I050] MRI-based synthetic CT applications for hadron dose planning

Abstract

Purpose The introduction of MRI as a preferred delineation modality in radiotherapy (RT) has sparked the idea of performing all steps of the radiotherapy chain on this modality. The main scientific argument for so-called MRI-only RT is the elimination of systematic registration errors between multiple modalities. The main challenge is the conversion of MRI intensities to CT numbers for dose calculation, a process commonly known as synthetic CT (sCT) generation. Here, we will review the literature for sCT generation with special focus on hadron dosimetry applications. Further, metal artifacts are especially critical for hadron dose planning and the potential of using sCT for metal artifact reduction (MAR) will be presented. Methods The main findings in two recent reviews [1] , [2] within sCT generation for MRI-only RT will be presented with respect to typical sCT generation strategies, MRI sequences, treatment sites and patient data used. The dosimetric agreement between CT and sCT based photon and hadron dosimetry is reviewed. Image quality improvement and dosimetric accuracy from an sCT based MAR study including both phantoms and (head and neck) patients is further reported on. Results A variety of different MRI sequences and sCT generation strategies exist which demonstrate a clinical acceptable agreement between MRI-only and traditional CT based dosimetry. Only a smaller part of the studies deals hadron dosimetry. sCT based MAR has a similar and sometimes better performance than existing clinical MAR techniques currently applied. Conclusions MRI-only hadron RT shows a promising potential for clinical implementation and sCT generation can further be used as a useful MAR technique.