| Microscopic specimens can be subdivided into two categories, those visible light opaque specimens and those visible light transparent specimens. The solution for three-dimensional imaging of the visible light opaque materials is X-ray cone-beam tomography. The solution for visible light transparent materials is two-photon laser scanning confocal microscopy.; To perform the X-ray cone-beam tomography, an experimental X-ray cone-beam microtomographic system based on a generalized Feldkamp reconstruction algorithm consists of a dental X-ray source, a sample stage, an X-ray scintillation phosphor screen, a slow scan cooled CCD camera, and a computer system.; Our experiments with a cover-glass sample demonstrated that 3D reconstruction can be achieved with the resolution of 266 {dollar}mu{dollar}m. We found that two major factors affect the results of the reconstruction. One factor is the number of projections and the other is the spot size of the X-ray source. The main factor for the resolution is the spot size of the X-ray source.; Unlike single-photon laser scanning confocal laser scanning microscopy using shorter wavelength (UV) as excitation light, two-photon laser scanning confocal microscopy used a longer wavelength (IR), femto-second pulse laser. Due to the quadratic dependence on the illumination intensity, the two-photon excitation induced photobleaching only happens around the focal point of the objective lens. These characteristics provide much deeper penetration ability into the specimens and less photobleaching damage except for the focal point. The use of infrared light allows the entire visible light spectrum for detection. |
