http://www.researchonline.mq.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:22722 Certain polymer gels become turbid on exposure to ionizing radiation, a property exploited in medical dosimetry to produce three-dimensional dose maps for radiotherapy. These maps can be read using optical computed tomography (CT). A test phantom of complex shape ("layered tube") was developed to investigate the optical properties of polymer gel dosimeters when read using optical CT. Extinction coefficient profiles from tomographically reconstructed slices of the phantom exhibited several artifacts. A simple model invoking scattered light in the gel was able to account for all artifacts, which in a real dosimeter may have been mistaken for other phenomena, resulting in incorrect readings of dose. 2012-11-28T02:28:40.123Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:22440 There is a need for stable gel materials for phantoms used to validate optical computerized tomography (CT) scanners used in conjunction with radiation-induced polymerizing gel dosimeters. Phantoms based on addition of light-absorbing dyes to gelatine to simulate gel dosimeters have been employed. However, to more accurately simulate polymerizing gels one requires phantoms that employ light-scattering colloidal suspensions added to the gel. In this paper, we present the initial results of using an optical CT scanner to evaluate a novel phantom in which radiation-exposed polymer gels are simulated by the addition of colloidal suspensions of varying turbidity. The phantom may be useful as a calibration transfer standard for polymer gel dosimeters. The tests reveal some phenomena peculiar to light-scattering gels that need to be taken into account when calibrating polymer gel dosimeters. 2012-10-30T18:44:58.912Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:22456 There is a need for stable gel materials for phantoms used to validate optical CT scanners for the evaluation of radiotherapy gel dosimeters. Phantoms have previously been proposed based on addition of food coloring dyes to gelatine to simulate polymer gels. However, because optical extinction in these dyes operates via light absorption, they would be more suitable for simulating radiation sensitive radiochromic dosimetry gels in which the exposed region of the gel becomes more optically absorbing. To correctly simulate polymer type gels which operate via light scattering, it would be more realistic to add light scattering centers such as colloidal suspensions (sols) to the gels used in such phantoms. In this paper we present some of the results of the evaluation of a Vista optical CT scanner (Modus Medical Devices Inc.) using novel gel phantoms in which radiation exposed polymer gels are simulated by the addition of largely colorless sols of varying turbidity. 2012-10-30T18:44:31.027Z ]]>