The prediction equations of the male and female chest wall thickness for measuring actinides within the lungs using HPGe detectors

This research was to empirically derive the male and female chest wall thickness (CWT) prediction equations, using ultrasonic technology and a two-, three- or six-detector hyperpure germanium (HPGe) array, for measuring actinides within the lungs. Presently, there is not a gender-specific CWT prediction equation derived for HPGe detection systems. The majority of the U.S. Department of Energy lung counting facilities are using HPGe detection systems for routine lung counting measurements and not the two-detector phoswich system. The current CWT equation was derived for photons with energy greater than 100 keV using a two-detector, 12.7-cm diameter phoswich lung counting system, male subjects only, positioned supine, and without measuring, the compositional thicknesses of the intercostal tissue (between the ribs) which are the muscle and adipose tissues. The lung areas observed by the phoswich and HPGe array detection systems are significantly different. The intercostal tissues observed by the HPGe arrays are presumed to be composed of more muscle tissue than the phoswich array due to the position of the HPGe detectors located closer to the sternum and encompassing a much smaller area of intercostal tissue. Therefore, the current CWT equation is presumed to be predicting CWT values which are less attenuating, thus, leading to overestimates in activity (nCi) reported within the lungs. Also, the current CWT equation is applied to both genders. According to the data specifications in ICRP75 Publication 23, the current CWT equation is presumed to be not applicable for estimating the female CWT due to the anatomical difference in male and female which is the breast tissue. Therefore, this paper empirically derives the male and female CWT prediction equations, using 33 male and 37 female subjects, ultrasonic technology and a two-, three- or six-detector HPGe array, for measuring actinides within the lungs.