Measurement of optic tracts in normal Chinese adults of the Han nationality based on the high-resolution MRI

Abstract

Objective To explore the morphological characteristics of optic tracts in healthy Chinese Han adults on the high-resolution MRI and fill the database of Chinese standard brain with morphological data of optic tracts.Methods Cerebral MRI scans with T1 WI 3D MPRAGE sequence of 1000 healthy Chinese volunteers from 15 hospitals were divided into five stages, ranging in age from 18 to 70.With the technique of multi-baseline, structure and morphology of optic tracts were displayed optimally on the images with multiplanar reconstruction.Data were measured as following: transverse distance of the cisternal optic tract (TD1) and peri-crural optic tract (TD2), length from the cisternal optic tract to the peri-crural optic tract (L) ,angle between optic tract(AOT) and height of optic tract from its first segment to plane of anterior commissure (H) including H1, H2, H3, H4 and HS.The measurements of optic tracts between sexualities and among age groups were compared by anasis of covariance; those among five age groups were compared pairwisedly by least significant difference analysis (LSD); and the differences of measurements between left and right optic tracts were analyzed using paired t test.Results (1) Comparisons of optic tract structures between male and female: the mean optic tract length of male [(11.69±1.45),(11.56±1.44) mm] was significant longer than that of female [(10.58±1.29),(10.40±1.34) mm] (F=22.236, 29.703, P=0.000); the mean H1 of male [(2.56±0.28),(2.60±0.29) mm] and female [(2.57±0.31 ), (2.63±0.32) mm] were significantly different ( F =11.130,7.805, P = 0.000, 0.005).No significant differences of the other measurements were found between male and female ( P > 0.05 ).(2) Comparisons among age groups: among 5 age groups, TD1 of both sides [left TD1 :(4.64±0.51 ), (4.64±0.57), (4.55±0.58), (4.39±0.53), (4.36±0.58)mm;right TD1 :(4.84±0.53) ,(4.80±0.60), (4.77±0.65), (4.60±0.59), (4.57±0.59) mm] and the right TD2[(3.33±0.45),(3.34±0.41),(3.33±0.36),(3.23±0.38),(3.23±0.39) mm] had statistical differences ( F = 3.458, 2.735, 4.711, P = 0.008,0.028, 0.001 ).The LSD analysis found that the 50 years old group was the watershed with significant differences ( P 0.05).(3) Comparisons of the measurements between left and right optic tracts: TD1 of bilateral optic tracts were (4.52±0.57)and(4.72±0.60) mm respectively; H1 of bilateral optic tracts were (2.56±0.30)and (2.61±0.30) mm respectively; H2 of bilateral optic tracts were (2.66±0.30)and (2.70±0.30) mm respectively; and L of bilateral optic tracts were ( 11.14±1.47 ) and ( 10.98±1.50 )mm respectively.There were significant differences in these measurements between left and right optic tracts( t =12.460, - 6.013,5.595,4.784, P = 0.000 ), while there were no significant differences in TD2, H3, H4 and H5( P > 0.05 ).Conclusions With high-resolution MR1 and 3D reconstruction, optic tract can be displayed clearly and measured accurately.There are definite differences in anterior segments of optic tracts between sexualities, sides and among ages in normal Chinese Han adults, while the posterior segments of optic tracts keep stable.Normal reference values of optic tracts in Chinese Han adults are provided to clinical practices and scientific researches, which are valuable for building of Chinese standard brain. Key words: Visual pathways; Magnetic resonance imaging; Organ size