Exploratory Evaluation of Photon-Counting CT for Bone Marrow Edema Detection Across Multiple Joints: A Pilot Study

To retrospectively evaluate the diagnostic performance and confidence of photon-counting computed tomography (PCCT) for detecting bone marrow edema (BME) in trauma patients, using magnetic resonance imaging (MRI) as the reference standard.

In this exploratory, bone-region-level analysis, a selected pilot cohort of ten patients (mean age 56.2 years, 80% female) underwent both PCCT and MRI of peripheral joints within a 10-day interval. A total of 123 bone regions across the knee, pelvis/hip, wrist/hand, and elbow were analyzed. Two readers, blinded to clinical and MRI findings, independently assessed BME on PCCT using color-coded maps and standard images, recording diagnostic confidence on a 5-point Likert scale. MRI served as the reference for BME. Sensitivity, specificity, predictive values, accuracy, and interrater agreement (weighted Cohen's κ) were calculated.

BME was present in all patients and in 28.5% (35/123) of bone regions on MRI. For PCCT, Reader 1 achieved a sensitivity of 0.63 (95% CI: 0.46-0.77), specificity of 0.97 (0.90-0.99), and accuracy of 0.87 (0.80-0.92) and Reader 2 achieved a sensitivity of 0.57 (0.41-0.72), specificity of 0.97 (0.91-0.99), and accuracy of 0.85 (0.78-0.91). Diagnostic specificity exceeded 0.93 across all joints, with the highest sensitivity in the knee. Inter-rater agreement was substantial (κ = 0.74). Both readers reported high diagnostic confidence. Reader 1 showed significantly higher confidence in correct classifications (p = 0.0017), whereas Reader 2 showed no significant difference between correct and incorrect classifications (p = 0.89).

PCCT showed high specificity but only moderate sensitivity for BME detection at the bone-region level, particularly in large joints. These preliminary findings suggest that the high specificity of PCCT may support confirmation of BME in selected clinical scenarios when MRI is unavailable, contraindicated, or redundant. However, moderate sensitivity requires continued clinical vigilance and MRI confirmation for negative or equivocal findings. Larger validation studies are warranted.

· PCCT shows high specificity for bone marrow edema detection. · Moderate sensitivity of PCCT limits standalone clinical use. · First multi-joint bone-region evaluation in a selected cohort of mainly trauma patients. · Substantial interrater agreement supports feasibility. · Positive PCCT findings are highly specific for BME; negative findings require MRI confirmation.

· Shahzadi I, Reimann G, Schneider C et al. Exploratory Evaluation of Photon-Counting CT for Bone Marrow Edema Detection Across Multiple Joints: A Pilot Study. Rofo 2026; DOI 10.1055/a-2888-7989.