ESTRO 2024 - Abstract Book

S4106

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2024

A method of emulating the ATP workflow was also developed, given data collected from ATS workflows, allowing for direct comparison (Figure 1(b). We emulated the most basic ATP workflow by rigidly registering the anatomy at the fraction one to each subsequent daily anatomy. The rigid shifts are applied to the dose from fraction one, with dose accumulation evaluated as before using these emulated doses, assuming dose invariance. We evaluated the dose accumulation using the MRI and dose plan for 64 prostate patients treated with SABR on the MRL under an ATS workflow with a prescription dose of 36.25Gy, collected from the MOMENTUM dataset. The differences in dose accumulation between the ATS and emulated ATP workflows were evaluated using a range of volumetric, near-maximum and near-minimum metrics. For brevity, we report mean and D 1cc differences.

Finally, we investigated the significance of volume change in OARs and target volumes between the start and end of treatment to assess the efficacy of each workflow for different degrees of anatomy change.

Results:

The accumulated difference over treatment (ATP-ATS) is displayed for each structure and metric in Table 1.

Structure

Metric

Average

accumulated

dose

difference (ATP-ATS) ± std (Gy)

CTV PTV

Mean Mean Mean Mean

-0.21 ± 0.84 -0.26 ± 1.42 -1.81 ± 2.51 3.93 ± 4.90 -1.68 ± 5.14 -0.18 ± 8.55 -0.23 ± 0.72

Bladder Rectum

CTV PTV

D 1cc D 1cc D 1cc

Bladder