(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: Application of 3D printing and plastic scintillators as investigative tools to propose a one plan solution for post mastectomy chest wall planning applicable to both rotational and tangential treatments. Quantifying skin dose resulting from varying either planning parameters or bolus thickness and regimens.
Methods: Variable parameters in planning were PTV-to-skin proximity (for rotational treatment) and bolus thickness. Variable parameters during treatment were thicknesses of superflab and 3D printed bolus, brass mesh as well as different fill factors for 3D printed bolus. Detectors used for quantifying skin dose were OSLDs, diamond detector, gafchromic EBT3 film and an in-house scintillator. A 3D chest wall phantom printed in-house replicated a real patient and included inserts for the various detectors. Monte Carlo calculations on curved geometry and OSLD/film measurements on select patients were performed.
Results: To maintain flash, the most promising technique in rotational planning was using a 1 cm synthetic bolus and extending the PTV 0.5 cm into the bolus during optimization. Final dose calculations were performed without the bolus. Plans with flash showed the smallest sensitivity to positional changes in set-up. Without bolus skin dose varied between 70% and 90% of prescription depending on the planning technique. The application of different boluses during treatment showed a general trend that the magnitude of skin dose enhancement in tangents versus rotational treatments was not constant. Generally increasing the bolus thickness beyond 3 mm did not result in significant skin dose enhancement for both rotational and tangential deliveries.
Conclusion: As reported by other investigators, we found brass mesh to be a good candidate for one plan solution for both rotational and tangential plans. In-house 3D printing and plastic scintillators make investigations of this type (many variables) more accessible. More work is in progress to quantify the effects of obliquity especially in rotational treatments.
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