Detection and Characterization of Monosodium Urate and Calcium Hydroxyapatite Crystals Using Spectral Photon-Counting Radiography: A Proof-of-Concept Study. Issue 129 (August 2020)

• Record Type: Journal Article
• Authors: Huber, Florian A.; Gkoumas, Spyridon; Thüring, Thomas; Becce, Fabio; Guggenberger, Roman
• Is Part Of: European journal of radiology. Issue 129(2020)
• Publication Date: 2020-08
• Subjects: photon-counting detector -- spectral radiography -- crystal-associated arthropathies -- gout -- monosodium urate -- calcium hydroxyapatite; Medical radiology -- Periodicals; Radiology -- Periodicals; Radiologie médicale -- Périodiques; Medical radiology; Periodicals; 616.075705
• DOI: 10.1016/j.ejrad.2020.109080
• Languages: English
• ISSNs: 0720-048X

Abstract

Abstract: Objective: To assess the potential of spectral photon-counting (PC) radiography (SPCR) for the detection and characterization of monosodium urate (MSU) and calcium hydroxyapatite (HA) crystals, based on effective atomic number (Zeff ) values derived from specific X-ray attenuation characteristics at different energy levels. Methods: Suspensions of either pure agar, synthetic MSU (200 mg/ml) or HA (100 and 150 mg/ml) crystals in agar were sealed in industry-standard polystyrene vials and supported on a 2.5-mm-thick plastic table. Samples were scanned using a vendor microfocus X-ray tube and a spectral PC detector prototype with four energy thresholds per acquisition (15, 25, 30, and 35 keV). Material decomposition calibration was performed using polymethyl methacrylate (PMMA) and polyvinylchloride (PVC) slabs. Using a custom post-processing software based on polynomial material decomposition, Zeff of the respective samples were computed. All samples were additionally scanned using dual-energy CT (DECT, 80 kV and tin-filtered 150 kV) and analyzed with a proprietary post-processing algorithm for gout. Results: MSU crystal suspension attenuated significantly less than both HA samples. MSU and HA suspensions differed significantly in Zeff (mean ± SD: 7.74 ± 0.28 vs. 9.43 ± 0.41, p < .001). Zeff values from SPCR were comparable to DECT-based reference values (p = 0.16) and were independent of the radiation dose level (0.18 – 18 mAs, p = 1). Discussion: This in vitro feasibility study demonstrates the potential of SPCR for discriminating MSU from HA crystal suspensions based on Zeff differences. Further studies have to corroborate these initial findings ex vivo and in vivo, and to compare the diagnostic performance of SPCR with DECT in imaging of crystal-associated arthropathies.