Computed tomography (CT) imaging was performed using a micro-CT scanner (Siemens Medical Solutions, Knoxville, TN). The scanning parameters were an X-ray voltage of 60 kV with an anode current of 250 µA and an exposure time of 1000 ms. 360 rotation steps were performed resulting in a total rotation of 360°. The field of view was set to 31.12 mm × 42.10 mm and the binning factor was 1. Under med-high magnification the effective pixel size was 14.30 μm and the protocol was Hounsfield Unit (HU) calibrated. HU were standardized relative to distilled water and air with cylinder size adapted to the specimen size. For image reconstruction, a downsample factor of 2 was used. Analysis of the reconstructed images was performed using the vendor software package Inveon™ Research Workplace (IRW) software 2.2.
Measurements were performed in the right tibiae using predefined regions of interest (ROI), i.e., in the middle of the tibia (=diaphysis), 3/4 of the distance between the measurement point of the diaphysis and the proximal end of the bone (=metaphysis) and 3/4 of the distance between the measuring point of metaphysis and the proximal end of the bone (=epiphysis) as well as for the whole tibia. The thresholds for determining the volumes and density values were defined as follows: “whole bone” 675–5900 HU, “cortical bone” 1800–5900 HU, “cancellous bone” 675–1800 HU.
Measurements were performed in the right tibiae using predefined regions of interest (ROI), i.e., in the middle of the tibia (=diaphysis), 3/4 of the distance between the measurement point of the diaphysis and the proximal end of the bone (=metaphysis) and 3/4 of the distance between the measuring point of metaphysis and the proximal end of the bone (=epiphysis) as well as for the whole tibia. The thresholds for determining the volumes and density values were defined as follows: “whole bone” 675–5900 HU, “cortical bone” 1800–5900 HU, “cancellous bone” 675–1800 HU.