Use of Radiation Detection, Measuring, and Imaging Instruments to Assess Internal Contamination from Intakes of Radionuclides Part III: Field Tests and Monte Carlo Simulations of Philips SKYLight Gamma Camera

ii PREFACE Part I of the present series described a study to evaluate radiation detection and imaging systems commonly found in hospitals to determine their suitability for rapidly scanning individuals for internal contamination, and to develop recommendations regarding their potential use (Anigstein et al. 2007a). That report described the measurement of count rates from single discrete radioactive sources of 241 Am, using a Philips AXIS gamma camera, an Atomlab thyroid uptake system, and a Ludlum waste monitor. A Monte Carlo computer model of the Philips AXIS camera was developed and validated against the experimental in-air measurements. The model was then applied to calculating count rates on two models of the AXIS camera from radionuclides uniformly distributed in the lungs of a stylized mathematical phantom of the human body, based on the ORNL phantom series described by Cristy and Eckerman (1987). Part II extended the earlier investigation by using realistic anthropomorphic phantoms to study the responses of four instruments to five radionuclides distributed in the lungs (Anigstein et al. 2007b). The experimental measurements were performed on a Rando Phantom—an anthropomorphic phantom that contains a human skeleton embedded in a tissue-equivalent 60 90 137 192 241 urethane rubber. The five radionuclides— Co, Sr, Cs, Ir, and Am—were selected from the 10 nuclides cited by the DOE/NRC Interagency Working Group on Radiological Dispersion Devices as being among the " isotopes of greatest concern " (DOE/NRC 2003, Appendix F). Ten encapsulated sources of each nuclide were placed in pre-drilled holes in the lung region of the phantom. Count rates from each nuclide were measured on the Siemens e.cam Fixed 180 gamma camera, an Atomlab thyroid probe, a Ludlum survey meter, and a Ludlum waste monitor. As described in Part II, the Los Alamos MCNPX (Monte Carlo N Particle eXtended) computer code was used to calculate calibration factors that relate count rates on these instruments to lung burdens of each of the five nuclides. A mathematical model of each of the instruments was constructed, using engineering drawings and other data obtained from the manufacturers. This model was combined with an MCNP model of a Rando Phantom, constructed from CT scans of this phantom (Wang et al. 2004). The combined model was used to simulate the response of each instrument to sources in the phantom, and the calculated results were compared to the experimental measurements. The agreement between the calculated and measured responses validated the MCNP …