To image blood vessels, we performed fundamental experiments of a red-ray computed tomography (RRCT) scanner using 650-nm-laser and high-sensitivity-photodiode (PD) modules. The line laser beam is irradiated to an object, and the photons penetrating through the object are detected using the PD module through a 1.0-mm-diameter graphite pinhole and a 0.7-mm-diameter 5-mm-length graphite collimator for the PD. The spatial resolutions were primarily determined by the collimator diameter for the PD and were approximately 0.7×0.7 mm2. RRCT was performed by repeating the reciprocating translations and rotations of the object, and the ray-sampling-translation and rotation steps were 0.1 mm and 0.5°, respectively. The image contrast was regulated using the digital amplifier, and the visible diameter of object was 0.5mm.
Photon-counting x-ray computed tomography (PCCT) is useful for selecting optimal energy photons to image various portions of the target object, and we performed fundamental experiments of PCCT to carry out gadolinium (Gd) K-edge CT using Gd-based contrast media. The scanner mainly consists of an x-ray generator with a 0.1-mm-focus tube, a turntable, a cadmium-telluride (CdTe) flat panel detector (FPD) with pixel dimensions of 100 Pm, and a personal computer. An object on the turntable is irradiated by the x-ray generator, 720 radiograms are taken using the FPD, and tomograms are reconstructed. We used 1.3-time magnification tomography, the effective pixel dimensions were approximately 80 Pm, and Gd-K-edge CT was carried out using Gd-based contrast media at a tube voltage of 100 kV, a tube current of 0.40 mA, and a threshold energy of 50 keV.
To perform energy-dispersive x-ray computed tomography (EDCT), we constructed a computer program to amplify the digital values of raw radiograms. The CT scanner consists of an x-ray generator with a 0.1-mm-focus tube, a turntable, a flat panel detector (FPD), and a personal computer (PC). An object on the turntable is irradiated by the x-ray generator, 1.3-magnified 720 radiograms are taken by the FPD, and tomograms are reconstructed using the PC. Utilizing the digital amplifier, the object projections obtained using low-energy photons disappeared with increasing amplification factor at a constant maximum value, and the effective energy increased according to increases in the amplification factor by beam hardening. Using the beam-hardening CT (BHCT) scanner, high-contrast tomography for various objects was performed by controlling effective energy. In particular, fine blood vessels were observed by K-edge CT using iodine media.
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