Improving detection of ischemic lesions at 3 Tesla with optimized diffusion-weighted magnetic resonance imaging.

ABSTRACT

BACKGROUND AND PURPOSE: This study compared three different combinations of DWI parameters three and six diffusion imaging directions (3dir and 6dir, respectively) using b=1000 or 2000 s/mm(2) (b1000 or b2000, respectively) to improve detection of recent ischemic lesions at 3 Tesla (3 T). MATERIALS AND METHODS: A total of 47 consecutive patients underwent three DWI scans 3dir b1000; 6dir b1000; and 6dir b2000. Qualitative visual analysis was performed by three readers based on evaluation of the number of lesions, presence of artifacts and diagnostic confidence. Interobserver agreement, sensitivity, specificity, and positive and negative predictive values were calculated. RESULTS: Forty-five lesions were detected by 3dir b1000, 52 by 6dir b1000 and 56 by 6dir b2000 in 30 patients. The additional lesions identified by 6dir b2000 were either small or located in the posterior fossa. Sensitivity with 6dir b2000 was significantly higher than with 3dir b1000 (98.1% vs 77.4%; P<0.05). CONCLUSION: At 3 T, 6dir b2000 DWI detected more acute ischemic lesions than 3dir b1000, particularly small lesions and those located in the brain stem.