Radiation-free assessment of the 3D morphology of the adolescent scoliotic spine: a feasibility study using MRI derived quantitative synthetic CT

INTRODUCTION: Treatment management of pediatric spinal deformity patients heavily relies on radiological imaging; always with X-rays and sometimes CT scans to better delineate 3D morphology, and increasingly for navigation purposes. It is important to minimize radiation exposure in this vulnerable pediatric population, since it increases the risk for cancer development. This pilot study investigates the feasibility and reliability of 3D-spinal parameters identified on MRI-based quantitative synthetic CTs (sCTs) to assess scoliosis in adolescents. METHODS: Ten pre-operative MRI's from adolescent idiopathic scoliosis patients (mean age: 13.5 years) with curves on standing x-ray > 40° were included. A 4-min 3D spoiled gradient echo MRI sequence capturing the main thoracic curve was added to the clinical sequences and quantitative sCTs were generated. Three independent observers measured Cobb angle, T4-T12 thoracic kyphosis (TK) and apical vertebral rotation (AVR). Interrater reliability and 95% confidence intervals (CI) were calculated. RESULTS: The sCTs clearly visualized the vertebral bodies and posterior elements, allowing for easy landmark identification to assess spinal morphology parameters of individual discs and vertebral bodies. Minor artifacts were observed in intervertebral discs and near the respiratory tract, not affecting the landmark positioning. The interrater reliability ICCs were Cobb angle: 0.99 (95% CI 0.98-1.00), TK: 0.98 (0.95-1.00) and AVR: 0.95 (0.86-0.99). CONCLUSION: This pilot study confirms that sCT derived from MRI allows for radiation-free and reliable measurement of 3D deformity parameters in AIS patients. While further research is needed, these findings demonstrate the potential for high-quality MRI-based bone imaging and its possible application in AIS treatment planning.