Number and distribution of roentgenologic examinations for 100,000 people.

Abstract

THE USE OF ionizing radiation in medicine has reached such proportions that the resulting exposure to man requires re-evaluation. The gonadal dose, particularly, needs scrutiny, since the induction of deleterious mutations is the most important effect produced by the amounts of radiation under investigation. The world literature can be reviewed in the United Nations Report (3). An accurate estimate of the gonadal or absorbed dose from diagnostic roentgenology is difficult. The estimate for the United States from all medical uses as given in the Laughlin and Pullman report of 1956 (2) is: “The thirty year effective gonad dose per person for both x-ray diagnostic examinations and radiation therapy treatments thus is estimated to be at least 2 ± 1 roentgens and is more probably about 5 ± 3 roentgens.” Later, in this same report, a figure of 4.0 r is given as the probable gonad dose resulting from diagnostic radiologic examinations. Estimates with such wide limits illustrate the difficulty of arriving at a precise figure. The figure of 4.5 r has been widely quoted as representing the dose per person from medical uses, and rarely are the limits of accuracy designated. To produce reliable estimates of the dose contributed by diagnostic radiology, the following information is required: 1. The number and distribution by age and sex of the diagnostic examinations in the population. 2. A knowledge of the mechanical and electrical characteristics of the radiologic equipment and their effect on dose. 3. A knowledge of the technics and their contribution to gonadal exposure. 4. The variability in gonadal exposure due to the size and weight of the patient. This report investigates only the first of these requirements. The“probable average exposure per examination" resulting from evaluation of numbers 2, 3, and 4 will be those of the Laughlin and Pullman study of 1956. Webster and Merrill (1) showed the decreases in the gonadal dose that were obtained by assuming different“average exposures,” such as prevailed in their installation. Such assumptions resulted in a calculated total dose at the lower level of the estimates of Laughlin and Pullman. Methods The group selected for this study were all members, for the full year studied, of the Kaiser Foundation Health Plan, which offers complete medical care to its registrants; thus any socio-economic bias is minimized. The study covered 2 consecutive years. No restrictions on the use of diagnostic radiology were practiced in any clinic of the facility studied. Thus, as far as could be determined, the results reflect the radiological needs of the sample in a Plan where a high percentage of the attending physicians are specialists.