Low-dose low-scattering X-ray computed tomography with high-spatial-energy resolutions using a cooled cadmium telluride detector

Fully digitalized triple-energy x-ray computed tomography with high spatial resolutions using beam hardening

To regulate the effective photon energy with a constant tube voltage and to perform enhanced K-edge x-ray imaging, we built a prototype fully digitalized triple-energy x-ray computed tomography (TECT) scanner utilizing beam hardening. An object on the turntable is irradiated by a 0.1-mm-focus x-ray tube at 1.4-time-magnification. 720 raw radiograms are obtained using a flat panel detector, and 512 tomograms are reconstructed. With an increasing digital amplification factor, the gray raw-density projections obtained using low-energy-photon absorption disappeared at a constant maximum raw density, and the effective energy was increased by x-ray beam hardening. TECT was performed at digital amplifier factors below 3.0, and the effective energy increased with increasing amplification factors. In particular, fine blood vessels were visible using gadolinium-K-edge CT.

Embossed x-ray computed tomography utilizing pixel-shifted dual-energy subtraction

To observe fine blood vessels as uneven tomographic images at a high contrast, we performed tentative experiments on embossed x-ray computed tomography (CT). We constructed a cone-beam CT scanner and carried out dual-energy CT with tube voltages of 60 and 100 kV. X-ray photons penetrating through an object were detected using an indirect-conversion flat panel detector, and radiograms were produced and sent to a personal computer to reconstruct tomograms. Embossed CT was performed using pixel-shifted dual-energy subtraction, and blood vessels filled with Gd medium were observed as uneven images at high contrast and spatial resolutions. Using 1.4-time magnification imaging in combination with a 0.1-mm-focus x-ray tube, the diameter of the object visible on the embossed CT was below 100 μm.

Whole cancer-region enhancement using meglumine-gadopentetate-glucose solution and 7.0-T magnetic resonance imaging

To visualize whole cancerous region including hypoxic cancer without radiation exposure, we developed meglumine-gadopentetate-glucose solution for 7.0-T magnetic resonance imaging. The infusion solution consists of meglumine-gadopentetate and glucose solutions, and these solutions are mixed before the vein drip infusion. We used readily available solutions, and the concentrations of the meglumine-gadopentetate and glucose solutions were 37.14 and 5.0%, respectively. In the first and second experiments, vein infusions were conducted from a rabbit ear using meglumine-gadopentetate-saline and meglumine-gadopentetate-glucose solutions, and T1 weighted imaging was performed to visualize cancerous region. Using the meglumine-gadopentetate saline, it was not difficult to image cancer-growth regions with new blood vessels. Using the meglumine-gadopentetate-glucose solution, the signal intensity of whole cancerous region including hypoxic cancer substantially increased. The visualizing duration for the meglumine gadopentetate glucose was beyond 90 min, and the rabbit survived after the infusion. The signal intensity in the hypoxic cancer was increasing until 90 min using the meglumine-gadopentetate-glucose solution, since the meglumine-gadopentetate molecules were absorbed into almost the whole cancerous region along with glucose-molecule flows.

Near-infrared-ray computed tomography with an 808 nm laser beam and high spatial resolutions

To increase the penetrating photons and to improve the spatial resolution in near-infrared-ray computed tomography (NIR-CT), we used an 808 nm laser module. The NIR photons are produced from the laser module, and an object is exposed to the laser beam. The laser power is controlled by the applied voltage, and the photodiode detects photons penetrating through the object. To reduce scattering photons from the object, a 1.0-mm-diameter graphite pinhole is set behind the object. The spatial resolutions were improved using a 1.0-mm-diameter 5.0-mm-length graphite collimator and were ∼1 × 1 mm². The NIR-CT was accomplished by repeating the object-reciprocating translations and rotations of the object using the turntable, and the ray-sampling-translation and rotation steps were 0.1 mm and 0.5°, respectively. The scanning time was 19.6 min at a total rotation angle of 180°. Triple-sensitivity CT was accomplished using amplifiers, and a graphite rod in the chicken fillet was visible when increasing amplification factor.