An Investigation of Dosimetric Effects From Handlebars During Total Skin Electron Therapy
Presentations
PO-GePV-T-38 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: Total skin electron therapy (TSET) is a radiotherapy technique to treat Mycosis Fungoides; a condition where tumors form on the skin. Spoiled, low-energy electron beams (3-7 MeV) can be utilized to treat very superficial lesions on the skin. The Stanford method consists of six patient-oriented dual-fields that uniformly deposit a prescribed dose of 36 Gy to the skin. Commonly, skin areas that do not react to the radiation require a radiation boost. To aid in patient comfort and treatment position reproducibility, handlebars may be used; however, poorly characterized handlebars may attenuate low-energy electrons. The purpose of this study is to assess the dosimetric effects from holding handlebars during TSET.
Methods: All measurements were performed with a newly commissioned high-dose rate (2500 MU/min) 6 MeV energy (Varian TrueBeam) that is spoiled by 10 mm Lucite. At our center, the Stanford six dual-field technique (gantry angles of 288° and 252°) is employed at an SSD of 424.5 cm on a total body irradiation stand by Radiation Products Design, Inc. Both, parallel-plate chamber (P11) and OSLD measurements were acquired at an off-axis (OAX) position typical for hand placement. Three configurations were investigated: no attenuation, handlebar, and handlebar with bolus (1cm, Superflab) to simulate additional self-shielding from fingers; all measurements were performed with an SAD of 424.5 cm to assess relative attenuation effects.
Results: The average dose from both measurement modalities (P11 and OSLD) decreased by 79.8 ± 6.3% and 82.2 ± 5.9% when comparing the handlebar and handlebar/bolus to the standard (i.e. no buildup), respectively, indicating a large attenuation by the handlebars.
Conclusion: We recommend investigating low-energy attenuation by handlebars when commissioning TSET to guide personalized clinical decisions, such as handlebar usage, radiation boosting of the palms, and, if possible, educating the patient to place opened-hands before the handlebars.
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Keywords
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Taxonomy
TH- External Beam- Electrons: dose measurement
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