Reduced Field-of-view Diffusion Tensor Imaging In The Optic Nerve Of Patients With Stargardt Disease

Background and purposeStargardt disease is the most common form of juvenile-onset macular dystrophy,with a prevalence of 1 in every 10000.It is predominantly inherited as an autosomal recessive trait which is caused by mutations in the ABCA4 gene.It is both clinically and genetically highly heterogeneous.Most cases present with bilateral central visual loss,with characteristic macular atrophy and yellow-white flecks at the posterior pole,which are at the level of the retinal pigment epithelium(RPE).The age of onset is usually between 10–20 years,but there is wide variation,with a later age of onset being associated with a better visual prognosis.Recently,several researches have indicated that there is a loss of retinal ganglion cells(RGCs)and the retinal nerve fiber layer is thinner in STGD patients compared with normal controls by using Optical coherence tomography.In addition,a study found volumetric reduction of the full extent of the visual pathways and cortex in STGD patients with Voxel-based morphometry.In summary,these study proved that the pathological changes are not only located in the retina,but also involve in the optic nerve.Diffusion tensor imaging(DTI)is a noninvasive magnetic resonance technique used to study the micro-structure of white matter,which was widely applied to study the optic neuropathy.Compared with traditional DTI,reduced field of view diffusion tensor imaging(rFOV-DTI)can improve spatial resolution and reduce artifacts,as well as allowing inherent fat suppression.Therefore,this research applied rFOV-DTI to study the optic nerve of patients with STGD in order to discover the application value of rFOV-DTI in STGD patients.Materials and methodsTwenty-two STGD patients and Twenty-five healthy control subjects were enrolled,with both eyes of each participant involved.Conventional MRI and rFOV-DTI were performed on all subjects using a 3T MR scanner(Discovery MR750,GE Healthcare)with a 8-channel head coil.Quantitative parameters of rFOV-DTI including fractional anisotropy(FA),mean diffusivity(MD),principal eigenvalue(?//),and orthogonal eigenvalue(??)were obtained by drawing ROI method.Best corrected visual acuity(BCVA)was also measured on all subjects and was converted to the logarithm of the minimal angle of resolution(logMAR)units.Independent-samples t-test was used to compared the difference of DTI parameters between patients group and control group,and paired t-test was used to compared the difference of DTI parameters between the left eyes and right eyes in patients group.We used Kruskal-Wallis test to compare the differences of DTI parameters among controls and patients in different stage,and a Dunn-Bonferroni test for post hoc comparisons.In addition,spearman correlations of DTI parameters of optic nerves with the logMAR was calculated.SPSS 19.0 soft-ware was used for all statistical analysis and the statistic significance standard was P<0.05.Results1.On conventional MRI,there were no morphological and signal intensity abnormality of the optic nerves in all subjects.2.Compared with control subjects,FA value decreased while MD,?// and ??values increased in patient group(p<0.05).But there was no significant difference between right optic nerves and left optic nerves in patient group(p>0.05).3.The differences of the DTI parameters(FA,MD,?//,??)among the control group and patients in four stage were statistically significant.4.There were no significant difference of the DTI parameters(FA,MD,?//,??)between control group and stage I patients(p>0.05).The FA value of patients in stage II was lower than control group(p<0.05).In addition,the FA values of patients in stage III and IV were lower than control group,and the MD,?//,??values of stage III and IV were higher than control group(p<0.05).5.A significant correlation between the DTI parameters of optic nerves and the logMAR in patient group were observed.(FA r=?0.641,p<0.05;MD r=0.707,P<0.05;?// r=0.698,P<0.05;?? r=0.668,P<0.05).Conclusion1.rFOV-DTI technique is more sensitive than conventional MRI to detect the optic neuropathy,which can provide the imaging basis for the diagnosis of optic nerve pathological alteration in STGD patients.2.rFOV-DTI parameters can quantitatively evaluate the severity of optic optic neuropathy in STGD patients and therewere correlations between the optic nerve rFOV-DTI parameters and LogMRA.3.The optic nerves of STGD patients in stage I have no pathological changes,but the rest stages patients have pathological changes in different degrees.