Effective doses for different techniques used for chest radiography

A survey of X ray units, used for diagnostic chest examinations in the Leiden region, showed considerable variation in exposure conditions and techniques (conventional radiography, mobile unit, lung-shaped filters). Varying the exposure conditions, including focus-skin distance (FSD) and beam quality, as employed in PA chest radiography according to the survey, effective dose (E) was calculated by Monte Carlo simulation of radiation transport. Adult male and female patients were simulated with the mathematical phantoms ADAM and EVA, respectively. For a typical exit dose of 4 μGy, E ranges from 7 to 17 μSv. Thus, proper choice of technique parameters allows a 2.5-fold dose reduction. For similar conditions, E for EVA may differ up to 28% from its value for ADAM. Varying FSD only, differences in E may reach 34%. Lowest doses were found for ADAM at medium FSD, for EVA at small FSD. A small vertical shift (5 cm) in beam position results in a 10% change in E. Best beam quality for radiation protection is offered by large-HVL beams or, for ADAM, small-HVL beams plus lung filters. (Author)