Speakers
Description
Background/Motivation: SBRT shows promising antiarrhythmic effects in refractory ventricular tachycardia (VT), but photon delivery increases healthy-tissue dose. Carbon ions offer superior conformity and favourable LET, but require accurate range due to motion. Mixed helium–carbon beams may enable in vivo range verification, as helium ions have ~3× the carbon range and exit the patient. We present first proof-of-principle measurements for VT carbon ion radiotherapy (VT-CIRT).
Methods: Cardiac motion was simulated with a Sun Nuclear Dynamic Phantom (Model 008C) using healthy and VT motion sequences differing in excursion and frequency. A motion prediction model binned the cycle into two phases corresponding to key ECG events. Beams with ~10% and ~20% helium were delivered; radially integrated depth-dose profiles were acquired every 10 ms with a downstream Giraffe multi-layer ionisation chamber and compared with reference profiles at the key phases.
Results:For a slow cycle with large excursion, a first analysis showed quantitative range differences between cardiac phases. For healthy and VT sequences, differences appeared mainly in profile shape due to range mixing.
Conclusions: Helium–carbon ion beams show potential for real-time range monitoring. However, accurate reconstruction of the carbon ion range from helium measurements is expected to be challenging due to range mixing and motion sensitivity. As the current baseline for VT-CIRT foresees cardiac-gating strategies, future range-monitoring studies should also investigate its effect on range monitoring capabilities.