Diagnostic benefit of high b-value computed diffusion-weighted imaging in acute brainstem infarction

Purpose Diffusion-weighted imaging (DWI) is a cornerstone in diagnostic of ischemic stroke. However, there are some false-negative results in patients with brainstem infarction. The aim of this study was to investigate the usefulness of high-b-value computed diffusion-weighted imaging (c-DWI) in comparison to standard DWI in patients with acute brainstem infarction.

Material und methods 56 patients with acute brainstem infarction were retrospectively analysed by two readers. A clinical DWI was obtained with the b-values 0, 500 and 1000 s/mm² on either a 1.5 or 3T MRI scanner. C-DWI was calculated with a monoexponential model with high b-values 2000, 3000, 4000 and 5000 s/mm². All c-DWI series with high-b-values were compared to the standard DWI sequence at b-value of 1000 s/mm² in terms of image artifacts, lesion extent and contrast.

Results There was no statistically significant difference between 1.5 and 3 T MRI regarding the measured ischemic lesion size from both raters. There were no statistically significant differences between the ischemic lesion sizes on DWI at b-values of 1000 s/mm² and on c-DWI at higher b-values. Overall, the contrast between the lesion and the surrounding normal areas improved with increasing b-value on the isotropic DWIs: maximum at b=3000-5000, followed by that at b 2000 and b 1000 s/mm², in order. The best relation between artifacts and lesion contrast was identified for b 2000 s/mm².

Conclusion High b-value DWI derived from c-DWI has a higher visibility for stroke brainstem lesions compared to standard DWI without additional time cost. The b-2000 image is recommended to use in clinical routine, higher b-value images lead to more imaging artifacts, which might result in misdiagnosis.