| 1. |
- Tillman, Carl, et al.
(författare)
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High-resolution spectroscopy of laser-produced plasmas in the photon energy range above 10 keV.
- 1997
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 394:3, s. 387-396
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Tidskriftsartikel (refereegranskat)abstract
- X-rays from a laser-produced plasma were analysed using single-photon counting germanium detectors. Special attention was given to the extremely high photon flux, requiring either a long source-detector distance and narrow collimated measurement geometry in order to avoid severe pile-up of pulses in the spectrometer, or the use of a Compton scattering geometry. With the use of these techniques, individual characteristic K-lines were resolved for the first time. Efficiencies for the conversion of the laser light into X-rays were determined, being up to 10−4 for Bremsstrahlung, and up to 10−5 for the characteristic K-line emission. Electron temperatures of not, vert, similar100 keV were assessed.
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| 2. |
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| 3. |
- Aznar, Marianne, et al.
(författare)
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Absorbed Dose Measurement in Mammography
- 2007
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Ingår i: Cancer imaging - Lung and breast carcinomas. - 9780123704689 - 0123704685 ; 1, s. 493-493
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Aznar, Marianne C., et al.
(författare)
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A Monte Carlo study of the energy dependence of Al2O3:C crystals for real-time in vivo dosimetry in mammography
- 2005
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 114:Nos 1-3, s. 444-449
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Tidskriftsartikel (refereegranskat)abstract
- In a previous experimental study, a novel method for in vivo dosimetry has been investigated, based on radioluminescence (RL) and optically stimulated luminescence (OSL). However, because of the large difference in atomic composition between the detector material and the breast tissue, relatively large energy dependence in low-energy X-ray beams can be expected. In the present work, the energy dependence of Al2O3:C crystals was modelled with the Monte Carlo code EGSnrc using three types of X-ray spectra. The results obtained (5.6-7.3%) agree with a previously determined experimental result (9%) within the combined standard uncertainty of the two methods. The influence of the size of the crystal on the energy dependence was investigated together with the effect of varying the thickness of the surrounding light-protective material. The results obtained indicate a minor effect owing to the thickness of the light-protective material, and a somewhat larger effect from reducing the diameter of the crystal. The outcome of this study can be used to improve the future design of the RL/OSL dosimetry system for use in mammography.
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| 5. |
- Aznar, MC, et al.
(författare)
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In vivo absorbed dose measurements in mammography using a new real-time luminescence technique
- 2005
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 78:928, s. 328-334
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Tidskriftsartikel (refereegranskat)abstract
- A dosimetry system based on radioluminescence (RL) and optically stimulated luminescence (OSL) from carbon doped aluminium oxide (Al2O3:C) crystals was developed for in vivo absorbed dose measurements in mammography. A small cylindrical crystal of Al2O3:C (diameter 0.48 mm and length 2 mm) was coupled to the end of a 1 mm diameter optical fibre cable. Owing to their small size and characteristic shape, these probes can be placed on the body surface in the field of view during the examination, without compromising the reading of the mammogram. Our new technique was tested with a mammography unit (Siemens Mammomat 3000) and screen-film technique over a range of clinically relevant X-ray energies. The results were compared with those obtained from an ionization chamber usually used for the determination of absorbed dose in mammography. The reproducibility of measurements was around 3% (1 standard deviation) at 4.5 mGy for both RL and OSL data. The dose response was found to be linear between 4.5 mGy and 30 mGy. The energy dependence of the system is around 18% between 23 kV and 35 kV. In vivo measurements were performed during three patient examinations. It was shown that entrance and exit doses could be measured. The presence of the small probes did not significantly interfere with the diagnostic quality of the images. Entrance doses estimated by RL/OSL results agreed within 3% with entrance surface dose values calculated from the ionization chamber measurements. These results indicate a considerable potential for use in routine control and in vivo dose measurements in mammography.
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| 6. |
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| 7. |
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| 8. |
- Börjesson, Sara, et al.
(författare)
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A software tool for increased efficiency in observer performance studies in radiology.
- 2005
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 114:1-3, s. 45-52
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Tidskriftsartikel (refereegranskat)abstract
- Observer performance studies are time-consuming tasks, both for the participating observers and for the scientists collecting and analysing the data. A possible way to optimise such studies is to perform them in a completely digital environment. A software tool-ViewDEX (Viewer for Digital Evaluation of X-ray images)-has been developed in Java, enabling it to function on almost any computer. ViewDEX is designed to handle several types of studies, such as visual grading analysis (VGA), image criteria scoring (ICS) and receiver operating characteristics (ROC). The results from each observer are saved in a log file, which can be exported for further analysis in, for example, a special software for analysing ROC results. By using ViewDEX for an ROC experiment, an evaluation rate of approximately 200 images per hour can be achieved, compared to approximately 25 images per hour using hard copy evaluation. The results are obtained within minutes of completion of the viewing. The risk of human errors in the process of data collection and analysis is also minimised. The viewer has been used in a major trial containing approximately 2700 images.
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| 9. |
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| 10. |
- Gennaro, Gisella, et al.
(författare)
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Quality Controls in Digital Mammography protocol of the EFOMP Mammo Working group
- 2018
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Ingår i: Physica Medica. - : Elsevier BV. - 1120-1797. ; 48, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- This article aims to present the protocol on Quality Controls in Digital Mammography published online in 2015 by the European Federation of Organisations for Medical Physics (EFOMP) which was developed by a Task Force under the Mammo Working Group. The main objective of this protocol was to define a minimum set of easily implemented quality control tests on digital mammography systems that can be used to assure the performance of a system within a set and acceptable range. Detailed step-by-step instructions have been provided, limiting as much as possible any misinterpretations or variations by the person performing. It is intended that these tests be implemented as part of the daily routine of medical physicists and system users throughout Europe in a harmonised way so allowing results to be compared. In this paper the main characteristics of the protocol are illustrated, including examples, together with a brief summary of the contents of each chapter. Finally, instructions for the download of the full protocol and of the related software tools are provided.
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