Update on patient radiation doses at a large tertiary care medical center

Radiation procedures in diagnostic radiology and nuclear medicine examinations, especially at referral centers, contribute a significant proportion to population dose; hence, there is a presumed detriment. Knowledge of the magnitude of dose from each type of exam is helpful in determining where to implement dose reduction efforts. Additionally, new records of dose data facilitate comparisons with past measurements. In this paper, updated patient exam dose data (frequency and effective dose equivalent) are provided for a large, comprehensive, tertiary care medical center that served more than 340,000 patients in 1997. Patient billing code data were used to study 31 different types of diagnostic exams encompassed in five major categories (angiography, fluoroscopy, radiography, nuclear medicine, and computerized tomography). Organ doses for each radiographic and nuclear medicine exam were estimated using published Monte Carlo conversion factors and appropriate exposure values. Estimates of organ doses were utilized to compute effective dose equivalent (EDE) per ICRP 26 and collective effective dose equivalent. Mean effective dose equivalent was also calculated for each exam category. Total collective effective dose equivalent had decreased from 1988 (2,030 person-Sv) to 1997 (1,817 person-Sv). The largest contributors to collective effective dose equivalent were angiography (768 person-Sv), computerized tomography (447 person-Sv), and nuclear medicine (355 person-Sv). Radiography (150 person-Sv) and fluoroscopy (97 person-Sv) contributed the least to collective effective dose equivalent. Mean effective dose equivalent contributions remained the same, with angiography accounting for the highest component, followed by nuclear medicine, computerized tomography, fluoroscopy, and radiography, respectively. Effective dose equivalent, collective effective dose equivalent, and mean effective dose equivalent values were calculated and tabulated in five major categories. These data provide updated information as to trends in exam and collective dose from 31 common types of radiologic exams performed at a large medical center, which can be used as an up to date baseline for analyses of trends in U.S. radiation doses due to medical imaging procedures. Although minor changes were observed in comparing the mean effective dose equivalent data to those of a previous study, substantial differences were evident in the collective effective dose equivalent data. This was due primarily to variations in the number of patients examined and changes in technology and practice.