Personnel protection during cardiac catheterization with a comparison of the hazards of undercouch and overcouch x-ray tube mountings.
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In order to calculate the thicknesses of protective barriers requried in departments of radiodiagnosis for walls, floors, ceilings, protective screens, etc., it is necessary to make an assessment of work load and occupancy factor in each direction. In order to ensure that barriers are safe, it is customary to assume that all the radiological procedures are carried out at the greatest kVp value used in the room in question, and to look up the necessary thicknesses from prepared tables. In fact, only a small fraction of work load is carried out at the highest kilovoltage, and also it is found that a considerable fraction of the total work load is directed downwards. A computer program has been written to use data available from comprehensive analyses of work load broken down into suitable kVp intervals. As the cost of providing the necessary protective barriers can be anything from a few hundred pounds to several thousand pounds, the use of exact values for work load separated into kVp ranges for each direction can lead to substantial savings in cost amounting to hundreds of pounds per room whilst still satisfying the requirements of the Code of Practice for the Protection of Persons against Ionizing Radiations arising from Medical and Dental Use (HMSO, 1972). Departmental surveys were carried out to establish the distribution of work load in kVp and direction, and also to ascertain dosage levels to the staff and within existing rooms. The results show that in practice the doses are such that the reduced barriers found by the method described would be entirely satisfactory.
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A simple rotational total skin electron irradiation technique utilising a single large field electron beam is presented. Clinical and technical aspects of the technique are discussed and treatment results for the first 10 patients treated for widespread mycosis fungoides reported. The technique is simple and well tolerated by patients, and can easily be implemented in centres utilising electron beam radiotherapy.
The radiation safety practices in a group of 25 UK and USA hospitals have recently been assessed. This took the form of detailed inspections of some 62 medical radiation departments, including Diagnostic X-ray, Radiotherapy, Nuclear Medicine and Pathology/Research (Radionuclide) Departments. Empirical expressions called "Radiation Safety Indices" were devised to evaluate the incidence of personal doses and radiological incidents occurring from 1977-82 and to characterise the safety facilities, procedures, supervision and educational techniques in each department. An outline is given of national legislative material and voluntary codes of conduct, together with the results of the departmental inspections. The computed indices are presented graphically and an analysis given of apparent national trends.
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A new high-energy neutron therapy facility has been installed at the Douglas Cyclotron Centre, Clatterbridge Hospital, Merseyside, in order to extend the clinical trials of fast neutrons initiated by the Medical Research Council. The neutron beam is produced by bombarding a beryllium target with 62 MeV protons. The target is isocentrically mounted with the potential for 360 degrees rotation and has a fully variable collimator. This gives a range of rectilinear field sizes from 5 cm x 5 cm to 30 cm x 30 cm. Basic neutron beam data including output, field flatness, penumbra and depth-dose data have been measured. For a 10 cm x 10 cm field, the 50% depth dose occurs at 16.2 cm in water and the output is 1.63 cGy microA-1 min-1 at the depth of dose maximum. The effectiveness of the target shielding and the neutron-induced radioactivity in the treatment head have also been measured. It is concluded that the equipment meets both the design specifications and also fully satisfies criticisms of earlier neutron therapy equipment. A full radiation survey of the centre was also carried out and it was found that radiation levels are low and present no significant hazard to staff.
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The sealed source operational policies employed at the Bristol Radiotherapy and Oncology Centre were originally designed to meet the requirements of the 1972 Code of Practice by ensuring that individual personnel doses were kept below the relevant quarterly and annual dose limits. In 1982-1983, measures were taken to improve personnel radiation safety within the brachytherapy treatment facility by (a) making preparations for the introduction of Selectron medium-dose-rate (MDR) afterloading systems at the centre for intracavitary brachytherapy and (b) reviewing the operational policies to ensure that they meet the more stringent requirements of the ALARA (as low as reasonably achievable) principle, a principle subsequently embodied in the 1985 UK ionising Radiations Regulations (IRR 85). When considering the implications of making existing single-bedded side wards, originally designed for low-dose-rate brachytherapy and suitable for the new systems, the cost of the extra protection required to reduce the instantaneous dose rate in the ward corridors adjacent to the treatment room to less than 7.5 microSv h-1 had to be determined. On the basis of the cost-benefit analysis, it was decided not to provide additional shielding but rather to introduce administrative controls based on local rules which contained systems of work and the operational policies for the afterloading systems. After using the MDR afterloading systems for 2 years, a period in which there has also been a marked increase in interstitial brachytherapy, an analysis was made of the doses received by nursing staff over the past 8 years. This has shown that, in spite of higher dose rates in the corridor areas because of the use of an MDR system and the increase in interstitial techniques, the doses to ward nurses have been significantly reduced by encouraging staff to comply with the ALARA principle and the introduction of afterloading systems.
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A numerical method has been developed to estimate the organ doses and effective dose-equivalent for patients undergoing three "complex" examinations (barium meal, barium enema and intravenous urography). The separation of radiological procedures into a set of standard numerical views is based on the use of Monte Carlo conversion factors and measurements within a Remab phantom. The radiation doses measured in a phantom for such examinations have been compared with the predictions of the "numerical" method. Dosimetric measurements with thermoluminescent dosemeters attached to the patient's skin along with measurements of the dose-area product during the examination have enabled us to derive organ doses and to estimate the effective dose-equivalent. Mean frequency weighted values of dose-area product, energy imparted to the patient, doses to a set of organs and effective dose-equivalent in the area of Madrid are reported. Comparisons of the results with those from similar surveys in other countries have been made.
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