We exploit the development of a clinical computed microtomography (micro-CT) system for dental imaging. While the
conventional dental CT simply serves implant treatment, the clinical dental micro-CT may provide clinicians with a
histologic evaluation. To investigate the feasibility of the realization of a dental micro-CT, we have constructed an
experimental test system which mainly consists of a microfocus x-ray source, a rotational subject holder, and a flat-panel
detector. The flat-panel detector is based on a matrix-addressed photodiode array coupled to a CsI:Tl scintillator. The
detective quantum efficiency (DQE) of the detector was measured as a function of magnification based on the measured
modulation-transfer function (MTF) and noise-power spectrum (NPS). The best MTF and DQE performances were
achieved at the magnification factor of 3. Similar tendency of the spatial resolving power in tomography was also
observed with a wire phantom having a 25 μm diameter. From the investigation of tomographs reconstructed from a
humanoid skull phantom, the application of magnification in the system largely reduced both signal-to-noise ratio (SNR)
and contrast-to-noise ratio (CNR) for a fixed dose at the entrance surface of the detector, 1.2 mGy, while this setup
increased the dose at the object plane from 4.7 mGy to 19.1 mGy for the magnification factor from 2 to 4, respectively.
Although the quantum mottles at the high magnification factor tackled the practical use in the clinic, the information
contained in the magnified CT images was quite promising.