Quantitative dual contrast photon-counting computed tomography for assessment of articular cartilage health

Petri Paakkari,Mithilesh Prakash,Miika T Nieminen,Mark W Grinstaff,Rubina Shaikh,Satu I Inkinen,Juha Töyräs,Miitu K M Honkanen,Juuso T J Honkanen,Janne T A Mäkelä

doi:10.1038/s41598-021-84800-x

Abstract

Photon-counting detector computed tomography (PCD-CT) is a modern spectral imaging technique utilizing photon-counting detectors (PCDs). PCDs detect individual photons and classify them into fixed energy bins, thus enabling energy selective imaging, contrary to energy integrating detectors that detects and sums the total energy from all photons during acquisition. The structure and composition of the articular cartilage cannot be detected with native CT imaging but can be assessed using contrast-enhancement. Spectral imaging allows simultaneous decomposition of multiple contrast agents, which can be used to target and highlight discrete cartilage properties. Here we report, for the first time, the use of PCD-CT to quantify a cationic iodinated CA4+ (targeting proteoglycans) and a non-ionic gadolinium-based gadoteridol (reflecting water content) contrast agents inside human osteochondral tissue (n = 53). We performed PCD-CT scanning at diffusion equilibrium and compared the results against reference data of biomechanical and optical density measurements, and Mankin scoring. PCD-CT enables simultaneous quantification of the two contrast agent concentrations inside cartilage and the results correlate with the structural and functional reference parameters. With improved soft tissue contrast and assessment of proteoglycan and water contents, PCD-CT with the dual contrast agent method is of potential use for the detection and monitoring of osteoarthritis.

Highlights

Photon-counting detector computed tomography (PCD-CT) is a modern spectral imaging technique utilizing photon-counting detectors (PCDs)
To enhance the capability of Contrast-enhanced computed tomography (CECT)-imaging, we developed a quantitative dual-energy CT (QDECT) technique that uses a mixture of non-ionic gadolinium-based gadoteridol and cationic iodinated CA4+ contrast agents[18,19,20,21]
The attenuation values reflected reliably the contrast agent concentrations used for the calibration, R2 = 0.997 and R2 = 0.998 for CA4+ and gadoteridol, respectively

Summary

Introduction

Photon-counting detector computed tomography (PCD-CT) is a modern spectral imaging technique utilizing photon-counting detectors (PCDs). For the first time, the use of PCD-CT to quantify a cationic iodinated CA4+ (targeting proteoglycans) and a non-ionic gadolinium-based gadoteridol (reflecting water content) contrast agents inside human osteochondral tissue (n = 53). The diffusion is simultaneously accelerated due to the increased porosity, water content, and increased surface area due to fibrillation For this reason, the use of cationic contrast agents has been limited in detecting structural degeneration at early time points after the administration. To enhance the capability of CECT-imaging, we developed a quantitative dual-energy CT (QDECT) technique that uses a mixture of non-ionic gadolinium-based gadoteridol and cationic iodinated CA4+ contrast agents[18,19,20,21]. The use of QDECT with the two contrast agents allows quantitative assessment of two important health reflecting properties of the articular cartilage, i.e., water and PG content. This technique could aid the physician to quantitatively evaluate the severity of the injury and select a suitable treatment

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Conclusion