A framework for voxel‐based assessment of biological effect after proton radiotherapy in pediatric brain cancer patients using multi‐modal imaging

Introduction The exact dependence of biological effect on dose and linear energy transfer (LET) in human tissue when delivering proton therapy is unknown. In this study, we propose a framework for measuring dependency using multi‐modal image‐based assays with deformable registrations within imaging sessions across time. Materials Methods 3T MRI scans were prospectively collected from 6 pediatric brain cancer patients before they underwent treatment, every 3 months year after treatment. Scans included T1‐weighted contrast enhancement (T1), T2‐FLAIR (T2) fractional anisotropy (FA) images. addition, the planning CT, distributions Monte Carlo‐calculated LET collected. A image registration was used to create dataset dose, intensities at baseline follow‐up voxel‐by‐voxel basis. We modelled changes over time as surrogate effect. investigated various models show feasibility model changes. To account interpatient intrapatient variations, nested generalized mixed regression model. applied predict function each modality. Results Using changes, saw decrease FA signal dose; however, increased increasing LET. Similarly, an increase T2 but no T1 voxel values either or Conclusions could successfully our proposed framework. Due low number patients, observed not marked enough draw any firm conclusions.