Subchondral high T2 signal in pediatric sacroiliac joint MRI : a normal finding that can mimic sacroiliitis
Bibliographic record
Abstract
O044 Subchondral high T2 signal in pediatric sacroiliac joint MRI: a normal finding that can mimic sacroiliitis N. Herregods1 , L. B. Jans1 , M. Chen1 , T. Renson2 , J. Dehoorne2 , R. Joos2 , R. G. Lambert3 , J. Jaremko3 1 Radiology and Nuclear Medicine;2 Pediatric Rheumatology, Ghent University Hospital, Ghent, Belgium, 3 Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Canada Correspondence: N. Herregods Pediatric Rheumatology 2020, 18(Suppl 2):O044 Introduction: Understanding of the normal magnetic resonance imaging (MRI) appearance of the developing sacroiliac joint (SIJ) is important for distinguishing normal developmental variations from disease. Subchondral signal changes in SIJ in children can give rise to diagnostic challenges and false positive diagnoses of sacroiliitis, as they can mimic bone marrow edema (BME). Objectives: To determine how subchondral signal intensity on T2- weighted images in SI-joints in children varies with age, sex and closure of segmental apophyses of the sacrum. Pediatric Rheumatology 2020, 18(Suppl 2):83 Page 23 of 115 Methods: MRI of 502 SIJ in 251 children (132 girls), mean age 12.4 years (range 6.1-18.0), were obtained. Ethics committee approval was obtained, informed consent was signed by all children and parents. 127/251 had asymptomatic joints and were imaged for nonrheumatologic reasons in whom we added semi-coronal T1 and STIR of the SI joints, and 124 had low back pain but no sign of sacroiliitis on initial clinical MRI review. Before the main reading exercise, images of 10 participants (20 SIJ) who had been excluded from the study were used for multi-step calibration exercises. Three calibration rounds were conducted over 8 months. Subchondral high signal (‘flaring’) was defined as increased signal in subarticular bone on STIR images compared to normal bone marrow in the centre of S1 and S2 vertebral bodies. After calibration, three subspecialist radiologists independently scored subchondral signal changes from 0-3 in 4 locations: vertical sacral (along the lateral apophyses of the sacrum), horizontal sacral (along the intersegmental apophyses), iliac (vertically along iliac side of SIJ), and iliac crest (horizontally along iliac wing upper margin), separately for left and right sides. The degree of closure of sacral segmental apophyses was graded as well. Readers were blinded to demographic, clinical and other imaging findings. Associations between patient age, sex, signal changes and apophyseal closure were analysed. Results: Rimlike subchondral increased T2 signal or ‘flaring’ was commonly seen in children at the margins of the SI joints, and is far more common on the sacral side (72% vs 16%, p<.001). It was symmetrical in >90% of children. Iliac flaring scores were always lower than sacral, except for 1 child. Signal changes decreased as sacral apophyses closed, and were seen in <20% of subjects with fully closed apophyses. Signal changes were more frequent in boys, and peaked in intensity later than for girls (ages 8-12 vs. 7-10). Subchondral signal in iliac crests was high throughout childhood and did not correlate with other locations. We found no significant difference between left/right side, boys/girls nor between both groups. Conclusion: Rimlike subchondral high T2 signal 'flaring' is commonly observed at MRI of sacroiliac joints in children, and should not be confused with pathology. It is generally sacral-predominant, symmetrical, and seen in less than 1/5 of children after segmental apophyses are closed. Flaring that is asymmetrical, greater in ilium than sacrum, or intense in a teenager with closed apophyses, is unusual for normal children and raises concern for pathologic bone marrow edema. Subchondral signal in iliac crests is high throughout childhood and cannot be used for reference in diagnostic criteria. Accurately distinguishing between normal and pathologic pediatric subchondral sacroiliac joint signal changes requires understanding the patterns of normal variation, to avoid misdiagnosis of sacroiliitis. Disclosure of Interest None declared
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".