A re-evaluation of the 'saturated scatter' method for estimating the energy imparted to patients during diagnostic radiology examinations

Abstract

Central-axis depth dose data for diagnostic qualities (1-4 mm Al HVL [half value layer]) were used to calculate the total energy imparted to patients or phantoms during X-ray examinations. A saturated scatter method was used and allowance is made for the finite dimensions of the patient by using PDD [periorbital directional Doppler] data for large but finite field sizes. For the purpose of integration, PDD data was represented as a function of depth by 2 exponential components. Data in the form of energy imparted per unit central-axis surface dose and per unit surface X-ray field are tabulated as functions of kVp, 1st HVL, phantom thickness and the field size of the original PDD data. Comparison with energy fluence calculations of total energy imparted made by other workers indicates good agreement under similar phantom and X-ray quality conditions, although it is noted that anatomical variations between patients will in practice lead to uncertainties in the total energy imparted.