| Since the discovery of x-rays, tissue substitute materials have been developed to aid in the investigation of irradiated tissues and improvement of diagnostic and therapeutic techniques. This research continues to explore their development with the fabrication of a solid tissue substitute material that simulates soft tissue. In this effort the soft tissue substitute defined in ICRU 46, was used as a filler material in a calibration BOMAB (Bottle Manakin Absorption Phantom) for In-Vivo counting systems. This type of phantom has utility during the calibration of gamma ray spectroscopy systems integral to in-vivo bioassay. Our tissue design was developed using guidance from ICRU 44, ICRU 46 and (Griffith 1980) research into polyurethane. The tissue substitute was made from commercially available materials, does not require unique laboratory equipment and can be modified to simulate different tissue types based on the ratio of our mixture and selective additives. A solid BOMAB offers significant advantages that resolve shipping hazards and leaking that arise from the use of aqueous filled phantoms, as well as the benefits of trapping off-gas in long lived natural chains, like radium, creating a calibration source in equilibrium that would outlive generations to come. The solid BOMAB was built using guidance from RESLs BOMAB procedure and ANSI 13.35. The concentration of radioactive material and its distribution in the solid BOMAB was developed using guidance from ANSI 13.30 and 49 CFR 173.436. The radionuclide 152Eu was used because it has a sufficient number of energy lines to create a multipoint calibration curve and based on the RESL development an adequate activity to minimize counting times. The solid BOMAB was verified against a NIST traceable aqueous filled BOMAB with the same radioactive material. The measured radioactivity in the solid BOMAB was found to be within 1% of its calculated spike activity at the 121, 344, 1112 and 1407 keV peaks. The In-Vivo counting system consists of two aluminum capped high purity germanium detectors, having 30% and 100% relative efficiency. This analysis was completed inside a vault made from pre-World War II steel, to minimize background interference. After calibrating the In-Vivo counting system with the solid BOMAB, empirical and cubic spline efficiency curves were developed and employed in the verification of a DOELAP performance testing BOMAB. It was found that these efficiency curves developed from the solid BOMAB calibration effort were able to verify the performance testing BOMAB based on the criteria set forth in ANSI 13.30. Therefore, this effort verified the tissue substitute for use in wide ranging applications and may serve as an adequate replacement for aqueous filled BOMABs for calibration and performance testing. |