• Nuclear Engineering and Technology
• /
• v.44 no.1
• /
• pp.61-70
• /
• 2012

In this study, a simple post-reconstruction dual-energy computed tomography (CT) method is proposed. A dual-energy CT algorithm for monochromatic x-rays was adopted and applied to the dual-energy CT of polychromatic x-rays by assigning a representative mono-energy. The accuracy of algorithm implementation was tested with mathematical phantoms. To test the sensitivity of this algorithm to the inaccuracy of representative energy value in energy values, a simulation study was performed with mathematical phantom. To represent a polychromatic x-ray energy spectrum with a single-energy, mean energy and equivalent energy were used, and the results were compared. The feasibility of the proposed method was experimentally tested with two different micro-CTs and a test phantom made of polymethyl methacrylate (PMMA), water, and graphite. The dual-energy calculations were carried out with CT images of all possible energy pairs among 40, 50, 60, 70, and 80 kVp. The effective atomic number and the electron density values obtained from the proposed method were compared with theoretical values. The results showed that, except the errors in the effective atomic number of graphite, most of the errors were less than 10 % for both CT scanners, and for the combination of 60 kVp and 70 kVp, errors less than 6.0 % could be achieved with a Polaris 90 CT. The proposed method shows simplicity of calibration, demonstrating its practicality and feasibility for use with a general polychromatic CT.

• Archives of Plastic Surgery
• /
• v.35 no.4
• /
• pp.419-422
• /
• 2008

Purpose: Absorbable bone fixation materials for operation of facial bone fracture are composed of poly- lactic acid(PLA) & poly-glycolic acid(PGA). These materials are absorbed after facial bone healing period. Therefore, these materials are harmless in human body. But because of it's radioopacity, the number and the location of the materials are not checked in follow-up X-ray examination. We studied absorbable bone fixation materials checked radiological examination. So, we made the absorbable plate composed of PLA, Hydroxyapatite (HA) and Gold(Au). Methods: Plate 1 was consisted of pure PLA. Plate 2 was consisted of PLA(50%) and HA(50%). Plate 3 - 7 were consisted of PLA(50%), and variable composition of HA & Au. The ratio of Au was as following. From the plate 3 to plate 7, the Au ratio was 1%, 5%, 10%, 17%, and 25%, respectively. Total 3 examinations were used-naked eye examination, simple X-ray examination, and Haunsfield unit of plate in CT examination. Results: Naked eye examination found out that the color of plate 1 was most white. As the Au ratio increases, the color of plate was getting close to khaki color. the radioopacity of plate 2 was similar cortical bone of face in simple X-ray. The Haunsfield unit of cortical bone of face was 1000 HU. Haunsfield unit of titanium plate was 2900 HU. Haunsfield unit of plate 1 through plate 7 were -242, 1489, 1776, 3052, 3092, 3095, and 3095, respectively. Conclusion: Radioopacity of plate 2 was similar to cortical bone of face. In CT examination, Hanusfield unit of plate 2 was similar to Hanusfield unit of cortical bone of face. Hanusfield unit of plate 4 - 7 were similar to Hanusfield unit of titanium plate. So to trace bone fixation materials after facial bone surgery, the best ratio of Au is about 1 - 5%. If this study is applied to facial bone surgery, radiologic follow up would be easy after facial bone surgery.

• Journal of Chest Surgery
• /
• v.22 no.3
• /
• pp.468-472
• /
• 1989

Bronchogenic cysts are uncommon congenital lesions which are derived from primitive foregut. Most of the bronchogenic cysts may occur at the tracheal bifurcation, both main bronchi, the lung parenchyme and the mediastinum. We experienced a case of bronchogenic cyst with a esophageal stalk. The diagnosis was made by simple chest x-ray and confirmed by bronchoscopy and chest CT. On the chest CT findings, 6.8X4.8 cm-sized oval shaped mass was located on the right posteroinferior side of the carina, elevating the right main bronchus and the thin wall of the mass was enhanced with contrast materials. On the operative findings, the esophagus and the cyst were connected with a stalk and the cyst was filled with mucinous materials. And on the histological findings, the mass was lined with pseudostratified ciliated columnar epithelium. Thus we report this case of bronchogenic cyst with review of literatures.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.9
• /
• pp.1341-1345
• /
• 2004

We developed a novel synthesis strategy of titania nanowire arrays by employing simple hydrothermal reaction and ion-exchange reaction techniques. Hydrothermal reactions of metallic titanium powder with $H_2O_2$ in a 10 M NaOH solution produced a new sodium titanate compound, $Na_2Ti_6O_{13}{\cdot}xH_2O$ (x~4.2), as arrays of nanowires of lengths up to 1 mm. Acid-treatment followed by calcination of this material produced arrays of highly crystalline anatase nanowires as evidenced by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy studies. In both cases of sodium titanate and anatase, the nanowires have exceptionally large aspect ratios of 10,000 or higher, and they form arrays over a large area of $1.5 {\times} 3 cm^2$. Observations on the reaction products with varied conditions indicate that the array formation requires simultaneously controlled formation and crystal growth rates of the $Na_2Ti_6O_{13}{\cdot}xH_2O$ phase.

• Transactions on Electrical and Electronic Materials
• /
• v.9 no.5
• /
• pp.209-212
• /
• 2008

We developed a simple and effective purification method to obtain high-purity single-walled carbon nanotubes (SWCNTs) with low surface damage. The purification process consists of oxidization at $430^{\circ}C$ for 1 h in a furnace system of air atmosphere and homogenization in dilute hydrochloric acid solution for extremely short time. The role of homogenizer was examined during purification process in terms of purity and quality of purified SWCNTs. High-purity and low surface damage of SWCNT products was obtained using homogenizer which was operated at 8500 rpm for 10 min in the environment of 7 % HCI solution. From XRD spectra, we observed that metal catalysts were thoroughly removed. Raman spectra showed that the intensity values of crystallization ($I_{G}/I_{D}$) of purified SWCNTs were very similar with that of pristine SWCNTs. Moreover, the structure damage of purified SWCNTs was hard to find from electron microscopy. Consequently, homogenizing, which is a quick and simple manner, can be promising method for obtaining final SWCNTs with clearly high purity and crystallinity.

• Journal of Korean Neurosurgical Society
• /
• v.49 no.5
• /
• pp.267-272
• /
• 2011

Objective : Although iliac crest autograft is the gold standard for lumbar fusion, the morbidity of donor site leads us to find an alternatives to replace autologous bone graft. Ceramic-based synthetic bone grafts such as hydroxyapatite (HA) and b-tricalcium phosphate (b-TCP) provide scaffolds similar to those of autologous bone, are plentiful and inexpensive, and are not associated with donor morbidity. The present report describes the use of Polybone$^{(R)}$ (Kyungwon Medical, Korea), a beta-tricalcium phosphate, for lumbar posterolateral fusion and assesses clinical and radiological efficacy as a graft material. Methods : This study retrospectively analyzed data from 32 patients (11 men, 21 women) who underwent posterolateral fusion (PLF) using PolyBone$^{(R)}$ from January to August, 2008. Back and leg pain were assessed using a Numeric Rating Scale (NRS), and clinical outcome was assessed using the Oswestry Disability Index (ODI). Serial radiological X-ray follow up were done at 1, 3, 6 12 month. A computed tomography (CT) scan was done in 12 month. Radiological fusion was assessed using simple anterior-posterior (AP) X-rays and computed tomography (CT). The changes of radiodensity of fusion mass showed on the X-ray image were analyzed into 4 stages to assess PLF status. Results : The mean NRS scores for leg pain and back pain decreased over 12 months postoperatively, from 8.0 to 1.0 and from 6.7 to 1.7, respectively. The mean ODI score also decreased from 60.5 to 17.7. X-rays and CT showed that 25 cases had stage IV fusion bridges at 12 months postoperatively (83.3% success). The radiodensity of fusion mass on X-ray AP image significantly changed at 1 and 6 months. Conclusion: The present results indicate that the use of a mixture of local autologous bone and PolyBone$^{(R)}$ results in fusion rates comparable to those using autologous bone and has the advantage of reduced morbidity. In addition, the graft radiodensity ratio significantly changed at postoperative 1 and 6 months, possibly reflecting the inflammatory response and stabilization.

• Korean Journal of Optics and Photonics
• /
• v.6 no.3
• /
• pp.188-200
• /
• 1995

A design of unit magnification 2-mirror system with high resolution is presented. It is for soft X-ray(wavelength of 13 nm) projection imaging and suitable for preparation of high density semiconductor chip. In general, a holosymmetric system with unit magnification has the advantage that both coma and distortion are completely eliminated. In our holosymmetric 2-mirror system, spherical aberration is addtionally removed by using two identical paraboloidal mirror surfaces and field curvature aberration is also corrected by balancing Petzval sum and astigmatism which depends on the distance between two mirrors, so that the system is a aplanatic flat-field paraboloidal 2-mirror holosymmetric system. This 2-mirror system is small in size, and has a simple configuration with rotational symmetry about optical axis, and has also small central obscuration. Residual finite aberrations, spot diagrams, and diffraction-based MTF's are analyzed for the check of performances as soft X-ray lithography projection system. As a result, the image sizes for the resolutions of$0.25\mum$and $0.18\mum$are 4.0 mm, 2.5 mm respectively, and depths of focus for those are $2.5\mum$, $2.4\mum$respectively. This system should be useful in the fabrication of 256 Mega DRAM or 1 Giga DRAM. DRAM.

• Korean Journal of Digital Imaging in Medicine
• /
• v.11 no.2
• /
• pp.101-107
• /
• 2009

With the recent development of diagnosis using radiation and increasing demand of the medical treatment, we need to minimize radiation exposure dose. So, This is the method which reduce patient dose by measuring surface dose of radiographic change factor and by comparing theoretical and actual dose, when we take an X-ray which is generally used. By changing the factor of kV, mAs, FSD, whose range is 60 to 120 kV, 20 to 100 mAs, 80 to 180 cm, we compared theoretical surface dose with actual surface dose calculated by the simple calculation program, Bit system, and NDD-M method As a result, when kV and mAs were higher, theoretical surface dose and actual surface dose were more increased. but the higher FSD was, the more decreased surface dose was. According to this, the error were measured about 0.1 to 0.2 mGy in low dose part and about 0.7 to 1.5 mGy in high dose part. Therefore, this shows that theoretical surface dose calculation method is more correct in low dose part than in high dose part. In conclusion, we will have to make constant efforts which can reduce patient and radiographer's exposure dose, studying methods which can predict patient's radiation exposure dose more exactly.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.11
• /
• pp.2450-2456
• /
• 2002

Microlenses and microlens arrays are fabricated using a novel fabrication technology based on the exposure of a resist (usually PMMA) to deep X-rays and subsequent thermal treatment. The fabrication technology is very simple and produces microlenses and microlens arrays with good surface roughness (less than 1 nm). The molecular weight and glass transition temperature of PMMA is reduced when it is irradiated with deep X-rays. The microlenses is produced through the effects of volume change, surface tension, and reflow during thermal treatment of irradiated PMMA. The geometry of the microlens is determined by parameters such as the X-ray dose applied to the PMMA, the diameter of the microlens, along with the heating temperature, heating time, and cooling rate in the thermal treatment. Microlenses are produced with diameters ranging from 30 to 1500 ${\mu}{\textrm}{m}$. The modified LIGA process is used not only to construct hemispherical microlenses but also structures that are rectangular-shaped, star-shaped, etc.

• Journal of Chest Surgery
• /
• v.15 no.4
• /
• pp.447-450
• /
• 1982

A 45 year old male officer was admitted due to upper substernal pain for 1 month, which was aggravated by swallowing. On past and family history, there was no specific history except heavy drinking. Simple chest x-ray revealed no specific abnormal findings. Preoperative esophagofiberscopy and Barium study showed midesophageal diverticulum, pulsion type, at about 2 cm below the left main bronchus. The opening of the diverticulum was located at the left posterolateral aspect of esophagus. Midesophageal false diverticulum, measuring 2 x 2 x 1 .S cm in size, was noted at about 5 cm under the aortic arch protruding through a slit-like muscular defect. After inversion of diverticular sac, interrupted sutures with 3-0 silks were done on muscular defect site, and mediastinal pleura was reinforced on the lesion with interrupted sutures. On 4th postoperative day, esophagography revealed no diverticulum or stenosis. Also esophagofiberscopy showed smooth mucosal tag without disturbance of passage. On 14th postoperative day, the patient was discharged uneventfully, and follow-up for 3 months after discharge revealed nothing abnormal symptoms. The authors report one case of midesophageal, pulsion type, false diverticulum.