Dual energy computed tomography cannot effectively differentiate between calcium pyrophosphate and basic calcium phosphate diseases in the clinical setting.

Background: Recent reports suggested that dual-energy CT (DECT) may help discriminate between different types of calcium phosphate crystals in vivo , which would have important implications for the characterization of crystal deposition occurring in osteoarthritis.
Purpose: Our aim was to test the hypothesis that DECT can effectively differentiate basic calcium phosphate (BCP) from calcium pyrophosphate (CPP) deposition diseases.
Methods: Discarded tissue after total knee replacement specimens in a 71 year-old patient with knee osteoarthritis and chondrocalcinosis was scanned using DECT at standard clinical parameters. Specimens were then examined on light microscopy which revealed CPP deposition in 4 specimens (medial femoral condyle, lateral tibial plateau and both menisci) without BCP deposition. Regions of interest were placed on post-processed CT images using Rho/Z maps (Syngo.via, Siemens Healthineers, VB10B) in different areas of CPP deposition, trabecular bone BCP (T-BCP) and subchondral bone plate BCP (C-BCP).
Results: Dual Energy Index (DEI) of CPP was 0.12 (SD ​= ​0.02) for reader 1 and 0.09 (SD ​= ​0.03) for reader 2, The effective atomic number (Z _eff ) of CPP was 10.83 (SD ​= ​0.44) for reader 1 and 10.11 (SD ​= ​0.66) for reader 2. Nearly all DECT parameters of CPP were higher than those of T-BCP, lower than those of C-BCP, and largely overlapping with Aggregate-BCP (aggregate of T-BCP and C-BCP).
Conclusion: Differentiation of different types of calcium crystals using DECT is not feasible in a clinical setting.
Competing Interests: AG has received consultancies fees from Pfizer, Novartis, AstraZeneca, Coval, Medipost, ICM and TissueGene and is a shareholder of Boston Imaging Core Lab (BICL), LLC a company providing image assessment services. CMM has received consultancy fees from Smith and Nephew. JC has received consultancy fees from Boston Imaging Core Lab.
(© 2024 The Authors.)