Roentgen doses during diagnostic procedures.

Abstract

The ever-increasing exposure of man to ionizing radiations in medicine, industry, and warfare presents the problem of determining, with practical accuracy, the doses to which an individual may be subjected. Skin, depth, and volume doses used in therapy can be determined from tables on these subjects formulated by Quimby (11), Mayneord (21), and others. Formulae for dosages delivered by radioactive isotopes also have been described in the literature (25, 26). This report is devoted to describing a method by which skin, depth, and integral doses resulting from diagnostic radiologic procedures can be estimated. Leonard (1), in 1898, was the first to describe an “x-ray burn” in the American literature. Leddy and his associates (2–5) published a series of articles in 1935 and 1937 warning of the dangers associated with fluoroscopy. Braestrup (6), in 1942, calculated the average radiation doses that a patient would receive during several types of diagnostic radiologic examination. Smedal (7), also in 1942, published tables of roentgen outputs with several different filters, target-film distances, kilovoltages, and milliampere-seconds used in some of the diagnostic procedures. Martin (8), in 1947, showed by means of graphs the effects of various filters and focal-skin distances on the radiation dose received per second per milliampere at 70 kv.p. for several common diagnostic examinations. The above-mentioned reports and the experimental data recorded in the next section of this study demonstrate large variations in dose rates from different types of roentgenographic and fluoroscopic machines under supposedly identical conditions. The graphic and tabular information presented in this paper was formulated primarily for use in the Department of Radiology of the Hospital of the University of Pennsylvania, in which the measurements were made, and it should not be assumed that they are applicable elsewhere. However, it is believed that anyone wishing to use these values can do so by making ionization chamber readings on his own machine, using 1 mm. Al added filter, 26.4 inches target-chamber distance, and any convenient milliampere-seconds and kilovoltage, and comparing his result with the values given herein. If such values check fairly closely with those shown in Figure 3, these curves can be used for that machine. If there is a great difference, the ratio of the measured value to the value from Figure 3 will be a correction factor which will enable practical estimates to be made. Experimental Data The basic data described herein are air-dose rates measured at focal spot-chamber distances of from 30 to 100 cm. in the central beams of x-rays produced by 12 fourvalve rectified, 1 mechanically rectified, and 1 self-rectified roentgenographic and fluoroscopic units. Measurements of air-dose rates were made by means of a Victoreen condenser r-meter.