Mass Radiography: A new Weapon against Tuberculosis

Mass-radiography is approximately twenty years old. The earliest application of X-rays to the chests of apparently healthy persons in selected social groups, such as that of Chadwick in I924 was for research or epidemiological purposes rather than as a practical measure of casefinding. The method continued to be used by research organisations, especially in the U.S.A., and a mass of valuable epidemiological material rapidly accrued. It became clearly established that pulmonary tuberculosis can arise and spread without manifest symptoms, and that such disease may on occasion proceed to caseation, excavation, and subsequent healing, presenting at a later date gross multiple areas-of fibrosis and calcification in an individual who has at no time been conscious of ill-health. Such observations were of immense value in building up the sum of our present knowledge of the pathology of tuberculosis, but the scope of the method was, by its relatively large cost, always limited to researchers whose results were not necessarily judged by financial standards. Technical improvements in the fluoroscopic screen allowed Fellows (1934) to examine, with an accuracy comparable with that of X-ray photography, large numbers of employees of the Metropolitan Life Assurance Company, at no more cost than the original price of the machine, the current used in operating it, and his own salary. The fluoroscopic method remains, however, a heavy strain on the operator, and must be expected to miss a proportion of small soft lesions; neither does it provide a permanent record. In 1936 the Powers Rapid Paper method introduced a drastic cut both in cost of materials and in time consumed per examinee, while the full-sized image on paper was accurate enough to satisfy all but the most fastidious. Parallel technical advances, however, had meanwhile brought us the fluoroscopic image photographed on cinematograph film. X-rays could be taken in this way as rapidly as by the Powers method and rather more cheaply, and when viewed by projection on to a screen were found to reach a remarkable degree of accuracy. This so-called "miniature" method is the most popular at present. There is some divergence of opinion as to the best size of film, but 35 mm. has become standard in this country. Films can be taken comfortably at the rate of 500 per day, and interpreted by a radiologist at the rate of 300-400 per hour; abnormal findings or technical errors are verified by re-takes on full-sized film, averaging about 5 per cent of total examinations. The cost of the whole procedure depends obviously on much more than the price of film consumed, which is very small. Capital charges on apparatus and current overheads, of which the salaries of the operating team are a large item, largely determine the cost of each individual examination. The more X-rays taken, the fewer the re-takes necessitated by bad technique, and the steadier the rate of employment of the unit-the more economical is the method. Working at a reasonable rate over a year, a fair figure for such examination has been computed at about a shilling. So the method, while much less costly than any hitherto devised, still demands an expenditute per capitum equivalent to a packet of twenty Woodbines, a comparison which perhaps enables the question of cost to be viewed in proper perspective.