TEST-RETEST ANALYSIS WITH FUNCTIONAL MR OF THE ACTIVATED AREA IN THE HUMAN VISUAL-CORTEX

PURPOSE: To investigate the intersubject and intrasubject variability of the activated area in the visual cortex with functional MR imaging. METHODS: Double-section gradient-echo MR images were acquired at 1.5 T in 28 healthy Volunteers using the fast low-angle shot (FLASH) techn ique. Visual stimulation was obtained with light-emitting diode (LED) goggles. Eighteen volunteers were studied twice. The size of the activ ated areas in the Visual cortex and the increase in signal were measur ed. A reproducibility ratio for size (R-size) and for location (R-over lap) was calculated on a scale of 0.0 to 1.0. RESULTS: Activation was seen in 89% of the subjects. The size of the activated area was widely variable among subjects: mean, 460 +/- 284 mm(2); range, O to 1029 mm (2) in the first study in all volunteers. Signal increases ranged from 3.2% to 10.9%, with a mean of 6.6 +/- 1.7%. The mean values of intras ubject variability testing were R-size = 0.83 +/- 0.16 and R-overlap = 0.31 +/- 0.11. CONCLUSION: Functional MR imaging with the FLASH techn ique is useful in identifying certain cortical areas that have quite v ariable locations among subjects. This study provides reference data f or the intrasubject and intersubject variability of the activation pat tern of the visual cortex.