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Dual-energy CT depicts uric acid crystals in gout and can add information to joint fluid aspiration, possibly replacing it in some patients with an acutely inflamed joint, and may be a diagnostic imaging modality in patients who do not undergo aspiration.


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.

Materials and Methods

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


  • 1 Roubenoff R, Klag MJ, Mead LA, Liang KY, Seidler AJ, Hochberg MC. Incidence and risk factors for gout in white men. JAMA 1991;266(21):3004–3007.
  • 2 Hak AE, Choi HK. Lifestyle and gout. Curr Opin Rheumatol 2008;20(2):179–186.
  • 3 Wallace KL, Riedel AA, Joseph-Ridge N, Wortmann R. Increasing prevalence of gout and hyperuricemia over 10 years among older adults in a managed care population. J Rheumatol 2004;31(8):1582–1587.
  • 4 Lawrence RC, Felson DT, Helmick CG, et al.. Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part II. Arthritis Rheum 2008;58(1):26–35.
  • 5 Choi HK, Mount DB, Reginato AM; American College of Physicians; American Physiological Society. Pathogenesis of gout. Ann Intern Med 2005;143(7):499–516.
  • 6 Terkeltaub R. Update on gout: new therapeutic strategies and options. Nat Rev Rheumatol 2010;6(1):30–38.
  • 7 Schlesinger N, Dalbeth N, Perez-Ruiz F. Gout—what are the treatment options? Expert Opin Pharmacother 2009;10(8):1319–1328.
  • 8 Swan A, Amer H, Dieppe P. The value of synovial fluid assays in the diagnosis of joint disease: a literature survey. Ann Rheum Dis 2002;61(6):493–498.
  • 9 Schlesinger N. Diagnosis of gout: clinical, laboratory, and radiologic findings. Am J Manag Care 2005;11(15 suppl):S443–S450; quiz S465–S468.
  • 10 Schlesinger N, Norquist JM, Watson DJ. Serum urate during acute gout. J Rheumatol 2009;36(6):1287–1289.
  • 11 Schlesinger N, Baker DG, Schumacher HR. Serum urate during bouts of acute gouty arthritis. J Rheumatol 1997;24(11):2265–2266.
  • 12 Buckley TJ. Radiologic features of gout. Am Fam Physician 1996;54(4):1232–1238.
  • 13 Peh WC. Tophaceous gout. Am J Orthop 2001;30(8):665.
  • 14 Primak AN, Fletcher JG, Vrtiska TJ, et al.. Noninvasive differentiation of uric acid versus non-uric acid kidney stones using dual-energy CT. Acad Radiol 2007;14(12):1441–1447.
  • 15 Graser A, Johnson TR, Bader M, et al.. Dual energy CT characterization of urinary calculi: initial in vitro and clinical experience. Invest Radiol 2008;43(2):112–119.
  • 16 Johnson TR, Krauss B, Sedlmair M, et al.. Material differentiation by dual energy CT: initial experience. Eur Radiol 2007;17(6):1510–1517.
  • 17 Choi HK, Al-Arfaj AM, Eftekhari A, et al.. Dual energy computed tomography in tophaceous gout. Ann Rheum Dis 2009;68(10):1609–1612.
  • 18 Nicolaou S, Yong-Hing CJ, Galea-Soler S, Hou DJ, Louis L, Munk P. Dual-energy CT as a potential new diagnostic tool in the management of gout in the acute setting. AJR Am J Roentgenol 2010;194(4):1072–1078.
  • 19 Bacani AK, McCollough CH, Glazebrook KN, et al.. Dual energy computed tomography for quantification of tissue urate deposits in tophaceous gout: help from modern physics in the management of an ancient disease. Rheumatol Int. Published December 17, 2009. Accessed May 16, 2011.
  • 20 Primak AN, Ramirez Giraldo JC, Liu X, Yu L, McCollough CH. Improved dual-energy material discrimination for dual-source CT by means of additional spectral filtration. Med Phys 2009;36(4):1359–1369.
  • 21 Primak AN, Giraldo JC, Eusemann CD, et al.. Dual-source dual-energy CT with additional tin filtration: dose and image quality evaluation in phantoms and in vivo. AJR Am J Roentgenol 2010;195(5):1164–1174.
  • 22 Clopper CJ, Perason ES. The use of confidence or fudicial limits illustrated in the case of the binomial. Biometrika 1934;26(4):404–413.
  • 23 Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33(1):159–174.
  • 24 McCarty DJ, Hollander JL. Identification of urate crystals in gouty synovial fluid. Ann Intern Med 1961;54:452–460.
  • 25 Chen CK, Chung CB, Yeh L, et al.. Carpal tunnel syndrome caused by tophaceous gout: CT and MR imaging features in 20 patients. AJR Am J Roentgenol 2000;175(3):655–659.
  • 26 Perez-Ruiz F, Dalbeth N, Urresola A, de Miguel E, Schlesinger N. Imaging of gout: findings and utility. Arthritis Res Ther 2009;11(3):232.
  • 27 Narváez JA, Narváez J, Ortega R, De Lama E, Roca Y, Vidal N. Hypointense synovial lesions on T2-weighted images: differential diagnosis with pathologic correlation. AJR Am J Roentgenol 2003;181(3):761–769.
  • 28 Thiele RG, Schlesinger N. Diagnosis of gout by ultrasound. Rheumatology (Oxford) 2007;46(7):1116–1121.
  • 29 Dalbeth N, Schauer C, MacDonald P, et al.. Methods of tophus assessment in clinical trials of chronic gout: a systematic literature review and pictorial reference guide. Ann Rheum Dis 2010;70(4):597–604.
  • 30 National Research Council. Committee to Assess Health Risks from Exposure to Low Level of Ionizing Radiation. Health risks from exposure to low levels of ionizing radiation: BEIR VII Phase 2. Washington, DC: National Academies Press, 2006.
  • 31 McCollough CH, Guimarães L, Fletcher JG. In defense of body CT. AJR Am J Roentgenol 2009;193(1):28–39.

Article History

Received December 20, 2010; revision requested February 21, 2011; final revision received July 6; accepted July 12; final version accepted July 13.
Published online: Nov 2011
Published in print: Nov 2011