High-b-Value Diffusion-Weighted MR Imaging of Hyperacute Ischemic Stroke at 1.5T

A–C, A 63-year-old man who had right hemiparesis for 6 hours. Abnormal hyperintensity is noted at left posterior limb of internal capsule on b = 2000 image (B, white arrow) but it is not definite on b = 1000 image (A). Follow-up T2-weighted image obtained 2 days later shows a small hyper-intense lesion in the same location (C, white arrow).

A–F, A 64-year-old man who had left hemiparesis for 1 hour 20 minutes. Initial b = 1000 images reveal subtle hyperintensity in the right corona radiata and basal ganglia (A, B). The lesion is more conspicuous and extensive on b = 2000 images (C, D). Follow-up T2-weighted image obtained 3 days later shows progression to infarction at the basal ganglia (E, F). Initial diffusion change is partly normalized in the posterior portion of the initial lesion. An old infarction is noted in the left posterior temporal cortex on the T2-weighted image.

A–C, A 57-year-old man who had left hemparesis for 4 hours 40 minutes. Initial b = 1000 image reveals subtle hyperintensity in the right pons (A). The lesion is more conspicuous on the b = 2000 image (B). Follow-up T2-weighted image obtained 2 days later shows the infarction at the corresponding location.

Mean volume of the lesions from initial b = 1000, b = 2000, and follow-up b = 2000 images. As the b value increases, the mean volume of the lesion increases by 47% (22.1 ± 27.9 mL on b = 1000 image versus 32.5 ± 36.5 mL on b = 2000 image, P < .001, n = 34). The mean volume of the lesion measured on follow-up b = 2000 images (52.3 ± 61.6 mL) is significantly larger than those of the initial trace images of b = 1000 or 2000 because of progression or edematous swelling of the infarction in most of the patients.