Does adding a high-resolution 3D sequence improve the accuracy of erosion detection in pediatric sacroiliac joint MRI?

OBJECTIVE: To evaluate whether adding an erosion-sensitive high-resolution 3D sequence to sacroiliac joint (SIJ) MRI protocols in children improves erosion detection and diagnosis of Juvenile Spondyloarthritis (JSpA). MATERIALS AND METHODS: SIJ-MRI were prospectively obtained in 84 children (50 girls, mean age 13.3 y) clinically suspected of JSpA, conforming to 2024 ASAS/SPARTAN recommendations including a volumetric interpolated breath-hold examination (VIBE) sequence. Three experienced radiologists recorded the presence of erosions, non-erosion bony defects, and the presence of JSpA, with confidence scoring for each, in 3 blinded re-randomized reading exercises: (1) T1-weighted spin-echo (T1) and short-tau inversion recovery (STIR) sequences only; (2) VIBE only; (3) all sequences. Discrepancies were resolved by consensus read-out. The reference standard was rheumatologist diagnosis of JSpA. RESULTS: MRI was considered indicative of JSpA in 14 cases (16.7%) on T1/STIR, 21 (25.0%) on VIBE only, and 15 (17.9%) with all sequences. In the three exercises, erosions were scored in 12 (14.3%), 22 (26.2%), and 13 (15.5%) cases, and non-erosion bony defects in 43 (51.2%), 79 (94.0%), and 80 (95.2%) cases. Sensitivity/specificity for JSpA diagnosis was 34.6/91.4%, 42.3/82.8%, and 38.5/91.4%, after consensus read-out 38.5/94.8%. Mean absolute values of confidence scores significantly improved for all features after adding VIBE, although inter-reader agreement did not consistently improve. CONCLUSION: Adding VIBE to T1/STIR significantly increased reader confidence in JSpA diagnosis. However, a trend toward improved sensitivity and specificity was not statistically significant. If the ASAS-SPARTAN SIJ MRI protocol is applied to children, all sequences must be interpreted together to avoid mistaking non-erosion defects for true erosions. KEY POINTS: Question Can the recently published ASAS-SPARTAN adult standardized image acquisition protocol for sacroiliac joint MRI be used for diagnostic evaluation of sacroiliitis in children suspected for Juvenile Spondyloarthropathy (JSpA)? Findings The ASAS/SPARTAN recommendations including a high-resolution 3D erosion-sensitive sequence can also be applied to children, resulting in significantly increased reader confidence, with a trend toward improved sensitivity/specificity for diagnosing JSpA, although not statistically significant. Clinical relevance The ASAS-SPARTAN adult sacroiliac joint MRI protocol can also be beneficially applied to children, as long as all sequences are interpreted together to avoid mistaking non-erosion defects (almost universally seen on the 3D erosion-sensitive sequences in children) for true erosions.