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Characterization of Real Time Surface-Tracked Deep Inspiratory Breath Hold (DIBH) Displacement in Left Breast Radiotherapy

N Cao

A Kalet , N Cao*, L Young , J Meyer , University of Washington, Seattle, WA


SU-I-GPD-J-8 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The purpose of this study is to evaluate the consistency of motion tracking during DIBH radiotherapy for left-sided breast cancer patients utilizing the Calypso real-time surface tracking system (v 3.0.924).

Methods: A retrospective set of 29 patients treated in 2016 for left breast cancer using DIBH technique was selected. Patients underwent 16, 20, 25, or 28 fractions depending on prescription. Patient tracking data were obtained by converting anonymized raw traces (~25Hz sampling) using research conversion software. Summary analyses were performed to characterize relative 3D displacement from a 'set-zero' point (where coordinates are zeroed out at maximum patient inspiration). Data were analyzed for mean and standard deviation (SD) of displacement for both the entire course of treatment and on a fractional basis. Data were also evaluated weekly to evaluate trends.

Results: Mean 3D (radial) displacement during beam-on breath hold over all patients, all fractions, was calculated to be 0.19 ± 0.03 cm. We found that the average displacement in fractions 6-10 was reduced compared to the first week (fractions 1-5) as well as lower SD (t = 2.18; p = 0.033). DIBH displacement and SD variations stabilized after the second week of treatment. When evaluated on weekly basis, both average and deviation do not significantly change compared to that of the whole course or among other weeks. Overall, the SD of breath hold motion is consistent with system evaluation presented in Belanger et. al.(JACMP, 17(4), 2016).

Conclusion: The distribution of displacement shows that reproducibility (hitting the same displacement mark for every breath) has potential for improvement. Future work includes associating BH performance to other clinical patient factors to better predict ability to produce stable breath holds and provide coordinated services to affect those factors during/prior to treatment.

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