Date: Monday, November 9, 2015
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Reporting of focal fat infiltrations (FFI) in sacroiliac joints (SIJs) is becoming more important in patients with axial spondyloarthritis (SpA) since this lesion has been shown to be an independent predictor of ankylosis. T1 relaxation times depend on magnetic field strength and hence T1 contrast behavior of bone marrow (i.e. the visualization of fat in the bone marrow) is magnetic field strengths dependent. Therefore FFI may be scored differently depending of the field strength.
19 SpA patients (10 males age 42.8±13.8 years, 9 females age 42.5±12.5 years) and 3 healthy volunteers (1 male age 49 years, 2 females age 39.5±9.1 years) underwent MRI at 1.5T (Time to repeat (TR)/ time to echo (TE) 550/14 ms voxel dimension 1×1.5×4 mm) and 3T (TR/TE: 700/20 ms voxel dimension 1×1.5×4 mm). The cartilaginous part of the SIJs were divided into 8 quadrants and evaluated on 5 consecutive slices (1) and were analyzed for FFI in two ways: 1. If FFI was present the signal intensity (SI) was measured. On every slice normal bone marrow SI and standard deviation of the noise (SDn) was measured. Contrast to noise ratio (CNR) was calculated as the difference between normal SI and FFI SI divided by SDn. 2. All quadrants were scored for presence/absence of FFI according to the Spondyloarthritis Research Consortium of Canada (SPARCC) SIJ Structural Score (SSS)(1). The intra-observer variation of both methods was assessed in six patients and expressed as the Intraclass Correlation Coefficient (ICC). The paired t-test was used for comparing CNR results. SSS results were compared using the Wilcoxon Signed Rank test.
The ICC for CNR was 0.90 at 1.5T and 0.77 at 3T, and for SSS 0.96 at 1.5T and 0.94 at 3T. On both right and left side, CNR was higher at 3T (p < 0.001) compared to 1.5T. SDn was lower (p < 0.001) at 3T compared to 1.5T. For SSS the sum of scores was 160 (mean 7.3) at 1.5T and 169 (7.7) at 3T (p = 0.87)
3T compared to 1.5T MRI provides a better contrast to noise ratio, but the intra-observer agreement and total scores of focal fat infiltration are identical.
To cite this abstract in AMA style:Møller JM, Jankovic J, Østergaard M, Sorensen IJ, Poggenborg R, Rintek Madsen O, Thomsen HS, Pedersen SJ. Assessment of Focal Fat Infiltration in Sacroiliac Joints in Patients with Spondyloarthritis By 1.5T Versus 3.0T Magnetic Resonance Imaging: Is the Field Strength Important to Contrast to Noise Ratios, Reproducibility and Total Scores? [abstract]. Arthritis Rheumatol. 2015; 67 (suppl 10). http://acrabstracts.org/abstract/assessment-of-focal-fat-infiltration-in-sacroiliac-joints-in-patients-with-spondyloarthritis-by-1-5t-versus-3-0t-magnetic-resonance-imaging-is-the-field-strength-important-to-contrast-to-noise-ratios/. Accessed May 26, 2018.
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