Session Item

Magnetic resonance imaging (MRI) and positron emission tomography (PET) are important diagnostic tools to identify location, size and stage of malignant tumors. More recently, new PET tracers and functional MRI using more advanced protocols such as diffusion-weighted MRI, dynamic contrast-based MRI and susceptibility contrast MRI allow visualization of a range of molecular and functional tissue properties. Together with post-processing tools, quantitative imaging biomarkers may be developed to measure a range of radiobiological tissue characteristics. These can be exploited to deliver more personalized radiotherapy to each patient, also having the possibility for adjustments during the course of treatment based on longitudinal changes in imaging parameters. The use of such biomarkers may therefore result in a more optimized treatment where the tumor response is improved, and the probability of normal tissue damage is decreased.

This talk will provide an overview of how MRI and PET imaging biomarkers can be applied for personalized radiotherapy. One example is imaging biomarkers quantifying intratumoral heterogeneity. Such information is largely ignored in radiotherapy planning today. Quantitative imaging biomarkers enable voxel-wise spatially defined mapping of biological characteristics, providing an opportunity for optimized radiotherapy dose distributions. Changes in imaging biomarkers during or after radiotherapy offer the possibility for adaptation of treatment during the course of radiotherapy, or early detection of disease recurrence.

Quantitative imaging biomarkers can provide objective decision-support tools in personalized patient management. To fully exploit the potential that lies in quantitative imaging biomarkers there is a need to reduce uncertainties through standardization of image acquisition and parameter quantification. Further, one needs to conduct prospective clinical imaging studies at multiple centers to achieve data from large patient cohorts that allow appropriate validation of methodology and biomarker results as well as the possibility to ensure reproducibility and repeatability of the biomarkers. Currently, there is a paucity of evidence on how quantitative imaging biomarkers potentially affects clinical decision-making and long-term patient outcome, highlighting a need to collect long-term survival data through prospective imaging biomarker studies. In the talk, examples will be shown on how multicenter quantitative imaging biomarker studies with PET and MRI in radiotherapy can implement standardized protocols and phantom studies to reduce uncertainties in parameter quantification.

The presentation will end with an outlook on recent progress within physics-informed models for quantitative imaging biomarker development, and how quantitative imaging data can be implemented into the concept of digital twins in order to improve personalized radiotherapy.