• 한국광학회지
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• 제12권2호
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• pp.83-90
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• 2001

주기적인 진폭물체를 가간섭광인 레이저광으로 조명하였을 때 이 물체가 렌즈없이 회절에 의하여 결상되는 Talbot 결상을 회절이론으로 해석하고 물체의 상이 1:1로 결상되는 Talbot 거리(Zr)를 정의 하였다. 그리고 실험적으로 이 Z/sub T//2 위치에서는 위상에서는 위상이 반전되는 현상도 동시에 관찰하였다. 이러한 Talbot 결상시 주기적인 물체의 개수, 즉 격자의 수에 따라 Talbot 상의 가시도를 Talbot 상의 FFT(Fast Fourier Transform)로부터 측정하였으며 그 결과 적어도 15개 이상의 격자들로 구성되어야 가시도 0.25로 정상적인(stationary) Talbot 결상이 됨을 알 수 있었다.

• Journal of Trauma and Injury
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• 제33권4호
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• pp.207-218
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• 2020

The following recommendations are presented herein: All trauma patients admitted to the resuscitation room should be constantly (or periodically) monitored for parameters such as blood pressure, heart rate, respiratory rate, oxygen saturation, body temperature, electrocardiography, Glasgow Coma Scale, and pupil reflex (1C). Chest AP and pelvic AP should be performed as the standard initial trauma series for severe trauma patients (1B). In patients with severe hemodynamically unstable trauma, it is recommended to perform extended focused assessment with sonography for trauma (eFAST) as an initial examination (1B). In hemodynamically stable trauma patients, eFAST can be considered as the initial examination (2B). For the diagnosis of suspected head trauma patients, brain computed tomography (CT) should be performed as an initial examination (1B). Cervical spine CT should be performed as an initial imaging test for patients with suspected cervical spine injury (1C). It is not necessary to perform chest CT as an initial examination in all patients with suspected chest injury, but in cases of suspected vascular injury in patients with thoracic or high-energy damage due to the mechanism of injury, chest CT can be considered for patients in a hemodynamically stable condition (2B). CT of the abdomen is recommended for patients suspected of abdominal trauma with stable vital signs (1B). CT of the abdomen should be considered for suspected pelvic trauma patients with stable vital signs (2B). Whole-body CT can be considered in patients with suspicion of severe trauma with stable vital signs (2B). Magnetic resonance imaging can be considered in hemodynamically stable trauma patients with suspected spinal cord injuries (2B).

• 전자공학회논문지SC
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• 제40권5호
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• pp.341-349
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• 2003

고속 디지털신호처리기를 사용한 자기공명영상 실시간 대화형 제어기(스펙트로미터)를 개발하였다. 개발린 제어기는 rf 파형과 경사자계 파형을 만들고, 신호 측정을 위한 다중 측정기를 제어한다. TMS320C6701과 간은 높은 계산 능력을 가진 디지털신호처리기를 사용함으로써 복잡한 경사자계파형의 실시간 계산 및 출력이 가능해졌다. 또한 회전 행렬을 실시간으로 계산함으로써 심장과 같이 움직임이 큰 장기의 실시간 영상에서 얻고자하는 평면을 대화식으로 조절이 가능해졌다. 개발된 스펙트로미터를 1.5 테슬라 전신자기공명 영상시스템에 성공적으로 적용하였다. 개발된 스펙트로미터를 고속스핀에코나 echo planar imaging(EPI) 등과 같은 초고속자기공명영상에 적용하여 성능을 검증하였다. 이것은 이들 초고속 자기공명영상기법들이 측정 시간을 단축해주는 대신에 스펙트로미터의 송신부와 수신부 또는 경사자계부간의 동기나 위상에 에러가 있을 경우 문제점을 크게 부각시켜 시스템의 성능 평가에 적합하기 때문이다.

• 전기학회논문지
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• 제60권6호
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• pp.1209-1214
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• 2011

Photoacoustics has been broadly studied in biomedicine, for both human and small animal tissues. Photoacoustics uniquely combines the absorption contrast of light or radio frequency waves with ultrasound resolution. Moreover, it is non-ionizing and non-invasive, and is the fastest growing new biomedical method, with clinical applications on the way. This paper provides a brief recap of recent developments in photoacoustics in biomedicine, from basic principles to applications. The emphasized areas include the new imaging modalities as well as translational research topics. A primary PA application in biomedicine is photoacoustic tomography (PAT). The past decade has seen fast developments in both theoretical reconstruction algorithms and innovative imaging techniques, and PAT has been implemented in imaging different tissues, from centimeter-large breast tumors to several micrometer-large single red blood cels (RBC). PAT now provides structural, functional and molecular imaging. Overall, PA techniques for biomedicine are maturing. They have been widely used to study both animal and human tissues. Recently, more and more research focuses on clinical applications. Commercialized PA systems are expected to be available in the near future, and wide clinical PA applications are foreseen.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.286-289
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• 2009

This paper presents an effective approach to minimize recursive computations for balancing stereo pairs by using disparity vector errors and its directional histogram. A stereo balancing function is computed from the correspondent pixels between two images, and a simple approach is to find the matching blocks of two images. However, this procedure requires recursive operation, and its computation cost is very high. Therefore, in this paper, we propose an efficient balance method using structural similarity index and a partial re-searching scheme to reduce the computation cost considerably. For this purpose, we determine if re-searching for each block is necessary or not by using the errors and the directional histogram of disparity vectors. Experiment results show that the performance of the proposed approach can save the computations significantly with ignorable image quality degradation compared with full re-search approach.

• Investigative Magnetic Resonance Imaging
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• 제25권4호
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• pp.252-265
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• 2021

Cardiac magnetic resonance imaging (MRI) serves as a clinical gold-standard non-invasive imaging technique for the assessment of global and regional cardiac function. Conventional cardiac MRI is limited by the long acquisition time, the need for ECG gating and/or long breathhold, and insufficient spatiotemporal resolution. Real-time cardiac cine MRI refers to high spatiotemporal cardiac imaging using data acquired continuously without synchronization or binning, and therefore of potential interest in overcoming the limitations of conventional cardiac MRI. Novel acquisition and reconstruction techniques must be employed to facilitate real-time cardiac MRI. The goal of this study is to discuss methods that have been developed for real-time cardiac MRI. In particular, we classified existing techniques into two categories based on the use of non-iterative and iterative reconstruction. In addition, we present several research trends in this direction, including deep learning-based image reconstruction and other advanced real-time cardiac MRI strategies that reconstruct images acquired from real-time free-breathing techniques.

• Nuclear Engineering and Technology
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• 제55권1호
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• pp.222-228
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• 2023

This study aimed to analyze the applicability of the improved median filter in positron emission tomography (PET)/magnetic resonance (MR) fusion images based on parallel imaging using generalized autocalibrating partially parallel acquisition (GRAPPA). In this study, a PET/MR fusion imaging system based on a 3.0T magnetic field and ¹⁸F radioisotope were used. An improved median filter that can set a mask of the median value more efficiently than before was modeled and applied to the acquired image. As quantitative evaluation parameters of the noise level, the contrast to noise ratio (CNR) and coefficient of variation (COV) were calculated. Additionally, no-reference-based evaluation parameters were used to analyze the overall image quality. We confirmed that the CNR and COV values of the PET/MR fusion images to which the improved median filter was applied improved by approximately 3.32 and 2.19 times on average, respectively, compared to the noisy image. In addition, the no-reference-based evaluation results showed a similar trend for the noise-level results. In conclusion, we demonstrated that it can be supplemented by using an improved median filter, which suggests the problem of image quality degradation of PET/MR fusion images that shortens scan time using GRAPPA.

• Korean Journal of Radiology
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• 제24권11호
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• pp.1114-1130
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• 2023

Magnetic resonance neurography (MRN) is increasingly used to visualize peripheral nerves in vivo. However, the implementation and interpretation of MRN in the brachial and lumbosacral plexi are challenging because of the anatomical complexity and technical limitations. The purpose of this article was to review the clinical context of MRN, describe advanced magnetic resonance (MR) techniques for plexus imaging, and list the general categories of utility of MRN with pertinent imaging examples. The selection and optimization of MR sequences are centered on the homogeneous suppression of fat and blood vessels while enhancing the visibility of the plexus and its branches. Standard 2D fast spin-echo sequences are essential to assess morphology and signal intensity of nerves. Moreover, nerve-selective 3D isotropic images allow improved visualization of nerves and multiplanar reconstruction along their course. Diffusion-weighted and diffusion-tensor images offer microscopic and functional insights into peripheral nerves. The interpretation of MRN in the brachial and lumbosacral plexi should be based on a thorough understanding of their anatomy and pathophysiology. Anatomical landmarks assist in identifying brachial and lumbosacral plexus components of interest. Thus, understanding the varying patterns of nerve abnormalities facilitates the interpretation of aberrant findings.

• Investigative Magnetic Resonance Imaging
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• 제1권1호
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• pp.135-141
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• 1997

목적: 초음파에서 의심된 국소적 간지방병변을 진단함에 있어 화학적 포화 방식의 지방억제를 호함한 호흡정지 급속 자기공명영상의 유용성을 알아보기 위함이다. 대상 및 방법: 초음파검사에서 발견된 국소 간병변의 진단을 위해 자기공명영상을 촬영할 때 별도의 parameter 조정없이 지방억제 전후의 영상을 얻을 수 있는 화학적 포화방식의 영상을 추가하였을 때 국소병변의 전체에 걸쳐 균일한 신호가도의 변화가 있었던 환자 13명을 대상으로 하였다. 지방억제 전후의 영상을 fast low-angle shot(FLASH) sequence를 이용한 T1강조영상과 turbo spin-echo sequence를 이용한 T2강조영상으로 호흡정지증의 급속영상을 얻었으며 각각의 병변에 대해 지방억제 전후 의 T1강조영상과 T2강조영상에서 주변 간실질에 대해 상대적인 신호강도의 증감과 초음파 소견상의 에코의 증감을 비교하였다. 결과: T1이나 T2강조영상에서 신호강도가 지방억제 후 감소했던 환자는 7명이었으며 이 중 3명은 지방억제 후의 T1강조영상에서만 신호강도가 감소하였으며 7명 모두 초음파상 고에코의 국소병변과 일치하여 국소지방침착 소견과 일치하였다. 지방억제 후 T2강조영상에서만 주변 간실질에 비해 신호강도가 높았던 2명을 포함하여 지방억제 후 T1과 T2강조영상에서 신호강도가 상대적으로 높아 보였던 6명은 모두 초음파에서 저에코의 병변을 가지고 있어서 국소지방결여와 잘 일치하였다. 국소지방침착의 경우 지방억제 후 T1강조영상의 신호강도의 감소가 T2강조영상에서의 변화에 비해 컸으며(P=0.0002) 국소지방결여의 경우는 T2강조영상에서의 변화가 T1강조영상에 비해 상대적으로 현저하였다(P=0.042). 결론: 호흡정지 급속영상방법의 T1과 T2강조영상에서 공히 화학적 포화방식을 이용한 지방억제 전후의 영상을 얻으면 초음파에서 발견된 국소병변을 간지방변화로 특성화하기에 충분할 것이다.

• Journal of Biosystems Engineering
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• 제41권4호
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• pp.396-407
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• 2016

Background: Although hyperspectral imaging was originally introduced for military, remote sensing, and astrophysics applications, the use of analytical hyperspectral imaging techniques has been expanded to include monitoring of agricultural crops and commodities due to the broad range and highly specific and sensitive spectral information that can be acquired. Combining hyperspectral imaging with remote sensing expands the range of targets that can be analyzed. Results: Hyperspectral imaging technology can rapidly provide data suitable for monitoring a wide range of plant conditions such as plant stress, nitrogen status, infections, maturity index, and weed discrimination very rapidly, and its use in remote sensing allows for fast spatial coverage. Conclusions: This paper reviews current research on and potential applications of hyperspectral imaging and remote sensing for outdoor field monitoring of agricultural crops. The instrumentation and the fundamental concepts and approaches of hyperspectral imaging and remote sensing for agriculture are presented, along with more recent developments in agricultural monitoring applications. Also discussed are the challenges and limitations of outdoor applications of hyperspectral imaging technology such as illumination conditions and variations due to leaf and plant orientation.