Dual‐Energy Computed Tomography for the Noninvasive Diagnosis of Coexisting Gout and Calcium Pyrophosphate Deposition Disease

Hajri, Rami; Hajdu, Steven D.; Hügle, Thomas; Zufferey, Pascal; Guiral, Laurent; Becce, Fabio

doi:10.1002/art.40907

Cited by 3 publications

(4 citation statements)

References 3 publications

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“…The influence of mixed substances can be studied further in vivo if crystal verification uses a technique independent of chemical mixtures (eg, Raman spectroscopy). Coexistence of MSU/CPP/HA crystals is also an issue, 9,35 and a case report have found DECT successful for detection of coexisting gout and CPPD, 36 suggesting coexistence of crystals is not an obstacle.…”

Section: Strength and Limitationsmentioning

confidence: 99%

Dual-Energy Computed Tomography for Detection and Characterization of Monosodium Urate, Calcium Pyrophosphate, and Hydroxyapatite

et al. 2021

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Objectives: The aim of this study was to determine the diagnostic performance of dual-energy computed tomography (DECT) to detect and distinguish crystal deposits in a phantom. The primary objective was to determine the cutoff DECT ratio and the cross-sectional area (CSA) of a crystal deposit necessary to differentiate monosodium urate (MSU), calcium pyrophosphate (CPP), and calcium hydroxyapatite (HA) using DECT. Our secondary objective was to determine the concentration for limit of detection for MSU, CPP, and HA crystal deposits. Exploratory objectives included the comparison between 2 generations of DECT scanners from the same manufacturer as well as different scanner settings. Materials and Methods: We used a cylindrical soft tissue phantom with synthetic MSU, CPP, and HA crystals suspended in resin. Crystal suspension concentration increased with similar attenuation between MSU, CPP, and HA in conventional CT. The phantom was scanned on 2 dual-source DECT scanners, at 2 dose levels and all available tube voltage combinations. Both scanners had a tin (Sn) filter at the high-energy spectra. Dual-energy CT ratios were calculated for a given tube voltage combination by dividing linear regression lines of CT numbers against concentration. Dual-energy CT ratios were compared using an analysis of covariance. Receiver operating characteristic curves and corresponding areas under the curve (AUCs) were calculated for individual crystal suspension comparisons (HA vs CPP, MSU vs CPP, and MSU vs HA). Results: At standard clinical scan settings with 8 mGy and 80/Sn150 kV, the DECT ratios were as follows: CPP, 2.02 (95% confidence interval [CI], 1.98-2.07); HA, 2.00 (95% CI, 1.96-2.05); and MSU, 1.09 (95% CI, 1.06-1.11). Ratios varied numerically depending on the scanner and tube voltage combination. Monosodium urate crystal DECT ratios were significantly different from HA and CPP (P < 0.001), whereas DECT ratios for HA and CPP crystals did not differ significantly (P = 0.99). The differentiation of MSU crystals from both calcium crystals (HA and CPP) was excellent with an AUC of 1.00 (95% CI, 1.00-1.00) and an optimal cutoff DECT ratio of 1.43:1.40 depending on the scanner. In addition, differentiation of MSU and calcium-containing crystals (HA and CPP) required a CSA of minimum 4 pixels of crystal at standard clinical scan conditions. In contrast, differentiation between CPP and HA crystals was moderate with AUCs ranging from 0.66 (95% CI, 0.52-0.80) to 0.80 (95% CI, 0.69-0.91) and an optimal cutoff DECT ratio of 2.02:2.06 depending on the scanner. Furthermore, differentiation between CPP and HA crystals required a CSA of minimum 87 pixels of crystal at standard clinical scan conditions, corresponding to a region of interest of 3.7 mm diameter. When scanning at highest possible spectral separation and maximum dose of 50 mGy, the limit of detection for crystals within a region of interest of 50 pixels was 14 mg/cm 3 for MSU and 2 mg/cm 3 for both CPP and HA. Conclusions: This phantom study shows that DECT can be used to ...

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Section: Strength and Limitationsmentioning

confidence: 99%

Dual-Energy Computed Tomography for Detection and Characterization of Monosodium Urate, Calcium Pyrophosphate, and Hydroxyapatite

et al. 2021

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“…It would be interesting to know whether MSU crystals were replaced by CPPD crystals in lobules where CPPD crystals were highly compacted. Examination of frozen or alcohol‐fixed samples with persistent MSU crystals and the use of DECT and spectral‐energy CT technology to distinguish MSU, CPPD, and apatite crystal deposition would help better characterize tophus composition, especially in tophi with dense granulations with a calcium‐like density like those seen in the present study (6,10).…”

Section: Discussionmentioning

confidence: 84%

“…The nature of the calcium crystals in tophi has seldomly been characterized; one autopsy study identified CPPD crystals (9). Recently, DECT scans revealed CPPD energy attenuation patterns within MSU crystal deposits around the metacarpophalangeal joint of an 82‐year‐old man with gout and CPPD deposition disease (10). Another study described the presence of CPPD crystals in 5 tophi, without characterizing the type of CPPD crystals and with no data on gout history (11).…”

Section: Introductionmentioning

confidence: 99%

Calcium Pyrophosphate Dihydrate Crystal Deposition in Gouty Tophi

Gauffenic

Nguyen³

et al. 2020

Arthritis & Rheumatology

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Objective The coexistence of calcium pyrophosphate dihydrate (CPPD) and monosodium urate monohydrate crystals in gouty tophi has rarely been reported. We undertook this study to investigate CPPD crystal deposits in a series of surgically removed gouty tophi and to identify factors associated with these deposits. Methods Twenty‐five tophi from 22 gout patients were analyzed using polarized light microscopy, field emission scanning electron microscopy (FESEM), and μ Fourier transform infrared (μFTIR) spectroscopy. Results Tophi consisted of multiple lobules separated by fibrous septa and surrounded by a foreign‐body giant cell reaction. CPPD crystal aggregates were identified in 9 of 25 tophi from 6 patients. CPPD crystals were dispersed or highly compacted, localized at the edge or inside the tophus lobules, with some lobules completely filled with crystals. Both monoclinic and triclinic CPPD crystal phases were identified using FESEM and μFTIR. Compared to patients without CPPD, those with CPPD‐containing tophi were older (mean 60.5 years versus 47.2 years; P = 0.009), and had longer‐term gout duration (mean 17.0 years versus mean 9.0 years; P < 0.05) and tophi duration (mean 10.0 years versus mean 4.6 years; P < 0.01). None of the patients had radiographic chondrocalcinosis of the knee or wrist. Conclusion CPPD crystal formation seems to be a late and frequent event of tophus maturation, occurring more frequently with aging, and could contribute to the speed of tophus dissolution and the apparent persistence of tophus sometimes observed even after effective, long‐lasting urate‐lowering therapy.

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“…Although the used medical imaging phantom was of high quality and crystal compounds were homogeneously fabricated, in vivo conditions may be more heterogeneous with even mixed deposits, that is, coexisting MSU and calcium crystals. 42 However, simulated conditions should rather reflect limits of reference range to extrapolate to real in vivo conditions. Although we were able to reliably differentiate compounds in all phantom and human specimen scans and could visually identify crystalline MSU regions from possible confounders, we did not investigate the impact of material overlay.…”

Section: Discussionmentioning

confidence: 99%

Differentiation of Crystals Associated With Arthropathies by Spectral Photon-Counting Radiography

et al. 2020

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Objectives: The aims of this study were to test whether spectral photon-counting radiography (SPCR) is able to identify and distinguish different crystals associated with arthropathies in vitro and to validate findings in a gouty human third toe ex vivo. Materials and Methods: Industry-standard calibration rods of calcium pyrophosphate, calcium hydroxyapatite (HA), and monosodium urate (MSU) were scanned with SPCR in an experimental setup. Each material was available at 3 different concentrations, and a dedicated photon-counting detector was used for SPCR, whereas validation scans were obtained on a clinical dual-energy computed tomography (DECT) scanner. Regions of interest were placed on SPCR images and consecutive DECT images to measure x-ray attenuation characteristics, including effective atomic numbers (Z eff). Statistical tests were performed for differentiation of Z eff between concentrations, materials, and imaging modalities. In addition, a third toe from a patient with chronic gouty arthritis was scanned with SPCR and DECT for differentiation of MSU from HA. Results: In both SPCR and DECT, significant differences in attenuation and Z eff values were found for different concentrations among (P < 0.001) and between different materials (P < 0.001). Overall, quantitative measurements of Z eff did not differ significantly between SPCR-and DECT-derived measurements (P = 0.054-0.412). In the human cadaver toe, gouty bone erosions were visible on standard grayscale radiographic images; however, spectral image decomposition revealed the nature and extent of MSU deposits and was able to separate it from bone HA by Z eff. Conclusions: Identification and differentiation of different crystals related to arthropathies are possible with SPCR at comparable diagnostic accuracy to DECT. Further research is needed to assess diagnostic accuracy and clinical usability in vivo.

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Dual‐Energy Computed Tomography for the Noninvasive Diagnosis of Coexisting Gout and Calcium Pyrophosphate Deposition Disease

Cited by 3 publications

References 3 publications

Dual-Energy Computed Tomography for Detection and Characterization of Monosodium Urate, Calcium Pyrophosphate, and Hydroxyapatite

Dual-Energy Computed Tomography for Detection and Characterization of Monosodium Urate, Calcium Pyrophosphate, and Hydroxyapatite

Calcium Pyrophosphate Dihydrate Crystal Deposition in Gouty Tophi

Differentiation of Crystals Associated With Arthropathies by Spectral Photon-Counting Radiography

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