MRI in musculoskeletal inflammatory disease in children, with a focus on technique, standardisation and findings

Abstract

Inflammatory musculoskeletal (MSK) diseases are common among children and adolescents, with early diagnosis and treatment crucial for long-term outcomes. Magnetic resonance imaging (MRI) has become a key tool in guiding treatment due to the challenges of clinical assessment of disease activity. However, there is a lack of validated, child-specific MRI tools for monitoring these diseases. This thesis aims to improve diagnostics and management of juvenile idiopathic arthritis (JIA) and chronic nonbacterial osteomyelitis (CNO) by exploring various aspects of MR-imaging. The research is based on three cohorts: 75 children with CNO, most of whom underwent whole-body MRI; 60 patients with JIA who had targeted MRI of the hips; and 196 healthy children who had whole-body MRI for research. Findings showed that 80% of CNO patients experienced pain, often in the lower limbs, with a median of six affected sites on whole-body MRI. Raised inflammatory markers significantly predicted the number of involved sites. For JIA patients, a set of MRI markers for hips involvement was developed and validated, showing good intra- and interobserver agreement for grading inflammation and acetabular erosions. T2 Dixon fat-only images showed high agreement with T1-weighted images for bone marrow assessment in healthy children, suggesting that T2 Dixon fat-only could replace T1-weighted sequences, thereby reducing scan time.