A Belgian study prospectively validated the BoneMRI Pelvic Region by MRIguidance for creating synthetic CT (sCT) images from MRI scans in 10 children. This research confirmed sCT's visual alignment with conventional CT in assessing the bony structure of pediatric sacroiliac joints, a method previously proven in adults. High inter-reader (0.945 to 0.996) and intra-reader (0.806 to 0.998) ICCs demonstrated quantitative reliability, particularly in measuring intervertebral disc space L5–S1 and spinal canal width. Kappa values for categorical scoring ranged from substantial to excellent (0.615–1), highlighting its precision yet indicating areas for improvement. The study advocates for sCT's inclusion in MRI protocols as a radiation-free option, providing clear visualization of children's sacroiliac joints and advancing safe pediatric imaging practices.
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MRI-based synthetic CT for assessment of the bony elements of the sacroiliac joints in children
Clinical Radiology, 2024
Abstract
Objectives: The purpose of this study is to assess the equivalency of MRI-based synthetic CT (sCT) to conventional CT for sacroiliac joint bony morphology assessment in children.
Methods: A prospective study was performed. Children who had (PET-)CT-scan underwent additional MRI. sCT-CT image quality was analyzed by two readers subjectively overall, semi-quantitatively in terms of cortical delineation, joint facet defects, growth plate fusion, ossified nuclei, lumbosacral transitional anomaly, and bony bridges, and quantitatively for disc space height, spinal canal width, and sacral vertebrae width and height. Cohen’s kappa and equivalence analyses with Bland–Altman plots were calculated for categorical and continuous measures respectively.
Results: Ten patients were included (6 boys; aged 9–16 years; mean age 14 years). Overall sCT image quality was rated good. Semi-quantitative assessment of cortical delineation of sacroiliac joints, bony bridges, and joint facet defects on the right iliac and sacral sides showed perfect agreement. Correlation was good to excellent (kappa 0.615–1) for the presence of lumbosacral transitional anomaly, fusion of sacral growth plates, joint facet defect, and presence of ossified nuclei. sCT-CT measurements were statistically equivalent and within the equivalence margins (–1–1 mm) for intervertebral disc space height and spinal canal width.
Intra- and inter-reader reliability was excellent for quantitative assessment (0.806 < ICC < 0.998). For categorical scoring, kappa ranged from substantial to excellent (0.615–1).
Conclusion: sCT appears to be visually equivalent to CT for the assessment of pediatric sacroiliac joints. sCT may aid in visualizing sacroiliac joints compared to conventional MRI, with the benefit that no ionizing radiation is used, especially important in children.
Critical relevance statement: MRI-based synthetic CT, a new technique that generates CT-like images without ionizing radiation, appears to be visually equivalent to CT for assessment of normal pediatric sacroiliac joints and can potentially assess structural damage as it clearly depicts bony cortex.
