R ECENT increases in the number of diagnostic X-ray examinations made in this country have caused attention to be paid to the quantity of radiation delivered to the population at large as a result of the X-ray examination of individuals. It is at present impossible to assess the possible genetical effects of such irradiation, and in all diagnostic measures it is essential that the least possible amount of radiation should reach the reproductive organs of patients, especially during childhood and the early part of adult life.Radiation can reach the reproductive organs either from the direct beam during investigations of the pelvic region or by scatter during investigations of other parts of the body. For males it can be measured directly by placing a suitable instrument in contact with the scrotum during the radiographic examination. For females, the quantity can only be deduced from measurements made on the skin, and the determination of factors to convert these into "ovary doses" becomes the primary problem. The work described in this paper included: measurement of the radiation reaching suitably a selected point on the skin for female patients during each routine type of diagnostic procedure; the determination of the factors necessary to convert these into ovary doses; deduction of the radiation received by the reproductive organs for male and female patients; and a statistical analysis to find the relative numbers of individuals exposed in each diagnostic procedure and how often they are exposed. The results were then used to indicate which procedures result in large doses, and the order of magnitude of the average dose to the reproductive organ per examination.Some "conventional" skin doses, i.e. radiation received on the axis of the beam on the surface of entry into the patient, have also been recorded.The quantity of radiation received by a patient can be influenced by a number of technical factors related to the apparatus used, e.g. beam filtration, field area, target-skin-distance, type of moving grid, type of film and screens and the kilovoltage. These have been investigated, and the results, which make it possible to indicate ways in which the radiation may be reduced, are included in this paper.

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Angiocardiography and cardiac catheterization have produced many new problems in radiology, and it is most important that both the cardiologist and radiologist should be aware of the dangers to which they may expose themselves and their patients. For example, in designing apparatus for angiocardiography it must be borne in mind that if this procedure is used for routine investigations care must be taken beyond that necessary in experimental work, since it is essential that all concerned should be adequately protected from both direct and scattered radiation. Unfortunately a knowledge of the output of the X-ray set, in terms of kilovoltage and.milliampere seconds, is insufficient to enable the quantity of radiation received by the patient and those in close proximity to the patient to be calculated. In this paper an attempt is made to show what factors must be considered in estimating the direct and scattered X-rays, and to give some indication as to how this estimation can be carried out. Little has been published in the past about the measurement of scattered radiation in diagnostic X-ray work, and the recommendations set out in the following paragraphs are based on experiments carried out in the X-ray Department at Guy's Hospital during investigations of routine cases.The measurements recorded in the following paragraphs were made with two main objects in view, (a) to ensure that the patient does not receive an excessive dose; and (b) to protect those near to the patient. Whereas the risk to the patient lies in administering a dose of X-rays sufficient to cause burning of the skin, the danger to those nearby arises from the fact that they are frequently exposed to radiation and must be protected from its long-term effects, viz. injury to the superficial tissues, and changes in the blood and bone marrow and reproductive organs. With the average quality ofthe X-ray beam used for these investigations, that is filtered by one millimetre of aluminium or its equivalent in other ways, the dose that will produce a first-degree erythema of the skin is about 150 rontgen units* delivered on one day. In connection with the filtration of the beam it is useful to note that an aluminium filter is necessary for safety and such a filter or its equivalent is frequently incorporated during manufacture. The purpose of this is to suppress the very soft radiation from the tube since such radiation is particularly harmful. The filter does not eliminate the risk of burning referred to previously, nor does it give any indication of the dosage. The maximum permissible whole body dose for persons who are regularly exposed to radiation, such as the radiologist, surgeon, and anmsthetist, has been fixed as 0 5 r. per week, or a dosage rate of 4 x 10-6 r. per second. For the hands, informed opinion tentatively regards 1'5 r. per week as the maximum permissible dose. At the outset we wish to emphasize the fact that although these investigations are diagnostic procedures nevertheless it is quite possible for the patient to receive a dose suff...

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