Automatic Mean Transit Time Lesion Outlining in Acute Stroke using Level Sets

Kim Mouridsen¹, Anders Neumann, Lars Riisgaard Ribe, Kristjana Yr Jonsdottir, Leif stergaard

The mismatch volume between perfusion weighted- and diffusion weighted imaging is an emerging target for thrombolytic therapy in clinical management and clinical trials. However, the critical delineation of the perfusion lesion boundary suffers extreme interobserver variability, due to diffuse gradients between normal and ischemic tissue. We propose estimating the perfusion lesion by finding a smooth contour, which minimizes variation around a patient-specific elevated MTT value inside the contour, and variation around a normal value outside the lesion, using variational calculus. We show that, in contrast to simple thresholding, this technique compares excellently with lesion outlines by four expert neuroradiologists