[en] The papers presented at the 15th Scientific Conference of the Deutsche Gesellschaft fuer Medizinische Physik, held from September 27-28, 1984 in Nuernberg, F.R.G., give an account of the advances made with regard to quality control and management and to radiological safety problems and requirements in the fields of radiological and nuclear medical diagnostics and radiotherapy. (WU)

[en] Due to the short half-life of 13.3 sec of Kr-81m, the patient is exposed to radiation only during the actual nuclear medical examination, so that the dose received in general is very low. The radiation exposure nevertheless may get comparably high refering to other types of nuclear medical examination, as a result of long examination times required, and the generation of high activities (> 1850 MBq = 50 mCi). Radiation dose assessments available so far only refer to direct, constant application of Kr-81m to a specific organ, and to timely constant infusion or inhalation. The paper in hand investigates the radiation dose applied through intravenous infusion or injection of Kr-81m as a function of time. (orig./WU)

[en] Computer-aided routine performance checking of linear accelerators contributes to enhancing the radiological safety and reliability of the equipment. This is achieved by the computer's capacity to process a relatively large number of data in comparably short time (20 min. in the example given here), and to store these data for subsequent analyses and processing. (orig.)

[en] This field study has been carried out in order to collect information on the dose values (entrance dose, exit dose) and mean optical densities (blackening) generally obtained in routine mammography with the equipment available at a variety of hospitals. Another goal was to find out to what extent recent applications of new methods in this field have had an effect on those values. About 300 physicians of hospitals in Bavaria have been asked to participate in this study, of which 170 agreed to cooperate. (orig.)

[en] Proper radiotherapy has to harmonize the tasks of achieving tumour killing and prevention of side effects. Achievement of these goals particularly depends on the dosage and distribution of the therapeutic agent in space and time. Unfortunately, currently available information on dose-response relationships for known tumours and normal tissue is insufficient so that in practical treatment planning, radiotherapists have to rely on empirically obtained data. Quality control and quality assurance standards cover three partial aspects: the structure of the medical department in terms of personnel and equipment, the processes in the course of radiation therapy, and the treatment achievements compared on a regional, national, and international level. In the USA, these aspects are systematically studied since 1974, and are defined as national standards. There is no such approach in German speaking countries, so that there are difficulties in describing German national standards for these three aspects. What has been achieved so far is progress in terms of technology, as e.g. the use of such means as CT, nuclear spin tomography, monoclonal antibodies, computer-assisted irradiation planning, megavoltage radiation sources, and brachycurie therapy, which solved problems such as exact spatial localization of target volume and critical area, optimized irradiation planning and clinical dosimetry. What remains to be improved is the biological assessment of the radiation dose prescribed with regard to the tumour and surrounding normal tissue, exact positioning of patients, reproducibility of daily routine for patient and equipment adjustment, and immobilization of patients for radiotherapeutical sessions. (orig.)

[en] Specifications and performance data given by the manufacturers and practical checking of such data for quality assurance purposes always will remain a difficult task of great importance. Although international standards in this subject field are indispensable and helpful, medical physicists have to keep in mind that quality in radiation therapy is affected not only by these standardizable factors, but to a significant extent also by organic and biological factors, medical care, and experience. It seems to be dangerous to overestimate physical and technical aspects simply because they are measurable, but neglecting minimum equipment operation standards will create the same risk potential. (orig.)

[en] The application of the effective dose equivalent, Hsub(E), concept for radiological protection assessments of occupationally exposed persons is justifiable by the practicability thus achieved with regard to the limiting principles. Nevertheless, it would be proper logic to further use as the basic limiting quantity the real physical dose equivalent of homogeneous whole-body exposure, and for inhomogeneous whole-body irradiation the Hsub(E) value, calculated by means of the concept of the effective dose equivalent. For then the required concepts, models and calculations would not be connected with a basic radiation protection quantity. Application of the effective dose equivalent for radiation protection assessments for patients is misleading and is not practical with regard to assessing an individual or collective radiation risk of patients. The quantity of expected harm would be better suited to this purpose. There is no need to express the radiation risk by a dose quantity, which means careless handling of good information. (orig./WU)

[en] Radiotherapy of seminoma or Hodgkin's disease proved to be quite efficient, as shown by the 10-year survival rate of patients with seminoma, which is about 90 p.c., and that of patients with Hodgkin's disease, which is 70 p.c. This favourable prognosis is the reason why it is of particular importance to guarantee an optimum radiation protection in order to maintain the fertility of the patients. A multi-stage screening method has been worked out for this purpose and has been tested by means of TLD measurements on the tests of a modified Alderson phantom, applying a photon radiation of 6 or 10 MV. (orig./WU)

[en] Diagnostic radiology is a field facing the medical physicist with a large variety of tasks, ranging from assistance in equipment planning and invitation of tenders to installation control and monitoring and radiological protection. Work at sophisticated systems for dynamic function studies also includes image quality control, a task that exceeds the framework of legal requirements. (orig.)

[en] The backscattering factors for Co-60 radiation and for 4, 8, and 45 MV bremsstrahlung have been determined for various field dimensions. Also, measurements have been made on a variety of materials, applying the same radiation qualities as above, in order to define a basis for evaluating the backscattering contribution from inhomogeneities in the body. As regards the irradiation of implants, the paper explains a number of relatively simple methods to prevent the unwanted dose increases to about 50 p.c. (orig.)