Review Draft An Evaluation of Hospital Radiation Detectors for Use in Screening Potentially Contaminated Individuals

The detonation of an improvised nuclear device or a radioactive dispersal device (RDD) would lead to widespread radioactive contamination, including the potential contamination of individuals. If such an event were to happen, it would be desirable to have various means of rapidly scanning individuals to determine if they have either external or internal contamination and to be able to determine when decontamination procedures have been successful. Nearly all hospitals provide nuclear medicine services for their patients. Therefore, most hospitals already possess various pieces of radiation detection equipment, including gamma cameras, thyroid uptake counters, Geiger-Mueller counters, and other portable radiation detection and measurement instruments. In addition, because of concerns over radioactivity inadvertently leaving the hospital in normal trash or over receiving patients in the emergency department who might be unknowingly contaminated with radioactive materials, a number of hospital have installed portal monitors that are capable of detecting low levels of radioactivity. SC&A, Inc., in collaboration with the Hershey Medical Center (HMC), performed studies to determine the suitability of radiation detection and imaging systems commonly found in hospitals for rapidly scanning individuals for internal contamination. The present chapter describes field studies to evaluate the potential use of nuclear medicine gamma camera systems, thyroid uptake counters, and portal monitors for detecting and measuring low levels of internal contamination. Chapter 2 describes the use of computer models to simulate the response of two models of gamma cameras to radionuclides distributed in the lungs of an anthropomorphic phantom based on Reference Man. Various phantoms were potentially available for this study, including a Rando Phantom, 1 and a chest and torso phantom 2 used in the nuclear power industry for whole body counting (see Figure 1-1). However, these phantoms could not be loaded with the readily available sources used for these measurements without permanently altering the phantom, such as by drilling larger holes, which made them unsuitable for use in the present study. To obviate these difficulties, a simplified phantom was constructed from slabs of poly(methyl methacrylate) (PMMA), a clear plastic commonly known as acrylic and sold under various brand names, including Plexiglas®, Lucite®, and Acrylite®. PMMA has the empirical chemical formula (C O H) and a typical density of 1.19 g/cm. 3 5 2 8 n Prior to adopting the acrylic phantom, its radiation absorption properties were compared to equal thicknesses of the Rando Phantom. When the results showed that the two materials produced the …