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- Gäfvert, Torbjörn, et al.
(författare)
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Thorium exposure during tungsten inert gas welding with thoriated tungsten electrodes
- 2003
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Ingår i: Radiation Protection Dosimetry. - 1742-3406. ; 103:4, s. 349-357
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Tidskriftsartikel (refereegranskat)abstract
- The exposure to Th-232 from TIG welding with thoriated electrodes has been determined at five different workshops. Welding with both alternating and direct current was investigated. The exposure levels of Th-232 were generally below 10 mBq m(-3) in the breathing zone of the welders. Two samples from AC welding showed significant higher exposure levels, probably due to maladjustment of the TIG welding power source. Samples of the respirable fraction of Th-232 from grinding thoriated electrodes were also collected showing exposure levels of 5 mBq m(-3) or lower. A dose estimate has been made for two scenarios, one realistic and one with conservative assumptions, showing that the annual committed effective dose from inhalation of Th-232, Th-230, Th-228 and Ra-228, for a full-time TIG welder, in the realistic case is below 0.3 mSv and with conservative assumptions around 1 mSv or lower. The contribution from grinding electrodes was lower, 10 muSv or lower in the realistic case and 63 muSv or lower based on conservative assumptions. The study does not exclude occurrence of higher exposure levels under welding conditions different from those prevailing in this study.
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- Hemdal, Bengt, et al.
(författare)
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Comparison of the European and Nordic protocols on dosimetry in mammography involving a standard phantom
- 2000
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Ingår i: Radiation Protection Dosimetry. - 1742-3406. ; 90:1, s. 149-154
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work was to implement the European Protocol on Dosimetry in Mammography in Sweden. The standard average glandular dose, AGD, was measured on 32 mammography units in southern Sweden, according to the European protocol as well as to the Nordic protocol. The most important difference is that the European protocol evaluates the half value layer, HVL, of the X ray beam with the compression paddle present, while it is absent in the Nordic protocol. This results in considerably higher HVL values from the European protocol and thus to higher conversion factors for the calculation of the standard AGD. When the European protocol is used instead of the Nordic protocol the standard AGD is increased by 5 ± 2% (total variation 0-9%) at clinical settings and by 9 ± 3% (4-17%) at a standardised net optical density of 1.00. These results should be considered in quality control programmes and optimisation procedures as well as in interpretation of trends and in future legislation programmes.
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- Herrmann, C., et al.
(författare)
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Simulation of nodule-like pathology in radiographs of the lumbar spine
- 2000
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Ingår i: Radiation Protection Dosimetry. - 1742-3406. ; 90:1-2, s. 113-116
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Tidskriftsartikel (refereegranskat)abstract
- For the evaluation of the imaging properties of medical radiographic systems there are well-established standards for measuring techniques available, e.g. ISO 9236 for the measurement of the H/D curve. However, such measuring techniques require sophisticated equipment which is not available in a clinical environment. For a clinical routine of image evaluation, techniques like contrast-detail diagrams or the visual inspection of radiographs of grid pattern with varying contrast and spatial resolution are very common. The disadvantage of these techniques is that the corresponding results are very hard to be transferred to real patient images. Therefore, observer studies on the detection of certain pathology are commonly used to e.g. investigate the influence of different radiographic techniques on diagnostic image quality. As it is very difficult to find a sufficient number of patients with real pathologies for such studies, the pathologies are often simulated by fixing e.g. aluminium disks or other nodule-like objects to healthy volunteers when the radiograph is produced. This approach is relatively simple and rather successful in chest imaging. For lumbar spine images, however, the situation is different because nodule-like tumours cannot only consist of bony material which is increasing the X-ray absorption, but tumours can also destroy the bone material resulting in an increased transparency of the corresponding anatomical region. Such a behaviour is extremely hard to be simulated by fixing an external object to the patient. However, it can be easily simulated in a computer and applied to digital radiographic data. The current paper presents a computer model for the simulation of nodules in lumbar spine images. The model has been applied within a CEC founded research project, which was investigating the influence of MTF and noise power spectra on the diagnostic quality of radiographs of the lumbar spine.
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