Session Item

Modern radiotherapy techniques, such as volumetric arc therapy (VMAT), MR-guided radiotherapy with MR-Linacs as well as proton therapy, are very flexible treatment techniques where one can obtain high dose coverage in the tumor volume at the same time as organs at risk (OARs) are spared. This flexibility is also providing the opportunity to escalate the radiation dose to more radioresistant areas of the gross tumor volume without increasing the side effects. In radiation oncology, technology has contributed to an evidence-based scientific discipline determining favorable strategies for radiotherapy delivery with optimal radiation doses at the right time and place to get the optimal outcome. In parallel we have also seen technological developments in medical image acquisition and analysis that increasingly are providing faster and more detailed imaging for contouring of both targets and OARs, treatment planning, response prediction and evaluation, as well as quality assurance.

Anatomical MRI has been used for a long time to identify healthy and diseased tissue, tumor, stage and location of the tumor. On the other hand, functional MRI comprises imaging methods that allow us to visualize a range of functional tissue properties using the more advanced protocols such as diffusion-weighted MRI, dynamic contrast-based MRI and susceptibility contrast MRI. These functional sequences can together with post-processing tools provide quantitative MRI (qMRI) measures of radiobiological tissue characteristics, which can be exploited to deliver more tailored radiotherapy to each patient, also having the possibility for adjustments during the course of treatment based on longitudinal changes in qMRI parameters. The use of qMRI may therefore result in a more optimized treatment where the tumor response is increased and normal tissue damage is decreased.

The presentation will provide an overview of some of the applications associated with qMRI in radiotherapy: 1) more accurate and automated target and OAR delineation, 2) faster and more accurate qMRI parameter estimation, 3) possibilities for treatment stratification and response monitoring for treatment adaptation, and 4) qMRI maps as input to heterogeneous dose escalation or dose-painting of radioresistant subvolumes. Strategies for how qMRI may be used in these situations will be presented along with examples. The presentation will introduce some challenges and research questions that need to be solved for qMRI to move forward in radiotherapy.