X-Ray Protection in Diagnostic Radiology

Abstract

Most studies of x-ray protection have been devoted to the high-voltage or supervoltage field, and a number of dependable reports are available on this subject. As a result there is today little difficulty in constructing and operating high-voltage therapy installations to meet even the most rigid requirements. This was demonstrated in a previous paper (1), where it was shown that the stray radiation was less than 1 per cent of the then accepted tolerance dose, 0.2 r per day, in those roentgen therapy departments which were provided with protection in accordance with the international recommendations (2). This has been further verified over a period of years by means of dental films carried by the staff of the roentgen therapy units of the Division of Cancer, Department of Hospitals, City of New York. In diagnostic roentgenology, on the other hand, it is more difficult to maintain such a high factor of safety, and in some instances the tolerance dose is greatly exceeded. There are several factors which make the question of protection in diagnostic radiology of particular importance. First of all, x-ray equipment is used most extensively for diagnostic purposes, and in many cases by physicians not specializing in radiology, to whom the main interest is the diagnostic result with too little consideration of safety. Often the use of so-called ray-proof apparatus results in a false sense of security. Furthermore, during fluoroscopy and certain radiographic examinations the staff is frequently exposed to stray radiation. Finally, the greatly increased diagnostic use of x-rays makes the cumulative dose received by the patient of possible significance from a genetic point of view. This phase of protection has been duly emphasized in various recent papers (3, 4). While this question will not be settled, at least quantitatively, for years to come, all reasonable steps should be taken to avoid unnecessary irradiation of the gonads of patients who have not passed the reproductive age. But neither should the other and more immediate effects be disregarded, as skin damage and detrimental systemic changes. In order to reduce these hazards, it is necessary to have a fundamental knowledge of all the physical factors affecting the protection problem, including the doses received by the patient and staff during various roentgenologic procedures. The purpose of this paper is to present information for some of the more common operating conditions, from which data for other and special technics may readily be calculated. The measuring instruments used in this work, shown in Figure 1, were similar to those described in our earlier study of stray radiation in the high-voltage field (1). The ionization chambers had a volume from 600 c.c. to less than 1.0 c.c., giving a sensitivity range from 0.001 to 35.0 r. Where still greater sensitivity and directional effect were required, a Geiger-Müller counter was used.