Hyung Do Choi

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There are public concerns regarding possible carcinogenic or cancer-promoting effects of radiofrequency electromagnetic fields (RF-EMFs) because of the extensive use of wireless mobile phones and other telecommunication devices in daily life. However, so far it is unclear if non-thermal exposure of single EMF exposure in animal studies has a direct(More)
PURPOSE We investigated the effect of whole-body exposure to 915-MHz radiofrequency identification (RFID) on rat cortical glucose metabolism by using (18)F-deoxyglucose positron emission tomography (FDG-PET). MATERIALS AND METHODS Male Sprague-Dawley rats were divided into three groups: Cage-control, sham-exposed and RFID-exposed groups. Rats were exposed(More)
INTRODUCTION Whether exposure to the 848.5 MHz code division multiple access (CDMA) signal affects adult neurogenesis is unclear. MATERIALS AND METHODS An animal experiment was performed with a reverberation chamber designed as a whole-body CDMA exposure system. Male Sprague-Dawley rats were assigned to three groups (n = 6 per group): Cage-control,(More)
The segmentation of breast Magnetic Resonance Imaging (MRI) has been a long term challenge due to the fuzzy boundaries among objects, small spots, and irregular object shapes in breast MRI. Even though intensity-based clustering algorithms such as K-means clustering and Fuzzy C-means clustering have been used widely for basic image segmentation, they(More)
Magnetic resonance imaging (MRI) is one of the high quality technologies to detect the breast cancer. This study proposes a new framework to extract abnormal features in Magnetic Resonance (MR) images by concentrating on the key aspect of the features: generating a unique input sequence to apply the Support Vector Machine (SVM) classifier. The main(More)
A multiplexed Cassegrain reflector antenna with a 2 × 2 open-ended rectangular waveguide (OERW) matrix feed and an orbital angular momentum (OAM) mode mux is proposed for the simultaneous generation of three OAM modes (l = 0, ±1). The OAM mode mux (OMM) was designed using sequential combinations of quadrature hybrids, crossovers, and phase shifters to(More)
Morphologic appearance plays a substantial role in presenting mass lesion in breast imaging. In this paper, we propose an innovative shape irregularity measurement based on roughness index - Enhance Roughness Index (ERI). This new irregularity measurement is taken as an input to Gaussian Mixture Model (GMM) classifier. By analyzing the similarity through(More)
About 1 in 8 women in the United States is expected to develop breast cancer over the course of herentire lifetime but a few medical imaging techniques have been applied for breast cancer screening. In addition, the feature extraction and comparison in medical images for breast cancer detection haverarely been reported in literature. We propose a new(More)
Morphologic appearance is one of intuitive diagnosis factors of mass lesions in breast imaging, and irregular shape is one of the most frequent appearances for malignant masses. Thus, an effective measure of morphological irregularity will provide a helpful reference to determine malignancy of breast masses. In this paper, a new measure based on Fourier(More)
Metabolomic analysis of urinary polyamines (PAs) from rat exposed to 915 MHz radiofrequency identification (RFID) signal for 8 h/day for 2 weeks was performed by gas chromatography–mass spectrometry as N-ethoxycarbonyl/N-pentafluoropropionyl derivatives. Large alterations in nine PA levels including four aliphatic and five acetylated PAs were monitored in(More)