To design a reliable and quick lesion volume estimation method for hyperintensities on diffusion-weighted images (DWI) for the evaluation of hyperacute stroke.

Twenty patients with obvious high signal lesions seen on DWI in the middle cerebral artery territory due to acute ischemia were enrolled to evaluate the performance of four tentatively designed semi-quantitative methods: the 25-area method, the 20-area method, the 10-area method, and the modified 10-area method. Two radiologists performed the volume analyses using these methods. Intraclass correlation coefficients were calculated to compare the correlation between the reference values and the measured values and to evaluate the interobserver agreement of each method.

For the correlation between the measured value and the reference value, the performance of the modified 10-area method was the most powerful, with a value of 0.8981 and 0.8090 for observer 1 and 2, respectively. The interobserver agreement was satisfactory for both the 25-area method and the modified 10-area method, with a value of 0.9212 (95% CI: 0.8123-0.9681) and 0.9063 (95% CI: 0.7790-0.9618), respectively.

The performance of the modified 10-area method was satisfactory for both lesion volume estimation and interobserver correlation in the evaluation of an acute cerebral infarction by the use of DWI.