Purpose: The purpose of this work was to evaluate the statistical distribution of patient dose for different examinations by using the data stored in a DICOM image archive of a direct digital radiography system.
Materials and methods: An automatic procedure to extract dose data and exposure parameters from the image archives was implemented. During a 4.5-month period, 8,292 images were collected. Exposure parameters and the air kerma area product (P (KA)) stored in the image DICOM header were examined for each image. The entrance surface air kerma (K (a,e)), a quantity comparable to the current diagnostic reference levels (DRL), was estimated considering the P (KA) and the geometric parameters of each examination.
Results: P (KA) and K (a,e ) distributions showed highly variable values. The obtained K (a,e ) values were substantially lower than the DRL. DRL were more than six times the mean value of K (a,e ) distribution for the abdomen anteroposterior (AP) and lumbar spine lateral (LAT) projections, whereas the ratio was equal to 2.7 for posteroanterior (PA) chest examinations.
Conclusions: The method adopted proved to be effective for characterising the dose of each examination by means of the statistical analysis of the dose quantities over extensive samples. The dose values obtained and the comparison with the DRL showed that this radiographic device allows substantial dose savings compared with estimations made for nondigital or for phosphor-based systems.