Real-time MRI-guided cardiac radiotherapy: adapting treatment within a heartbeat

The technical feasibility of treating a non-oncological cardiac arrhythmia condition with radioablation was explored on the MR-linac. We have shown that the 1.5 T Unity MR-linac is capable of simultaneously mitigating cardiac and respiratory motion during dose delivery and attain high PTV coverage and also address (cardio)toxicity concerns. Mitigating cardiac and respiratory motion is a technically demanding task in terms of treatment delivery and MR imaging.
Cardiac-synchronization was enabled on the MR-linac by installing ECG-equipment, which opens many possibilities for cardiac MRI on the Unity MR-linac before, during and after treatment. The MR-linac is also capable of monitoring patients during treatment with the installed ECG-equipment by continuously measuring an ECG-signal and real-time cine imaging. The presence of a CIED in a typical VT patient was also considered in this thesis and we demonstrated that CIED-induced imaging challenges can be mitigated. An initial exploration of treatment delivery techniques to facilitate conformal dose deliveries during MRI-guided STAR was demonstrated. Further research will be essential for the improvement of imaging and treatment delivery techniques for clinical feasibility purposes of MRI-guided STAR, which should also be followed by clinical demonstration(s) and clinical product implementations. The developments regarding MRI-guided STAR treatments can also be translated to the treatment of cardiac oncological targets. Additionally, the demonstrated technical feasibility of cardiorespiratory motion management could also be used for the treatment of (ultra-central) lung tumours in which the heart becomes an organ at risk.