Estimating diffusion fractional anisotropy of disease in patients with advanced prostate and breast cancers. A single-center study.

Motivation: Whole-body diffusion-weighted imaging in oncology assumes isotropic diffusion therefore that data probing the directional dependence of diffusion in body cancer applications is scarce. Goal(s): To report the distribution of fractional anisotropy (FA) values in metastatic bone disease for a cohort of patients who underwent multi-directional diffusion weighted imaging. Approach: Deep learning was used to auto-segment metastatic lesions; FA values are calculated for each segmented region and the distributions reported. Results: FA distributions from 85 patients with metastatic disease (50 prostate, 33 breast) are reported and are deemed to be low (mean FA range breast group: 0.2179 - 0.3132; prostate group: 0.2866 - 0.3717). Impact: We have conducted diffusion tensor imaging analysis for whole body DWI data and carried out the first bone lesion FA comparison study. This work provides a rationale for choice of diffusion-weighting gradient schemes in clinical imaging.