High spatial resolution imaging of bone mineral using computed microtomography. Comparison with microradiography and undecalcified histologic sections.

Rationale and Objectives: The application of various high-resolution (< 100 microns) imaging techniques for in vitro bone mineral analysis is explored.
Methods: The techniques of contact microradiography and microtomography, using the x-ray spectrum filtered out of synchrotron radiation (SR) and conventional staining techniques, are compared to each other by presenting a variety of different samples. The relationship between radiation exposure and spatial resolution micro-computed tomography (CT) images of a finger bone is explored. The relevant properties of SR are explained.
Results: In CT images, a spatial resolution of 100 microns was obtained. New bone mineral induced by mechanical periosteal irritation in a rabbit tibia was quantified. In one case a microradiogram and a microtomogram of the same slice were taken for comparison. Histologic sections and microradiograms taken from a specimen of a human femur for comparison are presented.
Conclusions: Microradiography and staining techniques require rather sophisticated sample preparation; quantitative image analysis is more difficult as the resulting image must be digitized. The CT technique requires almost no sample preparation and allows for accurate bone mineral quantification. However, CT images with a resolution of several microns limit the sample size to a few mm. Micro-CT and microradiography can be performed with conventional x-ray sources, but the use of SR is of particular interest in high resolution imaging, because its white spectrum allows for optimum x-ray energy selection and its high intensity for short scan times.