BoneMRI: optimizing axial spondyloarthritis evaluation with synthetic CT
A Dutch study evaluated BoneMRI (MRIGuidance), which generates synthetic CT (sCT) images from MRI scans, to assess spinal new bone formation (NBF) in 17 individuals with axial spondyloarthritis (axSpA). Four readers compared NBF detection using sCT and radiography, the latter currently used in clinical practice for structural damage assessment, with low-dose CT (ldCT) as the reference. The study showed that for the entire spine, sCT's sensitivity (0.67) was significantly higher than radiography's (0.13), although both had high specificity (>0.95). Mean inter-reader agreements (kappa) were 0.68 for ldCT, 0.58 for sCT, and 0.56 for radiography. The findings underscore sCT's potential to improve axSpA damage assessment, merging MRI’s inflammation visualization with effective NBF detection, surpassing radiography's limitations in sensitivity and monitoring short-term changes.
MRI-based synthetic CT: a new method for structural damage assessment in the spine in patients with axial spondyloarthritis – a comparison with low-dose CT and radiography
Annals of the Rheumatic Diseases, 2024
Abstract
Objective: To investigate the ability of MRI-based synthetic CT (sCT), low-dose CT (ldCT) and radiography to detect spinal new bone formation (NBF) in patients with axial spondyloarthritis (axSpA).
Methods: Radiography of lumbar and cervical spine, ldCT and sCT of the entire spine were performed in 17 patients with axSpA. sCT was reconstructed using the BoneMRI application (V.1.6, MRIGuidance BV, Utrecht, NL), a quantitative three-dimensional MRI-technique based on a dual-echo gradient sequence and a machine learning processing pipeline that can generate CT-like MR images. Images were anonymised and scored by four readers blinded to other imaging/clinical information, applying the Canada-Denmark NBF assessment system.
Results: Mean scores of NBF lesions for the four readers were 188/209/37 for ldCT/sCT/radiography. Most NBF findings were at anterior vertebral corners with means 163 on ldCT, 166 on sCT and 35 on radiography. With ldCT of the entire spine as reference standard, the sensitivity to detect NBF was 0.67/0.13 for sCT/radiography; both with specificities >0.95. For levels that were assessable on radiography (C2–T1 and T12–S1), the sensitivity was 0.61/0.48 for sCT/radiography, specificities >0.90. For facet joints, the sensitivity was 0.46/0.03 for sCT/radiography, specificities >0.94. The mean inter-reader agreements (kappa) for all locations were 0.68/0.58/0.56 for ldCT/sCT/radiography, best for anterior corners.
Conclusion: With ldCT as reference standard, MRI-based sCT of the spine showed very high specificity and a sensitivity much higher than radiography, despite limited reader training. sCT could become highly valuable for detecting/monitoring structural spine damage in axSpA, not the least in clinical trials.