Suitability of LiF:Mg,Cu,P and Al2O3:C for low dose measurements in medical imaging

The aim of the study was to demonstrate the applicability of LiF:Mg,Cu,P and Al2O3:C in two low dose applications in medical imaging - neonate X ray examinations and dual-energy X ray absorptiometry (DXA). Dose response was investigated using multiple exposures and shown to be linear for both applications. Neonate phantom measurements were performed at 54 kV(p). Reproducibility was evaluated at 2.5 mA.s, a value characteristic of a neonatal chest X ray. In-phantom doses using exposure factors as low as 54 kV(p) and 1 mA.s (correlating to an approximate skin entrance dose of 35 +/- 10 mu Gy) can be assessed with reproducibility +/-20% (1 SD), the same order of magnitude as the reproducibility of the exposure. DXA was performed at 135 kV(p) on a Lunar Expert bone densitometer with a scan area of 18 cm x 17.3 cm. Skin entrance dose was calculated to be 440 mu Sv, by extrapolation from a calibration at higher doses on a Stabilipan II X ray therapy unit. Total body effective dose for an AP spine and femur scan were estimated as 56 mu Sv and 4 mu Sv/13 mu Sv (ovaries excluded/included), respectively.