Track-weighted imaging for neuroretina: Evaluations in healthy volunteers and ischemic optic neuropathy.

BACKGROUND: The use of MRI-tractography to explore the human neuroretina is yet to be reported. Track-weighted imaging (TWI) was recently introduced as a qualitative tractography-based method with high anatomical contrast.

PURPOSE: To explore the human retina in healthy volunteers and patients with anterior ischemic optic neuropathy (AION) using TWI reconstructions.

STUDY TYPE: Prospective.

POPULATION: Twenty AION patients compared with 20 healthy volunteers.

FIELD STRENGTH/SEQUENCE: 3.0T MRI diffusion-weighted imaging (DWI) with b-value of 1000 s/mm2 and 60 diffusion-weighting noncollinear directions.

ASSESSMENT: We performed constrained spherical deconvolution from the diffusion-weighted signal and volumetric tractography method, whereby 10 million streamlines are initiated from seed points randomly distributed throughout the orbital area. We then reconstructed TWI maps with isotropic voxel size of 300 μm.

STATISTICAL TESTS: We tested the effect of the number of diffusion-weighting directions, ocular laterality, and ocular dominance on healthy retinal fascicles distribution. We then performed factorial analysis of variance to test the effects of the presence/absence of the fascicles on the visual field defect in patients.

RESULTS: In healthy volunteers, we found more temporal fascicle in right eyes (P = 0.001), more superior fascicles in dominant eyes (P = 0.014), and fewer fascicles with tractography maps based on 30 directions than those based on 45 directions (P = 9 × 10-8 ) and 60 directions (P = 6 × 10-7 ). Eight out of 20 AION patients presented with complete absence of neuroretinal fascicle, side of the disease, which was correlated with visual field mean deviation at the 6-month visit [F(1,17) = 6.97, P = 0.016]. Seven patients presented with a temporal fascicle in the injured eye; this fascicle presence was linked to visual field mean deviation at the 6-month visit [F(1,17) = 8.43, P = 0.009].

DATA CONCLUSION: In AION patients, the presence of the temporal neuroretinal fascicle in the affected eye provides an objective outcome radiological sign correlated with visual performance.

LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.