Session Title: Imaging of Rheumatic Diseases - Poster II: XR/CT/PET/MRI
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Background/Purpose: to assess increased SIJ uptakes on 18-FNa (an osteoblastic tracer) PET/CT according to a qualitative and quantitative approach and to compare with MRI SIJ assessments for inflammation and with CT-scan for structural damage in a population of 23 patients with SpA (IDRCB: 2012-A00568-35).
Methods: This single-center prospective study included 23 patients with active SpA according to ASAS and/or modified mNY criteria (males 43.5%, HLA-B27 30%, years 44, symptom duration 7.7 years, median CRP 8mg/L, median BASDAI 6.1). All patients had a pelvic AP-view radiograph, MRI of the SIJ and 18-FNa PET/CT examinations during the same month. For MRI, SIJ were assessed for the presence/absence of inflammation according to ASAS criteria and were quantitatively assessed according to SPARCC method for scoring inflammation. CT-scans were read by three readers blinded to MRI images. Structural lesions were scored in consecutive slices in SIJ quadrants (erosion, sclerosis) or SIJ halves (ankylosis) on a dichotomous basis (present/absent) using the same anatomical principles for defining SIJ quadrants as developed for the SPARCC MRI SIJ inflammation and structural scores. On the 18-FNa PET, SIJ were scored blinded to MRI and CT images by two nuclear physicians according to a slice by slice approach performed from the anterior to the posterior part of the joint. A positive PET was defined when unilateral (sacral or iliac part) uptake was observed on 2 consecutive slices or when bilateral uptake was depicted on a single slice. As for SPARCC MRI methods, quantitative assessment on 18-FNa PET was performed according to SIJ quadrants for six consecutive slices through the cartilaginous region of the joint (PET-activity score). The Standardized Maximal Uptake Value (SUV-max) was measured for each SIJ, corresponding to the highest uptake value of the SIJ.
Results: 7 patients had radiographic sacroiliitis, 9 had inflammatory sacroiliitis on MRI (mean SPARCC 7.65). On CT-scan, inter-reader reliabilities for ankylosis, erosion and sclerosis were excellent to mild (ICC=0.95; ICC=0.81; ICC=0.39) respectively. The concordance between the two readers for a positive PET was good (73.9%) as well as the inter-reader reliabilities for the PET-activity score (ICC= 0.69 (95%CI: 0.40 to 0.86)). 18 patients had a positive PET with a mean PET-activity score of 15.7 (± 14). The mean SUV-max for a positive PET was 1.91 versus 1.27 for a negative one. According to a binary approach, a positive PET did not correlate to a positive MRI (ASAS criteria) or to a structural sacroiliitis on CT-scan. The PET-activity score (r=0.57, p=0.005) and SUV-max (r= 0.02, p=0.046) correlated with the SPARCC inflammation score but not with erosion, ankylosis and both ankylosis-erosions scores on CT-scan (ICC=-0.04; p=0.85), (ICC=-0.30; p=0.16) and (ICC=-0.19; p=0.37) respectively.
Conclusion: In axial SpA, the frequency of a positive 18-FNa PET (78.3%) was higher than the frequency of an ASAS positive MRI for inflammatory sacroiliitis (39.1%) and was also higher than the frequency of structural damages on CT-scan (39.1%). PET activity score had a good correlation with inflammatory sacroiliitis but not with structural lesion on CT-scan.
To cite this abstract in AMA style:Raynal M, remy O, Melchior J, Chary-Valckenaere I, Ngueyon Sime W, Maksymowych WP, Lambert RG, Loeuille D. Performance of 18fluoride Sodium Positron Emission Tomography with Computed Tomography to Assess Inflammatory and Structural Sacroiliitis Respectively on Magnetic Resonance Imaging and Computed Tomography in Axial Spondyloarthritis [abstract]. Arthritis Rheumatol. 2016; 68 (suppl 10). https://acrabstracts.org/abstract/performance-of-18fluoride-sodium-positron-emission-tomography-with-computed-tomography-to-assess-inflammatory-and-structural-sacroiliitis-respectively-on-magnetic-resonance-imaging-and-computed-tomogr/. Accessed October 17, 2021.
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