Dual-energy computed tomography in calcium pyrophosphate deposition: initial clinical experience

Abstract

Objective: To determine the dual-energy computed tomography (DECT) attenuation properties of meniscal calcifications in calcium pyrophosphate deposition (CPPD) in vivo, and assess whether DECT was able to discriminate meniscal CPP deposits from calcium hydroxyapatite (HA) in subchondral and trabecular bone. Method: Patients with clinical suspicion of crystal-related arthropathy (gout and/or CPPD) and knee DECT scans were retrospectively assigned to CPPD (n ¼ 19) or control (n ¼ 21) groups depending on the presence/absence of chondrocalcinosis on DECT. Two observers drew standardized regions of interest (ROI) in meniscal calcifications, non-calcified menisci, as well as subchondral and trabecular bone. Five DECT parameters were obtained: CT numbers (HU) at 80 and 140 kV, dual-energy index (DEI), electron density (r e), and effective atomic number (Z eff). The four different knee structures were compared within/between patients and controls using linear mixed models, adjusting for confounders. Results: Meniscal calcifications (n ¼ 89) in CPPD patients had mean ± SD CT numbers at 80 and 140 kV of 257 ± 64 and 201 ± 48 HU, respectively; with a DEI of 0.023 ± 0.007, and r e and Z eff of 140 ± 35 and 8.8 ± 0.3, respectively. Meniscal CPP deposits were readily distinguished from calcium HA in subchondral and trabecular bone (p 0.001), except at 80 kV separately (p ¼ 0.74). Z eff and r e both significantly differed between CPP deposits and calcium HA in subchondral and trabecular bone (p < 0.0001). Conclusion: This proof-of-concept study shows that DECT has the potential to discriminate meniscal CPP deposits from calcium HA in subchondral and trabecular bone in vivo, paving the way for the noninvasive biochemical signature assessment of intra-and juxta-articular calcium crystal deposits.

Can Dual‐Energy Computed Tomography Be Used to Identify Early Calcium Crystal Deposition in the Knees of Patients With Calcium Pyrophosphate Deposition?

“…The present study addressed one of the issues recently raised by the first clinical use of DECT in CPPD (7,(9)(10)(11): does early calcium crystal deposition alter DECT attenuation characteristics in menisci and articular cartilage prior to the appearance of detectable chondrocalcinosis by conventional CT? In this study, with a large enough sample size to detect clinically relevant changes in DECT attenuation characteristics, we found that with currently available DECT technology (7), the answer was no.…”

“…P values were adjusted for each parameter within zone categories/knee structures (menisci, articular cartilage) using Holm's technique to avoid α risk inflation due to repeated comparisons of the same parameters and groups within zones. Additional details on the statistical methods have been published previously (7). The correlation between the calcification area within ROIs and DEI, rho, and Z eff was evaluated using Spearman's correlation coefficient including 95% confidence intervals (95% CIs).…”

Chondrocalcinosis does not affect functional outcome and prosthesis survival in patients after total or unicompartmental knee arthroplasty: a systematic review

“…Concerning the slight inferior implant survival rate in patients with histologically proven CC compared to radiologically diagnosed CC found by Kumar et al [22], one could argue that the preoperative diagnosis of CC, except for patients with clinical manifestation of inflammation, is usually established based on radiographic findings and not on histology, which questions the clinical relevance of this finding. On the other hand, the presence of CPP crystals either in the synovial fluid or in the cartilage, not yet visible on plane radiographs could be diagnosed non-invasively especially with ultrasound, which has a better sensitivity compared to plain radiographs, or with MRI or with dualenergy CT [30][31][32][33][34].…”

Cartilage icing and chondrocalcinosis on knee radiographs in the differentiation between gout and calcium pyrophosphate deposition

“…Dual-energy CT or multi-energy spectral photon-counting CT could have been key factors to analyze the causing crystals, show multi-crystal involvement, and show differential diagnoses, e.g. hydroxyapatite crystal deposits [40][41][42]. One final limitation is that we did not include a control group of aspiration negative diagnosis, because a high false negative rate for CPPD crystal analysis is known in the literature.…”