ESTRO 2024 - Abstract Book

S4303

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

performed (Fig. 2) and images were analyzed both qualitatively and quantitatively to define accuracy of the predicted vs achieved tissue targeting.

Results:

Gated irradiations of the animals were successfully completed with an average total irradiation time of 4 minutes. The animal 1 was irradiated with respiratory gating and animals 2-3 were irradiated with cardiorespiratory gating. The analysis of the tissue sections demonstrated strong γ-H2AX fluorescence signal in the targeted region between the fiducial markers with a size commensurate with the intended dose delivery for the animal 1 using only respiratory gating. For animal 2, cardiorespiratory gating was used. Treatment planning was performed on an end expiratory breath hold in an attempt to better match the CT volume to the planned, gated treatment volume. Analysis of the γ H2AX staining intensity for this animal demonstrated radiotherapy was delivered to an area slightly outside the targeted area between the fiducials. Upon further analysis of the methods used, we found differences in the shape, location and size of the LV volumes between the expiratory breath hold and CT average scans could account for this difference. Therefore, for animal 3 (as with animal 1), we used the CT average scan for treatment planning as a better estimate of the position/shape of the LV during gated treatment. Using this adjustment, we found that cardiorespiratory gating produced excellent correspondence between the targeted are between the fiducials and the γ-H2AX fluorescence signal intensity.

Conclusion:

The results of this study show the feasibility of proton irradiation of the heart left ventricle with an novel ultrasound based cardiorespiratory gating technology. Importantly, our results also suggest that changes in reproducibility in