Background The vertebrae of the cervical spine are rather small and it may be difficult to assess if small areas with signal intensity changes represent the bones, joints or entheses, or derive from the surrounding blood vessels.
Objectives To investigate if image resolution affects the assessment of inflammatory and structural lesions of the cervical spine.
Methods Forty-nine patients with axial spondyloarthritis according to the ASAS criteria started anti-TNF treatment and had “standard” resolution (std-res) and “high” resolution (high-res) MRI sequences of the cervical spine performed at baseline and after 48 weeks. 3 patients had follow-up scan already after 6–24 weeks due to study exclusion.
Std-res: STIR sequence: Voxel size 5.0 mm3 (slice thickness 4.0, spatial resolution 1x1.25); T1W sequence: voxel size 4.5 mm3 (slice thickness 4.0, spatial resolution 0.9x1.25).
High-res: STIR sequence: Voxel size 3.1 mm3 (slice thickness 3.5, spatial resolution 0.8x1.11); T1W sequence: voxel size 1.4 mm3 (slice thickness 3.0, spatial resolution 0.6x0.76).
Images were assessed in known chronology by an experienced axSpA MRI reader (SJP) blinded to clinical data. High-res and std-res were read in random order. MRI lesions of inflammation, fat and new bone formation were defined according to the Canada-Denmark working group [1,2]. Erosions were not assessed.
Results Inflammatory lesions: In 9 of 43 patients (21%), inflammatory lesions were detected in the cervical spine at baseline at std-res, while this was detected in 14 of 43 patients (33%) at high-res. Using high-res, as compared to std-res, 6 patients were reclassified from negative to positive for inflammation, 1 patient was reclassified from positive to negative, and 8/28 patients remained classified as positive/negative, p=0.13 by Exact McNemar test. The mean inflammation score was significantly higher at high-res compared to std-res (1.7 (SD 4.5) vs. 0.8 (SD 2.7), p=0.04 by paired t-test).
Fat lesions: 11 of 43 patients (26%) had fat lesions in the cervical spine at baseline using std-res, while 10 of 43 patients (23%) had this using high-res. The mean fat score was significantly higher at high-res compared with std-res (1.6 (SD 3.5) vs. 0.8 (SD 1.8), p=0.02 by paired t-test).
Bone spurs/ankylosis: 11 of 43 patients (26%) had bone spurs/ankylosis of the cervical spine at baseline at std-res, while 10 of 43 patients (23%) using high-res. The mean new bone formation score was significantly higher at high-res compared with std-res (2.7 (SD 6.1) vs. 1.4 (SD 3.5), p=0.01 by paired t-test).
Responsiveness: Standardized response mean for inflammation score at std-res was 0.15, and at high-res 0.14. Structural lesions remained largely unchanged in all patients.
Conclusions More patients were classified as having inflammatory lesions in the cervical spine when using high-res MRI, compared to std-res. Likewise, mean scores of inflammatory lesions, fatty lesions and new bone formation were significantly higher compared with std-res. Further studies are needed to investigate the clinical significance of these findings as well as the frequency of these minor lesions in healthy controls.
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Østergaard M, et al. J Rheumatol 2009;S84:18–34.
Disclosure of Interest None declared