Dual energy CT findings in gout with rapid kilovoltage-switching source with gemstone scintillator detector

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Abstract

Background

A definite diagnosis of gout requires demonstration of monosodium urate crystals in synovial fluid or in tophi, which in clinical practice today seldom is done. Dual energy CT (DECT) has repeatedly been shown to be able to detect monosodium urate crystals in tissues, hence being an alternative method to synovial fluid microscopy. The vast majority of these studies were performed with CT scanners with two X-ray tubes. In the present study we aim to investigate if and at what locations DECT with rapid kilovoltage-switching source with gemstone scintillator detector (GSI) can identify MSU crystals in patients with clinically diagnosed gout. We also performed a reliability study between two independent readings.

Methods

Patients with new or established gout who had been examined with DECT GSI scanning of the feet at Sahlgrenska University Hospital, Mölndal between 2015 and 2018 were identified. Their medical records were sought for gout disease characteristics using a structured protocol. Urate deposits in MTP1, MTP 2–5, ankle/midfoot joints and tendons were scored semiquantatively in both feet and presence of artifacts in nail and skin as well as beam hardening and noise were recorded. Two radiologists performed two combined readings and scoring of the images, thus consensus was reached over the scoring at each occasion (Espeland et al., BMC Med Imaging. 2013;13:4). The two readings were compared with kappa statistics.

Results

DECT GSI could identify urate deposits in the feet of all 55 participants with gout. Deposits were identified in the MTP-joints of all subjects but were also present in ankle/midfoot joints and tendons in 96 and 75% respectively. Deposition of urate was predicted by longer disease duration (Spearman’s Rho 0.64, p < .0001) and presence of tophi ( p = 0.0005). Artifacts were common and mostly found in the nails (73%), a minority displayed skin artifacts (31%) while beam hardening and noise was rare. The agreement between the two readings was good (Κ = 0.66, 95% CI = 0.61–0.71).

Conclusion

The validity of DECT GSI in gout is supported by the identification of urate in all patients with clinical gout and the good correlations with clinical characteristics. The occurrence of artifacts was relatively low with expected locations.

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Most cited references 14

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Dual-energy CT for the diagnosis of gout: an accuracy and diagnostic yield study

Tim Bongartz, Katrina Glazebrook, Steven Kavros … (2014)

Objectives To assess the accuracy of dual-energy CT (DECT) for diagnosing gout, and to explore whether it can have any impact on clinical decision making beyond the established diagnostic approach using polarising microscopy of synovial fluid (diagnostic yield). Methods Diagnostic single-centre study of 40 patients with active gout, and 41 individuals with other types of joint disease. Sensitivity and specificity of DECT for diagnosing gout was calculated against a combined reference standard (polarising and electron microscopy of synovial fluid). To explore the diagnostic yield of DECT scanning, a third cohort was assembled consisting of patients with inflammatory arthritis and risk factors for gout who had negative synovial fluid polarising microscopy results. Among these patients, the proportion of subjects with DECT findings indicating a diagnosis of gout was assessed. Results The sensitivity and specificity of DECT for diagnosing gout was 0.90 (95% CI 0.76 to 0.97) and 0.83 (95% CI 0.68 to 0.93), respectively. All false negative patients were observed among patients with acute, recent-onset gout. All false positive patients had advanced knee osteoarthritis. DECT in the diagnostic yield cohort revealed evidence of uric acid deposition in 14 out of 30 patients (46.7%). Conclusions DECT provides good diagnostic accuracy for detection of monosodium urate (MSU) deposits in patients with gout. However, sensitivity is lower in patients with recent-onset disease. DECT has a significant impact on clinical decision making when gout is suspected, but polarising microscopy of synovial fluid fails to demonstrate the presence of MSU crystals.

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Identification of intraarticular and periarticular uric acid crystals with dual-energy CT: initial evaluation.

Andre L. S. Guimarães, Ch Murthy, G. Fletcher … (2011)

To estimate the accuracy, sensitivity, specificity, and interobserver agreement of dual-energy computed tomography (CT) in detection of uric acid crystals in joints or periarticular structures in patients with arthralgia and patients suspected of having gout, with joint aspiration results as reference standard. With institutional review board approval, patient consent, and HIPAA compliance, 94 patients (age range, 29-89 years) underwent dual-source, dual-energy (80 and 140 kVp) CT of a painful joint. A material decomposition algorithm was used to identify uric acid. Two blinded musculoskeletal radiologists evaluated the dual-energy CT images and classified the examination findings as positive or negative for the presence of uric acid crystals. Reference standard was the result of joint aspiration. Forty-three of 94 patients (46%) underwent attempted joint aspiration within 1 month of dual-energy CT. Aspiration was successful in 31 of 43 patients (72%). In 12 of 31 patients (39%), uric acid crystals were identified at joint aspiration; in 19 patients, they were not. Readers 1 and 2 had no false-negative findings for uric acid at dual-energy CT. Sensitivity was 100% (12 of 12; 95% confidence interval (CI): 74%, 100%) for both readers. Specificity was 89% (17 of 19; 95% CI: 67%, 99% ) for reader 1 and 79% (15 of 19; 95% CI: 54%, 94%) for reader 2, with near-perfect agreement between the readers (κ = 0.87; range, 0.70-1.00) in the 31 patients who underwent aspiration. Initial retrospective assessment suggests that dual-energy CT is a sensitive, noninvasive, and reproducible method for identifying uric acid deposits in joints and periarticular soft tissues in patients suspected of having gout. RSNA, 2011

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Dual energy CT in gout: a prospective validation study.

Savvas Nicolaou, H. Ouellette-Kuntz, Penelope Burns … (2012)

The authors prospectively determined: (1) the specificity and sensitivity of dual energy CT (DECT) for gout; and (2) the interobserver and intraobserver reproducibility for DECT urate volume measurements. Forty crystal-proven gout patients (17 tophaceous) and 40 controls with other arthritic conditions prospectively underwent DECT scans of all peripheral joints using a gout protocol that color-codes the composition of tissues. A blinded radiologist identified urate deposition to calculate specificity and sensitivity of DECT for gout. Inter-rater volumetric reproducibility was determined by two independent radiologists on 40 index tophi from the 17 tophaceous gout patients using automated software. The mean age of the 40 gout patients was 62 years, the mean gout duration was 13 years and 87% had a history of urate-lowering therapy (ULT). The specificity and sensitivity of DECT for gout were 0.93 (95% CI, 0.80 to 0.98) and 0.78 (0.62 to 0.89), respectively. When the authors excluded three gout cases with unreadable or incomplete scans, the sensitivity was 0.84 (95% CI, 0.68 to 0.94). The urate volumes of 40 index tophi ranged from 0.06 cm(3) to 18.74 cm(3) with a mean of 2.45 cm(3). Interobserver and intraobserver intraclass correlation coefficients for DECT volume measurements were 1.00 (95% CI, 1.00 to 1.00) and 1.00 (95% CI, 1.00 to 1.00) with corresponding bias estimates (SD) of 0.01 (0.00) cm(3) and 0.01 (0.03) cm(3). These prospective data indicate high reproducibility of DECT urate volume measures. The specificity was high, but sensitivity was more moderate, potentially due to frequent ULT use in our patients.

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Author and article information

Contributors

Mats Dehlin: mats.dehlin@vgregion.se

Journal

Journal ID (nlm-ta): BMC Rheumatol

Journal ID (iso-abbrev): BMC Rheumatol

Title: BMC Rheumatology

Publisher: BioMed Central (London )

ISSN (Electronic): 2520-1026

Publication date (Electronic): 17 January 2020

Publication date PMC-release: 17 January 2020

Publication date Collection: 2020

Volume: 4

Electronic Location Identifier: 7

Affiliations

[1 ]ISNI 0000 0000 9919 9582, GRID grid.8761.8, Department of Radiology at Institute of Clinical Sciences, , Sahlgrenska Academy, ; Gothenburg, Sweden

[2 ]ISNI 0000 0000 9919 9582, GRID grid.8761.8, Department of Rheumatology and Inflammation Research, , Sahlgrenska Academy, ; Gothenburg, Sweden

[3 ]ISNI 0000 0004 1936 9457, GRID grid.8993.b, Center of Clinical Research (CKF) Dalarna, , Uppsala University, ; Uppsala, Sweden

Article

Publisher ID: 104

DOI: 10.1186/s41927-019-0104-5

PMC ID: 6966802

PubMed ID: 31989100

SO-VID: 922304f2-ca81-44ae-9b25-fa044de6159a

License:

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

History

Date received : 26 June 2019

Date accepted : 30 October 2019

Funding

Funded by: FundRef http://dx.doi.org/10.13039/501100007949, Reumatikerförbundet;

Award ID: .

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Keywords: gout,dual energy ct,monosodium urate crystals,foot,diagnostic imaging

Data availability:

Keywords: gout, dual energy ct, monosodium urate crystals, foot, diagnostic imaging

Dual energy CT findings in gout with rapid kilovoltage-switching source with gemstone scintillator detector

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Most cited references 14

Dual-energy CT for the diagnosis of gout: an accuracy and diagnostic yield study

Identification of intraarticular and periarticular uric acid crystals with dual-energy CT: initial evaluation.

Dual energy CT in gout: a prospective validation study.

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