• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1812-1824
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• 2016

The neural dynamics underlying the causal network during motor planning or imagery in the human brain are not well understood. The lack of signal processing tools suitable for the analysis of nonlinear and nonstationary electroencephalographic (EEG) hinders such analyses. In this study, noise-assisted multivariate empirical mode decomposition (NA-MEMD) is used to estimate the causal inference in the frequency domain, i.e., partial directed coherence (PDC). Natural and intrinsic oscillations corresponding to the motor imagery tasks can be extracted due to the data-driven approach of NA-MEMD, which does not employ predefined basis functions. Simulations based on synthetic data with a time delay between two signals demonstrated that NA-MEMD was the optimal method for estimating the delay between two signals. Furthermore, classification analysis of the motor imagery responses of 29 subjects revealed that NA-MEMD is a prerequisite process for estimating the causal network across multichannel EEG data during mental tasks.

• 대한의용생체공학회:의공학회지
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• 제12권4호
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• pp.303-308
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• 1991

Computer assisted cardiac mapping system has made it possible to display local activation times of the heart using a simultaneous multi-point data aquisition system, and opened an era in electrophyslology guided cardiac arrhythmia surgery especially in ventricular tachycardia. In this study, we have developed a 64 channel computerized cardiacmapping system us:ng a micro-computer for basic reasearch of electrophysiology and electrical propagation in cardiac arrhythmias. The significant tasks of this study were the simultaneous acquisition of large amount of data from 64 sites, accurate and rapid analysis, and the effective display of the analyzed data. To solve these problems, we made a 64 channel signal pre-processing board in order to amplify and fitter the raw signals. And we developed the soflu'are Yor cardiac isochronous mapping whictl is presented immediately ama computer-generated graphics. This system is expected 4o enable us to study pathophyslology of cardiac arrhythmia and to improve the results of diagnosis and surgical treatments for cardiac arrhythmia.

• 대한한의학회지
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• 제27권2호
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• pp.134-144
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• 2006

Tongue diagnosis is an important diagnostic method in traditional Oriental medicine. It has been especially accepted that quantitative analysis of tongue images allows the accurate diagnosis of the exterior-interior and cold-heat patterns of a patient. However, to ensure stable and reliable results, the color reproduction of such images must first be error-tree. Moreover, tongue diagnosis is much influenced by the surrounding illumination and subjective color recognition, so it has to be performed objectively and quantitatively using a digital diagnostic machine. In this study, 457 tongue images of outpatients were collected using the Digital Tongue Inspection System. Through statistical analysis, the result shows that the heat and cold patterns can be distinguished clearly based on the hue value of the tongue images. The average hue value (1.00) of the tongue's image in the cold pattern is higher than that in the heat pattern (0.99).

• 대한영상의학회지
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• 제84권1호
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• pp.240-252
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• 2023

목적 소아 환자에서 두부 컴퓨터단층촬영(이하 CT)에 대한 딥러닝 이미지 재구성(deep learning image reconstruction; 이하 DLIR; TrueFidelity; GE Healthcare, Milwaukee, WI, USA)의 효과를 평가하고자 한다. 대상과 방법 총 126개의 소아 두부 CT 이미지를 수집했으며, adaptive statistical iterative reconstruction (이하 ASiR)-V를 사용한 반복적 재구성 및 세 가지 수준의 DLIR을 사용한 재구성을 시행하였다. 각 이미지 세트 그룹은 환자의 연령에 따라 4개의 그룹으로 구분하였으며 각 연령군의 임상 및 방사선량 관련 데이터를 검토하였다. 양적 매개 변수에는 signal to noise ratio (이하 SNR) 및 contrast to noise ratio (이하 CNR)가 포함되었으며 질적 매개 변수로 영상의 잡음(noise), 회백질의 구분 정도, 선명도, 인공물 및 수용 가능성(acceptability), 영상의 질감이 포함되었고 이에 대한 평가와 비교를 시행하였다. 결과 모든 연령 그룹의 모든 수준의 SNR 및 CNR은 높은 수준의 DLIR 사용 시 증가하였다. ASiR-V와 비교했을 때 높은 수준의 DLIR은 SNR 및 CNR이 개선되었다(p < 0.05). 그리고 DLIR의 수준이 증가될수록 순차적인 잡음 감소, 회백질 구분 개선, 선명도 개선이 나타났다. 이러한 변수들에서 높은 수준의 DLIR 사용 시 ASiR-V와 유사한 정도의 수치가 측정되었다. 인공물과 수용 가능성의 경우에 적용된 DLIR 수준 간에 큰 차이를 보이지 않았다. 결론 소아 두부 CT에 고수준 DLIR을 적용하면 영상의 노이즈를 줄일 수 있으나 인공물 처리에 대한 개선이 필요하다.

• Korean Journal of Radiology
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• 제22권1호
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• pp.131-138
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• 2021

Objective: Iterative reconstruction degrades image quality. Thus, further advances in image reconstruction are necessary to overcome some limitations of this technique in low-dose computed tomography (LDCT) scan of the chest. Deep-learning image reconstruction (DLIR) is a new method used to reduce dose while maintaining image quality. The purposes of this study was to evaluate image quality and noise of LDCT scan images reconstructed with DLIR and compare with those of images reconstructed with the adaptive statistical iterative reconstruction-Veo at a level of 30% (ASiR-V 30%). Materials and Methods: This retrospective study included 58 patients who underwent LDCT scan for lung cancer screening. Datasets were reconstructed with ASiR-V 30% and DLIR at medium and high levels (DLIR-M and DLIR-H, respectively). The objective image signal and noise, which represented mean attenuation value and standard deviation in Hounsfield units for the lungs, mediastinum, liver, and background air, and subjective image contrast, image noise, and conspicuity of structures were evaluated. The differences between CT scan images subjected to ASiR-V 30%, DLIR-M, and DLIR-H were evaluated. Results: Based on the objective analysis, the image signals did not significantly differ among ASiR-V 30%, DLIR-M, and DLIR-H (p = 0.949, 0.737, 0.366, and 0.358 in the lungs, mediastinum, liver, and background air, respectively). However, the noise was significantly lower in DLIR-M and DLIR-H than in ASiR-V 30% (all p < 0.001). DLIR had higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) than ASiR-V 30% (p = 0.027, < 0.001, and < 0.001 in the SNR of the lungs, mediastinum, and liver, respectively; all p < 0.001 in the CNR). According to the subjective analysis, DLIR had higher image contrast and lower image noise than ASiR-V 30% (all p < 0.001). DLIR was superior to ASiR-V 30% in identifying the pulmonary arteries and veins, trachea and bronchi, lymph nodes, and pleura and pericardium (all p < 0.001). Conclusion: DLIR significantly reduced the image noise in chest LDCT scan images compared with ASiR-V 30% while maintaining superior image quality.

• Imaging Science in Dentistry
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• 제33권2호
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• pp.113-119
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• 2003

Purpose : To evaluate the relationship between morphometric analysis of bone microstructure from digital radiographic image and trabecular bone strength. Materials and Methods : One hundred eleven bone specimens with 5 mm thickness were obtained from the mandibles of 5 pigs. Digital images of specimens were taken using a direct digital intraoral radiographic system. After selection of ROI (100 × 100 pixel) within the trabecular bone, mean gray level and standard deviation were obtained. Fractal dimension and the variants of morphometric analysis (trabecular area, periphery, length of skeletonized trabeculae, number of terminal point, number of branch point) were obtained from ROI. Punch sheer strength analysis was performed using Instron (model 4465, Instron Corp., USA). The loading force (loading speed 1 mm/min) was applied to ROI of bone specimen by a 2 mm diameter punch. Stress-deformation curve was obtained from the punch sheer strength analysis and maximum stress, yield stress, Young's modulus were measured. Results: Maximum stress had a negative linear correlation with mean gray level and fractal dimension significantly (p<0.05). Yield stress had a negative linear correlation with mean gray level, periphery, fractal dimension and the length of skeletonized trabeculae significantly (p < 0.05). Young's modulus had a negative linear correlation with mean gray level and fractal dimension significantly (p < 0.05). Conclusions : The strength of cancellous bone exhibited a significantly linear relationship between mean gray level, fractal dimension and morphometric analysis. The methods described above can be easily used to evaluate bone quality clinically.