The utility of high b-value DWI in evaluation of ischemic stroke at 3T

The utility of DWI with high b-value in ischemic stroke is still unsettled. The purpose of this study is to compare high b-value (3000) and standard b-value (1000) diffusion-weighted images in patients with ischemic stroke at 3T.

27 patients with acute stroke who were admitted to the hospital during the first 24h after symptom onset were included in this study. All patients had a brain MRI study with stroke protocol including standard (b=1000) DWI and high b-value (b=3000) DWI sequences at 3T MR scanner. Number and localization of the lesions were assessed MR signal intensities (SI), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), contrast ratio (CR) and apparent diffusion coefficient (ADC) values of the lesions and normal parenchyma on DWI with b=1000 and b=3000 sequences were measured.

All patients with acute stroke revealed hyperintense lesions due to restricted diffusion on DWI with both b-values. However, lesions of restricted diffusion were more conspicuous in b=3000 value DWI than b=1000, and additional 4 ischemic lesions were detected on b=3000 DWI. SNR, CNR, SI and also ADC values in both stroke area and normal parenchyma were lower at b=3000 than the value at b=1000. At b=3000, CR was significantly greater than b=1000 images.

Although quantitative analysis shows higher SI, SNR and CNR values with standard b-value (b=1000) diffusion-weighted imaging, using higher b-value may still be beneficial in detecting additional subtle lesions in patients whose clinical findings are not correlated with standard b-value DWI in stroke.