• KIPS Transactions on Software and Data Engineering
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• v.6 no.4
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• pp.211-216
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• 2017

This paper proposes image processing techniques that improve usability and performance in a diagnostic system of the contrast-enhanced ultrasonography. For a methodology for visualizing diagnostic parameter data in an ultrasonic medical image, an expression of transition time data with successive pixel values and a method of generating a lesion diagnostic parameter image with four categorized values are presented. We also introduce a MRF-based image enhancement technique to eliminate noises from generated parametric images. Such parametric image generation technique can overcome the difficulty of discriminating dynamic change in patterns in the ultrasonography. The technique clarifies the contour of the region in the original image and facilitates visual determination of the characteristics of the lesion through four colors. With regard to this MRF-based image enhancement, we define the energy function of consecutive pixel values and develop a technique to optimize it, and the usability of the proposed theory is examined through experiments with medical images.

• Journal of Veterinary Clinics
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• v.18 no.3
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• pp.269-272
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• 2001

Fourteen dogs referred to veterinary Medical Teaching Hospital, Seoul National University were diagnosed as esophageal foreign body (9 cases), megaesophagus (4 cases) and esophageal stricture (1 case). Patients showed a variety of clinical signs including regurgitation, vomiting, anorexia, hypersalivation, and retching. Survey radiographic examination included the entire esophagus, including the caudal pharynx and cranial abdomen. contrast radiographs were done to identify lesions or to characterize abnormal radiographic findings on survey films. In case static contrast studies were not sufficient were not sufficient to differentiate the diseases, dynamic fluoroscopic studies were performed. In thoracic megaesophagus, when gas filled, it provided several hallmark findings such as visualization of paired longus colli muscle and tracheal stripe sign. When gas-distended, the caudal thoracic esophagus was seen as a pair of thin, soft-tissue stripes that converged into a point overlying the diaphragm and cranial abdomen. All cases of megaesophagus could be solely identified by survey radiographs. In esophageal foreign body, 6 cases out of 9 patients had the history of having foreign body and others not. Most of esophageal foreign body could be diagnosed on survey radiographs and one case with radiolucent foreign body was confirmed by esophagram. It appeared as radiopaque material along the path of esophagus and the radiopacity was determined by its nature. Obstruction caused by foreign body eventually led to dilation of the esophageal lumen cranial to the site in 3 cases. In esophageal stricture, there was no remarkable findings on survey radiograph of the thorax. However, esophagography with barium sulfate showed the narrowing of the esophagus near hiatus. On fluoroscopy, swallowed barium was stagnated cranial to the site despite the esophageal peristalsis.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.6
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• pp.643-650
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• 2017

Vascular dementia (VaD) is a group of heterogeneous diseases with the common feature of cerebral hypoperfusion. To identify key factors contributing to VaD pathophysiology, we performed a detailed comparison of Wistar and Sprague-Dawley (SD) rats subjected to permanent bilateral common carotid artery occlusion (BCCAo). Eight-week old male Wistar and SD rats underwent BCCAo, followed by a reference memory test using a five-radial arm maze with tactile cues. Continuous monitoring of cerebral blood flow (CBF) was performed with a laser Doppler perfusion imaging (LDPI) system. A separate cohort of animals was sacrificed for evaluation of the brain vasculature and white matter damage after BCCAo. We found reference memory impairment in Wistar rats, but not in SD rats. Moreover, our LDPI system revealed that Wistar rats had significant hypoperfusion in the brain region supplied by the posterior cerebral artery (PCA). Furthermore, Wistar rats showed more profound CBF reduction in the forebrain region than did SD rats. Post-mortem analysis of brain vasculature demonstrated greater PCA plasticity at all time points after BCCAo in Wistar rats. Finally, we confirmed white matter rarefaction that was only observed in Wistar rats. Our studies show a comprehensive and dynamic CBF status after BCCAo in Wistar rats in addition to severe PCA dolichoectasia, which correlated well with white matter lesion and memory decline.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.65.1-65.1
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• 2013

The 2011 August 09 Flare is one of the largest X-ray flares of Sunspot Cycle 24 to attract a lot of attention for its various activities detected in coronal images. In this study we concern ourselves mostly on information of high energy electrons produced during this flare provided by hard X ray data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and radio data from the Korean Solar Radio Burst Locator (KSRBL) and Ondrejov. EUV images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory are used to provide the context of magnetic reconnection. In our results, (1) HXR spectra have a rich spectral morphology. Initially it could be fit by one thermal component (T~30MK) and one single power law nonthermal spectrum, but later a better fit could be made by introducing an additional thermal component (T~55 MK). (2) Time delays between the KSRBL burst and the RHESSI hard X-ray emission were found which are more obvious at low frequencies and insignificant at high frequencies. (3) The HXR source lies in the core of the quadrupolar active region. In our interpretation based on AIA 94 A images, the outer part of the active region erupted to be blown out, leaving the intense hard X-ray emission concentrated in the core. We relate the appearance of the second thermal component to the evolution of the AIA 171 and 94 A images. The time delays of microwave peaks to HXR peaks are interpreted as indicating presence of trapped electrons in larger closed magnetic loops. With these result we conclude that the hard X ray and microwaves are due to impulsive acceleration in the low and high heights and a sigmoidal reconnection scenario.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.63.2-63.2
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• 2013

We have investigated the EUV coronal jets observed by Solar Dynamic Observatory (SDO) / Atmospheric Imaging Assembly (AIA). From the Heliophysics Events Knowledgebase (HEK), we consider all recorded 40 EUV jets in $171{\AA}$ from May 2010 to July 2011 and use 19 jets whose location can be clearly identified, excluding limb events because of the ambiguity of their positions. According to the positions of their roots, these coronal jets are classified into two types: bright point jet (BPJ, 9 jets) and active region boundary jet (ABJ, 10 jets). BPJs are located at the top of bright points and ABJs at the boundaries of active regions. There are significant differences in speed and size between two types. Here the speed and size of a jet are assumed to be its maximum values in the case that the jet has several ejections. The average speed and size of 9 BPJs are about 110 km/s and 69,000km, respectively. The average speed and size of 10 ABJs are about 660 km/s and 194,000 km, respectively. The speed distribution of ABJs has two peaks at about 270 km/s and 1700 km/s. It is very interesting to note that three ABJs have very high speeds larger than 1600 km/s and they are all composed of a group of recurrent jets with low and high speed at the same location. In addition, we are investigating these events in other wavelengths and compare their characteristics.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.112.1-112.1
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• 2012

We have investigated the relationship between EUV coronal jets and bright points observed by Solar Dynamic Observatory (SDO)/Atmospheric Imaging Assembly (AIA). For this we consider 39 EUV coronal jets from May 2010 to July 2011 in 171 A identified by Heliophysics Events Knowledgebase (HEK) which provides an automatic identification of coronal jets. We look for coronal jet-bright point pairs as follows. First, we select the size of event area as 360 arcsec * 360 arcsec where the coronal jets are located at the center of the area. Second, we select jet-bright point pairs in case that they are located at the same position or just adjacent. Third, we select jet-bright point pairs that are connected by loops each other. Otherwise, we select jet-bright points pairs as the nearest one. As a result, we present 19 coronal jet-bright point pairs. The mean distance of these pairs is 77.24 arcsec. According to their distance and morphological connection, we classify the following three groups: 1) Adjacent (6 events), 2) Loop connected (5 events), and 3) Not connected in appearance (8 events). The histogram of mutual distance has two peaks; the first peak corresponds to the first group and the other one to the second group. We compare these events with previous observations and theoretical models as well as discuss possible physical connections between jets and bright points.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.751-758
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• 2002

Boreholes that are drilled in soft or unconsolidated materials such as gravels and coals are prone to collapse. To maintain the hole, some kinds of casing pipes are needed. If thereby a plastic pipe e.g. PVC is used for the casing, Televiewer tool is still capable of detecting structural features such as fractures in the borehole wall behind the pipe, whereas other borehole-imaging logging devices such as BIPS (Borehole Image Processing System) and FMS(Formation Micro Scanner) won't provide any information about that. Televiewer's primary component is a piezoelectric transducer centered in the hole. It acts as both a transmitter and receiver, and sends an ultrasonic beam. That is reflected, in the same manner as the seismic wave propagation, from the both sides(inner and outer surfaces) of the casing pipe, transmits through the pipe and then reflected from the borehole wall. With an appropriate choice of time-windowing, it is possible to capture the returning signals from both the borehole wall and the outer side of casing pipe as well. A suite of laboratory tests were performed on various physical models composed of plastic pipes with different diameters. Although the amplitudes of returning signals were reduced to about half the usual value due to the transmission loss, the dynamic range of Televiewer tool was sufficient to observe the structural features behind the casing pipe. Besides, several representative case studies at various research areas in our country are presented. The results demonstrate the usefulness of the transmissivity of Televiewer acoustic km, which will assist in further structural interpretation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.278-284
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• 2010

In this paper, a millimeter-wave detector using zero-bias schottky diode is designed and fabricated at W-band. It consists of LNA(Low Noise Amplifier) and detector module to improve sensitivity. LNA case with a highly stop-band characteristic is designed to prevent the oscillation by LNA MMIC chip. Diode detector of planar structure is fabricated for the easy connection with LNA module and zero bias Schottky diode is utilized. In practice, the fabricated diode detector have shown the detection voltage of 20~500 mV to the RF input power of -45~-20 dBm. The proposed W-band detector can be applicable to the passive millimeter image system.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.143-152
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• 1998

In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at $4f_o$(where $f_o$ is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to $4f_o$/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.

• Journal of Korean Neurosurgical Society
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• v.29 no.3
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• pp.345-352
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• 2000

Objective : The purpose of this study was to compare computed tomographic angiography(CTA) with conventional cerebral angiography(CCA) and to assess usefulness of CTA in detection and anatomic definition of intracranial aneurysms of the circle of Willis in subarachnoid hemorrhage. Patients and Methods : Fifty consecutive patients with known or suspected intracranial saccular aneurysms underwent CTA with preoperative CCA from 1997 to 1999. Using surface shaded display post-processing technique, CTA was interpreted for the presence, location of aneurysms and anatomic features. The image obtained with CTA was then compared with CCA image. Results : In 47 patients, CCA revealed 57 cerebral aneurysms and CTA revealed 54 aneurysms. Two of the 57 cerebral aneurysms were located outside of the imaging volume of CTA and one case was misdiagnosed. The sensitivity of CTA was 94.7% and the specificity was 100%. The results obtained with CTA were, compared with the results obtained with CCA, equal in determining dome shape, direction and lobularity. However, CTA provided a 3-dimensional representation of aneurysmal lesion very useful for surgical planning. Moreover, CTA was useful for rapid and relatively noninvasive detection of aneurysms in the circle of Willis. Conclusion : CTA can be a diagnostic tool for the patients with acute subarachnoid hemorrhage due to a ruptured aneurysm of the circle of Willis and provides adequate anatomic detail for surgical planning, especially to complex cerebral aneurysms. However, we think CCA is necessary because of CTA limitations including its difficulty in detecting unusually located aneurysms(including those in cavernous sinus or distal artery) and combined vascular lesion (including arteriovenous malformation) and acquiring dynamic flow information.