Does Attenuation of Perfusion in Diffusion Weighted-MRI Behave as Exponential Decay or as Damped Oscillation?

Paul Martin Murphy¹, Nikolaus Szeverenyi¹, Claude Sirlin¹, Mark Bydder¹

In liver, the signal decay of diffusion-weighted MR images has been modeled both as a mono-exponential function, representing apparent diffusion, and as a bi-exponential function, representing the separate attenuation of perfusion. Parameters of these models vary in several hepatic disease processes. Early diffusion theory predicted that signal from small vessel perfusion may decay as a sinc function, rather than as an exponential. We demonstrate this form of damped oscillation in a flow phantom and in liver in vivo. This effect may allow measurement of small vessel flow velocity in hepatic disease if temporal confounders can be excluded as its cause.