title: Dual-energy computed tomography has limited sensitivity for non-tophaceous gout: a comparison study with tophaceous gout.
abstract: BACKGROUND
  Dual-energy computed tomography (DECT) is a new diagnostic tool for gout, but its sensitivity has not been established. Our goal was to assess the sensitivity of DECT for the detection of monosodium urate (MSU) deposits in non-tophaceous and tophaceous gout, both at the level of the patient and that of the individual joint or lesion.
  
  
  METHODS
  DECT was performed on 11 patients with crystal-proven non-tophaceous gout and 10 with tophaceous gout and included both the upper and lower extremities in 20/21 patients. DECT images were simultaneously acquired at 80 and 140 kV and then processed on a workstation with proprietary software using a two-material decomposition algorithm. MSU deposits were color coded as green by the software and fused onto grey-scale CT images. The number and location of these deposits was tallied independently by two DECT-trained radiologists blinded to the clinical characteristics of the patient. Sensitivity of DECT was defined as the proportion of patients with a confirmed diagnosis of gout which was correctly identified as such by the imaging technique. All patients provided informed consent to participate in this IRB-approved study.
  
  
  RESULTS
  MSU deposits were detected by DECT in ≥1 joint area in 7/11 (64 %) patients with non-tophaceous gout, but were only detected in 3/12 (25 %) joints proven by aspiration to be affected with gout. Inclusion of the upper extremity joints in the scanning protocol did not improve sensitivity. All 10 patients with tophaceous gout had MSU deposits evident by DECT. The sensitivity of DECT for individual gouty erosions was assessed in 3 patients with extensive foot involvement. MSU deposits were detected by DECT within or immediately adjacent to 13/26 (50 %) erosions.
  
  
  CONCLUSIONS
  A DECT protocol that includes all lower extremity joints has moderate sensitivity in non-tophaceous and high sensitivity in tophaceous gout. However, DECT has lower sensitivity when restricted to individual crystal-proven gouty joints in non-tophaceous disease or individual erosive lesions in tophaceous gout. The detection of MSU deposits by DECT relates to their size and density and the detection parameters of the DECT scanner and adjustment of the latter might improve sensitivity.
authors.affiliation: Department of Medicine (Rheumatology), Johns Hopkins University School of Medicine, 5200 Eastern Avenue, Suite 4000, Mason Lord Center Tower, Baltimore, MD, 21224, USA. alanbaer@jhmi.edu.
authors.forename: Alan N
authors.initials: AN
authors.lastname: Baer
authors.affiliation: Department of Medicine (Rheumatology), Johns Hopkins University School of Medicine, 5200 Eastern Avenue, Suite 4000, Mason Lord Center Tower, Baltimore, MD, 21224, USA. tkurano@gmail.com.
authors.forename: Tracie
authors.initials: T
authors.lastname: Kurano
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA. uma.j.thakur@gmail.com.
authors.forename: Uma J
authors.initials: UJ
authors.lastname: Thakur
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA. gthawai1@jhmi.edu.
authors.forename: Gaurav K
authors.initials: GK
authors.lastname: Thawait
authors.affiliation: Siemens Medical Solutions USA Inc., Malvern, PA, USA. matthew.fuld@siemens.edu.
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Fuld
authors.affiliation: Department of Medicine (Rheumatology), Johns Hopkins University School of Medicine, 5200 Eastern Avenue, Suite 4000, Mason Lord Center Tower, Baltimore, MD, 21224, USA. janetmaynard@gmail.com.
authors.forename: Janet W
authors.initials: JW
authors.lastname: Maynard
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. mara@jhu.edu.
authors.forename: Mara
authors.initials: M
authors.lastname: McAdams-DeMarco
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA. efishman@jhmi.edu.
authors.forename: Elliot K
authors.initials: EK
authors.lastname: Fishman
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA. carrinoj@hss.edu.
authors.forename: John A
authors.initials: JA
authors.lastname: Carrino
mesh_terms: D015502:Absorptiometry, Photon / Q000592:standards*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006073:Gout / Q000145:classification* / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed / Q000592:standards*; D014527:Uric Acid / Q000032:analysis
chemical_list: D014527:Uric Acid