Miniature thermoluminescent dosimeter absorbed dose measurements in tumor phantom models

Miniature teflon-imbedded CaSO4:Dy thermoluminescent dosimeter(s) (TLD) have been sized and cut to fit inside a syringe needle. These dosimeters have been shown to be linear in response to beta and high energy gamma radiation. This allows for their direct implantation into tumor-bearing animals undergoing radioimmunotherapy and subsequent measurement of dose deposition on a per organ basis. In order to perform these radiolabeled antibody dose measurements with sufficient accuracy, static calibration data must first be generated. Consequently, phantom models were constructed with artificial tumors of diameters ranging from 3-30 mm contained in a surrounding tissue equivalent medium. The TLD were used to characterize dose distributions in a radial direction from the center of the cylindrical tumor volumes containing 131I, 32P, or 90Y radionuclides. Absorbed dose measurements in the boundary region between tumor and outer medium were found to be dependent on the: tumor specific activity, average range of the beta radiation, and radial tumor dimensions.