Sci‐Fri PM: Planning‐07: A low diffusion radiochromic gel dosimeter for three‐dimensional radiation dosimetry

Abstract

To develop a low diffusion radiochromic leuco crystal violet (LCV) hydrogel utilizing micelles, for three-dimensional (3-D) radiation dosimetry. Concentrations of LCV dye, Triton X-100 and trichloroacetic acid were varied to determine the optimal gel sensitivity for optical computed tomography (CT). Using a laser optical CT scanner at λ = 594 nm, diffusion rate measurements were performed on half-irradiated (6 MV x-rays) cuvette gel samples made with and without surfactant, respectively. A cylindrical 1 L gel volume was irradiated with a 12 MeV electron beam (Varian Clinac 2100C) to a dose of 30 Gy and scanned with cone- beam optical CT at λ ∼ 590 nm (Vista™, Modus Medical Devices Inc.). The most radiation sensitive gel formulation was found to be: 1 mM LCV, 4 mM Triton X-100, 30 mM trichloroacetic acid and 4% gelatin. The diffusion rates of a LCV gel without and with surfactant present were about 2 and 20 times lower than the Fricke xylenol-orange gel system, respectively. Comparison of the central axis gel attenuation coefficients normalized at depth of maximum dose (dmax ) with TG21-corrected ion chamber data, were in agreement, thus, indicating energy and dose-rate independence. Radiochromic LCV micelle gels show minimal diffusion effects and a dose response that is linear, energy and dose-rate independent. Optical CT scanned LCV micelle gels are a promising system for 3-D dose verification. Two of the authors (JB, KJ) have a licensing agreement with Modus Medical Devices Inc. concerning the commercialization of Vista™.