title: Magnetic resonance imaging of active sacroiliitis: do we really need gadolinium?
abstract: BACKGROUND
  Magnetic resonance imaging (MRI) of active inflammatory changes of the sacroiliac joint (SIJ) in spondyloarthritis (SpA) is performed with short tau inversion recovery (STIR) sequences and fat-saturated T1-weighted fast spin-echo (FSE) sequences after administration of gadolinium-based contrast medium (T1/Gd). The aim of the present study was to compare these two pulse sequences in terms of diagnosis, diagnostic confidence, and quantification of inflammatory changes.
  
  
  METHODS
  The study included 105 patients with suspected SpA; 72 patients developed clinical SpA over time. All patients were examined with STIR and T1/Gd and each of the two sequences was analyzed separately in conjunction with unenhanced T1 FSE images. For quantitative estimation of inflammatory changes, each sacroiliac joint (SIJ) was divided into 4 quadrants (and severity per quadrant was assigned a score of 0-4, resulting in a maximum sum score of 16 per SIJ). Diagnostic confidence was assessed on a visual analogue scale ranging from 0 to 10.
  
  
  RESULTS
  Active sacroiliitis was diagnosed in 46 patients and ruled out in 34 using STIR, whereas findings were inconclusive in 25 patients. The corresponding numbers for T1/Gd were 47, 44, and 14. Diagnostic confidence was significantly lower for STIR (7.3+/-2.6) compared with T1/Gd (8.7+/-1.9) (p<0.001). The sum scores were 2.5 (+/-3.3) for STIR and 2.2 (+/-3.2) for T1/Gd for the right SIJ and 2.2 (+/-2.9) (STIR) and 1.9 (+/-3.1) (T1/Gd) for the left SIJ. Agreement was high with intraclass correlation coefficient (ICC) values of 0.86 for the right SIJ and 0.90 for the left SIJ and positive correlation (r=0.62 right, 0.60 left).
  
  
  CONCLUSIONS
  STIR sequences alone are sufficient for establishing a reliable diagnosis and quantify the amount of inflammation in active sacroiliitis. A contrast-enhanced study is dispensable in patients with established disease or in the setting of clinical follow-up studies. However, a contrast-enhanced MR sequence is beneficial to ensure maximum diagnostic confidence when patients with early sacroiliitis are examined.
authors.affiliation: Department of Radiology, Charité-Universitätsmedizin Berlin, Campus Mitte, Charitéplatz 1, 10117 Berlin, Germany. christian.althoff@charite.de
authors.forename: Christian E
authors.initials: CE
authors.lastname: Althoff
authors.forename: Eugen
authors.initials: E
authors.lastname: Feist
authors.forename: Elena
authors.initials: E
authors.lastname: Burova
authors.forename: Iris
authors.initials: I
authors.lastname: Eshed
authors.forename: Matthias
authors.initials: M
authors.lastname: Bollow
authors.forename: Bernd
authors.initials: B
authors.lastname: Hamm
authors.forename: Kay-Geert A
authors.initials: KG
authors.lastname: Hermann
mesh_terms: D000328:Adult; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012446:Sacroiliac Joint / Q000473:pathology*; D012680:Sensitivity and Specificity; D025241:Spondylarthritis / Q000175:diagnosis*
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA