D Dunkerley*, D Hyer, J Snyder, S Yaddanapudi, J St-Aubin, University of Iowa, Iowa City, IA

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  D Dunkerley

PO-GePV-M-77 (Sunday, 7/25/2021)   [Eastern Time (GMT-4)]

Purpose: The adaptive planning workflow on the Elekta Unity MR-Linac is a multi-step process for each treatment. These processes differ depending on whether the adapt-to-position (ATP) or adapt-to-shape (ATS) workflow has been selected. In the ATP workflow, a rigid registration is performed between the daily MR and the reference image and a warm-start gradient descent optimization is used. In the ATS workflow, deformable registration, re-contouring, and full objective-specific plan optimization is used. The time required for each step is dependent on the user’s experience and is likely to improve with time.

Methods: The total time required to complete online adaptive treatment planning and plan review was tracked at three separate time intervals, 18 days starting in December 2019 (146 fractions), 50 treatment days starting in March 2020 (133 fractions), and 26 treatment days starting in January 2021 for 125 fractions for ATP and ATS workflows. The distribution of time for each step in the planning process was recorded during treatment. The longitudinal mean and standard deviation of the times associated with each step in the planning process were calculated and a two tailed t-test was used to test if the time reductions were statistically significant.

Results: Although changes in time were not statistically significant (p>0.05), a reduction in the mean time for certain planning steps was observed. The mean total time for ATP decreased from 15.7 to 14 minutes and decreased from 34.7 to 25.0 minutes for ATS over the three tracked time intervals. The detailed analysis of ATS planning times demonstrated a 40% decrease in the average registration (1.8 minutes) and contouring (3.9 minutes).

Conclusion: Experience with the online adaptive RT planning tools and process is likely to decrease the time required for each treatment.

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Keywords

Not Applicable / None Entered.

Taxonomy

TH- External Beam- Photons: adaptive therapy

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