RELATIONS BETWEEN EFFECTIVE DOSE, EFFECTIVE DOSE-EQUIVALENT, AREA-KERMA PRODUCT, AND ENERGY IMPARTED IN CHEST RADIOGRAPHY

Knowledge of the relation between the effective dose, E (ICRP 60) and the area-kerma product or the energy imparted, epsilon, to the patient during a number of standardised X ray examinations would facilitate t he estimation of risk related dose values in clinical situations. To f acilitate comparisons with earlier data, it would also be interesting to establish the relationship between effective dose and effective dos e equivalent, H-E, (ICRP 26). To estimate both E and H-E in PA chest r adiography, measurements of the absorbed dose to different organs were performed with thermoluminescence dosemeters placed in a water-filled phantom with the geometry of a 70 kg adult. During the X-ray investig ations of the phantom, measurements of the air kerma integrated over t he beam area were performed to determine the energy imparted, epsilon. The ratios between E and epsilon for three different radiation qualit ies between 100 and 140 kV(P) were found to be between 13 and 15 mSv.J (-1). The corresponding ratios between E and the area-kerma product va ried between 1500 and 2800 mSv per mGy.m(2). The ratio between H-E and epsilon was found to be 17-18 mSv.J(-1). With the X ray equipment use d in this study, the mean value of E for 36 adult patients undergoing PA chest examinations was 35 +/- 10 mu Sv (1 SD) and the mean H-E valu e 44 +/- 11 mu Sv (1 SD). In chest radiography, the numerical value of the effective dose is thus approximately 20% lower than that of the e ffective dose equivalent.