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Computerised Microtomography: Non-invasive imaging and analysis of biological samples, with special reference to monitoring development of osteoporosis in small animals
Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
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 [en]
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: urn:nbn:se:liu:diva-5030ISBN: 91-7219-757-9 (print)OAI: oai:DiVA.org:liu-5030DiVA: diva2:20969
Public defence
2002-01-19, Brännströms sal, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2015-03-20Bibliographically approved
List of papers
1. Methodologic aspects of computed microtomography to monitor the development of osteoporosis in gastrectomized rats
Open this publication in new window or tab >>Methodologic aspects of computed microtomography to monitor the development of osteoporosis in gastrectomized rats
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1995 (English)In: Academic Radiology, ISSN 1076-6332, Vol. 2, no 9, 785-791 p.Article in journal (Refereed) Published
Abstract [en]

Rationale and Objectives

We investigated the methodologic development of computed microtomography (CMT) for monitoring the development of osteoporosis in male Sprague-Dawley rats.

Methods

Eight rats were gastrectomized and eight rats were sham operated. Femurs, tibias, and tails were prepared, and CMT scans with spatial resolutions of 5–500 μm were made. Bone diameters, bone areas, and moments of inertia were determined from the CMT scans. Optimal slice position and the need for spatial resolution and energy optimization for future in vivo applications were investigated.

Results

Gastrectomy caused dramatic changes in the bone architecture of the tibia and the femur. The main features were vacuolization of the bone and reduced amounts of compact bone. Although the outer diameters of tubular bones (femur and tibia) were largely unaffected, their inner diameters were greatly increased following gastrectomy. Relative bone area and moment of inertia were greatly reduced. The optimal photon energy was 12 keV.

Conclusion

It is possible to monitor gastrectomy-evoked changes in bone morphology at various sites in rats using CMT scanning. The changes are suggestive of osteoporosis. By optimizing the energy spectrum and spatial resolution, as well as choosing the proper slice position, it should be possible to keep absorbed doses low enough to avoid acute radiation injury in repeated in vivo measurements.

Keyword
Computed microtomography scanning, gastrectomy, osteoporosis, bone architecture, Sprague-Dawley rats
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-13564 (URN)10.1016/S1076-6332(05)80487-8 (DOI)
Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2015-03-20
2. A theoretical model for determination of the optimal irradiation conditions for computerised tomography
Open this publication in new window or tab >>A theoretical model for determination of the optimal irradiation conditions for computerised tomography
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1995 (English)In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, 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.

Keyword
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:nbn:se:liu:diva-13565 (URN)
Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2017-12-13
3. Maximising the signal-to-noise ratio in computerised tomography data using robust design
Open this publication in new window or tab >>Maximising the signal-to-noise ratio in computerised tomography data using robust design
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.

Keyword
Non destructive test ; Tomography ; Signal to noise ratio ; Image quality ; Scanner ; Signal analysis ; X ray
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-13566 (URN)
Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2017-12-13
4. Absorbed dose aspects on in vivo microtomography on small experimental animals
Open this publication in new window or tab >>Absorbed dose aspects on in vivo microtomography on small experimental animals
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2001 (English)In: Journal of Bone and Mineral Research, ISSN 0884-0431, E-ISSN 1523-4681Article in journal (Refereed) Submitted
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-13567 (URN)
Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2017-12-13
5. Bone mineral density and bone structure parameters as predictors of bone strength: an analysis using computerized microtomography and gastrectomy-induced osteopenia in the rat
Open this publication in new window or tab >>Bone mineral density and bone structure parameters as predictors of bone strength: an analysis using computerized microtomography and gastrectomy-induced osteopenia in the rat
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2000 (English)In: Journal of Biomechanics, ISSN 0021-9290, Vol. 33, no 3, 289-297 p.Article in journal (Refereed) Published
Abstract [en]

In this study the relationships of bone mineral density (BMD) and bone structure parameters calculated from 2D microtomography images to bone strength were investigated. Femurs from 21 male Sprague Dawley rats were subjected to dual-energy X-ray absorptiometry, computerized microtomography (CμT) and either three-point cantilever bending (femoral shaft) or two-point bending compression (femoral neck). Gastrectomy was performed on 12 animals and 9 were sham operated. From the tomograms bone structure analysis was performed using a software routine based on grey level run-length method. Correlations of BMD and bone structure parameters to mechanical parameters were investigated as were differences between the gastrectomized and the control samples. The reductions of BMD between the groups were 21 and 27% in the femoral neck and shaft, respectively. For the shaft, the correlations of BMD to all mechanical parameters were significant and BMD was a consistent predictor of bone strength for cortical bone. However, in the femoral neck where cancellous bone predominates, BMD was weakly correlated only to deflection. A significant correlation between trabecular thickness and neck bone strength was found. Hence, compared to trabecular thickness, BMD was of limited value in predicting bone strength in the femoral neck.

Keyword
Computerised microtomography, Bone structure, Bone strength, Bone mineral density, Osteopenia
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-13568 (URN)10.1016/S0021-9290(99)00181-5 (DOI)
Available from: 2001-02-20 Created: 2001-02-20 Last updated: 2015-03-20

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