients was significantly higher than unaffected side and control group,The difference of MD、AD、RD was statistically significant(P<0.0167).There was no significant difference in the FA,MD,AD,RD of the unaffected optic nerve compared with the control group(P>0.05).In the patient group,compared with the benign tumor group,the main parameters FA and AD of rFOV-DTI of optic nerve in the malignant tumor group changed significantly(P<0.05),there was no significant difference in MD and RD(P>0.05).In the diagnosis of affected optic nerve and normal optic nerve,FA,MD and RD had statistical difference(P<0.05),AD had no statistical difference(P>0.05),the area under the curve of FA was significantly higher than that of MD and RD,with statistical difference(P<0.05).3.In the IVIM sequence,the ADC value of the single exponential model in the patients with the optic nerve of the affected side increased compared with that of the healthy side and the control group,but the difference was not statistically significant.Compared with the control group and the healthy side,the D value of the patients with the parameters derived from the dual exponential model increased,and the D*and f value decreased,among which the difference of D and f value was statistically significant(P<0.05),while the difference of D* value was not statistically significant(P>0.05).In the patient group,compared with the benign tumor group,ADC,D*,f of the main parameters of IVIM did not change significantly,and the difference was not statistically significant(P>0.05).In the diagnosis of the affected optic nerve and the normal optic nerve,the values of D and f were different statistically,and the area under the curve of D was similar to that under the curve of f without statistical difference(P=0.473).4.There was significant correlation between FA values of affected side nerve and CVTS(r = 0.337,P = 0.025),and There was no correlation between RD values of affected side nerve and CVTS(P>0.05),There was significant correlation between main parameters of rFOV-DTI values of affected side nerve and VA,There was significant correlation between main parameters of IVIM values of affected side nerve and CVTS,VA.Conclusion1.rFOV-DTI can quantitatively evaluate optic neuropathy in patients with intraconal orbital tumors,and its the corresponding parameters can be used as biological markers for pathological changes of optic nerve axons and myelin damage in intraconal orbital tumors.2.IVIM can quantitatively evaluate optic neuropathy in patients with intraconal orbital tumors,and its the corresponding parameters can be used as biological markers for microcirculation and pathological changes of optic nerve tissue in patients withi intraconal orbital tumors.3.rFOV-DTI and IVIM are of certain value in the diagnosis of the affected lateral optic nerve and the normal optic nerve.rFOV-DTI has better diagnostic efficacy than the parameters D and f generated by IVIM,the parameter.