• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.396-399
• /
• 2002

Intense quasi-monochromatic x-ray irradiation from the linear plasma target is described. The plasma x-ray generator employs a high-voltage power supply, a low-impedance coaxial transmission line, a high-voltage condenser with a capacity of about 200 nF, a turbo-molecular pump, a thyristor pulse generator as a trigger device, and a flash x-ray tube. The high-voltage main condenser is charged up to 55 kV by the power supply, and the electric charges in the condenser are discharged to the tube after triggering the cathode electrode. The x-ray tube is of a demountable triode that is connected to the turbo molecular pump with a pressure of approximately 1 mPa. As electron flows from the cathode electrode are roughly converged to the molybdenum target by the electric field in the tube, the weakly ionized plasma, which consists of metal ions and electrons, forms by the target evaporating. In the present work, the peak tube voltage was almost equal to the initial charging voltage of the main condenser, and the peak current was about 20 kA with a charging voltage of 55 kV. When the charging voltage was increased, the linear plasma x-ray source grew, and the characteristic x-ray intensities of K-series lines increased. The quite sharp lines such as hard x-ray lasers were clearly observed. The quasi-monochromatic radiography was performed by a new film-less computed radiography system.

• Journal of the Korean Society of Radiology
• /
• v.17 no.1
• /
• pp.107-114
• /
• 2023

X-ray fluorescence analysis has been widely used in the field of science and industry because it gives information about elements and their concentrations without destruction of samples. To increase analysis accuracy of fluorescence generated by photons of the transmission-type X-ray tube for mixture and compound samples would be recommend to have strong energy near 10 keV and 20 keV simultaneously. Tungsten of 9.65 keV and molybdenum of 17.48 keV were considered as targets with dual deposition structure for obtaining two strong characteristic X-rays, and the transmission-type X-ray tube was analyzed using Geant4 Monte Carlo simulation. The W-Mo structure resulted in strong characteristic X-ray near 10 keV and 20 keV simultaneously. A structure with Mo-W multilayers of 5 ㎛ thick also gave optimal spectrum. Various material combination and thickness optimization for the dual-structured target can give X-ray spectrum with strong characteristic X-ray of specific energies.

• Journal of the Korean Society of Radiology
• /
• v.12 no.1
• /
• pp.39-46
• /
• 2018

The purpose of this study was to determine suitable angle of Tibia-foot and the X-ray tube for scaphoid in foot X-ray examination. A total of twenty patients(mean age $32.12{\pm}years)$ are participated in this study. In the positions of Foot AP, internal and external oblique, tibia-foot angle was defined as $90^{\circ}$ and $135^{\circ}$, and x-ray tube angle was defined as $0^{\circ}$, $5^{\circ}$, $10^{\circ}$, $15^{\circ}$ and $20^{\circ}$ respectively. The image quality was evaluated with blind test yielding scores ranging from 0 to 5 by the evaluation team consisted of 2 radiogical technologists, 2 radiologists, and 2 orthopedic surgeons. In case of Foot AP position, the degree of overlap between cuneiform and navicular was 3% and the blind test result was 4.89 at tibia-foot angle of $90^{\circ}$ and $15^{\circ}$ X-ray tube angle. When the tibia-foot angle is $135^{\circ}$, the degree of overlap was 5%, also the blind test result was 4.30 at $15^{\circ}$ X-ray tube angle. The degree of overlap and blind test result were 30% and 3.75 respectively at $0^{\circ}$ X-ray tube angle. In case of internal oblique position, at tibia-foot angle of $90^{\circ}$ and $0^{\circ}$ X-ray tube angle, the degree of overlap was 4% and the blind test result was 4.70. The 5% overlapping and highest score as 4.55 were obtained on tibia-foot angle of $135^{\circ}$ and $0^{\circ}$ X-ray tube angle. In case of external oblique position, at tibia-foot angle of $90^{\circ}$ and $15^{\circ}$ X-ray tube angle, the degree of overlap was 4% and the blind test score was 4.85. The 5% overlapping and highest score as 4.75 were obtained on tibia-foot angle of $135^{\circ}$ and $15^{\circ}$ X-ray tube angle. In conclusion, we confirmed suitable angle of tibia-foot and X-ray tube for scaph46oid in foot X-ray examination in this study. These findings will be helpful for us to reading for navicular fracture.

• Restorative Dentistry and Endodontics
• /
• v.37 no.3
• /
• pp.160-164
• /
• 2012

Objectives: This study was aimed to investigate the methods to reduce operator's radiation dose when taking intraoral radiographs with portable dental X-ray machines. Materials and Methods: Two kinds of portable dental X-ray machines (DX3000, Dexcowin and Rextar, Posdion) were used. Operator's radiation dose was measured with an 1,800 cc ionization chamber (RadCal Corp.) at the hand level of X-ray tubehead and at the operator's chest and waist levels with and without the backscatter shield. The operator's radiation dose at the hand level was measured with and without lead gloves and with long and short cones. Results: The backscatter shield reduced operator's radiation dose at the hand level of X-ray tubehead to 23 - 32%, the lead gloves to 26 - 31%, and long cone to 48 - 52%. And the backscatter shield reduced operator's radiation dose at the operator's chest and waist levels to 0.1 - 37%. Conclusions: When portable dental X-ray systems are used, it is recommended to select X-ray machine attached with a backscatter shield and a long cone and to wear the lead gloves.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.1315-1318
• /
• 2003

In this paper, a neural network based approach using a self-organizing feature map is proposed for the segmentation of X ray images. A number of algorithms based on such approaches as histogram analysis, region growing, edge detection and pixel classification have been proposed for segmentation of general images. However, few approaches have been applied to X ray image segmentation because of blur of the X ray image and vagueness of its edge, which are inherent properties of X ray images. To this end, we develop a new model based on the neural network to detect objects in a given X ray image. The new model utilizes Mumford-Shah functional incorporating with a modified adaptive SOFM. Although Mumford-Shah model is an active contour model not based on the gradient of the image for finding edges in image, it has some limitation to accurately represent object images. To avoid this criticism, we utilize an adaptive self organizing feature map developed earlier by the authors.[1] It's learning rule is derived from Mumford-Shah energy function and the boundary of blurred and vague X ray image. The evolution of the neural network is shown to well segment and represent. To demonstrate the performance of the proposed method, segmentation of an industrial part is solved and the experimental results are discussed in detail.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.11
• /
• pp.1612-1617
• /
• 2003

Synchrotron X-ray micro imaging technique was employed to non-invasively monitor the water flow inside xylem vessels in a bamboo leaf. The phase contrast X-ray images clearly visualized plant anatomy and the rise of a water front inside the vessels. Consecutive X-ray images taken for 60 seconds revealed water rise kinetics against gravity in the xylem of a cut dry leaf taken from a bamboo tree. For the first time, traces of water rise, variation of contact angle between water and xylem wall as well as the internal structure of xylem were obtained. In xylem vessels, a repeating flow pattern has a typical flow velocity of 30.7$\mu\textrm{m}$/s and faster flow is established intermittently. It is concluded that the transmission type of X-ray micro imaging can be used as a powerful tool to investigate the ascent of sap in the xylem vessels at a resolution higher than that of MRI.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.639-639
• /
• 2013

In this research we report the significant contribution of the as-spun multi-walled carbon nanotube (MWCNT) on the x-ray images formation using a low tube voltage x-ray source. The MWCNT, which was used for the fabrication of the spun CNT, was grown using a microwave plasma-enhanced chemical vapor deposition machine. Electrical-optics simulation software was utilized to determine the electron field emission trajectory of the triode-structure-as-spun CNT-based x-ray source. It was shown that a significant amount of converging electrons hit the target anode producing a clear x-ray image. These x-ray images where produced at a small amount of anode current of 0.67 mA at a tube voltage of 5 kV with the gate voltage of 0 V. Also, comparisons of the radiographs at various exposure times of the sample where analyzed with and without an x-ray dose filter. Results showed that spatially-resolved images were formed using the as-spun CNT at a low tube voltage with a $54-{\mu}m$ Al x-ray filter. This study can be used for low-voltage medical applications.

• Journal of radiological science and technology
• /
• v.21 no.2
• /
• pp.5-10
• /
• 1998

In the mammography, X-ray beam quality is one of the most important factors. Using X-ray mammography unit model GE/CGR Senography 600T Senix H.F, Authors studied four subjects. 1. The aluminum attenuation rate in 30 kVp when used with or without compression plate. 2. HVLs at 5 different area of the X-ray field of $26{\sim}32kVp$. 3. HVLs to know the influence of corrected measurement or parallel measurement. 4. Film density with microdensitometer along and cross to the long axis of X-ray tube, in terms of the Heel effect in the X-ray field. The following results were obtained. 1. Beam quality of anode area was harder than cathode area. 2. The dose reduction rate of compression plate was approximately $65.5%{\sim}88.1%$ and the beam quality with compression plate was hardened up to 4kVp accordingly. 3. If the X-ray beam enters the attenuation plate obliquely, HVL was $2.6{\sim}2.9%$ harder than perpendicular to it. 4. Because of heel effect, the film density of cathode area is higher than anode area to film density of 0.5.

• Macromolecular Research
• /
• v.14 no.2
• /
• pp.166-172
• /
• 2006

This is a short review article of our recent studies on the ATP-induced, allosteric conformational transition of the chaperonin GroEL complex by solution X-ray scattering. We used synchrotron X-ray scattering with a two-dimensional, charge-coupled, device-based X-ray detector to study (1) the specificity of the chaperonin GroEL for its ligand that induced the allosteric transition, and (2) the identification of the allosteric transition of GroEL in its complicated kinetics induced by ATP. Due to the dramatically increased sensitivity of the X-ray scattering technique based on the use of the two dimensional X-ray detector and synchrotron radiation, different allosteric conformational states of GroEL populated under different conditions were clearly distinguished from each other. It was concluded that solution X-ray scattering is an extremely powerful tool for investigating the equilibrium and kinetics of cooperative conformational transitions of oligomeric protein complex, especially when combined with other spectroscopic techniques such as fluorescence spectroscopy.

• Transactions on Electrical and Electronic Materials
• /
• v.5 no.4
• /
• pp.133-137
• /
• 2004

The development of digital x-ray detector has been extensively progressed for the application of various medical modalities. In this study, we introduce a new hybrid-type x-ray detector to improve problems of a conventional direct or indirect digital x-ray image technology, which composed of multi-layer structure using a CaWO$_4$ phosphor and amorphous selenium (a-Se) photoconductor. The leakage current of our detector was found to be ∼180 pA/cm$^2$ at 10 V/m, which was significantly reduced than that of a single a-Se detector. The x-ray sensitivity was measured as the value of 4230 pC/cm$^2$/mR at 10 V/m. We found that the parylene thin film between a CaWO$_4$ phosphor and an a-Se layer acts as an insulator to prevent charge injection from indium thin oxide (ITO) electrode into an a-Se layer under applied bias.