• 대한의용생체공학회:의공학회지
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• 제24권3호
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• pp.217-231
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• 2003

상보적인 특성을 갖는 골레이 수열을 이용하여 코드화된 신호를 송신하는 것은 SNR과 침투도를 향상시킬 수 있는 효과적인 방법이다. 그러나 각 주사선을 형성하기 위해 두 개의 상보적인 이진 코드를 연속하여 두 번 송신하기 때문에 프레임 율이 반으로 감소하게 된다 특히 이 방법은 측방향 해상도를 향상시키기 위해 다중 집속 기법(multi-zone focusing method)을 적용하면 송신 집속점의 개수에 따라 송신 횟수가 늘어나므로 프레임 율(frame rate)이 크게 저하된다. 본 논문에서는 이러한 문제를 해결하기 위해 변형된 직교 골레이 코드를 이용한 동시 다중 송신 집속 기법을 제안하였다 제안한 방법은 프레임 율의 저하 없이도 두 쌍의 직교 골레이 코드를 사용하여 서로 다른 위치에 동시에 송신 집속할 수 있다. 그리고 수신시에 정합 과정을 통해 분리, 압축한 다음 일반적인 다중 집속 기법과 같이 집속된 빔들을 결합함으로써 기존의 골레이 코드를 사용하는 송신 고정 집속 기법과 같은 프레임 율을 유지하면서도 측방향 해상도를 개선할 수 있다. 실제 초음파 영상을 위해 송신 신호로 사용되는 골레이 코드는 전송 전력 효율(Transmit Power Efficiency)을 높일 수 있도록 변형되었다. 컴퓨터 모사 실험과 실제 실험 결과는 제안한 방법이 기존의 방법에 비해 매우 향상된 측방향 해상도와 침투도를 갖는 초음파 영상을 제공한다는 것을 보여준다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권15호
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• pp.6177-6186
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• 2015

Sensitivity and specificity are the two most important indicators in selection of medical imaging devices for cancer screening. Breast images taken by conventional or digital mammography, ultrasound, MRI and optical mammography were collected from 2,143,852 patients. They were then studied and compared for sensitivity and specificity results. Optical mammography had the highest sensitivity (p<0.001 and p<0.006) except with MRI. Digital mammography had the highest specificity for breast cancer imaging. A comparison of specificity between digital mammography and optical mammography was significant (p<0.021). If two or more breast diagnostic imaging tests are requested the overall sensitivity and specificity will increase. In this literature review study patients at high-risk of breast cancer were studied beside normal or sensitive women. The image modality performance of each breast test was compared for each.

• 대한의용생체공학회:의공학회지
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• 제37권4호
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• pp.140-146
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• 2016

The ultrasound imaging in medical diagnosis has become a popular modality because of its safe, noninvasive, portable, relatively inexpensive, and provides a real-time image formation. However, usefulness of ultrasound imaging is at times limited due to the presence of signal-dependent noise like as speckle. Therefore, noise reduction is very important, as various types of noise generated limits the effectiveness of medical image diagnosis. This paper introduces a speckle noise reduce algorithm using total variation denoising (TVD) in Laplacian pyramid. With this method, speckle is removed by TVD of bandpass ultrasound images in Laplacian pyramid domain. For TVD in each pyramid layer, a ${\lambda}$ is selected by trial-and-error method. The visual comparison of despeckled 'in vivo' ultrasound images from pancreas shows that the proposed method could effectively preserve edges and detailed structures while thoroughly suppressing speckle. For a Simulated B-mode image, contrast-to-noise-ratio (CNR) and signal-to-noise-ratio (SNR) were obtained like 4.65 dB and 14.11 dB, respectively. The results show that the proposed method can conduct better than some of the existing methods in terms of the CNR and the SNR.

• 대한디지털의료영상학회논문지
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• 제12권2호
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• pp.81-87
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• 2010

The setting parameters of ultrasound scanner give influences to change of image. Sonographers have used a Matlab program to make Low Contrast Sensitivity(LCS) value and compared original images in order to evaluate the use of the supersonic diagnosis machinery. We confirmed the change of image in Grayscale values using Photoshop program. Experiment equipment of our research used A Medison Accuvix V10, A Multi-Tissue Ultrasound Phantom(040 GSE) of CHRIS Company, A Adobe Photoshop CS4 Program, A Convex Probe, A USB memory stick, A Probe Fixation Equipment. The method used Gain, Dynamic Range(DR) of the setting parameters of ultrasound scanner and researched Gain and DR was set to 10 dB. We changed the different settings to see the changes of images using Grayscale values of a Photoshop program about tissue images of a phantom. This study evaluated DR and Gain whether it is an image controller to get the optimum contrast to produce an image to see the how effect on the images. We did not use Gateway in supersonic diagnosis machinery. We can easily open to open the files through Photoshop program before we get Digital Imaging and Communications in Medicine(DICOM) files use USB memory stick in supersonic diagnosis machinery. When we diagnosed the lesion of the patient with ultrasound, the contrast and the Gray scale value of image are very important. In this research, we determined the optimum setting parameters that provided useful information to diagnose disease and evaluated the change of improved images.

• PNF and Movement
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• 제17권2호
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• pp.329-337
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• 2019

Purpose: Ultrasound imaging is commonly used to measure the pennation angle of human skeletal muscles in vivo. However, manual assessment of the pennation angle using ultrasound images is subjective and time-consuming and requires a high level of examiner skill. The architectural analysis of human skeletal muscles is thus challenging. Automated approaches using image processing techniques are therefore required to estimate the pennation angle in ultrasound images. The purpose of this study was thus to assess the intra-tester and inter-tester reliability and validity of the pennation angle using an automatic measurement program. Methods: Twenty-two healthy young adults (mean age = 22.55 years) with no medical history of neurological or musculoskeletal disorders voluntarily participated in this study. Ultrasound imaging was used to measure the pennation angle of the gastrocnemius muscle at rest. One examiner acquired images from all the participants. The intra-tester and inter-tester reliability were evaluated using the intraclass correlation coefficient (ICC) to estimate reliability. Validity was measured using Pearson's correlation coefficient. Results: The intra-rater reliability was excellent for the automatic pennation angle measuring program and the manual pennation angle assessment method (ICC>0.95). The inter-rater reliability was also excellent for both methods (ICC>0.93). All the correlation coefficients for the automatic pennation angle measuring program and the manual pennation angle assessment method were 0.79, which indicated a significantly positive correlation (p<0.05). Conclusion: Pennation angle measurement using the automatic pennation angle measuring program showed acceptable reliability and validity. This study therefore demonstrated that the automatic measuring program was able to automatically measure the pennation angle of skeletal muscles using ultrasound images, and thus made it easy to investigate skeletal muscle architecture.

• 한국음향학회지
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• 제41권5호
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• pp.525-533
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• 2022

초음파 영상 시스템의 수신 집속 과정에서, 채널 데이터를 2차원 푸리에 변환하여 부엽과 격자엽을 억제하는 방법을 제안하였다. 영상점에서 온 신호를 집속하면 모든 채널의 신호는 같은 위상을 가지는 직류로 나타난다. 그러나 영상점 밖에서 오는 신호를 집속하면 입사각에 따라서 다른 공간 주파수를 가지는 채널 신호로 나타난다. 따라서 집속 후의 채널 신호를 2차원 푸리에변환을 하면 입사각을 가지는 신호를 주파수 영역에서 효과적으로 분리할 수 있다. 수신 집속 지연 시간이 인가된 시간-채널 데이터를 2차원 푸리에변환을 하여 주파수 영역에서 직류 성분과 그 밖의 주파수 성분으로 분리하고, 두 값의 비율을 이용하여 가중치를 정의하였다. 초음파 영상에 가중치를 곱함으로써 부엽과 격자엽을 억제하였다. 64채널 선형 어레이에서 5 MHz의 주파수의 초음파 영상을 계산하였다. 초음파 영상에서 나타나는 격자엽은 제안한 방법을 적용하여 완전히 제거되었다. 또한 부엽이 줄어들어 측방향 해상도가 크게 증가되었다. 인체모사 영상의 시뮬레이션에서 대조도가 증가하여 병변의 진단에 도움을 줄 수 있음을 확인하였다.

• 대한의용생체공학회:의공학회지
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• 제20권4호
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• pp.503-513
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• 1999

본 논문에서는 일반적인 합성구경기법에 대한 통합 모형을 제시하고 수학적인 해석을 통하여 합성구경 기법들에 대한 초음파 빔패턴의 단일 표현식을 유도하였다. 이 결과를 이용하여 기존의 합성구경 기법들에 대한 성능을 분석하고 비교하였으며, 선형주사 영상에 적합한 새로운 합성구경 기법을 제안하였다. 제안된 방법은 모든 영상점에서 양방향 동적 집속이 가능하며, 이를 실제 영상에 적용하여 의료용 초음파 B-모드 영상의 해상도를 획기적으로 개선할 수 있다. 제안된 방법에 의하여 집속된 초음파 빔패턴은 기존의 방식과 비교하여 주엽의 폭이 절반으로 감소하고 측엽의 크기는 유사하다. 컴퓨터 모사실험을 통하여 본 논문의 해석결과와 제안된 합성구경 기법의 타당성을 검증하였다.

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 동계학술발표회 논문집
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• pp.359-360
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• 2006

Functional photoacoustic tomography is a new non-invasive imaging modality, and it is emerging as a very practical method for imaging biological tissue structures by means of laser-induced ultrasound. Structures with high optical absorption, such as blood vessels, can be imaged with the spatial resolution of ultrasound, which is not limited by the strong light scattering in biological tissues. By varying wavelengths of the laser light and acquiring photoacoustic images, optical absorption spectrum of each image pixel is found. Since the biochemical constituents of tissues determine the spectrum, useful functional information like oxygen saturation ($SO_2$) and total haemoglobin concentration (HbT) can be extracted. In this study, as a proof-of-principle experiment, hypoxic brain tumor vasculature and traumatic brain injury (TBI) of small animal brain are imaged with functional photoacoustic tomography. High resolution brain vasculature images of oxygen saturation and total hemoglobin concentration are provided to visualize hypoxic tumor vasculature, and hemorrhage on the cortex surface by the TBI.

• 대한의용생체공학회:의공학회지
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• 제9권1호
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• pp.87-92
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• 1988

In this paper, a new focusing method, to be called the pipelined sampled delay focusing (PSDF), is implemented. This method improves the lateral resolution in ultrasound imaging system. In PSDF, the analog belay lines are no longer necessary because sampling sum process can replace the conventional delay sum process. Also, the method offers continuous dynamic focusing on the resolution pixel basis, and eliminates the constraint that the maximum delay time is less than the sampling interval. Second order sampling is adopted in order to extend the sampling interval.

• 한국임상수의학회지
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• 제21권2호
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• pp.181-183
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• 2004

Hepatic mass was aspirated under the guidance with ultrasound in 9-year old female maltese with signs of anorexia, hematochezia, vomiting, depression, and abdominal distension. Radiographic and abdominal ultrasonographic examinations were performed, which revealed enlarged tubular shaped uterine mass and solitary, small round hyperechoic hepatic mass dorsal to gall bladder as an incidental finding. Ultrasound-guided fine needle aspiration was completed, but histologic confirmation should be made for definitive diagnosis by tissue core or wedge biopsy.