title: Evaluation of sacroiliitis: contrast-enhanced MRI with subtraction technique.
abstract: OBJECTIVE
  The purpose of the study was to investigate the diagnostic value of contrast-enhanced MRI using the subtraction technique in the detection of active sacroiliitis.
  
  
  METHODS
  Magnetic resonance imaging was performed in 8 asymptomatic volunteers and 50 patients with clinically suspected active sacroiliitis. On precontrast MR images, T1-weighted spin-echo images with and without fat saturation (T1WFS and T1W), STIR and 3D-FLASH images with fat saturation were obtained in the semicoronal plane using a 1.5 Tesla imager. Postcontrast MRI was performed using the same T1WFS sequence as before contrast injection for all volunteers and patients. Postcontrast images were subtracted from fat-suppressed precontrast images. Enhancement within the joint space and bone marrow was considered to demonstrate active sacroiliitis.
  
  
  RESULTS
  In 50 patients (100 sacroiliac joints [SIJs]), 40 (76 SIJs) were considered to have active sacroiliitis based on MR images. Bone marrow edema was present in 33 patients (62 SIJs) on STIR images. Routine MRI allowed identification of contrast enhancement in SIJs on postcontrast T1WFS images in 31 patients (49 SIJs). Contrast enhancement was observed in 40 patients (76 SIJs) who were examined by MRI using the subtraction technique. Contrast enhancement was significantly more conspicuous on subtraction images than on non-subtracted postcontrast T1WFS images (Mann-Whitney U test, p<0.001).
  
  
  CONCLUSIONS
  Contrast-enhanced MRI with subtraction technique may be useful for early detection of active sacroiliitis.
authors.affiliation: Medical Faculty, Department of Radiology, Uludag University, Bursa, Turkey. droktayalgin@gmail.com
authors.forename: Oktay
authors.initials: O
authors.lastname: Algin
authors.forename: Gokhan
authors.initials: G
authors.lastname: Gokalp
authors.forename: Bulent
authors.initials: B
authors.lastname: Baran
authors.forename: Gokhan
authors.initials: G
authors.lastname: Ocakoglu
authors.forename: Zeynep
authors.initials: Z
authors.lastname: Yazici
mesh_terms: D000328:Adult; D001168:Arthritis / Q000175:diagnosis*; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012446:Sacroiliac Joint / Q000473:pathology*; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D055815:Young Adult
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA