The justification for the safety of these machines rests on two assertions. The first
assertion is that the radiation used does not penetrate beyond the skin (for references
on this subject see (Kaufman 2010)), second, that the effective dose is no more than
0.1 (or variously 0.05, 0.03, 0.02 or 0.01) microSv (National Council on Radiation
Protection and Measurements 2003a, 2003b).
As we discuss below, at the kilovoltage (kVp) setting of the units in use, 50 kVp
and 125 kVp, penetration is a given since these are diagnostic x-ray unit settings,
and diagnosis depends on penetration through a subject.