Comparison of image sensitivity between conventional tensor-based and fast diffusion kurtosis imaging protocols in a rodent model of acute ischemic stroke

摘要

Diffusion kurtosis imaging (DKI) can offer a useful complementary tool to routine diffusion MRI for improved stratification of heterogeneous tissue damage in acute ischemic stroke. However its relatively long imaging time has hampered its clinical applications in the emergency setting. Recently proposed fast DKI approach substantially shortens the imaging time, which may help overcome the scan time limitation. However, to date, the sensitivity of fast DKI protocol for imaging acute stroke has not yet been fully described. In this study, we performed routine and fast DKI scans in a rodent model of acute stroke, and compared sensitivity of diffusivity and kurtosis indices (i.e. axial, radial and mean) in depicting acute ischemic lesion. In addition, we analyzed the contrast-to-noise ratio (CNR) between the ipsilateral ischemic and contralateral normal regions using both conventional and fast DKI methods. We found that mean kurtosis shows a relative change of 47.1±7.3% between the ischemic and contralateral normal regions, being the most sensitive parameter in revealing acute ischemic injury. The two DKI methods yielded highly correlated diffusivity and kurtosis measures and lesion volumes (R²≥0.90, P<0.01). Importantly, the fast DKI method exhibited significantly higher CNR of mean kurtosis (1.6±0.2) compared to the routine tensor protocol (1.3±0.2, P<0.05), with its CNR per unit time (CNR efficiency) approximately doubled when the scan time is taken into account. In conclusion, the fast DKI method provides excellent sensitivity and efficiency to image acute ischemic tissue damage, which are essential for imaging-guided and individualized stroke treatment.