Abstract #0449

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

Koen P.A. Baas¹, Sabine Visser¹, Vivian W.J. van Pelt¹, Damien McHugh², Daniela Thorwarth³, Andreas Wetscherek⁴, Tim Schakel⁵, Marijn Kruiskamp⁶, Jihong Wang⁷, Marlies E Nowee¹, Uulke A van der Heide¹, Eric S Paulson⁸, and Petra J van Houdt¹

¹Radiation Oncology, the Netherlands Cancer Institute, Amsterdam, Netherlands, ²Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, United Kingdom, ³Section for Biomedical Physics, Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany, ⁴Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom, ⁵Radiotherapy, UMC Utrecht, Utrecht, Netherlands, ⁶MR Clinical Science, Philips Healthcare, Best, Netherlands, ⁷Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States, ⁸Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI, United States

Synopsis

Keywords: Diffusion Acquisition, Radiotherapy, ADC, MR-linac, abdomen, repeatability

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.

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