We present the feasibility of digital Carbon Nanotube (CNT)-based X-ray source for the development of portable Chest Radiography X-ray system. The X-ray images of human chest phantom were taken at varying anode voltages and current. The result shows that the X-ray image taken at 100 kV 9 mAs was good enough with detailed visualization of rib bones and bronchi of phantom’s lungs.
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.
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.
In this paper, we demonstrated the comparison of digital-based CNT and analogue-based filament X-ray sources by taking the X-ray images of ACR mammo phantom for developing the intraoperative specimen X-ray system. The X-ray image of ACR mammo phantom taken at 25 kV 1 mA by filament shows overall the better image quality. However, when X-ray images of phantom were compared at 40 kV 1 mA by both sources, it showed that CNT X-ray source showed better image quality because of Aluminum window.
This paper investigates a bipolar high voltage driven carbon nanotube-based X-ray tube. For field electron emission, an electric field must be formed between the gate and the cathode, and a strong negative voltage must be applied to the cathode. A circuit capable of field emission and cathode negative voltage application is designed with a negative power supply using only one negative high voltage source and a resistor for this purpose. The CNTs grown on the metal substrate can generate a stable tube current of 3 mA, and X-ray images were obtained using this tube. Both bipolar driving and unipolar driving are tested under the same conditions to determine the difference between the two driving methods. This result confirms that there is no difference in image quality when only the anode is subjected to 60 kV and when the anode and cathode are subjected to +30 kV and -30 kV, respectively. As a result, it has been confirmed that bipolar driving is less prone to arcing and that image quality can be maintained because the burden on the anode is lower than in unipolar driving.
In fluoroscopy, X-rays are used to obtain the real-time moving images of the human anatomy. To do so, a pulsed fluoroscopy is used so that patient and staffs are exposed to minimum radiation possible. However, in most medium priced pulsed fluoroscopy systems, X-ray tube without grid is used. The grid-less X-ray tube cannot produce perfect digital pulses due to inherent problem associated with thermionic emission of filament. Thus, the patient is exposed to unnecessary radiation using conventional Fluoroscopic system. This problem can be easily solved using carbon nanotube (CNT) based digital X-ray tubes and are much cheaper to manufacture than grid controlled filament based X-ray tubes. In this study, we have developed 120 kV CNT-based digital X-ray tubes for pulsed fluoroscopy that can be operated at very high frequency (~ MHz) producing low radiation dose during X-ray imaging. The DC and pulsed performance of Xray tube is studied, and the X-ray imaging of human skull is done with relatively low X-ray dose by pulsing the X-ray tube at 25 kHz. The commercial high voltage sources, function generator and N type-MOSFET were used for high-speed switching of E-beam during X-ray emission. This paper could help the radiologists and all the medical personnel understand the advantages of CNT based X-ray technology over filament for X-ray imaging use low dose radiation.
When designing an X-ray monoblock for portable systems, the size and compactness of X-ray tube plays an important role. The monoblocks normally contains high voltage unit and X-ray tube immersed together inside the sea of insulating oil and sealed by Aluminum or plastic frame. Normally, mononblocks built for 100 kV or higher X-ray tube are quite bulky, not because of the high voltage source unit but because of the huge size of glass enveloped X-ray tube. The compactness of X-ray tube can decrease the size of mononblock and it can subsequently increase the portability of X-ray system. There are efforts done to decrease the size of X-ray tube by replacing the glass envelope with metal ceramic frames in CT X-ray tubes which are categorized as Rotating X-ray tubes. However, there are few or almost no researches on looking for an alternative to avoid making bulky glass X-ray tubes for Stationary tubes. It might be partially because the discovery of Xray tubes is all connected to the glass vacuum tubes. Other reasons could be due to matureness of glass making technology, which though still lacks automation but is cheaper and easier. Our group has realized that using ceramic to maintain vacuum and use it as an alternative to glass envelop can increase the robustness and compactness of filament X-ray tubes. Moreover, it can also help engineers to develop smaller and lighter monoblock for high-end X-ray systems. Thus, in this study, we report a development of compact 120 kV ceramic-based filament type X-ray tube for panoramic dental imaging. We have compared in-house built ceramic X-ray tube with commercial glass X-ray tube which is most commonly used for 100 kV panoramic dental X-ray imaging system. The result shows that despite the 38 % reduction in size, ceramic tube has better IV characteristic with similar filament size and higher limiting spatial resolution compared to glass X-ray tube. Moreover, we have successfully performed all the X-ray experiments using 100 kV 500W custom built high voltage source which can be used for making monoblocks.
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 fully commercialized intraoperative specimen radiographic system (IOSRS) based on carbon nanotube (CNT) emitter has been developed and the optimization of electron beam (E-beam) focusing characteristic of X-ray source is analyzed in this paper. The IOSRS can be used inside the operation theatre and helps reduce the surgery time during breast conserving surgery by confirming the extent of margin on specimen. For this, a highly focused X-ray source is required which depends on the focusing structure of Electron gun (E-gun). Normally, a separate focuser and grid are added in the filament X-ray tube to produce a narrow E-beam and perfectly digitalized X-ray pulses, respectively. However, in CNT based X-ray tubes, the focuser and grid can be integrated as one structure called self-focusing gate structure. The self-focusing gate structure can extract electrons and focus the E-beam producing perfect pulses of X-ray dose and simultaneously enhancing the spatial resolution quality of X-ray source. In this study, we have investigated the effect of changing the length of selffocusing gate structure on the spatial resolution capability of X-ray system and its effect on the field electron emission performance of CNT E-gun.
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.
A Carbon nanotube (CNT) cold cathode emitter-based compact X-ray tube for X-ray application is studied in this paper. In the electron gun, the conventional filament was replaced by CNT emitter; CNTs were grown on metal alloy substrate. Using this electron gun, electron emission can be controlled by applying voltage rather than heating. Up to 2 mA tube current can be generated by this CNT electron gun. Also, the pulsed tube current and pulsed radiation dose can be generated by using MOSFET circuit. We measured the radiation dose generated in 30 frames per second, and confirmed that the waveform was generated as a square wave. From that waveform, it was confirmed that unnecessary radiation exposure can be minimized. The body of the X-ray tube is made of ceramic, which has strong durability against impact and high temperature. The ceramic used for the tube has an insulation distance of 30 mm and shows stable insulation performance in an environment where a voltage of 70 kV is applied. Using this X-ray tube, we successfully obtained X-ray images of various objects with acceleration voltages between 45 kV and 70 kV.
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.
We developed a compact vacuum X-ray tube using an alumina body instead of glass. A filament is implanted as a cathode which follows Richardson-Dushman equation. After aging the filament to eliminate impurities on the filament which improves performance of filament before tubing, tube current was obtained from anode voltage of 6kV, 3mA to 40kV, 3.15mA. The pulse high voltage generator is designed and developed to make the tube less stressful. With the ceramic X-ray tube, X-ray images of human breast and teeth phantom were successfully obtained, verifying the potential of the compact alumina vacuum sealed X-ray tube in X-ray application for medical imaging.
We designed and developed the vacuum sealed x-ray tube based on carbon nanotube(CNT) field emitter for mobile medical x-ray devices and also design the test bed for CNT x-ray tube. The CNT was synthesized by chemical vapor deposition(CVD) method on a metal alloy substrate. The grown CNT is assembled with a gate and a focuser and then combined into an electron gun(e-gun) through a brazing process. The the e-gun had an aging process inside the vacuum chamber. As a result of aging, the CNT e-gun was able to generate anode current of 1.5 mA at electric field of about 4 V/μm, and field emission current was also stabilized. After the aging process, the e-gun was brazed into a ceramic X-ray tube inside a high-temperature furnace at a vacuum degree of E-06 torr and vacuum sealed. Field emission characteristic was measured using this X-ray tube and compared with an e-gun, and almost similar results were obtained. Incase of Xray tube, we applied a higher electric field while controlling the current at 500ms intervals through pulse driving. As a result, X-ray images of human teeth were successfully acquired using CNT X-ray tubes.
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.
Based on the breast imaging and reporting data system (BI-RADS) for mammography (MMG) and types of cancer cells detected, a patient is listed into various categories which determine whether they should undergo biopsy or not. Generally, patients under the BI-RADS category 4 or 5 have to go through surgery. During the surgery, a pathological examination is performed with the help of a microscope and additional X-ray images of the removed tissue or breast specimen are taken to determine the positive and negative surgical margins. Although the pathological examination is the best way to determine carcinoma at the inked margin, it consumes a significant amount of time and makes the duration of the surgery longer. In this study, we propose the open-type carbon nanotube (CNT)-based X-ray system, which can be helpful to determine the carcinoma on breast specimen during breast surgery. The technique proposed in this study successfully obtained X-ray images of a breast specimen with visibly clear cancer masses. These results could pave the way for efficient determination of surgical margins by eliminating the time-consuming histological procedures.
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.
We report the design and fabrication of a carbon nanotube (CNT) based micro-resolution field emission mobile open type x-ray system for breast imaging. It can be used efficiently during the surgery of breast cancer removal to obtain accurate resection margin in partial resection of breast specimen. The obtained x-ray image of breast specimen with the proposed system shows the clear detection of micro-calcifications.
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