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

Purpose: 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 3 T. Materials and methods: 27 patients with acute stroke who were admitted to the hospital during the first 24 h 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 3 T 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. Results: 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. Conclusions: 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. (C) 2009 Elsevier Ireland Ltd. All rights reserved.