The carbon nanotubes (CNTs) were used as an X-ray source in a micro computed tomography (CT) system. Several types of substrates have been employed to enhance the resolution, with a single-pillar substrate demonstrating the potential to produce high flux, high-resolution images. The current density of 4 A/cm2 was achieved and the focal spot size of 863 μm was calculated through X-ray image. This approach was applied to reconstruct CT images of dental phantoms, and it was successful.
A carbon nanotube (CNT) emitter-based high-speed micro-computed tomography (CT) system is designed herein. CT scans result in prolonged exposure to radiation, thus, pulsed-field emission is performed to generate pulsed X-rays to reduce radiation dose. The radiation dose rates of continuous X-rays and X-rays generated by different pulses were compared. X-rays were stably generated 40 times per second through a pulsed-field emission current with MOSFET circuit. The CNT field emitter characteristic was maintained for more than 35 hours continuously, which means more than 5 million X-ray shots can be taken when sufficient current flows on pulse mode. X-ray images were also successfully acquired through such pulse driving.
A microfocus X-ray source based on carbon nanotube (CNT) emitter grown by chemical vapor deposition is presented in this paper. The microfocus X-ray source is developed for the intraoperative specimen radiographic system, which can be used inside the operation theatre and helps reducing the surgery time during breast conserving surgery by confirming the extent of margin on specimen. This high focusing X-ray source is realized by growing CNTs on pointed structures. The field emission characteristic shows that maximum anode current of 1mA, which corresponds to a maximum emission current density of 500 mA/cm2 from the CNT-based point emitter. The optimized parameter for the assembly of electron gun was achieved by using commercially available CST simulation software. Consequently, this microfocus X-ray tube could produce X-ray image of multilayer printed circuit board showing fine lines of integrated circuit.
In order to diagnose diseases in complex areas such as the chest, an X-ray system of a suitable type is required. Chest tomosynthesis, which acquires a reconstructed 3D image by taking X-ray images from various angles, is one of the best image acquisition technologies in use. However, one major disadvantage of tomosynthesis systems with a single X-ray source is the motion blur which occurs when the source moves or rotates to change the acquisition angle. To overcome this, we report a stationary digital tomosynthesis system, which uses 85 field-emission type X-ray sources based on carbon nanotubes (CNTs). By using CNT-based electronic emitters, it is possible to miniaturize and digitize the X-ray system. This system is designed such that a maximum of 120 kV can be applied to the anode to obtain chest X-ray images. The field emission characteristics of the CNT-based emitters are measured, and X-ray images were obtained using the stationary multi X-ray source system, confirming its applicability to chest Tomosynthesis.
The properties of carbon nanotubes (CNTs) show a variety of application possibilities in the next generation industries. Among them, application to a field emission device is expected due to a high emission current at a low critical electric field. Compared with conventional thermionic emission X-ray sources, field emission X-ray sources have many advantages. Their electric field can be turned on and off quickly, minimizing radiation exposure times. Additionally, the size of the imaging system can be reduced because no cooling device is required. Using these advantages, we created a micro computed tomography (CT) system based on a CNT field emission X-ray source. The main advantages of the micro- CT lie in the high-spatial resolution, sensitivity to skeletons and lungs, and low cost. We optimized the field emission characteristics of the CNTs and the system geometry for high resolution.
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