Noise Measurement by Percentage of Effective Linear Attenuation Coefficient of Water in CT Imageof AAPM CT Performance Phantom

김종언(JongEon Kim),이상훈(Sang Hun Lee) 한국방사선학회 2022 한국방사선학회 논문지 Vol.16 No.6

이 연구의 목적은 임상에서 AAPM CT 성능 팬텀을 이용한 CT영상 노이즈 정도관리에 사용할 수 있는 물 유효선감쇠계수의 백분율에 의한 노이즈 측정의 방법을 제시하는 데 있다. 120 kVp CT X-선 빔으로 AAPM CT 성능 팬텀을 스캔하여 얻어진 CT영상에서, CT수 직선성 삽입부분의 각 핀과 물에 대하여 평균 CT수를 측정하였다. 유효에너지는 각 핀과 물에 대하여 측정된 평균 CT수와 광자에너지별 선감쇠계수의 선형회귀분석의 상관계수들로부터 가장 큰 상관계수를 갖는 광자에너지로 결정하였다. 그리고 물과 아크릴에 대하여 측정된 평균 CT수와 유효선감쇠계수로부터 대조도 척도는 0.000188 cm-1 · HU-1으로 산출되었다. 산출된 대조도 척도, 물 유효선감쇠계수, 그리고 AAPM CT 성능 팬텀에서 고정핀 부분의 물에서 측정된 표준편차를 사용하여, 물 유효선감쇠계수의 백분율에 의한 노이즈 측정값은 100 ~ 300 mAs의 범위에서 0.31 ~ 0.52%를 얻었다. The purpose of this study is to present a method of measuring noise by the percentage of effective line attenuation coefficient of water that can be used for quality control of CT image noise using AAPM CT performance phantom in clinical practice. In the CT images obtained by scanning the AAPM CT performance phantom with a 120 kVp CT X-ray beam, the mean CT number was measured for each pin and water in the CT number linearity insert part. The effective energy was determined as the photon energy with the largest correlation coefficient from the correlation coefficients of the linear regression analysis of the measured mean CT number for each pin and water and the linear attenuation coefficient for each photon energy. And for water and acrylic, the contrast scale was calculated as 0.000188 cm-1 · HU-1 from the measured mean CT number and effective line attenuation coefficient. Using the calculated contrast scale, the effective line attenuation coefficient of water, and the standard deviation measured in the water of the alignment pin part of the AAPM CT performance phantom, The noise measurement value by the percentage of effective line attenuation coefficient of water obtained 0.31 ~ 0.52% in the range of 100 ~ 300 mAs.

안면부에 잔류된 다양한 이물질을 측정한 CT 계수

위서영,최환준,김미선,최창용 대한성형외과학회 2008 Archives of Plastic Surgery Vol.35 No.4

Purpose: Computed tomography theoretically should improve detection of foreign bodies and provide more information of adjacent soft tissues. And the CT scanner and PACS program proved to be an excellent instrument for detection and localization of most facial foreign bodies above certain minimum levels of detectability. The severity of injury in penetrating trauma to the face, it is often underestimated by physical examination. Diagnosis of a retained foreign object is always critical. Methods: From March, 2005 to February 2008 a study was done with 200 patients who had facial trauma. Axial and coronal CT images were obtained with a General Electric(Milwaukee, Wis) 9800 CT scanner at 130kV, 90mA, with a 2-mm section thickness and a 512×512 matrix. Received March 4, 2008 Revised April 2, 2008 Accepted May 2, 2008 Address Correspondence: Hwan Jun Choi, M.D., Department of Plastic & Reconstruction Surgery, Soon Chun Hyang University Gumi Hospital, Gongdan-dong, Gumi-si, Kyunsangbuk-do 730-706, Korea. Tel: 054) 468-9150/Fax: 054) 468-9150/E-mail: medi619@hanmail.net Results: Axial and coronal CT images at various window widths should be used as the first imaging modality to detect facial foreign bodies. The attenuation coefficients for the metallic and nonmetallic foreign bodies ranged from -437 to +3071 HU. As a general rule, metallic foreign bodies produced more Hounsfield artifacts than nonmetallic foreign bodies, thus providing a clue to their composition. All of the metallic foreign bodies were represented by a single peak and had a maximum attenuation coefficient of +3071 HU. Of the nonmetallic foreign bodies, glass had an attenuation coefficient that ranged from +105 to +2039, while plastic had a much lower coefficient that ranged from -62 to -35. wood had the lowest range of attenuation coefficients: -491 to -437. Conclusion: The PACS program allows one to distinguish metallic from nonmetallic foreign bodies and to individually identify the specific composition of many nonmetallic foreign bodies. This program does not, however, allow identification of the specific composition of a metallic foreign body. We recommend this type of software program for CT scanning of any patient with an injury to the face in which a foreign body is suspected.

인가신호 제거를 이용한 STDR의 케이블 고장 검출 성능 향상

전정채(Jeon, Jeong-Chay),김택희(Kim, Taek-Hee) 한국산학기술학회 2016 한국산학기술학회논문지 Vol.17 No.3

케이블에 인가되는 신호로 의사잡음 수열을 사용하여 인가신호와 반사신호의 시간 상관 분석을 실시하여 케이블 고장을 검출하는 STDR (sequence time domain reflectometry)은 노이즈 환경에 강하고, 단선, 합선을 포함한 간헐적 고장의 검출이 가능한 것으로 알려져 있다. 하지만 고장 위치의 거리가 멀거나 경미한 고장의 경우 반사신호의 감쇄가 크고 상관계수가 작아지게 되어, 케이블 고장 판별이 어렵거나 측정 거리 오차가 커진다. 또한 위상과 피크치 검출에 의한 고장 탐지 자동화가 어렵게 된다. 따라서 본 논문에서는 기존의 STDR의 고장 검출 성능을 향상시키기 위해 케이블에 인가되는 인가신호의 상관계수의 최댓값을 검출하고, 다음으로 인가신호를 제거하여 반사신호의 상관계수의 최댓값을 검출하는 알고리즘을 제안하였다. 제안된 방법은 저압 전력 케이블에서의 고장 검출 실험을 통해 성능을 입증하였다. 그 결과 제안된 방법은 신호가 감쇄되더라도 전통적인 STDR보다 고장 여부의 정확한 구분과 위치의 추적이 가능하였다. 또한 기준신호 제거와 상관계수의 정규화를 통해 위상과 최대값 검출 방법을 사용함으로써 자동 고장 판별과 거리 계산에 오류가 발생하지 않았다. STDR (sequence time domain reflectometry) to detect a cable fault using a pseudo noise sequence as a reference signal, and time correlation analysis between the reference signal and reflection signal is robust to noisy environments and can detect intermittent faults including open faults and short circuits. On the other hand, if the distance of the fault location is far away or the fault type is a soft fault, attenuation of the reflected signal becomes larger; hence the correlation coefficient in the STDR becomes smaller, which makes fault detection difficult and the measurement error larger. In addition, automation of the fault location by detection of phase and peak value becomes difficult. Therefore, to improve the cable fault detection of a conventional STDR, this paper proposes the algorithm in that the peak value of the correlation coefficient of the reference signal is detected, and a peak value of the correlation coefficient of the reflected signal is then detected after removing the reference signal. The performance of the proposed method was validated experimentally in low-voltage power cables. The performance evaluation showed that the proposed method can identify whether a fault occurred more accurately and can track the fault locations better than conventional STDR despite the signal attenuation. In addition, there was no error of an automatic fault type and its location by the detection of the phase and peak value through the elimination of the reference signal and normalization of the correlation coefficient.

Dependencies of Acoustic Properties on the Frequency and the Porosity for Biot’s Slow Wave in Water-saturated Copper Foams

이강일 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.4

The present study investigated the dependencies of acoustic properties, such as the phase velocity and the attenuation coefficient, on the frequency and the porosity for Biot’s slow wave in 13 watersaturated copper foams used as trabecular-bone-mimicking phantoms. The acoustic properties were measured over a frequency range from 0.8 to 1.2 MHz by using a matched pair of broadband, unfocused transducers with a diameter of 12.7 mm and a center frequency of 1.0 MHz. The Biot model for elastic wave propagation in fluid-saturated porous media was employed to predict the experimental measurements in the water-saturated copper foams. A strong slow wave and a very weak fast wave were consistently observed in the transmitted signals for all the phantoms. The experimental phase velocity showed good agreement with that of the Biot model, increasing with the frequency and the porosity. The experimental and the theoretical attenuation coefficients were found to increase linearly or quasi-linearly with increasing frequency. In contrast, the porosity dependency of the experimental attenuation coefficient showed a behavior opposite to that of the Biot model. These results suggest that the Biot model can be usefully employed as a practical tool for predicting the phase velocity in trabecular bone, but is not suitable for predicting the attenuation coefficient.

6 MV X-선 빔의 등가에너지 결정

김종언(Jong-Eon Kim),박병도(Byung-Do Park) 한국방사선학회 2016 한국방사선학회 논문지 Vol.10 No.8

본 연구의 목적은 실험으로 6 MV X-선 빔의 등가에너지를 결정하는 데 있다. 6 MV X-선 빔에 대한 납 의 반가층은 전리함을 사용하여 측정하였다. 선감쇠계수는 측정된 반가층을 사용하여 계산하였다. 그리고 질량감쇠계수는 납의 밀도로 선감쇠계수를 나누어 얻었다. 얻어진 질량감쇠계수의 등가에너지는 미국표준 기술연구소에서 주어진 납의 광자에너지 대 질량감쇠계수 자료를 사용하여 결정하였다. 그 결과로서, 6 M V X-선 빔에 대한 등가에너지는 1.61 MeV로 결정되었다. 이 등가에너지는 Reft가 보고한 것 보다 약 30% 낮게 결정되었다. 그 원인은 납 감쇠기 사이의 공기공동의 존재에 기인한 것으로 추정된다. The purpose of this study is to determine the equivalent energy of a 6MV X-ray beam in the experiment. The half-value layer (HVL) of lead for the 6 MV X-ray beam was measured using an ionization chamber. The linear attenuation coefficients were calculated with HVL. And, the mass attenuation coefficient was obtained by dividing the linear attenuation coefficient by the density of lead. The equivalent energy of mass attenuation coefficient was determined using the photon energy versus mass attenuation coefficient data of lead given by National Institute of Standards and Technology (NIST). In conclusion, the equivalent energy of the 6 MV X-ray beam was determined to be 1.61 MeV. This equivalent energy was determined to be about 30% lower than reported by Reft. The reason is presumed to be due to the presence of an air cavity between the lead attenuators.

Pressure waves in bubbly liquids

Shahid Mahmood,Ho-Young Kwak 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

It is well known that sound propagation in liquid media is strongly affected by the presence of gas bubbles that interact with sound and in turn affect the medium. An explicit form of a wave equation in a bubbly liquid medium was obtained in this study. Using the linearized wave equation and the Keller-Miksis equation for bubble wall motion, a dispersion relation for the linear pressure wave propagation in bubbly liquids was obtained. It was found that attenuation of the waves in bubbly liquid occurs due to the viscosity and the heat transfer from/to the bubble. In particular, at the lower frequency region, the thermal diffusion has a considerable affect on the frequencydependent attenuation coefficients. The phase velocity and the attenuation coefficient obtained from the dispersion relation are in good agreement with the observed values in all sound frequency ranges from kHz to MHz.

A COMPARATIVE STUDY ON APPLICABILITY AND EFFICIENCY OF MACHINE LEARNING ALGORITHMS FOR MODELING GAMMA-RAY SHIELDING BEHAVIORS

Bayram Bilmez,Ozan Toker,Selçuk Alp,Ersoy Oz,Orhan _ Içelli 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.1

The mass attenuation coefficient is the primary physical parameter to model narrow beam gamma-rayattenuation. A new machine learning based approach is proposed to model gamma-ray shieldingbehavior of composites alternative to theoretical calculations. Two fuzzy logic algorithms and a neuralnetwork algorithm were trained and tested with different mixture ratios of vanadium slag/epoxy resin/antimony in the 0.05 MeVe2 MeV energy range. Two of the algorithms showed excellent agreementwith testing data after optimizing adjustable parameters, with root mean squared error (RMSE) valuesdown to 0.0001. Those results are remarkable because mass attenuation coefficients are often presentedwith four significant figures. Different training data sizes were tried to determine the least number ofdata points required to train sufficient models. Data set size more than 1000 is seen to be required tomodel in above 0.05 MeV energy. Below this energy, more data points with finer energy resolution mightbe required. Neuro-fuzzy models were three times faster to train than neural network models, whileneural network models depicted low RMSE. Fuzzy logic algorithms are overlooked in complex functionapproximation, yet grid partitioned fuzzy algorithms showed excellent calculation efficiency and goodconvergence in predicting mass attenuation coefficient.

Progressive Dehazing and Depth Estimation from a Single Hazy Image

Jeonghoon Kim,Sungyoon Kim,Changhoon Pyo,Hyeongmyeon Kim,Changhoon Yim 대한전자공학회 2022 IEIE Transactions on Smart Processing & Computing Vol.11 No.5

We propose a progressive dehazing and depth estimation (PDDE) method with optimal estimation of the attenuation coefficient. We investigated the characteristics of dehazing operations related to the depth and attenuation coefficient for PDDE. Entropy was used as a non-reference image quality metric for optimality assessment of dehazed images. The proposed PDDE method provides an optimal dehazed image and depth estimation from a single hazy image. Experimental results show that the proposed method provides clearer and subjectively better results for single image dehazing than previous image dehazing methods. It also results in a significant improvement in the accuracy of depth estimation from a single hazy image compared with previous depth estimation methods.

Evaluation of photon radiation attenuation and buildup factors for energy absorption and exposure in some soils using EPICS2017 library

Hila, F.C.,Javier-Hila, A.M.V.,Sayyed, M.I.,Asuncion-Astronomo, A.,Dicen, G.P.,Jecong, J.F.M.,Guillermo, N.R.D.,Amorsolo, A.V. Jr. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.11

In this paper, the EPICS2017 photoatomic database was used to evaluate the photon mass attenuation coefficients and buildup factors of soils collected at different depths in the Philippine islands. The extraction and interpolation of the library was accomplished at the recommended linear-linear scales to obtain the incoherent and total cross section and mass attenuation coefficient. The buildup factors were evaluated using the G-P fitting method in ANSI/ANS-6.4.3. An agreement was achieved between XCOM, MCNP5, and EPICS2017 for the calculated mass attenuation coefficient values. The buildup factors were reported at several penetration depths within the standard energy grid. The highest values of both buildup factor classifications were found in the energy range between 100 and 400 keV where incoherent scattering interaction probabilities are predominant, and least at the region of predominant photoionization events. The buildup factors were examined as a function of different soil silica contents. The soil samples with larger silica concentrations were found to have higher buildup factor values and hence lower shielding characteristics, while conversely, those with the least silica contents have increased shielding characteristics brought by the increased proportions of the abundant heavier oxides.

Measurements of Acoustic Properties of Tofu and Acorn Curd as Potential Tissue-mimicking Materials

Li Ying,Guntur S.R.Anjaneya Reddy,Choi Min Joo,Paeng Dong-Guk The Acoustical Society of Korea 2005 韓國音響學會誌 Vol.24 No.e4

The purpose of this study is to measure the acoustic properties of Tofu and Acorn Curd (Dotori Muk), which are possibly used as tissue mimicking materials (TMMs). Due to its availability and low cost, Tofu was suggested as a TMM by several researchers who measured only sound speed and attenuation. The acoustic properties of Tofu and Muk including the backscattering coefficient were measured in this paper. Sound speed was measured by the time shift in a pulse echo setup. Attenuation coefficients and backscattering coefficients were measured by a broadband method using both 5 MHz and 10 MHz transducers in the frequency domain. The measured acoustic properties of both Tofu and Muk are observed to be similar to those of biological tissues such as beef liver or beef heart.