Technical validation of DWI in the abdomen using different motion compensation techniques on a 1.5T MR-Linac

Motivation: The apparent diffusion coefficient (ADC), derived from diffusion-weighted imaging (DWI), is a promising quantitative biomarker for treatment response during radiotherapy. However, DWI in the abdomen is complicated by respiratory motion. Goal(s): To compare the repeatability of the ADC acquired with different motion compensation techniques on a 1.5T MR-linac. Approach: A phantom and test-retest study (26 healthy volunteers) were performed, evaluating four DWI acquisitions (free breathing, navigator-triggered, and both repeated with an abdominal compression belt). Results: From the 11 datasets analyzed so far, absolute ADC values and repeatability were comparable between the acquisitions in healthy regions of the liver, spleen and kidney. Impact: This study initiates defining the optimal DWI acquisition strategy to measure treatment-related ADC changes of abdominal tumors on an MR-linac.