• Proceedings of the KOSOMBE Conference
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• v.1989 no.05
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• pp.35-37
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• 1989

A new MR angiography technique using a composite sequence for the suppression of static sample signals is proposed and verified with experiments. When the composite [$90^{\circ}-{\tau}-180^{\circ}-2{\tau}-180^{\circ}-{\tau}$] sequence is applied, the large signal from the static sample is sufficiently suppressed but the signal from fresh inflow sample of which amplitude. is observed without suppression. These properties are appropriate for angiographic applications. In this paper, a modified line scan method (Block line scan angiography) incorporated with the composite [$90^{\circ}-{\tau}-180^{\circ}-2{\tau}-180^{\circ}-{\tau}$] sequence is used to obtain flow-only images, i.e., angiograms. The block line scan method improves the resolution in the flow-direction at the expense of imaging time. With the composite sequence, there is no need for subtraction procedure as in the most conventional angiographic methods. Experimental results for a phantom and a normal volunteer with KAIS 2.0 Tesla MRI system are shown.

• Corrosion Science and Technology
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• v.11 no.3
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• pp.89-95
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• 2012

U.S. Electric Power Research Institute (EPRI) has developed CHECWORKS program and applied it to power plant piping lines since some lines were ruptured by flow-accelerated corrosion (FAC) in 1978. Nowadays the CHECWORKS program has been used to manage pipe wall thinning phenomena caused by FAC. However, various erosion mechanisms can occur in carbon-steel piping. Most common forms of erosion are cavitation, flashing, liquid droplet impingement erosion (LDIE), and Solid Particle Erosion (SPE). Those erosion mechanisms cause pipe wall thinning, leaking, rupturing, and even result in unplanned shutdowns of utilities. Especially, in two phase condition, LDIE damages a wide scope of plant pipelines. Furthermore, LDIE is the major culprit to cause such as power runback by pipe leaking. This paper describes the methodologies that manage wall thinning and also predict LDIE wall thinning area. For this study, current properties of two-phase condition are investigated and LDIE areas are selected. The areas are checked by B-Scan method to detect the effect of wall thinning phenomena.

• Progress in Superconductivity
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• v.3 no.1
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• pp.125-129
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• 2001

NiO buffer layers were deposited on texture Ni tapes fur YBCO coated conductors by MOCVD(metal organic chemical vapor deposition) method, using a single solution source. Variables were deposition temperature and flow rate of $0_2$carrier gas. At higher temperatures, The NiO(111) texture was well developed, but the NiO(200) texture was developed at low temperatures. The best result was obtained at the deposition temperature of$ 470^{\circ}C$ and the gas flow rate of 200 sccm. FWHM value of $\omega$-scan fur NiO(200) of the film and $\Phi$-scan for NiO(111) of the film was $4.2^{\circ}$ and $7^{\circ}$, respectively.

• Nuclear Medicine and Molecular Imaging
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• v.41 no.4
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• pp.337-338
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• 2007

A 20-year-old man underwent a Tc-99m HMPAO labeled leukocyte scan for the evaluation of an infection at the stump of an AK amputation, which was conducted due to an open communicated fracture of the left lower leg. Blood-flow and blood-pool images demonstrated a pseudoaneurysm with a focus of intense activity medial to the stump, and centered within a large photopenic defect by surrounding hematoma. Delayed image obtained at 3 hours post-injection showed persistent intense and slight increased activity, Contrast angiography confirmed the presence of a pseudoaneurysm arising from a branch of the left superficial femoral artery.

• Proceedings of the KOSOMBE Conference
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• v.1989 no.05
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• pp.27-28
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• 1989

In conventional line scan angiography, flow signal has been enhanced by the time_of_flight effect while the signal from stationary tissues has been suppressed by the saturation rf pulse followed by spoiling gradients. Due to the inhomogeneous rf field and the tissue dependent T1 relaxation time, however, stationary tissues can not be suppressed completely or uniformly, and the remnant stationary signal deteriorates the resultant angiogram. Here, the complete cancellation of stationary tissues is made possible by the spectral analysis of a series of repetitive line images of the same slice. The Fourier transformation of a set of line images results in the spectrum images, where stationary tissues are collected into the dc component while arteries are included in harmonic components because of the variation of the flow velocity and the resultant flow signal in arteries according to the cardiac cycle. The summation of harmonic components excluding the dc component results in the angiogram of arteries with the complete cancellation of stationary tissues.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1205-1210
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• 2005

The behavior of rock mass and solute(e.g. groundwater, radioactivity) flow in fractured rock can be directly influenced by joint roughness. The characteristics of joint roughness is also a main factor for the rock classification(e.g. RMR, Q system) which is usually used in tunnel design. Nevertheless, most of JRC estimation has been carried out only by the examination with the naked eye. This JRC estimation has a lack of objectivity because each investigator judges JRC by his subjective opinion. Therefore, it will be desirable that the assessment of JRC is performed by a numerical analysis which can give a quantitative value corresponding to the characteristics of a roughness curve. Meanwhile, roughness curves for joint surfaces which are observed in drill cores have been obtained only along linear profiles. Although roughness curves are measured in the same joint surface, they can frequently show diverse aspects in a standpoint of roughness characteristics. If roughness curves can be measured along the elliptical circumferences of joint surfaces from core scanning images or Televiewer images, they will certainly be more comprehensive than those measured along linear profiles for roughness characteristics of joint surfaces. This study is focus on dealing with (1) extracting automatically roughness curves from core scan image or Televiewer image, (2) improving the accuracy of quantitative assessment of JRC using fractal dimension concept.

• The Korean Journal of Nuclear Medicine
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• v.39 no.3
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• pp.151-162
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• 2005

Hemangioma is the most common benign tumor of the liver, with a prevalence estimated as high as 7%. Tc-99m red blood cell (RBC) hepatic blood pool scan with single photon omission computed tomography (SPECT) imaging is extremely useful for the confirmation or exclusion of hepatic hemangiomas. The classic finding of absent or decreased perfusion and increased blood pooling ("perfusion/blood pool mismatch") is the key diagnostic element in the diagnosis of hemangiomas. The combination of early arterial flow and delayed blood pooling ("perfusion/blood pool match") is shown uncommonly. In giant hemangioma, filling with radioactivity appears first in the periphery, with progressive central fill-in on sequential RBC blood pool scan. However, the reverse filling pattern, which begins first in the center with progressive peripheral filling, is also rarely seen. Studies with false-positive blood pooling have been reported infrequently in nonhemangiomas, including hemangiosarcoma, hepatocellular carcinoma, hepatic adenoma, and metastatic carcinomas (adenocarcinoma of the colon, small cell carcinoma of the lung, neruroendocrine carcinoma). False-negative results have been also reported rarely except for small hemagniomas that are below the limits of spatial resolution of gamma camera.

• The Korean Journal of Nuclear Medicine
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• v.28 no.3
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• pp.397-401
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• 1994

A twenty-one-year-old man visited our hospital due to abdominal distension for a month. On the physical examination, there was severe abdominal distension with fluctuation and shifting dullness. The routine laboratory results were within normal range. On the Magnetic Resonace angiography, there wasn't any blood flow within the right and middle hepatic vein. So we concluded that the etiologic disease was Budd-Chiari syndrome. On the liver scan, there was cold area(absence of radiouptake) on entire right lobe of the liver, increased uptake on the bone marrow and showed splenomegaly. This finding was similar to the liver mass occupying right lobe with underlying chronic liver disease. On the previous reports, it is quite uncommon finding that Budd-Chirari syndrome shows lesion like space occupying one on the liver scan. So we report this case with a review of the literature.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.6
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• pp.293-301
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• 2006

Purpose: The aim of the study was to evaluate the hemodynamic changes after successful bypass surgery in patients with atherosclerotic stenosis in ICA using $^{99m}Tc-ECD$ SPECT. Materials and Methods: Fourteen patients (M:F=8:6, mean age; $60{\pm}9$ years) who underwent STA-MCA anastomosis for unilateral atherosclerotic cerebrovascular disease were enrolled. $^{99m}Tc-ECD$ basal/acetazolamide perfusion SPECT studies were performed before, 10 days and 6 months after bypass surgery. Perfusion reserve was defined as the % changes after acetazolamide over rest image. Regional cerebral blood flow and perfusion reserve were compared preoperative, early-postoperative and late-postoperative scans. Results: The mean resting perfusion and decrease in perfusion reserve in affected ICA territory on preoperative scan was $52.4{\pm}3.5\;and\;-7.9{\pm}4.7%$, respectively. The resting perfusion was significantly improved after surgery on early-postoperative scan (mean $53.7{\pm}2.7$) and late-postoperative scan (mean $53.3{\pm}2.5$) compared with preoperative images (p<0.05, respectively). Resting perfusion did not showed further improvement on late-postoperative scan compared with early-postoperative scan. The perfusion reserve was $-3.7{\pm}2.6%$ on early-postoperative scan, and $-1.6{\pm}2.3%$ on late-postoperative scan, which was significantly improved after surgery. Additionally, further improvement of perfusion reserved as observed on late-postoperative scan (p<0.05). While, in the unaffected ICA territory, no significant changes in the resting perfusion and perfusion reserve was observed. Conclusion: The improvement of resting perfusion and perfusion reserve in early-postoperative scan reflects the immediate restoration of the cerebral blood flow by bypass surgery. In contrasts, further improvement of perfusion reserve showing on late-postoperative scan may indicate a good collateral development after surgery, which may indicate good surgical outcome after surgery.

• Imaging Science in Dentistry
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• v.49 no.4
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• pp.301-306
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• 2019

Purpose: This report presents a procedure for performing power Doppler ultrasound-guided sialography using the phenomenon of increased blood flow and illustrates its application to practical patient cases. Materials and Methods: The salivary gland was scanned using ultrasound equipment (GE LOGIQ5 Expert^® device; GE Medical Systems, Milwaukee, WI, USA) to identify pathological findings related to the patient's chief complaint. To identify the orifice of the main duct, it should be cannulated using a lacrimal dilator. After inserting the catheter into the cannulated main duct, the position of the catheter within the duct was confirmed by ultrasound. A contrast agent was injected until the patient felt fullness, and ultrasound (B-mode) was used to confirm whether the contrast agent filled the main canal and secondary and tertiary ducts. Then, power Doppler ultrasound was performed to determine whether the salivary gland had increased blood flow. Results: In 2 cases in this report, a power Doppler ultrasound scan showed a significant increase in blood flow after contrast medium injection, which was not observed on a preoperative scan. Conclusion: Power Doppler ultrasound was found to be a simple, safe, and effective tool for real-time sialography monitoring.