Performance of MRI-based synthetic CT for detecting spinal new bone formation in patients with inflammatory arthritis and healthy controls: a comparison with MRI, CT, and radiography

Willesen, ST; Møller, JM; Gosvig, KK; Pedersen, SJ; Hadsbjerg, AEF; Georgiadis, S; Østergaard, M

doi:10.1016/j.ard.2026.09.012

Performance of magnetic resonance imaging (MRI)-based synthetic CT for detecting spinal new bone formation in patients with inflammatory arthritis and healthy controls: a comparison with MRI, CT, and radiography

Ann Rheum DisPublished 27 Oct 2026comparison of MRI-based synthetic CT, T1-weighted magnetic resonance imaging (T1wMRI), low-dose CT and radiography for detecting spinal new bone formation

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Authors' conclusion

Using ldCT as a reference standard, sCT demonstrated substantially higher sensitivity than T1wMRI and radiography. Intra- and inter-reader reliability and inter-modality agreement between ldCT and sCT were comparable, suggesting that discrepancies in lesion detection primarily reflect reader variability rather than inter-modality differences.

Study context

Population: Participants with axial spondyloarthritis (axSpA), psoriatic arthritis (PsA), rheumatoid arthritis (RA) and healthy controls (HCs)36 males, mean age 51.4 years · axSpA 30 · PsA 19 · RA 10 · HCs 10
Participants: 69 participants

Index test or model: Synthetic computed tomography (sCT), T1wMRI and radiography against low-dose CT (ldCT) as the reference standard
Target condition: spinal new bone formation (NBF)

Methodological detailsreaders blinded to other imaging and clinical information, ldCT as the reference standard

Readers blinded to other imaging and clinical information
ldCT as the reference standard

Performance

As reported in the abstract

Test or model	Sensitivity	Sensitivity, cervical/lumbar	Sensitivity, whole-spine
sCT	70%	— not stated in the abstract	— not stated in the abstract
Radiography	— not stated in the abstract	50%	21%
T1wMRI	28%	— not stated in the abstract	— not stated in the abstract

Sensitivity

sCT70%

Radiography—

T1wMRI28%

Sensitivity, cervical/lumbar

sCT—

Radiography50%

T1wMRI—

Sensitivity, whole-spine

sCT—

Radiography21%

T1wMRI—

— not stated in the abstract

Specificity across modalities: ≥93%

Further findings

Mean number of new bone formation (NBFs) per participant

ldCT: 25.8
sCT: 24.0
T1wMRI: 9.3
Radiography: 6.9

Inter-reader reliability

sCT and ldCT: high (excellent intraclass correlation coefficient (ICCs), substantial kappas)
Radiography and T1wMRI: good ICCs with substantial/moderate kappas

Intra-reader reliability and inter-modality agreement for sCT and ldCT

Excellent/substantial (ICCs/kappas)

Original publication

Performance of MRI-based synthetic CT for detecting spinal new bone formation in patients with inflammatory arthritis and healthy controls: a comparison with MRI, CT, and radiography. Ann Rheum Dis. Published 27 October 2026. doi:10.1016/j.ard.2026.09.012

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