Objectives: To evaluate the diagnostic performance of dual-energy CT with water-hydroxyapatite (HAP) imaging for bone marrow edema in patients with non-traumatic hip pain.
Methods: Forty patients (mean age, 58 years; 16 male and 24 female) who underwent rapid kVp-switching dual-energy CT and MRI within 1 month between April 2018 and February 2019 with hip pain but no trauma were enrolled. Two radiologists retrospectively evaluated 80 hip joints for the presence, extent (femoral head involved, head and neck, and head to intertrochanter), and severity (mild edema, moderate, severe) of bone marrow edema on dual-energy water-HAP images. Water mass density (mg/cm3) on water-HAP images was determined with region of interest-based quantitative analysis. MRI served as the standard of reference.
Results: Sensitivity, specificity, and accuracy of readers 1 and 2 for the identification of bone marrow edema in water-HAP images were 85% and 85%, 93% and 73%, and 89% and 79%, respectively. The area under the receiver operating characteristic curve was 0.96 for reader 1 and 0.91 for reader 2 for differentiation of the presence of edema from no edema. The optimal water mass density to classify the presence of edema for reader 1 was 951 mg/cm3 with 93% sensitivity and 93% specificity and for reader 2 was 957 mg/cm3 with 80% sensitivity and 80% specificity. The more severe the edema, the higher was the mean water density value (p < 0.035).
Conclusion: Dual-energy water-HAP images showed good diagnostic performance for bone marrow edema in patients with non-traumatic hip pain.
Key points: • Dual-energy water-HAP imaging depicts bone marrow edema in patients with non-traumatic hip pain and may serve as an alternative to MRI in select patients. • A cutoff value of 951 mg/cm3mean water mass density results in 93% sensitivity and 93% specificity for the detection of bone marrow edema. • The more severe the bone marrow edema, the higher the mean water density value.
Keywords: Bone marrow; Dual-energy scanned projection radiography; Edema; Hip joint; X-ray computed tomography.