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Maximising the signal-to-noise ratio in computerised tomography data using robust design
Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
1996 (English)In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 38, no 2, 112-117 p.Article in journal (Refereed) Published
Abstract [en]

Image quality in Computerised Tomography (CT) depends strongly on the quality of the CT-projection data, which vary with the imaged sample and the equipment used. The objective has been to find a setting of the CT-scanner Control Factors (CF) maximising the signal-to-noise ratio in CT projection data (SNRCT) of a contrasting detail (for example a defect) and a surrounding cylindrical sample, and to present a general optimisation methodology. An optimisation case study was carried out, valid for a CT-scanner equipped with a polyenergetic X-ray source (conventional) with tungsten target and a partially energy-integrating detector system (image intensifier and optical video chain), with and without consideration qf the exposure limits associated with the microfocal X-ray source used. The CF of interest were tube potential, exposure (product of tube current and exposure time), material and thickness of the primary filter, optical aperture and attenuation equalising filter design. The settings yielding the highest values of SNRCT were found using thick filter of high atomic number, small iris and use of an X-ray attenuation equalisation filter design. The exposure limits make the CF interdependent, yielding another optimal setting. The CF setting was also found to be independent of the contrasting detail, in the particular case study.

Place, publisher, year, edition, pages
1996. Vol. 38, no 2, 112-117 p.
Keyword [en]
Non destructive test ; Tomography ; Signal to noise ratio ; Image quality ; Scanner ; Signal analysis ; X ray
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-13566OAI: oai:DiVA.org:liu-13566DiVA: diva2:20966
Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2017-12-13
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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