Quantitative imaging of excised osteoarthritic cartilage using spectral CT
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To quantify iodine uptake in articular cartilage as a marker of glycosaminoglycan (GAG) content using multi-energy spectral CT.
We incubated a 25-mm strip of excised osteoarthritic human tibial plateau in 50 % ionic iodine contrast and imaged it using a small-animal spectral scanner with a cadmium telluride photon-processing detector to quantify the iodine through the thickness of the articular cartilage. We imaged both spectroscopic phantoms and osteoarthritic tibial plateau samples. The iodine distribution as an inverse marker of GAG content was presented in the form of 2D and 3D images after applying a basis material decomposition technique to separate iodine in cartilage from bone. We compared this result with a histological section stained for GAG.
The iodine in cartilage could be distinguished from subchondral bone and quantified using multi-energy CT. The articular cartilage showed variation in iodine concentration throughout its thickness which appeared to be inversely related to GAG distribution observed in histological sections.
Multi-energy CT can quantify ionic iodine contrast (as a marker of GAG content) within articular cartilage and distinguish it from bone by exploiting the energy-specific attenuation profiles of the associated materials.
• Contrast-enhanced articular cartilage and subchondral bone can be distinguished using multi-energy CT.
• Iodine as a marker of glycosaminoglycan content is quantifiable with multi-energy CT.
• Multi-energy CT could track alterations in GAG content occurring in osteoarthritis.
KeywordsOsteoarthritis Articular cartilage Spectral CT Glycosaminoglycan Ionic contrast media
Application-specific integrated circuit
Contrast to noise ratio
Delayed gadolinium contrast-enhanced magnetic resonance imaging of cartilage
Medipix All Resolution System
Magnetic resonance imaging
Phosphate buffered saline
Simultaneous algebraic reconstruction technique
The scientific guarantor of this publication is Nigel Anderson. The authors of this manuscript declare relationships with the following companies: MARS Bioimaging Ltd.: Nigel Anderson holds 14 shares. Anthony Butler is a director and shareholder. This study has received funding by the Ministry of Business, Innovation and Employment, New Zealand (grant number: UOCX0805) and Arthritis Foundation New Zealand (grant number: R210). We are also grateful to Medipix2 and Medipix3 collaborations at CERN, and X-ray Imaging Europe, GmbH. The first author would like to acknowledge support from the Royal Society of New Zealand through the R. H. T. Bates award. No complex statistical methods were necessary for this paper. Institutional review board approval was obtained: Upper South B Regional Ethics Committee (URB/07/04/014). Written informed consent was obtained from all subjects (patients) in this study.
Methodology: prospective, experimental, performed at one institution.
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