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Play-Doh as a Bolus Material in Electron Radiotherapy

H Shi

N Kahler, H Shi*, M West, C Nguyen, Tulsa Cancer Institute, Tulsa, OK 74133

SU-E-T-317 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

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.

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