Objective. To assess the ability of dual-energy computed tomography (DECT) in identifying early calcium crystal deposition in menisci and articular cartilage of the knee, depending on the presence/absence of chondrocalcinosis seen on conventional CT. Methods. One hundred thirty-two knee DECT scans from patients with suspected crystal-associated arthropathy were reviewed and assigned to a calcium pyrophosphate deposition (CPPD) group (n = 50) or a control group (n = 82). Five DECT attenuation parameters were measured in preset regions of interest (ROIs) in menisci and articular cartilage and compared between groups using linear mixed models with adjustment for confounders. Subgroup analysis, excluding ROIs with chondrocalcinosis seen on conventional CT, was performed. Results. In both menisci and articular cartilage, and for all 5 DECT attenuation parameters, calcified ROIs in CPPD patients showed significantly higher values than ROIs in controls (P ≤ 0.036). Conversely, noncalcified ROIs in CPPD patients were comparable with those in controls (P ≥ 0.09). While specific DECT parameters yielded good accuracy (area under the curve [AUC] 0.87-0.88) in differentiating calcified ROIs in CPPD patients from ROIs in controls, DECT failed to distinguish between noncalcified ROIs in CPPD patients and controls (AUC 0.58-0.59). Conclusion. While DECT has the potential to characterize knee intraarticular mineralization, this technique cannot yet accurately identify early calcium crystal deposition that is not visible as chondrocalcinosis on conventional CT.
BackgroundCalcium crystals are below the spatial resolution limit of currently available imaging techniques, and only aggregates can be identified in vivo at more advanced stages of the disease. Although dual-energy computed tomography (DECT) has the potential to discriminate the various calcium crystal types owing to its biochemical signature assessment capabilities, it remains to be seen whether this technique would be able to identify early-stage calcium crystal deposition in vivo.ObjectivesWe aimed to assess whether DECT was able to identify calcium crystal deposition in the knee prior to the onset of chondrocalcinosis (CC), more specifically if DECT attenuation properties differed between patients with CC and controls without CC on DECT.MethodsConsecutive patients with clinical suspicion of crystal arthritis and knee DECT scans were retrospectively reviewed and assigned to either CPPD (n=50) or control (n=82) groups depending on the presence/absence of CC on DECT. Regions of interest (ROI) were drawn in the following knee zones on a specific coronal DECT image: hyaline cartilage of the patellofemoral and medial and lateral tibiofemoral joint spaces, as well as medial and lateral menisci. The presence or absence of CC in these predefined ROIs were noted. Five DECT parameters were obtained: CT numbers (HU) at 80 and 140 kV, dual-energy index (DEI), electron density (ρe), and effective atomic number (Zeff). Knee zones were compared between groups using mixed linear models adjusting for age and the presence of osteoarthritis. A subgroup analysis was performed excluding zones were calcifications were visible on DECT images.ResultsMenisci from CPPD patients and controls had a mean Zeff of 7.9±0.4 and 7.6±0.2 (p<0.0001), mean ρe of 85±23 and 74±14 (p<0.0001) and mean DEI of 0.0036±0.0046 and -0.0001±0.0042 (p<0.001), respectively. DEI values differed significantly between patients and controls in tibiofemoral cartilage (0.0026±0.0041 in CPPD and 0.0023±0.0045)(p=0.013) but not in patellofemoral cartilage (p=0.57). When considering only the various regions from CPPD patients without CC in the selected ROIs, the ρe in menisci (n=79/185) did not differ between groups and differences in Zeff (p=0.15) and DEI (p=0.09) did not reach statistical significance after adjustment for age and osteoarthritis.ConclusionDECT has the potential to discriminate between meniscal fibrocartilage and articular cartilage of CPPD patients and controls in predefined regions of interest. DECT’s ability to improve the sensitivity of conventional CT to identify invisible CPP deposits remains unclear as the trend did not reach statistical significance.Disclosure of InterestsNone declared
Background:Dual-energy computed tomography (DECT) is increasingly used in gout to assess monosodium urate (MSU) crystal deposition in soft tissues. In contrast to ultrasound (US) with its typical double-contour (DC) sign, DECT seems unable to identify MSU deposition deep within joints, where flares occur. DECT has recently shown its potential for discriminating between the various crystal types owing to their biochemical signature.Objectives:We aimed to assess whether DECT attenuation properties differed between knees of gout patients with and without deep articular MSU deposition characterized by the DC sign on US; more specifically if MSU deposition altered the electron density (ρe) of various knee structures.Methods:Consecutive patients with gout were included in this cross-sectional study and their knee MSU burden was assessed using combined DECT and US. Knees were assigned to either DC+ or DC- groups depending on the presence/absence of the DC sign on US. Regions of interest (ROI) were drawn in the following knee zones on a specific coronal DECT image: hyaline cartilage of the patellofemoral and medial and lateral tibiofemoral joint spaces, as well as medial and lateral menisci. Regions of interest that exhibited chondrocalcinosis were excluded. Five DECT parameters were obtained: CT numbers (HU) at 80 and 140 kV, dual-energy index (DEI), electron density (ρe), and effective atomic number (Zeff). Knee zones were compared between groups using mixed linear models.Results:A total of 115 patients were included. Gout duration was 9.8±9.0 years, mean serum urate was 7.3±2.3 mg/dL and 48 (41.7%) patients were under urate lowering therapy. Out of a total 230 knees, 46 (20%) were assigned to the DC+ group. Menisci from DC+ and DC- patients had a mean (± standard deviation) Zeff of 7.5±0.2 and 7.6±0.2 (p=0.49), mean ρe of 77±14 and 73±13 (p=0.15) and mean DEI of -0.0003±0.0036 and 0.0001±0.0042 (p=1), respectively. Hyaline cartilage from DC+ and DC- patients had a mean Zeff of 7.6±0.2 and 7.7±0.2 (p=0.49), mean ρe of 65±21 and 60±18 (p=0.17) and mean DEI of 0.0020±0.0049 and 0.0025±0.0043 (p=1), respectively. No differences were noted between groups in the patellofemoral joint space.Conclusion:There is an expected increased electron density (ρe) in meniscal fibrocartilage and hyaline cartilage of gout patients with MSU deposition, even though DECT measures do not reach statistical significance. Particular attention will be given to patients with high MSU burden (large DC signs on US).Disclosure of Interests:None declared
Objective To characterize dual-energy computed tomography (DECT) changes depicting hyaline cartilage changes in gout patients with and without osteoarthritis (OA) and in comparators without gout. Design Patients with suspected crystal-associated arthropathy were enrolled and underwent bilateral DECT scans of the knees. Standardized regions of interest were defined in the femorotibial hyaline cartilage. Five DECT parameters were obtained: CT numbers in Hounsfield units (HU) at 80 and 140 kV, the electron density (Rho), the effective atomic number (Zeff), and the dual-energy index (DEI). Zones were compared between patients with gout, with and without knee OA, and between patients with gout and comparators without gout, after adjustment for confounders. Results A total of 113 patients with gout (mean age 63.5 ± 14.3 years) and 15 comparators without gout (mean age 75.8 ± 11.5 years) were included, n = 65 (51%) had knee OA, and 466 zones of hyaline cartilage were analyzed. Older age was associated with lower attenuations at 80 kV ( P < 0.01) and 140 kV ( P < 0.01), and with Rho ( P < 0.01). OA was characterized by lower attenuation at 140 kV ( P = 0.03), but the lower Rho was nonsignificant after adjustment for confounders. In gout, hyaline cartilage exhibited lower Rho values (adjusted P = 0.04). Multivariable coefficients of association with Rho were −0.21 [−0.38;−0.04] ( P = 0.014) for age, −4.15 [−9.0;0.7] ( P = 0.093) for OA and 0.73 [−0.1;1.56] ( P = 0.085) for monosodium urate volume. Conclusion Gout was associated with DECT-detected changes in cartilage composition, similar to those observed in older patients, with some similarities and some differences to those seen in OA. These results suggest the possibility of potential DECT biomarkers of OA.
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