Room: Exhibit Hall
Purpose: Evaluate the dosimetric performance of pliable, self-fading, radiochromic sheets of polyurethane.
Methods: Variations of the radiochromic plastic Presage were prepared in 1 cm cuvettes and 22x22x0.32 cm pliable sheets. Leuco crystal violet was chosen for its high dose sensitivity and slow fading rate. Cuvettes samples were measured in an custom absorption spectrometer and sheets were imaged with a prototype optical cone beam computed tomography scanner or a prototype scanning spot densitometer at 590 nm. Irradiations were performed with 6 MV photon beam. Sheet thickness was measured on a 5 cm grid using a machinistâ€™s dial gauge.
Results: Sheets had a thickness of 0.32 cm with a measured uniformity to 1%. Local variations in dose response exceeding 20% were recorded. Optical transmission varied due to residual mold release on the samples. Gentle cleaning with methanol and soapy water improved optical uniformity. Samples were visibly sensitive to ambient lighting and unnecessary exposures were minimized. Color change due to absorbed dose was stable in less than 5 minutes. The dose response of ~0.3 cm-1 Gy-1 at 590nm, was linear to > 60 Gray. Dose images faded over several days. Dose response decreases following fading. After higher doses, for example 40 Gy, fading is incomplete.
Conclusion: A high sensitivity, pliable, radiochromic plastic sheet is under development. It appears to be reusable at lower doses, for example <20 Gy. More effective cleaning techniques are required before the uniformity of dose response can be accurately assessed. This may become a very useful clinical, 2D dosimeter.
Funding Support, Disclosures, and Conflict of Interest: John Adamovics is President of Heuris Inc.