Functional MR imaging on an open 1T MR imaging system: exploiting the advantages of an open MR imaging system for functional MR imaging.

BACKGROUND AND PURPOSE Open MR imaging scanners are designed for imaging of specific patient groups that cannot be routinely scanned with conventional MR imaging scanners (eg, patients with obesity and claustrophobia). This study aims to determine whether BOLD sensitivity on an open 1T scanner is adequate for fMRI for diagnostic and research purposes by directly comparing fMRI results with a standard 3T MR imaging scanner. The optimal TE was also determined. MATERIALS AND METHODS Twelve healthy adults were scanned by using both an open 1T scanner and a standard 3T scanner. Gradient-echo echo-planar images were acquired for all subjects while performing motor and affective paradigms, each at 5 different TEs per scanner (range, 40-80 ms at open 1T; 20-40 ms at 3T). To compare BOLD sensitivity between scanners and TEs, we determined maximum statistical t scores per TE for all relevant brain areas (motor cortex, visual cortex, amygdala, and OFC) for individual subjects and group analyses. Additionally, T2* values were determined per scanner for the relevant brain areas. RESULTS Maximum t scores were significantly lower in the relevant brain areas on the open 1T compared with the 3T for single subjects but not for group analyses. The optimal TE for fMRI on an open 1T MR imaging system was found to be approximately 70 ms. CONCLUSIONS Although for single-subject studies as used in diagnostics, 3T was found to be superior, fMRI on an open 1T MR imaging scanner is suitable for research designed to analyze data at a group level.