Dose evaluation of transmission full-body scanners used in the Brazilian Penitentiary System

In this study we analyze the dose received by individuals inspected in a transmission full-body scanner used in Brazilian prisons and airports. As seen on different papers on this matter, the dose received per scan is very low and the total dose accumulated over a year can be neglected since people are seldom scanned, i.e. airports. However, in the particular case of Brazilian penitentiaries, these devices are used to scan the weekly visitors that come to see the inmates. In this situation, through the course of a year, the number of inspections can be of a significant amount, resulting in a non-neglectable dose for the inspected person. These full-body scanners consist of an X-Ray tube, usually in the range of 130-170 kV, that emits a narrow fan-shaped beam, with a detector across from the tube where the image is generated. In a transmission type scanner, the person being inspected is positioned between the tube and the detector. To evaluate the dose per scan in such equipment, several measurements were taken in three full-body scanners of the same model, so that not only the dose measurement could be done but also the assessment of the variation that occurs in the dose measured within a model type. These measurements were taken using an ionization chamber, due to the low dose produced by these scanning systems. Results of dose per scan for each type of device are presented. An assessment based on Brazilian regulations suggests a limitation to the number of times a person can be inspected using each type of full-body scanners analyzed. (author)