Do TIAs require investigation by thin-slice high-resolution diffusion MRI with a 3T MR unit?

Contribution of high-b-value diffusion-weighted imaging in determination of brain ischemia in transient ischemic attack patients

BACKGROUND AND PURPOSE

High-b-value diffusion-weighted imaging (DWI) (b = 2,000 and b = 3,000 second/mm(2)) offers theoretical advantages over DWI examinations at b = 1,000 second/mm(2) for detection of acute ischemic stroke. The purpose of this study was to determine whether high-b-value DWI are better than b = 1,000 images in TIA patients.

METHODS

We compared DWI obtained with 3 different b-values (1,000, 2,000, and 3,000 second/mm(2)) and fluid-attenuated inversion recovery (FLAIR) sequences in 75 consecutive TIA patients. DWI examinations were performed within 3.25 ± 1.5 days after the onset of symptoms. Presence of ischemic lesion, volume, lesion conspicuity, and lesion distinction were determined.

RESULTS

A total of 40 (53.3%) patients revealed ischemic acute lesions with b = 1,000 while 34 (45.3%) were positive on FLAIR. High-b-value DWI did not increase the sensitivity for the detection of acute brain ischemia. The median lesion value increased as the b-value did: .17 mL (interquartile range [IQR] .12-.78) at b = 1,000; .19 mL (IQR .13-1.00) at b = 2,000; .29 mL (IQR .14-1.02) at b = 3,000; and .12 mL (IQR .04-.62 mL) on FLAIR (P < .001). As b-value increased, we observed hyperintensities in white matter that could erroneously be considered as acute ischemia.

CONCLUSION

High-b-value DWI did not improve the conspicuity and distinction of the ischemic lesions.