Characterization of rotating gantry micro-CT configuration for the in vivo evaluation of murine trabecular bone.

The objective of this study is to determine the optimal physical parameters of a rotating gantry micro-CT system to assess in vivo changes to the trabecular bone of mice. Magnification, binning, peak kilovoltage, beam filtration, and tissue thickness are examined on a commercially available micro-CT system. The X-ray source and detector geometry provides 1.3×, 1.8×, or 3.3× magnification. Binning is examined from no binning to 2 to 4. Energy is varied from 40 to 80 kVp in 10 kVp increments and filter thickness is increased from no filtration to 1.5 mmAl in 0.5 mmAl increments. Mice are imaged at different magnifications and binning combinations to evaluate changes to image quality and microstructure estimation. Increasing magnification from 1.3× to 3.3× and lowering binning from 4 to 1 varies the spatial resolution from 2.5 to 11.8 lp/mm. Increasing the beam energy or filtration thickness decreases Hounsfield unit (HU) estimation, with a maximum rate of change being -286 HU/kVp for 80 kVp. Images for murine trabecular bone are blurred at effective pixel sizes above 60 μm. By comparing resolution, signal-to-noise ratio, and radiation dose, we find that a 3.3× magnification, binning of 2.80 kVp beam with a 0.5 mmAl filter comprises the optimal parameters to evaluate murine trabecular bone for this rotating gantry micro-CT.