A survey of X ray units, used for diagnostic chest examinations in the
Leiden region, showed considerable variation in exposure conditions a
nd techniques (conventional radiography, mobile unit, lung-shaped filt
ers). Varying the exposure conditions, including focus-skin distance (
FSD) and beam quality, as employed in PA chest radiography according t
o the survey, effective dose (E) was calculated by Monte Carlo simulat
ion of radiation transport. Adult male and female patients were simula
ted with the mathematical phantoms ADAM and EVA, respectively. For a t
ypical exit dose of 4 mu Gy, E ranges from 7 to 17 mu Sv. 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 w
ere found for ADAM at medium FSD, for EVA at small FSD. A small vertic
al shift (5 cm) in beam position results in a 10% change in E. Best be
am quality for radiation protection is offered by large-HVL beams or,
for ADAM, small-HVL beams plus lung filters.