Simple quantitative measurement based on DWI to objectively judge DWI-FLAIR mismatch in a canine stroke model

Diffusion-weighted imaging (DWI) -fluid attenuated inversion recovery (FLAIR) mismatch refers to the situation where an ischemic lesion is detected on DWI in the absence of a corresponding lesion on FLAIR imaging.Recently, several studies indicated that DWI-FLAIR mismatch might aid to predict whether the stroke onset time is within 4.5 hours or not (1-6).Furthermore, this mismatch pattern, which is based on the detection time difference between DWI and FLAIR imaging, would help to time the stroke lesions in patients with unclear onset time.This information is important for clinicians to select the optimal treatment, because more ischemic stroke patients would benefit from thrombolytic therapy (7).However, in previous studies, assessment of FLAIR imaging has been subjective.An objective, simple, and quantitative measurement to help judge the status of FLAIR imaging is yet to be found.DWI can detect a hyperacute ischemic lesion as soon as 30 minutes after stroke, and it is viewed as a sensitive and effective tool to detect ischemic stroke events (8, 9).Meanwhile, several studies observed that the relative signal intensity (SI) of lesions on DWI could be a reliable parameter to demonstrate the secondary pathologic process after ischemic stroke (10).Therefore, we hypothesized that, quantitative parameters derived from DWI, such as relative DWI signal intensity (rDWI) and relative ADC value (rADC), might be useful to evaluate the status of FLAIR imaging.In this study, we aimed to determine the value of rDWI and rADC in evaluating the status of FLAIR imaging, based on our embolic canine ischemic stroke model, considering different temporal evolution of the volume of ischemic lesions demonstrated on DWI and FLAIR imaging.Simple quantitative measurement based on DWI to objectively judge DWI-FLAIR mismatch in a canine stroke model