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Skin Dose Evaluation From Three Different IMRT Planning Technique On Beast Cancer Radiotherapy

R He*, J Martinez, C Yang, University of Mississippi Medical Center, Jackson, MS

Presentations

PO-GePV-T-284 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: To study the dose to skin on a phantom from three different IMRT planning techniques and compare the measured doses using metal–oxide–semiconductor-field-effect-transistor (MOSFET) dosimeters to the calculated ones for breast cancer radiotherapy

Methods: Three different breast IMRT plans with 180 cGy per fraction were generated on a hypothetical planning target volume (PTV) representing a chest wall and two organs at risk (OAR), such as heart and lung drawn on a phantom (CIRS) image set. The PTV was contoured touching the surface of the patient. First plan was optimized to the PTV, while the second plan was optimized to a PTV-3mm, which is PTV subtracted by 3 mm from skin to prevent hot spots in skin. The last plan was optimized to the PTV+1cm by adding 1 cm virtual bolus as skin flash on top of the PTV for plan optimization only, which was taken away when performing dose calculation and the treatment was delivered without bolus. The skin doses were measured using 5 MOSFET dosimeters on top of the PTV delineated. The treatment planning system (TPS) and treatment machine used are RayStation version 10A and Elekta Versa HD.

Results: The biggest difference between calculation and measurement is 26.7% +-1.2% one Standard Deviation (SD) for plan 1 that optimizes directly on PTV including the skin, which means the TPS calculation has the biggest uncertainty on skin dose calculation in this scenario. The other two differences are 10.5% +-3.2% one SD for plan 2 and 9.9% +-3.3% one SD for plan 3. Plan 3 delivered the closed prescribed dose to skin and plan 2 did the least.

Conclusion: This study provided us some guidance in planning breast or chest wall using IMRT to use which planning technique to reduce or increase skin dose depending on the clinical consideration.

Keywords

Breast, Radiation Therapy, Surface Dose

Taxonomy

Not Applicable / None Entered.

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