7T MRI of Distal Radius Trabecular Bone Microarchitecture: How Trabecular Bone Quality Varies Depending on Distance From End-of-Bone

Purpose: To use 7T magnetic resonance imaging (MRI) to determine how trabecular bone microarchitecture varies at the epiphysis, metaphysis, and diaphysis of the distal radius. Materials and Methods: The distal radius of 24 females (mean age=56 years, range=24-78 years) was scanned on a 7T MRI using a 3D fast low-angle shot sequence (0.169 x 0.169 x 1mm). Digital topological analysis was applied at the epiphysis, metaphysis, and diaphysis to compute: total trabecular bone volume; trabecular thickness, number, connectivity, and erosion index (a measure of network resorption). Differences and correlations were assessed using standard statistical methods. Results: The metaphysis and epiphysis had 83-123% greater total bone volume and 14-16% greater trabecular number than the diaphysis (both P < 0.0001). The erosion index was significantly higher at the diaphysis than the metaphysis and epiphysis (both P < 0.01). The most elderly volunteers had lower trabecular number (<66 years mean 0.290.01; 66 years, 0.270.02, P < 0.05) and higher erosion index (<66 years mean 1.180.17; age 66 years, mean 1.42 +/- 0.46, P < 0.05) at the epiphysis; differences not detected by total trabecular bone volume. Conclusion: 7T MRI reveals trabecular bone microarchitecture varies depending on scan location at the end-of-bone, being of overall higher quality distally (epiphysis) than proximally (diaphysis). Age-related differences in trabecular microarchitecture can be detected by 7T MRI. The results highlight the potential sensitivity of 7T MRI to microarchitectural differences and the potential importance of standardizing scan location for future clinical studies of fracture risk or treatment response.