51. Evaluation of silicona microstrip detectors as X-ray sensors in digital mammographyTadej Mali, Vladimir Cindro, Marko Mikuž, Urban Zdešar, Breda Jančar, 1999, original scientific article Abstract: Background. Position sensitive silicon microstrip detectors are used as sensors for X rays in a digital imaging system. Silicon detectors were used inan edgeon geometry, yielding high X ray detection efficiency. Material and methods. A small detector system was assembled and tested. Images of a standard, 5 cm thick phantom were made and evaluated. It is demonstrated, thatthe use of silicon detectors in mammography could significantly contributeto a reduction of dose. All images were made with skin entrance doses lower than 1 mGy. Results and conclusion. Microcalcifications with a diameter of 350microm could still be detected with skin entrance doses of about 0.25 mGy. It was demonstrated that a 5 Ip/mm pattern can be detected. Image processing should further improve the image quality.
Published in DiRROS: 22.01.2024; Views: 225; Downloads: 44
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52. Epithermal neutron beam for BNCT at the JSI TRIGA reactor - modelling and experimental verificationMarko Maučec, Bogdan Glumac, Jože Rant, Edvard Krištof, 1999, original scientific article Abstract: It has been reported that satisfactory thermal/epithermal neutron beams for Boron lVeutron Ćapturc, Therapy (BNCT) could be designed at TRIGA research reactors, which are generally perceived as being safe to install and operate in populated areas. This contribution presents the most recent research activities in this field at the Jožef Stefan Institute TRIGA reactor, where anepithermal neutron beam for BNCT is being developed. Experimental verification of Monte Carlo simulation results proves the quality and wide applicability of the developed 3-D model, particularly of the reactor core andirradiation channels. Due to high attenuation of the epithermal neutron flux (fi epi = 4.1x106 n/cmZs, two orders of magnitude belozu the therapeutic limit) the irradiation facility in the current stage of development is not appropriate for the clinical BNCT treatments. Furthermore, the contribution ofthe 2.5 mm airgap surrounding the facility is unacceptably high, thus makingthe relative gamma dose (Dy/fiepi) almost 60-times higher than therapeutically rcc- ommended. Nevertheless, using gamma shielding of Pb or Biand LiF or Li2C03 (thermal neutron cut-off, the quality of the epithermal neutron beam would be significantly upgraded and hecome appropriate fnr iii vitro studies of boron compound transport in malignant tumour cells or smallerlahoratory animals.
Published in DiRROS: 22.01.2024; Views: 139; Downloads: 33
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53. Apparatus for positron emission tomographyMarko Starič, Samo Korpar, Erik Margan, Marko Šifrar, Aleš Stanovnik, Nataša Budihna, Metka Milčinski, Boris Šket, 1998, original scientific article Published in DiRROS: 19.01.2024; Views: 166; Downloads: 41
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54. Diagnostic value of planar myocardial perfusion scintigraphy in patients with coronary artery diseaseMarko Klančič, Metka Milčinski, Darko Zorman, 1997, original scientific article Abstract: Patients with suspected or proven coronary artery disease are investigated using noninvasive and invasive diagnostic methods. Noninvasive myocardial perfusion scintigraphy provides data on myocardial perfusion during stress andat rest. Coronary angiography is invasive morphologic method, performed before coronary artery dilatation or surgery. Aim of our retrograde analysis of planar thallium myocardial perfusion scintigrams and coronary angiograms was to assess sensitivity and specificity of rnyocardial perfusion planar scanning and to evaluate causes of possible disagreement. Original readings ofmyocardial perfusion scans and coronary angiograms of 156 patients with coronary artery disease were compared. When results of both investigations were partially concordant or discordant, the original studies were reviewed. Concordant results of both examinations were found in 62% of patients. In only3% (5 patierrts) the results were discordant and the reason for disagreement of results of both studies could not be detected. Most of the remaining 55 patients had more pronounced myocardial perfusion defects than was the estinrated severity of cororsary artery stenosis, attributed to the different nature of both irtvestigations. Anonralous coronary artery was foundirt 3% of all patients, tortuous coronary arteries with slow ftow of coritrast media in 9 patients (6% of all) and arterial hypertension with extreme left ventricular wall hypertrophy in one patient. Serrsitivity of the rnyocardial perfusion scintigraphy was l00% and specificity 50%. Positive predictive valrre for coronary artery disease was 96% and negative predictive value was 100 %. We cconclude that myocardial perfusion scintigraphy has a definite role in: diagnosis and follow-up of patients with suspected or provencoronary artery disease. (Abstracts truncated at 2000 characters)
Published in DiRROS: 18.01.2024; Views: 153; Downloads: 33
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57. Impact assessment of the Gajke and Brstje landfills on groundwater status using stable and radioactive isotopesSonja Cerar, Luka Serianz, Polona Vreča, Marko Štrok, Tjaša Kanduč, 2023, original scientific article Abstract: Waste disposal in landfills represents a severe threat to aquatic environments on the local, regional, and global levels. In Slovenia, there are 69 registered landfills where groundwater is regularly monitored. However, isotope techniques are not regularly employed. Therefore, we employed isotope analysis of hydrogen, carbon, and oxygen in combination with total alkalinity to assess the impact of the selected landfill on groundwater and to evaluate the biogeochemical processes at work. The δ18O, δ2H, δ13CDIC, 3H activity and total alkalinity were determined in October 2020 at 12 sampling points from the surrounding area of the Gajke and Brstje landfills and leachate from the Gajke landfill. The δ18O (-9.24 ± 0.3 ‰) and δ2H (-64.9 ± 2.7 ‰) in groundwater indicate that the main water source consists in direct infiltration of precipitation, with no significant isotopic fractionation. Total alkalinity in the investigated area ranges from 5.45 to 73 mM and δ13CDIC from –14.9 to +6.1 ‰, respectively. Higher values of total alkalinity (up to 73 mM), δ13CDIC (up to +6.1 ‰), δ18O (-7.64 ‰) and 3H (209.8 TU) are detected in the leachate, indicating biogeochemical process related to CO2 reduction or methanogenesis. Methanogenesis could be present at locations GAP-10/13 (Brstje landfill) and G-2 (Gajke landfill) with δ13CDIC values ranging from –8.2 to –7.6 ‰ and with dissolved oxygen values around 0 % and elevated 3H values (from 16 to 18 TU). This study demonstrates the effectiveness of isotopic analysis as a valuable tool for monitoring landfills, revealing shifts in biogeochemical processes within the groundwater there.
Keywords: groundwater, monitoring, landfill, stable isotopes, tritium, Gajke, Brstje
Published in DiRROS: 16.01.2024; Views: 194; Downloads: 69
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