| 1. |
- Alm Carlsson, Gudrun, et al.
(author)
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Monte Carlo metoden : ett verktyg inom strålningsfysiken
- 1995
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Reports (other academic/artistic)abstract
- Detta kompendium är tänkt att användas som ett propedeutiskt kursmaterial för kursdeltagare i kursen "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter". Först följer en kort repetition av den grundläggande statistik som utnyt1jas i beräkningarna. Därefter följer en beskrivning av slumptal. det fundament som metoden bygger på. Vidare beskrivs val ur olika frekvensfunktioner. Valet kan även göras ur så kallade falska fördelningar för att reducera variansen i den skattade storheten. Metoderna belyses i ett avsnitt om problemlösningsmetodik. först i allmänna termer för att sen gå in på ett specifikt problem (Buffons nålproblem) där en analys och strukturering av problemet görs varefter flödesschema och kodning exemplifieras. Så följer två moment där en beskrivning görs av färderna av fotoner respektive elektroner genom materia. För elektronfärderna gör man en indelning i klass 1- och klass II-färder. Vad detta innebär och hur deltapartiklar tas om hand beskrivs i ett kapitel. Till sist kommer en kort introduktion till de tre laborationerna med laborationshandledningar. Speciell vikt har lagts vid att initiera laboranten att fundera på fysiken i de simulerade experimenten. Detta kompendium har tillkommit som examinationsarbete vid en kurs i "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter", med andra ord den kurs du själv nu ämnar studera. Författarna önskar dig lycka till med kursen och hoppas att du kommer att få glädje av den. Speciellt hoppas vi att denna skrift ska underlätta för dig att tillgodogöra dig informationen vid föreläsningarna och under laborationerna.
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| 2. |
- Larsson, Peter, et al.
(author)
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Evaluation of the uncertainties in KAP-meter calibrations
- 1996
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Reports (other academic/artistic)abstract
- This report was prepared in order to give more details to the uncertainty evaluation of the Kerma area product meter calibration procedure described in the paper: Larsson J P Persliden J Sandborg S and Alm Carlsson G 1996 Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration. Phys. Med. Biol. 41 2381-2398. Figures and equations referred to in this report will be found in the paperabove. For convenience, however, the equations in the paper that are used in the uncertainty analysis are retyped on the next two sides, see text in section 2.7. in the paper for further details. The numbering of the equations are kept as in the paper.
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| 3. |
- Sandborg, Michael, et al.
(author)
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Collection and analysis of patient and image data for calibration of a voxelphantombased Monte Carlo code and for the modelling of important structures
- 1997
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Reports (other academic/artistic)abstract
- The contribution of the Medical Physics Departments at Linköping University (LKP) and The Royal Marsden NHS Trust (RMH) to the joint project ‘Predictivity and Optimisation in Medical Radiation Protection’ is in modelling of the chest and lumbar spine radiographic examinations. This involves:the development of quantitative imaging requirements;an investigation of the effect of imaging technique on image quality and patientdose, andan optimisation of system design.One of the objectives for this first reporting period (0-12 months) was to collect a set of chest and lumbar spine radiographs of patients for subsequent analysis in order to establish patient doses and important features in the images. The set of radiographs and the outcome of the image feature analysis will during this project’s second year be used to calibrate our Monte Carlo computational model of the conventional chest and lumbar spine screen-film X-ray imaging systems.
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| 4. |
- Sandborg, Michael, et al.
(author)
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Implementation of unsharpness and noise into the model of the imaging system : Applications to chest and lumbar spine screen-film radiography
- 1999
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Reports (other academic/artistic)abstract
- A model of the complete x-ray imaging system including the patient is a powerful tool for imaging system analysis and the optimisation of image quality and patient dose. It allows flexible variation of the system components (i.e. x-ray source, antiscatter device and image detector) and study of their effect on image quality and patient risk. Our group has developed, validated and calibrated a Monte Carlo model of the complete imaging system for chest and lumbar spine examination including voxalised human male anatomy. The Monte Carlo program calculates the contrast and signal-to-noise ratio (SNR) of various contrasting details within the voxel phantom. Important details in the images have been selected by consulting radiologist and the EU document of image quality criteria. The entrance surface dose without back-scatter and the effective dose are used as measures of patient radiation risk. The contrasts of the details are derived initially from Monte Carlo estimates of the energy imparted per unit area to the image detector beside and behind the detail. However, this ignores the effects of unsharpness in the imaging chain (such as screen-film, geometric and motion unsharpness) and the influence on contrast of the film characteristic curve. In the Monte Carlo program, SNR is calculated assuming that the noise arises from the random fluctuations in the energy imparted per unit area to the image detector only. However, other noise sources also contribute to the total noise, such as screen and film noise. Hence the model of the imaging system needs to be further developed to take these effects into account. The methods used to extend the model are described below together with illustrations of their effect on the difference in optical density, DOD, and SNR in chest and lumbar spine imaging.
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