Motion management for real-time adaptive MRgRT in liver and rectal cancer

• Applicants: Dr. Cihan Gani; Professor Dr. Sergios Gatidis; Professor Dr. Daniel Zips
• Subject Area: Nuclear Medicine, Radiotherapy, Radiobiology
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 438106095

The aim of this project is to investigate tumour motion during irradiation (intrafraction) and between fractions (interfraction) at the hybrid 1.5 T MR-Linac system. Such a hybrid device may facilitate the development of novel and innovative treatment strategies by individualized dose prescriptions based on both anatomical and functional MRI. This is particularly interesting in liver tumors where the surrounding healthy liver tissue is often dose limiting and in rectal tumors when dose escalation is planned in order to increase complete response rates and facilitate organ preservation. However both tumor sites are moving targets due to respiration (liver) or changes of rectal and bladder filling. Thus, a pre-requisite for highly precise individualized dose prescriptions is the assessment of the intrafractional and interfracional tumor motion. In this project we will establish an optimized four-dimensional imaging protocol for the 1.5 T MR-Linac with both anatomical and functional imaging sequences. Based on this we will develop a 4D-response-adaptive protocol for stereotactic body radiotherapy (SBRT) of liver tumors. The idea is to individualize the dose prescription based on the risk of the development of radiation induced liver disease (RILD) and the response seen on anatomical and functional imaging between fractions. For rectal cancer the goal is to assess intrafractional and interfractional motion of the entire tumour and of potential subvolumes that might serve as targets for a “bioBoost”. This bioBoost subvolume is defined by changes observed on diffusion weighted imaging which has already been shown to be predictive of tumor regression. In this project we will further refine these models with the available imaging data assessed through the course of treatment and test different bioBoost strategies such as a sequential boost or a stereotactic integrated boost. The developed methodologies will result in prospective interventional trials that test the concept of 4D motion corrected MR guided adaptive radiotherapy.

• DFG Programme: Research Grants