The detecting module based on gallium arsenide detectors in digital mammography
Success in early breast cancer diagnostic depends on technical characteristics of detecting module. The most important is detector resolution. In this paper we represent quantum-sensitive detectors of X-rays based on GaAs for digital mammography systems. Electron/hole pairs created by radiation, which interact with the GaAs detectors, result current pulse at the detector output and specialist can see image immediately. Progress in development and investigation of a semiconductor material capable to provide reliable registration of single quanta of roentgen radiation. It is supposed to reduce patient radiation doze. At the same time, the system delivers high-quality images with resolution, contrast and clarity equal to film X-rays, or even better. Main advantages which can be achieved by using these detectors are analyzed.
THE DOSE AND IMAGE QUALITY IN MAMMOGRAPHY PRACTICE IN FINLAND
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Radiation Dose Assessments for Materials with Elevated Natural Radioactivity
SUMMARY This report provides practical information needed for evaluating the radiation dose to the general public and workers caused by materials containing elevated levels of natural radionuclides. The report presents criteria, exposure scenarios and calculations used to assess dose with respect to the safety requirements set for construction materials in accordance with the Finnish Radiation Act. A method for calculating external gamma exposure from building materials is presented in detail. The results for most typical cases are given as specific dose rates in table form to enable doses to be assessed without computer calculation. A number of such dose assessments is presented, as is the corresponding computer code. Practical investigation levels for the radioactivity of materials are defined. PREFACE The radioactivity of building materials, industrial by-products and waste has been investigated by the Finnish Centre for Radiation and Nuclear Safety (STUK) for some 20 years. As a result, STUK now has a detailed view of Finns' exposure to these sources of natural radiation. Most of these investigations have been conducted by Dr. Raimo Mustonen. Finnish radiation legislation was revised in 1992, taking into account the 1990 ICRP recommendations. Practices causing occupational or public exposure to natural radiation were considered. On the basis of the new legislation, STUK has issued general guides concerning exposure to natural radiation. The radiation protection criteria adopted in the ST Guide 12.2 'Radioactivity of Construction materials, Fuel Peat and Peat Ash' are based on the work of Dr. Mustonen who has also presented the activity indexes for construction materials given in Sections 2.4 and 5.1. All other criteria and exposure scenarios presented in and assessments performed for this report were done by the author.