• Progress in Medical Physics
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• v.11 no.2
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• pp.91-99
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• 2000

This is a preliminary study for developing the method of the dose reconstruction in the patients, irradiated by mega-voltage photon beams from the linear accelerator, using the transit dose distributions. In this study we present the method of three-dimensional dose reconstruction and evaluate the method by computer simulation. To acquire the dose distributions in the patients (or phantoms) we first calculate the differences between the doses at the arbitrary points in the patients and the doses at the corresponding points where the transit doses are measured. Then, we can get the dose in the patients from the measured transit dose and the calculated value of the difference. The dose differences are calculated by applying the inverse square law and using the linear attenuation coefficient. The scatter to primary dose ratios, which are calculated by the Monte Carlo program using the CT data of the patient (or phantoms), are also used in the calculations. For the evaluation of this method we used various kinds of homogeneous and inhomogeneous phantoms and calculated the transit dose distributions with the Monte Carlo program. From the distributions we reconstructed the dose distributions in the phantom. We used mono-energy Photon beam of 1.5MeV and Monte Carlo program EGS4. The comparison between the dose distributions reconstructed using the method and the distributions calculated by the Monte Carlo program was done. They agreed within errors of -4%∼+2%. This method can be used to predict the dose distributions in the patient

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.486-493
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• 2010

This article introduces a novel ultra wideband(UWB) bandpass filter(BPF) with sharp roll-off characteristics in stripline structure. The UWB characteristic is basically obtained from capacitive coupled cross resonator. The resonator has ${\lambda}/2$ length. And at the center of the resonator, two stubs are loaded, one is a ${\lambda}/8$ short-circuited stub and the other is a ${\lambda}/8$ open-circuited stub. The two stubs provide two attenuation poles at lower and upper cutoff frequencies. For input and output lines, two identical capacitively coupled lines have been installed to suppress the unwanted signals in the lower and upper stopbands. The filter has been designed for the U.S. UWB band(3.1~10.6 GHz) with two transmission zeros at 2.4 and 11.1 GHz. The filter has been realized with Low Temperature Core-fired Ceramic(LTCC) green tape which has the dielectric constant of 7.8. Measurement results agree well with HFSS simulation results. Insertion loss less than 0.7 dB and return loss better than 14 dB in the pass band have been measured. The group delay in the center frequency is 0.27 ns and the group delay variation within pass band is less than 0.5 ns. The size of the filter is $6{\times}18{\times}0.6\;mm^3$.

• Journal of radiological science and technology
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• v.31 no.2
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• pp.135-140
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• 2008

Purpose: Fatty liver is one of the most commonly found disease by abdominal ultrasonography. The status of fatty liver is classified into mild, moderate and severe degrees. The study was conducted to investigate the clinical significance of fatty liver using ultrasonography. Materials and method: Test set consisted of 2,185 patients who visited D healthcare center in Daejeon to receive an abdominal ultrasonic test from January to December 2007. Out of the 2185 patients, 524 patients was diagnosed as fatty liver (290 male and 234 female patients). They were divided into three groups, group I for mild degree. II for moderate degree, and III for severe degree, depending on the echo of liver parenchyma, the sound attenuation, and the visibility of intrahepatic blood vessels and diaphragm. Then the correlation of obesity indices, liver function tests and metabolic syndrome was analyzed for males and females separately. Results : As for the degree of fatty liver, 350 cases (66.8%) were classified as group I, 153 cases (29.2%) as group II, and 21 cases (4.1%) as group III. In addition, severe degree of fatty liver was more frequently found in males than in females. The mean ages of three groups for males were 46.1, 44.5, and 39.1, and those for females were 48.8, 50.2, 52.4, respectively. Males with lower mean ages have severely of fatty liver for both males and females. Conclusion: The results in this study show that the classification into three degrees of fatty liver in ultrasonography practice is helpful to treat and observe the progress of fatty liver. In addition, careful examination is required to measure the severity of fatty liver as well as detection of it. A standardized method to classify the degree of fatty liver is also needed for more objective measurement.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.2
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• pp.163-168
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• 2007

Ecological risk assessment(ERA) to 5 abandoned mine drainage was investigated by using chemical measurement and bioassay experiment. From the results of chemical analysis, the high concentration of heavy metals are detected in most area. The Arsenite were mostly detected in Songcheon, Nakdong, and Dukum abandoned mine area, and various heavy metals were highly dispersed in Nakdong area. The study area have also high biological toxicity, resulted from the bioassay based on WET(Whole Effluent Toxicity) test by using Vibrio fisheri, Selenastrum copricornutum, and Daphnia magna. The maximum toxicity was shown in the point where the mine waters start to flow. The sensitivity of toxicity by S. capricornutum was relatively high considering the values of toxicity in all samples, from 1.3 to 32.0 TU. The different sensitivities of toxicity recommends the use of battery system, resulted from at least two test species for bioassay or ecological risk assessment of mine drainage. Besides, the results showed high hazard quotient(i.e., greater than 1 HQ value indicating potentially significant toxic risks) with regard to abandoned mine drainage area in this study. On the other hand, the biological toxicity results were sharply decreased by attenuation along further distance from discharging of mine waters. Therefore, environmental parameters including the dilution factor, dissolved organic matter, and hardness should be considered when the remediation and ERA of abandoned mine drainage is planned.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.43-49
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• 2017

Generally, loop filter based scalar tracking loops (LF-STL) have been used for global positioning system (GPS) signal tracking algorithm. This paper introduces the accuracy and robustness of linear-quadratic-Gaussian based vector tracking loop (LQG-VTL) algorithm instead of LF-STL. To verify the accuracy of LQG-VTL, we confirm that the measurements estimation errors of the LQG based scalar tracking loops (LQG-STL) are improved by more than 60 % compared to LF-STL. Also, when LQG-VTL is used, measurements estimation errors decrease compared to LQG-STL, and position/velocity estimation errors also decrease as the number of satellites increases. To verify the robustness of LQG-VTL, we confirm that LQG-VTL can estimate position/velocity and measurements successively compared to LF-STL in temporal signal attenuation of 30 dB-Hz during 4 seconds.

• The Journal of Korean Society for Radiation Therapy
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• v.18 no.2
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• pp.75-80
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• 2006

Purpose: In radiation therapy, precise calculation of dose toward malignant tumors or normal tissue would be a critical factor in determining whether the treatment would be successful. The Radiation Treatment Planning (RTP) system is one of most effective methods to make it effective to the correction of dose due to CT number through converting linear attenuation coefficient to density of the inhomogeneous tissue by means of CT based reconstruction. Materials and Methods: In this study, we carried out the measurement of CT number and calculation of mass density by using RTP system and the homemade inhomogeneous tissue Phantom and the values were obtained with reference to water. Moreover, we intended to investigate the effectiveness and accuracy for the correction of inhomogeneous tissue by the CT number through comparing the measured dose (nC) and calculated dose (Percentage Depth Dose, PDD) used CT image during radiation exposure with RTP. Results: The difference in mass density between the calculated tissue equivalent material and the true value was ranged from $0.005g/cm^3\;to\;0.069g/cm^3$. A relative error between PDD of RTP and calculated dose obtained by radiation therapy of machine ranged from -2.8 to +1.06%(effective range within 3%). Conclusion: In conclusion, we confirmed the effectiveness of correction for the inhomogeneous tissues through CT images. These results would be one of good information on the basic outline of Quality Assurance (QA) in RTP system.

• The Korean Journal of Physiology
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• v.23 no.1
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• pp.43-49
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• 1989

Effects of atrial natriuretic peptide (ANP) on the development of hypertension in 2-kidney, 1-clip (2-K, 1-C) rats were examined. In one group of rats, ANP infusion (500 ng/hr, iv) started immediately after clipping the renal artery. Another group of rats with one kidney-clipped was without ANP infusion and served as a control. Blood pressure was measured on days 4, 7, and 10 following clipping the renal artery. Upon the last blood pressure measurement finished, blood sample was collected by decapitation to measure plasma renin activity (PRA), and both kidneys were taken to weigh and to measure renin content. The ANP-infused group showed an attenuation of increases in blood pressure compared to the non-infused control group. PRA was lower in the ANP-infused group than in the non-infused group. Cortical renal renin content (RRC) of the clipped kidneys was not different between ANP-infused and non-infused groups. The clipped kidneys showed a higher RRC and weighed less than the non-clipped contralateral kidneys within each group. In contrast, sham-clipped rats did not show significant changes in any of the parameters examined regardless of whether ANP was infused or not. These results demonstrate that chronic ANP infusion does not prevent but does attenuate the development of hypertension in 2-K, 1-C rats. It is suggested that ANP plays a role in the long-term regulation of blood pressure, at least in part, by antagonizing the renin-angiotensin-system.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.407-410
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• 2002

Monochromatic x-ray CT has several advantages over conventional CT, which utilizes bremsstrahlung white x-rays from an x-ray tube. There are several methods to produce such monochromatic x-rays. The most popular one is crystal diffraction monochromatization, which has been commonly used because of the fact that the energy spread is very narrow and the energy can be changed continuously. The alternative method is the use of fluorescent x-ray, which has several advantages such as large beam size and fast energy change. We have developed a parallel-beam and a fan-beam monochromatic x-ray CT, and compared some characteristics such as accuracy of CT numbers between those systems. The fan beam monochromatic x-rays were generated by irradiating target materials by incident white x-rays from a bending magnet beam line NE5 in 6.5 GeV Accumulation Ring at Tukuba. The parallel beam monochromatic x-rays were generated by using a silicon double crystal monochromator at the bending magnet beam line BL-20BM in Spring-8. A Cadmium telluride (CdTe) 256 channel array detector with 512mm sensitive width capable of operating at room temperature was used in the photon counting mode. A cylindrical phantom containing eight concentrations of gadolinium was used for the fan beam monochromatic x-ray CT system, while a phantom containing acetone, ethanol, acrylic and water was used for the parallel monochromatic x-ray CT system. The linear attenuation coefficients obtained from CT numbers of those monochromatic x-ray CT images were compared with theoretical values. They showed a good agreement within 3%. It was found that the quantitative measurement can be possible by using the fan beam monochromatic x-ray CT system as well as a parallel beam monochromatic X-ray CT system.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• Atmosphere
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• v.21 no.2
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• pp.131-142
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• 2011

Spectral solar irradiances were observed using a visible and UV Multi-Filter Rotating Shadowband Radiometer on the rooftop of the Science Building at Yonsei University, Seoul ($37.57^{\circ}N$, $126.98^{\circ}E$, 86 m) during one year period in 2006. 1-min measurements of global(total) and diffuse solar irradiances over the solar zenith angle (SZA) ranges from $20^{\circ}$ to $70^{\circ}$ were used to examine the effects of clouds and total optical depth (TOD) on enhancing four solar irradiance components (broadband 395-955 nm, UV channel 304.5 nm, visible channel 495.2 nm, and infrared channel 869.2 nm) together with the sky camera images for the assessment of cloud conditions at the time of each measurement. The obtained clear-sky irradiance measurements were used for empirical model of clear-sky irradiance with the cosine of the solar zenith angle (SZA) as an independent variable. These developed models produce continuous estimates of global and diffuse solar irradiances for clear sky. Then, the clear-sky irradiances are used to estimate the effects of clouds and TOD on the enhancement of surface solar irradiance as a difference between the measured and the estimated clear-sky values. It was found that the enhancements occur at TODs less than 1.0 (i.e. transmissivity greater than 37%) when solar disk was not obscured or obscured by optically thin clouds. Although the TOD is less than 1.0, the probability of the occurrence for the enhancements shows 50~65% depending on four different solar radiation components with the low UV irradiance. The cumulus types such as stratoculmus and altoculumus were found to produce localized enhancement of broadband global solar irradiance of up to 36.0% at TOD of 0.43 under overcast skies (cloud cover 90%) when direct solar beam was unobstructed through the broken clouds. However, those same type clouds were found to attenuate up to 80% of the incoming global solar irradiance at TOD of about 7.0. The maximum global UV enhancement was only 3.8% which is much lower than those of other three solar components because of the light scattering efficiency of cloud drops. It was shown that the most of the enhancements occurred under cloud cover from 40 to 90%. The broadband global enhancement greater than 20% occurred for SZAs ranging from 28 to $62^{\circ}$. The broadband diffuse irradiance has been increased up to 467.8% (TOD 0.34) by clouds. In the case of channel 869.0 nm, the maximum diffuse enhancement was 609.5%. Thus, it is required to measure irradiance for various cloud conditions in order to obtain climatological values, to trace the differences among cloud types, and to eventually estimate the influence on solar irradiance by cloud characteristics.