ESTRO meets Asia 2024 - Abstract Book

S337

Physics – Motion management and adaptive radiotherapy

ESTRO meets Asia 2024

each DIR strategy was evaluated using mean distance to agreement (mDTA) and Hausdorff distance (HD) metrics between contoured and deformably mapped OARs

Results:

48# for 10 patients were delivered. For one patient the final fraction was omitted, yielding 4# for analysis. For another, #3 was delivered on a conventional cone beam computed tomography (CBCT) Linac, therefore the dosimetric weighting for the CBCT # was split over the available #. Geometric evaluation results for each DIR strategy are summarised in Table 1. OW_OW DIR demonstrated superior geometrical performance with more optimal contour similarity over global FOR strategies, except in large and small bowel. Differences in mean dose ranged from -174 to 12 cGy, -139 to 93 cGy, and -145 to 131 cGy when accumulating doses using Global, GL-OW and OW_OW DIR, respectively (Fig 1a). D0.5 cc values are shown in Fig 1B.

Conclusion:

We evaluated three DIR strategies for estimating delivered dose for abdominal OAR. In this study, a clear geometrical advantage was observed for OW_OW DIR compared to global FOR-based DIR strategies. Further work is required to improved geometric accuracy of DIR in small and large bowel and estimate dose mapping uncertainties.

Keywords: dose accumulation, pancreas SABR, MR-guidance

References:

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3. Barber J, Yuen J, Jameson M, Schmidt L, Sykes J, Gray A, et al. Deforming to Best Practice: Key considerations for deformable image registration in radiotherapy. J Med Radiat Sci. 2020;67(4):318–32.

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