• 대한영상의학회지
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• 제82권5호
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• pp.1218-1230
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• 2021

목적 고위험 환자에서 초기 간암 선별 검사로써 단축 자기공명영상 검사의 환자별 진단능을 기존의 고식적 간 자기공명영상검사와 비교하고자 한다. 대상과 방법 간암 고위험군에서 간 자기공명영상 검사를 시행 받은 총 201명의 환자에 대해 연구를 시행하였다. 단축 자기공명영상 검사 군의 프로토콜은 T2 강조영상, 담도기 T1 강조영상, 확산강조영상 등으로 구성되며, 두 명의 영상의학과 의사가 각각의 환자에 대해 후향적으로 단축 자기공명영상검사 군 및 고식적 자기공명영상검사 군, 두 군의 영상을 독립적으로 평가하였다. 두 연구자 간 일관성은 Cohen's kappa 값을 이용하여 비교하였다. 복합적인 참조표준을 이용하여 두 군에서 각각 진단능을 평가하여 비교하였다. 결과 79 명의 환자에서 총 93개의 간암이 발견되었다. 두 연구자 간 일관성은 두 군에서 모두 매우 양호하였다(κ = 0.839, 0.948). 단축 자기공명영상검사 군에서 민감도 및 음성예측도는 각각 94.9% 및 96.4%였으며, 이는 고식적 자기공명영상검사 군과 큰 차이를 보이지 않았다(96.2%, 97.5%). 결론 단축 자기공명영상검사는 고식적 자기공명영상검사에 비교하여 임상적으로 허용 가능한 민감도와 음성예측도를 갖는다. 따라서 간암 고위험군 환자에서 간암 선별검사로써 새로운 대안이 될 수 있을 것이다.

• 전자공학회논문지D
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• 제36D권3호
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• pp.1-11
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• 1999

자기공명영상 시스템의 신호 대 잡음 비(SNR, Signal-to-Noise Ratio)를 향상시키기 위해서 quadrature RF 코일을 사용하는 것은 최근의 일반적인 방법이다. 그렇지만 이 때 SNR의 향상을 가져오기 위해서는 완벽한 3dB 커플링과 90°위상차를 가지는 잘 설계된 quadrature coupler가 필수적이다. 또한 RF 여기 주기와 검파 주기 동안 각 포트의 임피던스 정합 조건이 잘 만족되어야 한다. 본 논문에서는 분석과 시뮬레이션 및 제작을 통해 임피던스 부정합 조건(특히,환자)의 영향을 살펴보았고 이의 영향을 최소화하고 시스템의 신뢰성을 향상시키기 위한 회로 기술로 동적 로딩(dynamic loading)을 처음으로 quadrature coupler 와 송수신 스위치 모듈에 적용하는 것을 제안했다. 또한 quadrature coupler와 송수신 스위치 모듈을 마이크로 스트립을 이용해 설계하고 제작 하였다. 결과적으로 자기공명영상 시스템의 SNR은 수신 동적 부하가 없고 불연속 소자로 된 종전 모듈을 사용했을 때보다 시스템의 SNR이 3dB 높아졌다. 또한 이 모듈은 자기공명영상 시스템이의 최대 5kw의 고출력 RF 신호의 처리가 가능하다. 전력 손실과 크기를 고려할 때, 고유전율을 가진 R/Tduroid 6010 기판을 사용하였으며, 시뮬레이션은 Compact Software을 사용 했다.

• Investigative Magnetic Resonance Imaging
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• 제14권2호
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• pp.145-150
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• 2010

소아에서 췌장의 악성 종양은 매우 드물게 발생하고 있으며, 특히 악성 신경내분비 종양은 더더욱 드물다. 저자들은 16세 소아 환자에서 발생한 비기능성 악성 신경내분비 종양의 증례를 경험하여 CT와 MRI 소견을 보고하고자 한다. 췌장 두부에서 발생한 고형 종양으로 조영증강 MRI의 문맥기에서 지연기로 갈수록 조영증강이 잘 되고, 주변의 혈관 침습, 총담관 폐색, 림프절병증 등 악성 소견을 동반할 때 췌장의 비기능성 악성 신경내분비 종양을 감별 진단에 포함하여야 한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권1호
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• pp.105-125
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• 2024

Gliomas are the most common malignant brain tumor and cause the most deaths. Manual brain tumor segmentation is expensive, time-consuming, error-prone, and dependent on the radiologist's expertise and experience. Manual brain tumor segmentation outcomes by different radiologists for the same patient may differ. Thus, more robust, and dependable methods are needed. Medical imaging researchers produced numerous semi-automatic and fully automatic brain tumor segmentation algorithms using ML pipelines and accurate (handcrafted feature-based, etc.) or data-driven strategies. Current methods use CNN or handmade features such symmetry analysis, alignment-based features analysis, or textural qualities. CNN approaches provide unsupervised features, while manual features model domain knowledge. Cascaded algorithms may outperform feature-based or data-driven like CNN methods. A revolutionary cascaded strategy is presented that intelligently supplies CNN with past information from handmade feature-based ML algorithms. Each patient receives manual ground truth and four MRI modalities (T1, T1c, T2, and FLAIR). Handcrafted characteristics and deep learning are used to segment brain tumors in a Global Convolutional Neural Network (GCNN). The proposed GCNN architecture with two parallel CNNs, CSPathways CNN (CSPCNN) and MRI Pathways CNN (MRIPCNN), segmented BraTS brain tumors with high accuracy. The proposed model achieved a Dice score of 87% higher than the state of the art. This research could improve brain tumor segmentation, helping clinicians diagnose and treat patients.

• Korean Journal of Radiology
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• 제23권6호
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• pp.598-614
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• 2022

While ultrasound (US) is considered an important tool for hepatocellular carcinoma (HCC) surveillance, it has limited sensitivity for detecting early-stage HCC. Abbreviated MRI (AMRI) has recently gained popularity owing to better sensitivity in its detection of early-stage HCC than US, while also minimizing the time and cost in comparison to complete contrast-enhanced MRI, as AMRI includes only a few essential sequences tailored for detecting HCC. Currently, three AMRI protocols exist, namely gadoxetic acid-enhanced hepatobiliary-phase AMRI, dynamic contrast-enhanced AMRI, and non-enhanced AMRI. In this study, we discussed the rationale and technical details of AMRI techniques for achieving optimal surveillance performance. The strengths, weaknesses, and current issues of each AMRI protocol were also elucidated. Moreover, we scrutinized previously performed AMRI studies regarding clinical and technical factors. Reporting and recall strategies were discussed while considering the differences in AMRI protocols. A risk-stratified approach for the target population should be taken to maximize the benefits of AMRI and the cost-effectiveness should be considered. In the era of multiple HCC surveillance tools, patients need to be fully informed about their choices for better adherence to a surveillance program.

• 대한정형외과 초음파학회지
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• 제2권2호
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• pp.107-112
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• 2009

회전근 개 질환에 대한 초음파 검사는 비침습적이며 동적인 검사이며, 최근의 발달을 통해 MRI에 비견할 만한 결과를 보여주고 있다. 또한 초음파 유도하의 주사 치료뿐 만 아니라 회전근 개 복원술 등의 수술적 치료 후 추적 검사로도 유용하게 사용될 수 있다. 초음파 장비의 발전, 검사자의 숙련도 및 병증에 대한 사전 지식은 초음파를 이용한 회전근 개 질환의 진단과 치료에 있어 무엇보다 중요한 요소로 알려지고 있다.

• Investigative Magnetic Resonance Imaging
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• 제19권3호
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• pp.200-204
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• 2015

Image findings of hepatic lymphoma have been reported as variable, ranging from single or multiple small nodules to diffuse infiltrative patterns. On MRI, most hepatic lymphomas show T1 low signal intensity, T2 high signal intensity. Dynamic imaging reveals a hypointense appearance in the arterial phase, followed by delayed enhancement in the portal venous and transitional phase. In the hepatobiliary phase using a hepatocyte-specific contrast agent (which have recently aided in increasing the access to the focal liver lesions), hepatic lymphoma is known to exhibit low signal intensity. We report a case of hepatic lymphoma, which shows iso-signal intensity on hepatobiliary phase, using gadoxetic acid (Gd-EOB-DTPA).

• Investigative Magnetic Resonance Imaging
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• 제19권2호
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• pp.127-130
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• 2015

Direct injection of foreign material, such as liquid paraffin and silicone, into the breast can induce a foreign body granulomatous reaction and fibrosis, resulting in hard, nodular breast masses and architectural distortion that can mimic neoplasm. Conventional methods, including physical examination, mammography, and ultrasonography are of little use to differentiate between foreign body-induced mastopathy and breast cancer. In patients with foreign body injection such as breast augmentation, dynamic contrast enhanced MR imaging is an excellent imaging modality. Here, the authors report the MR imaging and pathological findings of ductal carcinoma in situ (DCIS) with multicystic changes in a 41-year-old woman with a previous history of interstitial mammoplasty by paraffin injection.

• 한국자기공명학회논문지
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• 제23권1호
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• pp.6-11
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• 2019

Parahydrogen induced hyperpolarization (PHIP) technique is extensively studied to increase the sensitivity of the conventional NMR spectroscopy and recently try to apply this advanced technique into the revolutionary future of the MRI. The other hyperpolarization technique, which is widely utilized, is DNP (Dynamic Nuclear Polarization)-based hyperpolarization one. Despite its great advances in these fields, it contains several drawbacks to overcome: fast relaxation time, expensive equipment is needed, long build-up time is required (several hours), and batch scale material is hyperpolarized. To overcome all those limitations, one can effectively harness the hyperpolarized spin state of parahydrogen. One important step for utilizing the spin state of parahydrogen is doing well-developed experiments of ALTADENA and PASADENA. Based on those concepts, we successfully obtain the hydrogenation signals of ALTADENA and PASADENA from styrene by using benchtop NMR spectrometer. Also those signals were conceptually analyzed and confirmed with different mechanisms. To our best knowledge, those experiments using 1.4T (benchtop NMR) is the first reported one. Considering these experiments, we hope that parahydrogen-based hyperpolarization transfer studies in NMR/MRI will be broadened in Korea in the future.

• 한국자기공명학회논문지
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• 제9권2호
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• pp.93-102
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• 2005

Purpose: To develop an advanced non-linear curve fitting (NLCF) algorithm for dynamic susceptibility contrast study of brain. Materials and Methods: The first pass effects give rise to spuriously high estimates of $K^{trans}$ in voxels with large vascular components. An explicit threshold value has been used to reject voxels. Results: By using this non-linear curve fitting algorithm, the blood perfusion and the volume estimation were accurately evaluated in T2*-weighted dynamic contrast enhanced (DCE)-MR images. From the recalculated each parameters, perfusion weighted image were outlined by using modified non-linear curve fitting algorithm. This results were improved estimation of T2*-weighted dynamic series. Conclusion: The present study demonstrated an improvement of an estimation of kinetic parameters from dynamic contrast-enhanced (DCE) T2*-weighted magnetic resonance imaging data, using contrast agents. The advanced kinetic models include the relation of volume transfer constant $K^{trans}\;(min^{-1})$ and the volume of extravascular extracellular space (EES) per unit volume of tissue $\nu_e$.