Inner ear volumetric measurements using high-resolution 3D T2-weighted fast spin-echo MR imaging: Initial experience in healthy subjects

BACKGROUND AND PURPOSE: Adult size is achieved in the inner ear labyrinth b y approximately 25 weeks' gestation, and minimal variability in age, sex, s ide, and race is found after birth. In this study, we opted to determine th e reproducibility of inner ear volumetric measurements generated from high- resolution heavily T2-weighted 3D fast spin-echo MR images. METHODS: The temporal bones of 23 volunteers were imaged using a heavily T2 -weighted 3D fast spin-echo MR imaging technique. The images were assessed by a neuroradiologist for the presence of inner ear configurational anomali es and, most important, for complete coverage of the inner ear labyrinth. S ubsequently, the volume of the fluid in the inner ear was determined by two observers using a semiautomated segmentation algorithm. The mean, SD, rang e, and coefficient of variation of fluid volume in the inner ear were calcu lated. Age-, sex-, and side-related differences in the inner ear volumetric measurements were evaluated using analysis of variance. Interrater consist ency in the inner ear volumetric measurements was evaluated by comparing th e calculated coefficients of reliability. RESULTS: Volumetric measurements were available from 46 inner ears in 23 vo lunteers. The mean volume was 227.8 mm(3) (SD, 24.4 mm(3)), and the coeffic ient of variation was 10.7%. No age-, sex-, or side-related differences in the inner ear volumetric measurements were found (F ratios were 4.33, 5.04, and 0.26, respectively). Interrater consistency, as assessed by the coeffi cient of reliability, was 5.3%. CONCLUSION: Reproducible volumetric measurements of the inner ear labyrinth can be obtained by applying a semiautomated segmentation algorithm to a he avily T2-weighted 3D fast spin-echo MR imaging data set. These volumetric m easurements may help identify patients,vith congenital sensorineural hearin g loss and normal inner ear configuration.