In the June Issue of Medical Physics, Hoppe and Schmidt presented estimates of the organ and effective dose from an x-ray backscatter scan using a Rapiscan Secure 1000 single pose system . The paper presents Monte Carlo modeling results and takes its estimates of the spectrum and air kerma from existing measurements in the literature (e.g. the air kerma is taken from a report by Johns Hopkins University APL ). Hence the results of that study depend critically upon the method of converting air kerma to dose (organ and effective). We conclude that the source fluence and therefore all doses were overestimated by a factor of about 3.5 due to a mistake in the air kerma normalization. The geometry of some simulations was also incorrect due to a misreading of the location of the air kerma measurement with respect to the source.
Citation: Medical Physics
Pub Type: Journals
x-ray backscatter, air kerma, security screening, effective dose