Three-dimensional x-ray microtomography is used in this work to assess the internal morphology and mineral density of human tooth specimens. Of particular interest is the demonstration of the character of the distal root canal morphology, which can be as small as 10 microns. Human teeth are individually embedded in a low atomic number material. Each tooth is then identically scanned on an advanced design bench-top cone-beam microtomography system under controlled conditions. The specimens are scanned using an 80 kVp technique and a CsI(Tl) scintillator mounted via a taper to a thermoelectrically cooled CCD camera with an overall nominal pixel size of 15 microns at the plane of the specimen. Scanning a ruby sphere phantom independently assessed the resolution of the system. The full width at half-maximum of the plane spread function is nominally 53 microns in the axial direction and 60 microns in the transverse plane. The visualization of the x-ray data consists of several complimentary techniques, including a three-dimensional stack of the reconstructed tomogram slices with 30 micron reconstruction voxel, a 360 degree rotating view of the tooth comprised from a sequence of projection images processed for detail contrast enhancement and edge restoration, and a surface model of each tooth. In total, 237 human teeth representing multiple samples of each of the varied tooth types have been individually scanned, analyzed, and visualized to date. The set of tooth data is being compiled into a comprehensive human tooth atlas, which is to be made available on CD for students and investigators as a resource for anyone studying tooth morphology and mineralization.
The use of x-ray microtomography to evaluate 3D volumes of bone has become wide spread with the introduction of numerous commercial systems intended for the examination of small animals and specimens. However, a consistent method for describing the spatial resolution has not been employed in characterizing the performance of these units. In this paper, we report the blur factors which contribute to a system's performance, methods to experimentally assess the performance of microtomography system components, and an experimental method to assess tomographic resolving power. By scanning a 1.5 mm diameter ruby sphere, the overall system resolving power of a classic microtomography system was measured to have a 98 micron FWHM of a determined plane spread function, while the FWHM for a contemporary system was determined to be 23 microns.
X-ray imaging detectors capable of very high resolution for a small field of view are important for x-ray micro-tomography, small specimen radiography, and certain x-ray scattering experiments. We have investigated the performance of small field detectors using scintillation phosphors coupled to a scientific CCD detector. The specific detector designs considered had fields of 8-12 mm that were used to record x-ray energies of 8-20 keV. The purpose of this work is to report the resolution (MTF) of designs that employed different optical coupling methods and different scintillation phosphor materials. For one detector system with a thin Gd2O2S phosphor a resolution of 48 lp/mm (presampled MTF = 0.10) was measured with pixels of 10.54 microns (Nyquist = 47.44) and a field of view of 12.14 mm x 13.09 mm.
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