title: Characterization of a new radiochromic three-dimensional dosimeter.
abstract: The development of intensity-modulated radiotherapy (IMRT) has created a clear need for a dosimeter that can accurately and conveniently measure dose distributions in three dimensions to assure treatment quality. PRESAGE is a new three dimensional (3D) dosimetry material consisting of an optically clear polyurethane matrix, containing a leuco dye that exhibits a radiochromic response when exposed to ionizing radiation. A number of potential advantages accrue over other gel dosimeters, including insensitivity to oxygen, radiation induced light absorption contrast rather than scattering contrast, and a solid texture amenable to machining to a variety of shapes and sizes without the requirement of an external container. In this paper, we introduce an efficient method to investigate the basic properties of a 3D dosimetry material that exhibits an optical dose response. The method is applied here to study the key aspects of the optical dose response of PRESAGE: linearity, dose rate dependency, reproducibility, stability, spectral changes in absorption, and temperature effects. PRESAGE was prepared in 1 x 1 x 4.5 cm3 optical cuvettes for convenience and was irradiated by both photon and electron beams to different doses, dose rates, and energies. Longer PRESAGE columns (2 x 2 x 13 cm3) were formed without an external container, for measurements of photon and high energy electron depth-dose curves. A linear optical scanning technique was used to detect the depth distribution of radiation induced optical density (OD) change along the PRESAGE columns and cuvettes. Measured depth-OD curves were compared with percent depth dose (PDD). Results indicate that PRESAGE has a linear optical response to radiation dose (with a root mean square error of -1%), little dependency on dose rate (-2%), high intrabatch reproducibility (< 2%), and can be stable (-2%) during 2 hours to 2 days post irradiation. Accurate PRESAGE dosimetry requires temperature control within 1 degrees C. Variations in the PRESAGE formulation yield corresponding variations in sensitivity, stability, and density. CT numbers in the range 100-470 were observed. In conclusion, the small volume studies presented here indicate PRESAGE to be a promising, versatile, and practical new dosimetry material with applicability for radiation therapy.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: P Y
authors.initials: PY
authors.lastname: Guo
authors.forename: J A
authors.initials: JA
authors.lastname: Adamovics
authors.forename: M
authors.initials: M
authors.lastname: Oldham
mesh_terms: D004307:Dose-Response Relationship, Radiation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D021621:Imaging, Three-Dimensional / Q000295:instrumentation* / Q000379:methods; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D041622:Tomography, Optical / Q000295:instrumentation*; D014965:X-Rays