Dynamic Fluence Modulation using Proton CT for Low-dose Imaging in Particle Therapy
Résumé
Dynamic fluence modulation for computed tomography (CT), i.e. the acquisition of tomographic images with variable, patient-and task-specific fluence fields, offers the potential to substantially reduce local imaging dose. In particular, volume-of-interest (VOI) imaging allows to limit imaging dose to a clinically relevant volume and reduce it elsewhere. In the context of particle therapy, where tomographic data is required for treatment planning the VOI is the treatment beam path. VOI imaging is of particular interest for particle therapy given the very low integral out-of-VOI treatment dose. Proton CT imaging allows for a direct measurement of the proton stopping power with an increased accuracy and a decreased imaging dose compared to x-ray-based CT. In addition, frequent imaging is required to verify patient positioning and to monitor potential anatomical changes, which over the course of a treatment may compromise the planned dose. In this work, we evaluate the performance of a fluence-modulated proton CT algorithm for low-dose in-room imaging. This would allow for recalculation or replanning of the treatment dose according to the anatomy of the day with out-of-VOI dose below 1 mGy. We performed a simulation study and acquired experimental data using a prototype proton CT scanner. By employing a bow-tie-like fluence modulation aiming for constant noise, imaging dose was reduced by 9%. For a VOI imaging task, out-of-VOI dose was reduced by 41% and substantially below 1 mGy. This may pave the way for daily imaging prior to every treatment session aiming to eventually reduce safety margins in particle therapy, thus further reducing normal tissue exposure to therapeutic doses.
Domaines
Imagerie médicale
Origine : Fichiers produits par l'(les) auteur(s)