Biomedical subjects
Publications and source records attributed to K Ewen.
To estimate risks involved in x-ray diagnosis, it is useful to employ the concepts of organ dose and integral dose, whereas the surface dose should be considered as unsuitable. Although the methods of measurement differ from each other, they can lead to comparable results, as is demonstrated in this article, eg, for computerised tomography of the skull.
The article gives the organ doses for whole body CT examinations of the thoracic region, the upper abdomen, the mesogastric and pelvic regions as well as of the lumbar vertebral column and for CT scanning of the skull. The examinations were performed using an Alderson-Rando phantom with the whole body computer tomograph Somatom DR2 supplied by Siemens and with the skull computer tomograph Siretom 2000, also supplied by Siemens. It was found that the magnitude of radiation exposure of the patient depends not only on instrument-specific properties, but also to a very large measure on the examination parameters and techniques which can vary considerably from one clinic to another.
The authors give a survey of the somatic radiation risk in X-ray diagnostics. A somatic dose index is calculated for different examination methods containing the organ doses to the red bone marrow, the lung, the female breast, and the thyroid gland and evaluating their somatic significance. If this somatic dose index by which the individual radiation risk is described, is multiplied by the examination frequencies per year in the German Federal Republic, one gets the somatically significant dose index, which is a measure of the collective somatic radiation risk. In this sense, mammography has the highest, and dental radiography the lowest collective radiation risk.
The roentgenologist is often confronted with the problem of checking on the proper adjustment of the tube voltage as part of quality control of medical x-ray equipment, either when it is in the process of installation or when servicing is required. The article describes a few non-invasive methods which differ from each other in respect of cost, effort and accuracy. With increased precision of voltage determination, the cost of the measuring instrument also increases, and in some cases the total amount of equipment and effort as well. However, the few relatively simple methods can also be employed with satisfactory results.
The doses received by the organs in case of spinal thin-layer computed tomography, conventional tomography and myelography of the inferior lumbar spine (with first portion of the sacrum) were determined with CaF2 thermoluminescence dosemeters in the Alderson Rando phantom. As compared to computed tomography, the organ doses of the conventional examination methods were lower within the region of primary radiation and higher within the region of scattered radiation. Generally, patients examined by spinal thin-layer computed tomography of the inferior lumbar spine run a greater somatic radiation risk than those submitted to conventional examination methods.
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The somatically significant dose index can be considered as a measure for the somatic radiation risk to which the population is exposed. Figures are stated for conventional tomography of the skull and thorax. These are compared with the corresponding data for other x-ray examinations, especially computerised tomography.
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During eleven high cervical percutaneous cordotomies using the image intensifier, the amount of exposure to X-radiation was measured at various sites on both the patient and the operator. The values lay below the maximum doses allowed by the radiation protection regulations (Röv; section 33. Para 1).
The risks from radiation exposure during radiological diagnosis has usually been estimated in relation to genetic changes. Relevant information has been expressed as the genetically significant dose. In this paper we attempt to produce an analogous measure for evaluating the somatic risk in the form of a somatically significant dose index for radiological and CT examinations. It is shown that, for both types of examination, the two risk factors may be entirely different.
A Federal German x-ray directive prescribes certain precautionary measures and modes of behaviour for persons professionally, i.e. occupationally, exposed to radiation. An essential prerequisite, which may appear trivial at first sight, is that both those responsible for radiation protection and the exposed persons themselves should know who must be classified as occupationally exposed to radiation. The present article goes into this problem by examining the conditions governing four groups of x-ray examinations involving the relatively most frequent periods of stay in the x-ray room on the part of the radiologist and his staff: x-ray examinations of the internal organs, urological x-ray examinations, angiographic/neuroradiologic x-ray examinations, surgery involving use of an image intensifier. It was found that even when taking a pessimistic view, e.g. regarding the switch-on periods, the number of occupationally radioexposed persons in an x-ray department is relatively low in relation to the total staff employed in that department.
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Phantom measurements in the vicinity of an angiographic installation with the image intensifier below the table and subsequently with the intensifier above the table have shown that the former arrangement produces three times as much radiation to the head, gonads and leg during screening than when the intensifier is above the table. This has been confirmed in clinical practice during angioplastic procedures in other units. There is also a factor of 2.6 in favour of the above table intensifier applied to the lens of the eye of the investigator Radiation to the hand of the investigator is at least half with the above table arrangement.
Exposure and image quality in xeroradiography were studied in a test object and in patient tomographic examinations of the chest. With increased tube voltage and added copper filtration, skin exposure was reduced up to a factor of 10 without loss of image quality.
The relatively high radiation exposure when applying mobile X-ray image intensifiers to surgical radiology can be distinctly reduced by the ultilzation of an electronic image memory, which makes visible as long as you like the last fluoroscopic image of a fluoroscopic scene on the viewing monitor without switching on the X-ray tube. As an average over various surgical examinations, the dose reduction compared with facilities lacking these image memories amounts to about 30%.
The somatic and genetic radiation exposure in abdominal CT examinations with Delta 50 and Delta 50 fast was measured via thermoluminescent dosimeters and compared with the exposure in conventional methods of x-ray diagnosis. With Delta 50 fast, the dose surface product for on examination of the pancreas is about 2900 Rcm2, and for an examination of the kidneys about 3400 Rcm2. It is thus comparable with a gastrointestinal examination or a urogram. The gonadal doses determined for CT are lower than those received from standard x-ray examination.