Development of a three-dimensional radiation dosimetry system

Abstract

A radiochromic gel dosemeter in which ionizing radiation causes a color change in the visible wavelength region was produced. The roles of the dosemeter's active components were quantified with special consideration given to their effect on the system sensitivity and stability. Optimal composition was found to be 0.5 mM ferrous sulfate, 0.1 mM xylenol orange, and 25 mM sulfuric acid. The dose response is linear in the range 0.1–30 Gy and the dosemeter sensitivity was [formula omitted] where A is the optical absorbance measured at a wavelength of 585 nm. An optical tomography scanner with parallel light beam and charged coupled device detector was designed, built, and used to interrogate cylindrical samples of the dosemeter. The current version of the scanner can cope with samples up to 10 cm in diameter limited by the width of the light beam. A maximum of 512×512 pixels per slice images are obtainable with this scanner. Slice thickness as small as 0.14 mm was achieved that is much narrower than the value of about 6 mm achieved when using the MRI method of three-dimensional (3D) readout. The time to acquire a stack of 100 cross-sectional images with a resolution of 128×128 pixels per slice is about 20 min. The 3D imaging performance was tested with collimated x-ray beams, and the scanner high-resolution presentation demonstrated. © 2002, American Association of Physicists in Medicine. All rights reserved.