Exchange-driven Microscopic Kurtosis in Correlation Tensor MRI

Correlation Tensor MRI (CTI) provided strong evidence for non-vanishing microscopic kurtosis (µK) in neural tissues, both in animals and in humans. However, µK sources remain to be elucidated. Standard Model with Exchange (SMEX) contrasts have been recently proposed by Olesen et al. for mapping exchange properties, especially in gray matter. Here, we derive an expression for µK originating from the SMEX biophysical model due to exchange, and in a model of stroke compare µK derived from SMEX to µK measured with CTI. Our findings suggest that µK(CTI)>µK(SMEX), suggesting a degree of microstructural origin for the CTI contrast.