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A theoretical model for determination of the optimal irradiation conditions for computerised tomography
Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.ORCID iD: 0000-0003-3352-8330
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1995 (English)In: Insight (Northampton), ISSN 1354-2575, Vol. 37, no 12, 978-985 p.Article in journal (Refereed) Published
Abstract [en]

Image quality in Computerised Tomography (CT) depends strongly on the quality of the CT-projection data. These depend on sample composition and geometry, contrasting details within the sample and the equipment used, i.e. X-ray spectra, filtration, detector response and geometry. This paper focuses on the problem of selecting the optimal physical parameters to maximise the signal-to-noise in CT projection data (SNRCT) between a contrasting detail and the surrounding sample for CT-scanners equipped with poly-energetic X-ray sources (conventional X-ray tubes) and energy-integrating detector systems (image intensifier and optical video chain). The work includes the derivation and verification ofa theoretical model for SNRCT which can be used for predicting the optimal physical parameters for specific imaging tasks. It is shown that simplified calculations valid for mono-energetic X-ray sources and/or photon counting detectors do not correctly predict the optimal settings. This study also includes measurements of the actual X-ray source and photon transport Monte Carlo simulations of the response of the detector system.

Place, publisher, year, edition, pages
1995. Vol. 37, no 12, 978-985 p.
Keyword [en]
Non destructive test ; Optimization ; Tomography ; Image quality ; Filtration ; Experimental study ; Optical method ; X ray irradiation ; Verification ; Measurement method ; Numerical method ; Numerical convergence
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-13565OAI: oai:DiVA.org:liu-13565DiVA: diva2:20965
Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2015-03-20
In thesis
1. Computerised Microtomography: Non-invasive imaging and analysis of biological samples, with special reference to monitoring development of osteoporosis in small animals
Open this publication in new window or tab >>Computerised Microtomography: Non-invasive imaging and analysis of biological samples, with special reference to monitoring development of osteoporosis in small animals
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of Computerised microtomography (CμT) in biomedical research is well established, with most applications developed at synchrotron facilities. The possibility to non-invasively monitor morphological changes in biological samples, makes it an attractive technique in biomedicine. However, high absorbed doses and long examination times are a disadvantage that limits the possibilities of performing longitudinal examinations.

The aim of this work was to optimise CmT using conventional X-ray tubes for applications in non-destructive material testing and for skeleton research in small animals (rat). A calculational model of the imaging system was developed and used to optimise the relation between image quality, expressed as the signal-to-noise ratio (SNR) in detecting a contrasting detail, and imaging time in material testing. The model was modified to optimise the relation between the SNR in detecting a trabecular detail in cancelleous bone and the mean absorbed dose in spongiosa and skin for (rat) tibia and femur.

Gastrectomized Sprague-Dawley rats were used to initiate osteoporotic changes. In order to detect differences in between gastrectomized rats and controls, spatial resolutions of 150 mm or better were needed. The minimum absorbed doses in femur spongiosa at SNR = 5 were 1mGy - 700 mGy at spatial resolutions from 100 mm to10 mm. In femur skin, the corresponding minimum absorbed doses were 2 mGy - 2000 mGy. Corresponding values for tibia were 0.3 mGy - 300 mGy for both spongiosa and skin (spatial resolution of 100 mm to10 mm). Taking 0.5 Gy as the tolerance limit for the spongiosa dose, longitudinal studies with six repeated examinations will be possible at a spatial resolution of 25 mm in femur and 17 examinations in tibia.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2001. 59 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 656
Keyword
Computed microtomography, CμT, signal-to-noise ratio (SNR), non-invasive monitoring, morphological changes, Gastrectomized Sprague-Dawley, osteoporosis
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-5030 (URN)91-7219-757-9 (ISBN)
Public defence
2002-01-19, Brännströms sal, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 09:00 (English)
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Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2015-03-20Bibliographically approved

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Sandborg, MichaelAlm Carlsson, Gudrun

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