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High-resolution short- exposure small-animal laboratory x-ray phase-contrast tomography
KTH, School of Engineering Sciences (SCI), Applied Physics. Stanford University, United States.ORCID iD: 0000-0002-9487-669X
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.ORCID iD: 0000-0003-2391-9848
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2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 39074Article in journal (Refereed) Published
Abstract [en]

X-ray computed tomography of small animals and their organs is an essential tool in basic and preclinical biomedical research. In both phase-contrast and absorption tomography high spatial resolution and short exposure times are of key importance. However, the observable spatial resolutions and achievable exposure times are presently limited by system parameters rather than more fundamental constraints like, e.g., dose. Here we demonstrate laboratory tomography with few-ten mu m spatial resolution and few-minute exposure time at an acceptable dose for small-animal imaging, both with absorption contrast and phase contrast. The method relies on a magnifying imaging scheme in combination with a high-power small-spot liquid-metal-jet electron-impact source. The tomographic imaging is demonstrated on intact mouse, phantoms and excised lungs, both healthy and with pulmonary emphysema.

Place, publisher, year, edition, pages
Nature Publishing Group, 2016. Vol. 6, article id 39074
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-199480DOI: 10.1038/srep39074ISI: 000389631500001Scopus ID: 2-s2.0-85006105732OAI: oai:DiVA.org:kth-199480DiVA, id: diva2:1067253
Note

QC 20170120

Available from: 2017-01-20 Created: 2017-01-09 Last updated: 2018-09-06Bibliographically approved
In thesis
1. High-resolution biomedical phase-contrast tomography
Open this publication in new window or tab >>High-resolution biomedical phase-contrast tomography
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Improved three-dimensional biomedical imaging can give a better understanding of tissue structure, growth and diseases. Most present imaging techniques that provide cellular spatial resolution are based on visible or infrared light. These methods cannot image deeper than a millimeter into tissue. Consequently, larger samples cannot be completely imaged without sectioning. Techniques that are typically used to image larger samples don't provide sufficient contrast and resolution to image cellular-sized features in soft tissues. There is a need for new imaging methods that can fill the gap between present methods. For practical reasons, compact equipment is preferred, to enable close connection to other research and applications. Furthermore, minimized sample preparation both reduces the work needed and the time until results are ready.

In this Thesis, propagation-based phase-contrast tomography with liquid-metal-jet x-ray sources has been investigated for high-resolution three-dimensional biomedical imaging. By using phase contrast, the contrast for cellular-sized features in soft tissue is vastly increased compared to absorption, also in larger samples. The high resolution relies on using an x-ray source with small emission spot, but also with high power to keep exposure times reasonable.

This Thesis is about developing and optimizing experimental methods and image reconstruction algorithms. A new method to remove ring artifacts was developed and tested, and a comparison of multi-material phase-retrieval algorithms was made. The improvements provide better contrast and resolution, as well as reduce noise and artifacts. The improved image quality is demonstrated in a few biomedical applications. It is shown that the method can image 5 µm large myofibrils in whole-body zebrafish, despite the small size and low contrast of myofibrils. A high-resolution tomography of a mouse can be done fast by using a specialized high-power source. The image quality in tomographies of both human coronary arteries and a mummified human hand is sufficient to analyze the tissues and cellular-sized features, which is something that could be called virtual histology. 

Abstract [sv]

Förbättrad tredimensionell biomedicinsk avbildning kan ge en bättre förståelse av vävnadsstruktur, tillväxt och sjukdomar. De flesta av dagens avbildningstekniker som ger cellulär upplösning är baserade på synligt eller infrarött ljus. Dessa metoder kan inte avbilda mer än en millimeter ner i vävnad. Därför kan inte större prov avbildas i sin helhet utan att snittas. Tekniker som vanligen används för att avbilda större prover ger inte tillräcklig kontrast och upplösning för att avbilda strukturer av cellulär storlek i mjuk vävnad. Det finns ett behov av nya avbildningsmetoder som kan fylla utrymmet mellan befintliga metoder. Av praktiska skäl föredras att använda kompakt utrustning, för att möjliggöra nära koppling till annan forskning och tillämpningar. Dessutom, minimerade förberedelser av proven reducerar både arbetsinsatsen och tiden tills resultaten är klara.

I den här doktorsavhandlingen har propagationsbaserad faskontrast- \mbox{tomografi} med metallstråleröntgenkällor undersökts för högupplöst tredimensionell avbildning. Genom att använda faskontrast kan kontrasten för strukturer av cellulär storlek i mjukvävnad ökas markant jämfört med absoption, även i större prover. Den höga upplösningen hänger på användandet av en röntgenkälla med liten emissionsspot, men även med hög effekt för att hålla exponeringstider korta.

Den här doktorsavhandlingen handlar om att utveckla och optimera experimetella metoder och bildrekonstruktionsalgoritmer. En ny metod för att ta bort ringartefakter utvecklades och testades, och en jämförelse av flermaterials-fasrekonstruktion gjordes. Förbättringarna ger bättre kontrast och upplösning, men minskar också brus och artefakter. Den förbättrade bildkvaliteten visas i några biomedicinska tillämpningar. Det visas att metoden kan avbilda 5 µm stora myofibriller i hela zebrafiskar trots den lilla storleken och låga kontrasten hos myofibriller. En högupplöst tomografi av en mus kan göras snabbt genom att använda en specialiserad högeffektskälla. Bildkvaliteten i tomografier av både mänskliga kranskärl och en mummifierad mänsklig hand är tillräcklig för att analysera vävnader och strukturer av cellulär storlek, vilket är något som skulle kunna kallas virtuell histologi.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 63
Series
TRITA-SCI-FOU ; 2018:34
Keywords
x-ray, x-ray imaging, biomedical, phase contrast, tomography, zebrafish, coronary artery, virtual histology, ring artifacts, phase retrieval, mummy
National Category
Physical Sciences Radiology, Nuclear Medicine and Medical Imaging
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-234300 (URN)978-91-7729-915-8 (ISBN)
Public defence
2018-10-05, FD5, Albanova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
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Supervisors
Note

QC 20180907

Available from: 2018-09-07 Created: 2018-09-06 Last updated: 2018-09-07Bibliographically approved

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Larsson, Daniel H.Hertz, Hans

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