• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1994년도 춘계학술대회
• /
• pp.96-99
• /
• 1994

Despite the simplicity of processing, a conventional autocorrelation function(ACF) method for the precise determination of fetal heart rate (FHR) has many problems. In case of weak or noise corrupted Doppler ultrasound signal. the ACF method is very sensitive to the threshold level and data window length. It is very troublesome to extract FHR when there is a data loss. To overcome these problems, the high resolution pitch detection algorithm was adopted to estimate the FHR. This method is more accurate, robust and reliable than the ACF method. With a lot of calculation, however, it is impossible to process real time FHR estimation. This paper is presented a new FHR estimation algorithm for real time processing.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1993년도 춘계학술대회
• /
• pp.81-85
• /
• 1993

Despite the simplicity of processing, conventional autocorrelation function (ACF) method for the precise determination of fetal heart rate (FHR) has many problems. In the case of weak or noise corrupted Doppler ultrasound singnals, the ACF method is very sensitive to the threshold level and data window length. It is real troublesome to extract FHR when there is a data loss. To overcome these problems, the high resolution pitch detection algorithm is adapted to estimate the FHR. The FHR is determined from the correlation of two interconnected segments by its maximum correlation value. FHR is compensated with a constant correlation threshold in a greatly smeared noise signal. This method yields more accurate, robust and reliable than the ACF method.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제54권3호
• /
• pp.198-205
• /
• 2005

In this paper, we proposed a new algorithm for the separation of fetal ECG from single channel abdominal ECG. The algorithm consists of a stage of demixing vector calculation for initial signal and a stage of fetal beat detection for the rest of signal. The demixing vector was obtained by applying independent component analysis technique to projected signals into time-frequency domain. For the test of this algorithm, simulation signals, De Lathauwer's data and some measured data, which was acquired from 8 healthy volunteers whose pregnant periods ranged from 22 weeks to 35 weeks and whose ages from 27 to 37, were used. For each data, the accuracy of fetal beat detection was $100\%$ and with the location of fetal beats, fetal heart rate variability and morphology could be offered. In conclusion, this proposed algorithm showed the possibility of fetal beat separation with a single channel abdominal ECG and it might be adopted to a fetal health monitoring system, by which a single channel abdominal ECG is acquired.

• 전자공학회논문지
• /
• 제49권10호
• /
• pp.202-208
• /
• 2012

태아심박의 모니터링은 태아의 안녕을 평가하기 위해 중요한 정보이다. 비관혈적인 태아심전도는 산모의 복부 신호로부터 추출될 수 있다. 따라서 산모 복부의 혼합 신호로부터 태아심전도를 추출하기 위해 많은 유망한 신호처리 방법들이 개발되어 왔다. 그러나 비관혈적인 태아심전도는 안정적인 신호 측정법이 부족하고 신호처리 방법의 어려움으로 여전히 임상에서 널리 적용되지 못하고 있다. 태아심전도를 추출하는 신호처리 결과는 가우시안 백색잡음에 의해 신호대잡음비가 낮아질 수 있다. 본 논문에서는 태아심전도에서 시간에 따라 변하는 백색잡음 신호를 제거하여 신호대잡음비를 높이기 위한 방법으로 시변 칼만 평활기를 제안하였고 그 가능성을 확인하였다. Wiener 과정을 시스템 모델로 설정하고 백색잡음 크기에 따라 공분산 행렬을 수정하였으며, 이를 통해 칼만 이득을 변화시켜 평활화 정도를 가변시킬 수 있도록 설계하였다. 5채널 태아심전도 모델을 이용하여 백색잡음의 크기에 따른 최적 공분산 행렬 값을 구하였고, 모의실험을 통해 제안된 방법의 가능성을 확인할 수 있었다.

• 산업경영시스템학회지
• /
• 제35권4호
• /
• pp.55-62
• /
• 2012

In this study, it was observed through the ability of performing secondary tasks and baseline fetal heart rate how the supply of lavender, peppermint and highly concentrated oxygen (40%) affected distraction due to the performance of secondary tasks in the driving environment. Twelve male university students conducted secondary tasks while driving in the environments (6 in total) mixed and designed with oxygen concentration (21%, 40%) and the condition of odors (Normal, Lavender, Peppermint). The test was proceeded in order of stable state (5mins), driving (5mins), and secondary tasks (1min), and by extracting ECG data from every section by 30secs, the mean value of baseline fetal heart rate was calculated. As a result of analysis, in the ability of performing secondary tasks, a percentage of correct answers showed no difference in oxygen concentration and the condition of odors (p > 0.05). In performance completion time, a percentage of correct answers decreased showing a statistically significant difference in the condition of odors compared with the condition where odors were not provided (p < 0.05). As for baseline fetal heart rate, in the comparison between sections, while performing secondary tasks, it increased showing a significant difference compared with stable state and driving state (p < 0.05). The effect of interaction was observed in oxygen concentration and the condition of odors. When odors were not provided, baseline fetal heart rate decreased in 40% oxygen concentration compared with 21% oxygen concentration (p < 0.05), however, when peppermint was provided, it increased in 40% oxygen concentration compared with 21% oxygen concentration (p < 0.05). In conclusion, the fact that the condition of odors increased the ability of calculation, and when only the highly concentrated oxygen was provided, parasympathetic nerve system was activated, however, when highly concentrated oxygen was provided with peppermint at the same time, sympathetic nervous system (sns) was activated, which had a negative effect on the autonomic nervous system was drawn.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 추계학술대회논문집
• /
• pp.760-763
• /
• 2007

We studied how linear and nonlinear heart rate dynamics differ between normal fetuses and uncomplicated small-forgestational age (SGA) fetuses, aged 32-40 weeks' gestation. We analyzed each fetal heart rate time series for 20 min and quantified the complexity (nonlinear dynamics) of each fetal heart rate (FHR) time series by approximate entropy (ApEn) and correlation dimension (CD). The linear dynamics were analyzed by canonical correlation analysis (CCA). The ApEn and CD of the uncomplicated SGA fetuses were significantly lower than that of the normal fetuses in all three gestational periods (32-34, 35-37, 38-40 weeks). Canonical correlation ensemble in SGA fetuses is slightly higher than normal ones in all three gestational periods, especially at 35-37 weeks. Irregularity and complexity of the heart rate dynamics of SGA fetuses are lower than that of normal ones. Also, canonical ensemble in SGA fetuses is higher than in normal ones, suggesting that the FHR control system has multiple complex interactions. Along with the clear difference between the two groups' non-linear chaotic dynamics in FHR patterns, we clarified the hidden subtle differences in linearity (e.g. canonical ensemble). The decrease in non-linear dynamics may contribute to the increase in linear dynamics. The present statistical methodology can be readily and routinely utilized in Obstetrics and Gynecologic fields.

• Communications for Statistical Applications and Methods
• /
• 제13권1호
• /
• pp.73-88
• /
• 2006

In this paper, we construct data-base for fetal heart rate (FHR) data and develop the FHR Monitering system to diagnose fetus, HYFM-III. For diagnostic system, a few statistical decision making mechanism are adopted, such as approximate entropy, neural networks, and logistic discrimination. Since FHR data is very chaotic, we mostly adopt nonlinear statistical methods. On the basis of this system, we expect to develop expert system for early detection of abnormal fetus.

• 대한의용생체공학회:의공학회지
• /
• 제16권2호
• /
• pp.175-182
• /
• 1995

태아 심음을 측정하기 위한 기존의 자기상관 함수 법은 처리과정이 간편한 반면에 많은 문제점을 가지고 있다. 초음파 도플러 신호가 열악할 경우 고전적인 자기상관 함수 법은 문턱 값의 선정과 창 함수 크기에 매우 민감하다. 특히 데이터 손실이 생길 때 정확한 태아 심박동 수를 찾기가 어렵다. 이들 문제점들을 보완하기 위하여 초음파 도플러 신호로부터 정확한 태아 심박동 수를 찾는 고해상 피치검출 알고리듬이 제안되었다. 이 알고리듬은 자기상관 함수법 보다 정확하고, 잡음에 강하며, 높은 신뢰성을 갖으나 계산량이 많아 실시간 처리가 어렵다. 본 논문에서는 실시간 처리에 적합한 새로운 태아 심음 추출 알고리듬을 제안하고, 제안된 알고리듬을 적용한 실시간 태아 심음 감시시스템에 관하여 연구하였다.

• Biomaterials and Biomechanics in Bioengineering
• /
• 제2권3호
• /
• pp.173-183
• /
• 2015

In obstetrics, cardiotocography is a procedure to record the fetal heartbeat and the uterine contractions usually during the last trimester of pregnancy. It helps to monitor patterns associated with the fetal activity and to detect the pathologies. In this paper, random forest classifier is used to classify normal, suspicious and pathological patterns based on the features extracted from the cardiotocograms. The results showed that random forest classifier can detect these classes successfully with overall classification accuracy of 93.6%. Moreover, important features are identified to reduce the feature space. It is found that using seven important features, similar classification accuracy can be achieved by random forest classifier (93.3%).

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1991년도 추계학술대회
• /
• pp.79-82
• /
• 1991

Digital FHR monitoring system based on the personal computer combined wi th the digital signal processing (DSP) board was implemented. The DSP board acquires and digitally processes ultrasound fetal Doppler signal for digital rectification, envelope detection, autocorrealtion function calculation and its peak position detection. The personal computer interfaced with the DSP board is in charge of graphic display, hardcopy, data taransmission and on-line analysis of fetal heart rate change including on-line warning system, base-line estmation, acceleration, deceleration and variability. The advantages of PC-DSP based system can be summarized as follows: 1) Minimum hardware realization. 2) Increased flexibility. 3) Total care system.