SU-E-T-317: Play-Doh as a Bolus Material in Electron Radiotherapy

Abstract

Purpose: The purpose of this study is to determine dosimetric properties of Play‐Doh as bolus in clinical electron beam radiotherapy. Methods: Electron beam energies of 6, 9 and 12 MeV were used. Play‐Doh with a thickness of 0.5 and 1cm were placed on top of a plastic water phantom. During all PDD curve measurements the SSD was maintained at 100cm, while utilizing a PTW Markus Model N23343 parallel plate chamber for the measurements. Shifts and absolute dose ratio at Dmax between the Play‐Doh PDD curve and plastic water PDD curve were calculated using an unconstrained nonlinear optimization method. The same procedure was repeated using the Superflab bolus material for comparison. Results: The comparison of depth dose curves normalized to Dmax of the plastic water for each electron energy and bolus material show that the Play‐Doh and Superflab cause the PDD curve to shift upstream. For a bolus of 0.5 cm of Play‐Doh or Superflab, the shifts were approximately 0.1cm upstream relative to plastic water. However, for 1cm of Play‐Doh the shift was approximately 0.5cm upstream for all energies while Superflab still had a shift of about 0.1cm. The absolute dose at Dmax for each set of measurements using the different bolus materials were all within ±1% of plastic water. Conclusion: The PDD curve shifts for 0.5cm of the bolus material were within 0.1cm for all configurations. For 1cm of Play‐Doh the shift was about 0.5cm upstream; while shifts for Superflab were within 0.1cm. The absolute dose with different bolus material was within 1% of plastic water. Based upon this investigation, it is important that clinicians understand the effect of bolus material on the PDD for electrons.