Apparent Exchange Rate and Isotropic and Anisotropic Kurtosis in Meningioma and Glioma Tumors

Abstract

Event Abstract Back to Event Apparent Exchange Rate and Isotropic and Anisotropic Kurtosis in Meningioma and Glioma Tumors Filip Szczepankiewicz1, Björn Lampinen1 and Markus Nilsson2* 1 Lund University, Department of Medical Radiation Physics, Sweden 2 Lund University, Lund University Bioimaging Center, Sweden Filtered exchange imaging (FEXI) [1-2] was used to estimate tumor AXR in a test-retest study. The protocol was optimized to the employed hardware which resulted in an acquisition time of 13 minutes. A group-level comparison of AXR in the tumor tissue showed that meningiomas and gliomas exhibit different levels of AXR. Further, a statistical power analysis estimated that a clinically relevant effect can be inferred at relatively small group sizes (~5-10 per group). We conclude that FEXI can be used during clinically feasible acquisition times to infer relevant differences between relatively small groups. The µFA was calculated from data using directional and isotropic encoding, where the isotropic encoding was achieved through magic angle spinning of the q-vector [3-4]. Group-level comparison of diffusion parameters showed that the most prominent difference between the tumor types was the presence of anisotropic tissue structures. For example, this was observed as an elevated µFA in the meningiomas compared to the gliomas. The tumors were also histologically examined after excision. Automated light microscopy was used to examine the tissue, and structure tensor analysis was applied to the images to evaluate the presence of structural anisotropy quantitatively [4]. A strong correlation was found between microscopic diffusion anisotropy (from dMRI) and the presence of structural anisotropy (from light microscopy). We conclude that metrics of microscopic anisotropy may provide a more comprehensive description of tissue microstructure, and that such metrics can be corroborated by independent examination of the tissue.