Quantitative spectral micro-CT of a CA4+ loaded osteochondral sample with a tabletop system

Simone Fantoni; Francesco Brun; Paolo Cardarelli; Fabio Baruffaldi; Virginia Cristofori; Angelo Taibi; Claudio Trapella; Luca Brombal

doi:10.1140/epjp/s13360-024-05428-0

2023 Impact factor 2.8

EPJ PLUS - Condensed Matter and Complex Systems

Focus Point on Recent Advances in X-ray and Neutron Imaging for Cultural Heritage and Biomedicine

Open Access

Eur. Phys. J. Plus (2024) 139: 735
https://doi.org/10.1140/epjp/s13360-024-05428-0

Regular Article

Quantitative spectral micro-CT of a CA4+ loaded osteochondral sample with a tabletop system

Simone Fantoni¹, Francesco Brun²^,3, Paolo Cardarelli⁴^c, Fabio Baruffaldi¹, Virginia Cristofori⁵, Angelo Taibi⁴^,6, Claudio Trapella⁵ and Luca Brombal³^,7^h

¹ Medical Technology Laboratory, IRCCS Istituto Ortopedico Rizzoli, via di Barbiano 1/10, 40136, Bologna, Italy
² Department of Engineering and Architecture, University of Trieste, via A. Valerio 10, 34127, Trieste, Italy
³ INFN, Division of Trieste, via A. Valerio 2, 34127, Trieste, Italy
⁴ INFN, Division of Ferrara, via G. Saragat 1, 44122, Ferrara, Italy
⁵ Department of Chemical, Pharmaceutical and Agricultural Sciences, University of Ferrara, via Luigi Borsari 46, 44121, Ferrara, Italy
⁶ Department of Physics and Earth Science, University of Ferrara, via G. Saragat 1, 44122, Ferrara, Italy
⁷ Department of Physics, University of Trieste, via A. Valerio 2, 34127, Trieste, Italy

^c cardarelli@fe.infn.it
^h lbrombal@units.it

Received: 16 February 2024
Accepted: 4 July 2024
Published online: 16 August 2024

Abstract

Micro-computed tomography ( $μ$ $\upmu$ CT) is the gold standard for nondestructive 3D imaging of biomedical samples in the centimeter scale, but it has limited effectiveness in revealing intricate soft tissue details due to the limited attenuation contrast. Radiopaque contrast agents that accumulate in the structures of interest are employed to enhance their visibility. However, the increased attenuation provided by the contrast agents does not guarantee discrimination among tissues. This issue can be solved by spectral $μ$ $\upmu$ CT (S $μ$ $\upmu$ CT) systems employing small-pixel chromatic photon-counting detectors. These detectors, combined with material decomposition algorithms, allow the generation of high-resolution material-specific 3D maps. This work aims to demonstrate the potential of photon-counting X-ray S $μ$ $\upmu$ CT on osteochondral samples loaded with a cationic iodinated contrast agent (CA4+) at a spatial resolution below 50 $μ$ $\upmu$ m, and to compare the results against a conventional $μ$ $\upmu$ CT system. An osteochondral sample extracted from a bovine stifle joint was loaded with CA4+ and imaged with a novel multimodal X-ray imaging system, featuring a 62 $μ$ $\upmu$ m pixel CdTe spectral detector (Pixirad1-PixieIII). After material decomposition, quantitative 3D density maps of iodine and hydroxyapatite were reconstructed. The same sample was also scanned with a commercial $μ$ $\upmu$ CT scanner with matched spectrum and exposure time. SCT $μ$ $\upmu$ images at a (measured) spatial resolution comparable with the commercial scanner ( $\sim$ $\sim$ 45 $μ$ $\upmu$ m) were obtained. Spectral images allowed for a fully automatic segmentation of cartilage and subchondral bone. The unambiguous discrimination between iodine and hydroxyapatite revealed a more realistic representation of proteoglycan distribution compared to conventional imaging.

© The Author(s) 2024

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