We present an electron emitter for multi-X-ray source system such as computed tomography (CT) or tomosynthesis. The electron emitter used in the X-ray source was fabricated using carbon nanotubes with excellent electrical properties as a cold cathode. A metal-oxide-semiconductor field-effect transistor (MOSFET) circuit was added between the cathode of the electron emitter and the ground to enable pulse driving according to the input signal. The field emission characteristics of the electron emitter were tested in a self-made vacuum system. Pulse driving of the electron emitter was performed at a frequency of 10 kHz and a duty of 50%, and a maximum cathode current of 3.9 mA flowed at a gate voltage of 2.1 kV. In addition, it was possible to take X-ray images of the chest phantom and metronome using an X-ray source made with a CNT-based electron emitter.
We designed an X-ray source using a carbon nanotubes-based electron emitter. Carbon nanotubes (CNTs) having a cylindrical structure have excellent electrical and mechanical properties. For this reason, it is suitable as an electron emitter device of a field emission method and can be used as the X-ray source. CNTs were synthesized on an alloy substrate through chemical vapor deposition (CVD) method, and the substrate was used as a cathode in an electron emitter. The CNT-based emitter consists of a gate and a CNT cathode, and the emitter together with an anode constitutes an X-ray source. To improve the emitter's electron emission characteristics and durability, a MOSFET circuit was added between the CNT cathode and ground to enable pulse driving. In addition, the possibility of using the miniaturized X-ray sources as a multi-X-ray source arrays were confirmed by using the deMUX circuit to switch multiple emitters. The field emission characteristics of the CNT-based X-ray sources were analyzed, and it was confirmed that an X-ray image could be obtained.
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.
KEYWORDS: X-ray sources, X-rays, X-ray imaging, Chest, 3D image reconstruction, Carbon nanotubes, Sensors, Medical research, 3D image processing, Digital imaging
Digital chest tomosynthesis that provides a reconstructed 3D chest image is a superior technique to detect chest diseases. As it is difficult to detect diseases like lung cancer with conventional 2D digital chest X-ray technology (CXT), digital chest tomosynthesis improves upon the many of the limitations inherent in the 2D digital CXT. In this study, we report a digital chest tomosynthesis system (D-CTS) that can generate multi X-ray information for the reconstruction of a 3D Xray chest image. The D-CTS reported herein employs an array of carbon nanotube (CNT) emitter-based cold cathode electron-guns that are triggered in sequence to provide a gantry-less system (Figure 1). The CNTs are achieved by direct growth on a metal substrate and have a spaghetti-like structure (Figure 2) with fast response to electrical bias under vacuum conditions. Unlike conventional rotating type systems with gantries, our CTS has the advantage of less motion blur in image acquisition, given its stationary position. Additionally, the switching from one electron-gun (e-gun) to the next is much faster than the speed of conventional gantries, allowing faster acquisition time t required for digital operation. This system shows outstanding field emission property for taking X-ray images. The design, fabrication process and imaging processing of the multi-beam CNT X-ray system will be discussed during the presentation.
An x-ray microscope is a useful tool in medicine and biology. The performance of an x-ray microscope critically depends on its x-ray optics. In this paper, a Wolter type-I x-ray mirror is considered for biological applications. It was fabricated using an epoxy replication method. Fabrication tolerances (figure error and surface roughness) of the soft x-ray mirror were examined. A master mandrel was prepared using single-point diamond turning and polishing, and a mirror with axial symmetry was successfully manufactured by coating of a parting agent, epoxy molding, and separation steps. The replicated mirror showed 1.4-nm rms surface roughness and 160-nm peak-to-valley (and 34.3-nm rms) figure error. Several mirrors were manufactured from only one master mandrel.
The micro-CT system has been developed for small animal imaging. The system is mainly composed of CCD detector coupled with CsI (Tl) phosphor, X-ray source with micro focal spot, linearly moving couch, and rotation gantry. This system was developed as a gantry rotation type and designed to get CT images of small living animals. In this paper, the requirements of main parts of the system to acquire micro spatial resolution are described. The characteristics of the system, such as field of view, geometries of main components, gantry movement, and X-ray analysis are mainly considered. Resolution of the CT system was evaluated under variable conditions. Typically, the spatial resolution of the CT system was obtained about 37 micron at 10% of MTF curve.
This paper presents a method of a nano-positioning control for the high precision focusing of a doubled ellipsoidal condenser reflective mirror using 5-axis manipulator. We have developed the compact vertical type of soft X-ray microscopy system with 50nm resolution for biomedical application. This microscopy system is composed of a laser plasma x-ray source, doubled ellipsoidal condenser reflective optics, diffractive zone plate optics and MCP coupled with CCD to record an x-ray image. The X-ray source was focused on a sample by a doubled ellipsoidal condenser reflective mirror. X-ray source focusing will increase the photon density in the object plane and is very important to approach high resolution imaging. Required degree of freedom (DOF) of optics aligner in X-ray microscope is dependent on the kind of optics, but generally 5-DOF is needed. We used 5-axis manipulator that consists of three linear motions (X, Y and Z) and two tilting motions (θx, θy). A linear translation stage is adopted a kind of DC motor with a linear resolution 50nm and travel range of 5mm. The mechanism was controlled with PID controller augmented with closed feedback loop for precision control. A two axis tilt stage is employed a design resolution of 0.23μrad and tilt range of ±7deg. We have designed 5-axis manipulator for the precision position control of condenser mirror optics and have developed to control algorithm by inverse kinematics. The performance of the proposed 5-DOF manipulator is evaluated by using a laser interferometer system with two plane mirror reflectors. The experimental results are depicted in this paper.
We demonstrate compact transmission soft X-ray microscope system with 50 nm spatial resolution for the life and physical science. This x-ray microscope operates at photon energy from 284 eV to 543 eV, so called 'water window' region (2.3~4.4nm), where natural contrast between carbon (protein) and oxygen(water) allows imaging of unstained biological material in their natural, hydrated environment. The compact transmission soft x-ray microscope is based on a laser plasma x-ray source, tandem ellipsoidal condenser reflective optics, diffractive zone plate optics and x-ray sensitive charge-coupled device (CCD) to record an x-ray image. The source is a liquid-jet target laser plasma source, which is practically debris free and suitable for high average power operation. The flux, brightness and bandwidth of this source has been simulated and optimized for X-ray microscopy for biology application. A tandem ellipsoidal reflective mirror operates as condenser and illuminates the sample. The high resolution imaging is currently performed with a ~12% efficient nickel zone plate with an outmost zone width of 35nm. In conclusion, we suggested a possibility of the compact soft x-ray microscopy system with 50 nm spatial resolution as a suitable tool for the wide range of studies such as biological imaging, environmental samples, and nanostructure analysis.
A compact soft X-ray microscope system has been developed for biological applications with nano-scale resolution. Soft X-ray used to the system is emitted from a solid target by using Nd-YAG pulsed laser. Boron nitride (BN) is used as the target materials in the system. The optics of the microscope system is adopted with wolter type-I mirrors, which is consisted of a condenser mirror with demagnification of 1/4× and an object mirror with magnification of 32×. The surface roughness of the machined wolter mirrors is about 0.8 nm (Ra) after polishing. In this paper, the X-ray characteristics, i.e., spectrum and intensity emitted from laser plasma-based x-ray source was measured. Imaging test using the system was performed with gold 2000 mesh. The spatial resolution of the soft x-ray microscope system was obtained about 900 nm.
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