X-RAY-BEAM ENERGY, SCATTER, AND RADIATION RISK IN CHEST RADIOGRAPHY

Effective doses for patients undergoing chest radiography were compute d utilizing updated weighting factors, published organ doses and measu red entrance doses, The effective dose decreases with beam energy (kVp ) and reaches a minimum value after 100 kVp, with the values when a gr id is used (6.90 mu Sv) being 145% higher at this energy than when no grid is used (2.82 mu Sv). The uncertainties associated with derivatio n of the tissue weighting factors are shown not to affect the point at which risk is minimized, Use of the effective dose as the measure of risk does not require special treatment of the remainder tissue as wit h use of effective dose equivalent, The effective dose required for ra diographs of constant optical density was examined to incorporate the behavior of the detector's response to energy and compare results to p revious work where exit dose was held constant. The effective dose at 120 kVp with a grid (6.84 mu Sv) is compared to an estimate of that as sociated with the current kVp distribution (14.55 mu Sv). Since image quality is enhanced by the grid, its use in conjunction with a beam en ergy of 120 kVp could maximize the benefit/risk ratio in chest radiogr aphy and should be considered for universal implementation, Such adopt ion could reduce the population risk compared to current practice.