Reliability of MR perfusion-weighted and diffusion-weighted imaging mismatch measurement methods.

BACKGROUND AND PURPOSE We investigated 2 methods of measuring MR imaging perfusion-diffusion mismatch to determine whether reliability is improved by direct measurement on a single, blended map. MATERIALS AND METHODS Image software was used for measurement of lesion volumes from diffusion-weighted images (DWI) and mean transit time (MTT) calculated from perfusion-weighted (PWI) images on 64 patients with acute stroke. For the first method, the DWI and MTT lesions were measured separately. For the second method, the mismatch volume was measured directly on the blended images created from the registered DWI and MTT images. RESULTS Test-retest agreement was 100% and 97% for the separate and blended methods using mismatch cutoffs of 20% or more versus less than 20%. There were no significant differences in the mismatch statistics between the methods. CONCLUSIONS Mismatch volumes by a single reader can provide highly reliable and consistent results even when separately measuring DWI and MTT lesions. Propagation of measurement error was not demonstrated, and the methods were statistically comparable.