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Dive into the research topics where Jeiwon Cho is active.

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Featured researches published by Jeiwon Cho.


Breast Cancer Research and Treatment | 2004

Microwave detection of metastasized breast cancer cells in the lymph node; potential application for sentinel lymphadenectomy.

Jin Wook Choi; Jeiwon Cho; Yangsoo Lee; Jounghwa Yim; Byoungjoong Kang; Ki Keun Oh; Woo Hee Jung; Hee Jung Kim; Changyul Cheon; Hy-De Lee; Youngwoo Kwon

Metastasis is the leading cause of death in breast cancer patients and an appropriate detection of metastasis can provide better prognosis and quality treatments. Microwaves can reveal the unique electromagnetic properties of materials, and this study aims to unleash the electromagnetic properties of breast cancer cells, especially, metastasized cancer cells in the lymph nodes, using broad-band microwaves in attempts to detect metastases. To distinguish the cancer-specific patterns of cancer tissues, three primary microwave parameters were assessed, i.e., permittivity in mid-band frequency (3–5 GHz), conductivity in high-band frequencies (25–30 GHz) and slope changes of permittivity at high-band frequencies (15–30 GHz). An additional parameter, Cancer Metastasis Index (CMI), was developed to effectively represent all parameters. Broadband microwave scanning can reveal cancer specific electromagnetic behaviors in all three parameters, and these were reliably reflected by CMI. CMI effectively magnified the difference of the electromagnetic properties between normal nodal tissues and cancer tissues. immunohistochemistries were performed to verify the origin of electromagnetic changes represented by CMI values.


international microwave symposium | 2005

Novel low-cost planar probes with broadside apertures for nondestructive dielectric measurement of biological materials at microwave frequencies

Byoungjoong Kang; Jae-Hyoung Park; Jeiwon Cho; Kihyun Kwon; Sungkyu Lim; Jeonghoon Yoon; Changyul Cheon; Yong-Kweon Kim; Youngwoo Kwon

Novel planar-type probes were developed to demonstrate the possibility of replacing the existing high-cost open-ended coaxial probes. The planar probes of this study define an aperture on the broadside of the probe body. In this way, the contact area can be maximized and/or customized according to specific medical needs. The probes with various aperture sizes and shapes can also be fabricated simultaneously in a single batch process. Three probes are developed in this paper: a probe combining two laminates, a microelectromechanical systems (MEMS)-based probe with a single benzocyclobutene (BCB) layer on a quartz substrate, and another MEMS probe with two BCB layers defined on a silicon substrate. The third probe was specifically designed for monolithic integration with driving circuits on a single substrate. Limitations in the high-frequency performance of the planar probes were carefully studied, and higher order modes and incomplete shielding were found to be the main causes. The measurement results of each probe showed excellent compatibility with those of the open-ended coaxial probe up to almost 40 GHz. The proposed planar-type probes have great potentials for practical medical applications in view of low cost, disposability, and monolithic integration capability with the driving circuits.


IEEE Microwave and Wireless Components Letters | 2005

Nondestructive measurement of complex permittivity and permeability using multilayered coplanar waveguide structures

Byoungjoong Kang; Jeiwon Cho; Changyul Cheon; Youngwoo Kwon

A method for simultaneous measurement of both complex permeability and permittivity is presented using a multilayered conductor-backed coplanar waveguide (MCBCPW) structure to evaluate the possibility of MCBCPW as a sensor for nondestructive electromagnetic measurement. Formulae and methods are developed to extract the electromagnetic parameters of material under test (MUT) placed on the topside of CPW. The measurement results for magnetic powder on MCBCPW sensor showed good agreement with those using coaxial sensors. The method allows both permittivity and permeability to be measured in a single-step measurement without modifying or reshaping the material, making this method particularly attractive for inhomogeneous materials such as biological materials.


international microwave symposium | 2003

110 GHz broadband measurement of permittivity on human epidermis using 1 mm coaxial probe

Hyeonseok Hwang; Jounghwa Yim; Jeiwon Cho; Changyul Cheon; Youngwoo Kwon

In this work, we have characterized the permittivity of human epidermis (outer skin layer) using microwave up to 110 GHz. A one mm-diameter coaxial probe was adopted to increase measuring bandwidth as well as to enhance the spatial resolution. Pork was used to discriminate the permittivities between muscle tissues and fat tissues. The influence of the sample thickness was also. studied. Considering several factors, the permittivity was measured on epidermis of the human palm and the wrist. In addition, a relaxation phenomenon observed in the wrist skin, revealed by Cole-Cole parameters, suggested that it originated from high water content beneath the thin epidermis of the wrist skin. A relaxation phenomenon revealed by Cole-Cole parameters was observed in the wrist skin. This explains that high water content cells exist beneath the thin epidermis of the wrist skin.


Journal of Micromechanics and Microengineering | 2005

Permittivity measurements up to 30 GHz using micromachined probe

Jung-Mu Kim; Dong Hoon Oh; Jae-Hyoung Park; Jeiwon Cho; Youngwoo Kwon; Changyul Cheon; Yong-Kweon Kim

We implemented a micromachined probe for the measurement of biological properties using MEMS technology, and experimentally showed the suitability of the micromachined probe in biological applications. The micromachined probe was fabricated on a silicon substrate, and to remove wave transmission through the silicon substrate, we etched the silicon substrate from beneath a lower ground and made the etched silicon surface conducting by using thermal evaporation of Cr/Au and a coating of conductive epoxy. The micromachined probe consists of a CPW and strip line between benzo cyclo butene (BCB) layers, which is known to be a material with high resistivity, low loss tangent, and low permittivity at high frequency. We measured the permittivity of a number of well-known liquids—0.5%, 0.9% and 1.3% saline, acetone, ethanol, and muscle and fat of pork—as biological samples using the micromachined probe after liquid calibration. The measured permittivity of 0.9% saline agreed well with the expected value of the Cole–Cole equation. In this paper, we first demonstrate that the micromachined probe can provide broadband measurement of measurable solid materials, such as biological samples, and also of well-known liquids at microwave frequencies. The size of the micromachined probe is 2000 µm (width) × 580 µm (thickness) × 30u2009000 µm (length), and the aperture size of the micromachined probe is only 650 µm × 70 µm. Therefore, we can extract the biological information from very small biological tissues and reduce radiation effects. Thus we show the feasibility of low-cost, small and portable permittivity measurement systems using a micromachined open-ended coaxial RF MEMS probe.


International Journal of Cancer | 2006

In-vivo measurements of the dielectric properties of breast carcinoma xenografted on nude mice.

Jeiwon Cho; Jeonghoon Yoon; Sungjoon Cho; Kihyun Kwon; Sungkyu Lim; Dae-Duk Kim; Eun Sook Lee; Chul Hwan Kim; Jin Wook Choi; Changyul Cheon; Youngwoo Kwon

A developing method of cancer detection is to use electromagnetic waves to compare the dielectric properties of normal and cancerous tissue. Because most of the previous studies consisted of dielectric measurements taken ex‐vivo, this study investigated the advantages of in‐vivo measurements, obtained using the newly developed insertion‐type planar probe, through the measurements of cancer (MDA MB 231), which was cultivated and implanted into the mammary fat pad of nude mice. Reflection coefficients were obtained in the broadband frequency range from 0.5 to 30 GHz, from which broadband complex permittivity data was extracted. Complex permittivity, in addition to other parameters such as conductivity and characteristic frequency, were used to make comparisons between cancerous tissue, normal muscle tissue and fat tissue, as well as comparisons between in‐vivo and ex‐vivo measurements. This study investigated the suitability of in‐vivo cancer detection using microwaves with the newly developed insertion‐type planar probe. Results showed that both sensitivity and specificity of the current method was 97%. In addition, predictive values were 99% for the positive and 94% for the negative, thus greatly enhancing the practicality of this method. In conclusion, it was demonstrated that in‐vivo measurements are highly beneficial in studying the potential of microwaves as a diagnostic tool of breast cancer, especially in combination with the newly developed insertion‐type planar probe.


IEEE Microwave and Wireless Components Letters | 2006

Planar type probe with multiple-polarization response for in-vivo permittivity measurements of heterogeneous biological tissues

Kihyun Kwon; Sungkyu Lim; Sungjoon Cho; Jeonghoon Yoon; Jeiwon Cho; Changyul Cheon; Youngwoo Kwon

A three-way planar-type probe optimized for in-vivo permittivity measurements of biological materials has been developed. The probe in this letter consists of three orthogonally-faced probing apertures, which allows one to make accurate and uninterrupted measurements in three different directions per each insertion. As a result, this probe is significantly less invasive for the collection of the desired information of the biological materials, thus providing a vastly improved solution for in-vivo measurements. This probe can also be used for microwave ablation, in which case the treating region can be significantly expanded


Journal of Micromechanics and Microengineering | 2006

In vitro measurement using a MEMS probe array with five-strip lines for permittivity measurement

Jung-Mu Kim; Dong Hoon Oh; Chang-Wook Baek; Jeiwon Cho; Youngwoo Kwon; Changyul Cheon; Yong-Kweon Kim

This paper describes a single-aperture MEMS probe and a MEMS probe array for the measurement of biological properties. We designed and fabricated the single-aperture MEMS probe using surface micromachining and verified it by measuring the permittivity of a standard liquid before introducing the MEMS probe array. The actual aperture size of the single-aperture MEMS probe is only 390 µm × 80 µm, which is very small in comparison with the conventional laser-machined coaxial probe. In order to show the feasibility of the proposed single-aperture MEMS probe for permittivity measurements, we performed in vitro measurements of 0.9% saline. Once the single-aperture probe was verified, we proposed the concept of a probe array for biological measurements and experimentally showed the suitability of the MEMS probe array for biological applications through experiments using pork. The MEMS probe array consists of five microstrip feed lines, each of which is followed by open-ended strip lines, and the permittivity measurement of each port is separately performed through the use of a conventional multiport coaxial switch (Agilent, HP 87106 C), followed by a network analyzer (HP 8510 C). Through broadband measurements of 0.9% saline and pork using the MEMS probe array, we were able to discriminate the muscle and fat of pork through just one contact by placing the MEMS probe array on the boundary of muscle and fat. This newly proposed MEMS probe array has great potential in terms of disposability, low cost, integration with planar circuits and a short detection time for biological measurements.


international microwave symposium | 2004

A planar-type probe with a coaxial aperture for nondestructive complex permittivity measurement of biological materials up to 30 GHz

Byoungjoong Kang; Jeiwon Cho; Changyul Cheon; Youngwoo Kwon

In this paper, a planar probe structure is developed to evaluate the possibility of replacement of existing open-ended coaxial probes. The body of the probe is a planar transmission line that can propagate TEM mode and is completely shielded. For proper comparisons with open-ended coaxial probes, the proposed probe is designed to have a coaxial aperture on the top of the probe body using a via structure. The results of complex permittivity measurement show good agreement with those of open-ended coaxial-probes. Furthermore, it can reduce the fabrication cost and simplify the fabrication process by adopting the photolithography technique. Therefore the proposed planar type probe is a promising candidate for nondestructive dielectric measurement with respect to low cost and easier fabrication. In particular, it can be advantageous for in-vivo measurements due to its small size and disposability.


Journal of Micromechanics and Microengineering | 2005

Silicon MEMS probe using a simple adhesive bonding process for permittivity measurement

Jung-Mu Kim; Dong Hoon Oh; Jeonghoon Yoon; Sungjoon Cho; Namgon Kim; Jeiwon Cho; Youngwoo Kwon; Changyul Cheon; Yong-Kweon Kim

We developed a silicon MEMS probe for permittivity measurements using an adhesive bonding process. Only two photolithographic masks are required to fabricate the probe, which can be implemented through simple bonding processes using silicon substrates and a benzo cyclo butene (BCB) adhesive layer. Undoped silicon substrates with thicknesses of 300 ?m are used as the dielectric layers of the proposed probe. BCB layers, which have good electrical properties at high frequencies as well as adhesive properties for the bonding process, play the role of bonding materials between the two silicon substrates. The length of the probe is 30 mm, and the aperture located at the tip of the probe is 1.1 mm ? 0.62 mm. The permittivity of 0.5% saline was measured, and the results agreed with the values obtained through the Cole?Cole equation. To validate the feasibility of this probe for practical biological applications, we also performed in vivo measurements of the muscle, skin and blood of mice. Due to the simple fabrication process, the cost of the probe can be reduced in comparison with the previous micromachined probe (Kim et al 2005 J. Micromech. Microeng. 15 543?50) as well as the conventional laser machined probe. Low cost leads to disposability, which is an important factor for practical biomedical applications; and thus, coupled with the probes capabilities of MMIC integration and CMOS compatibility, this probe has excellent potential in the field of microwave permittivity measurements.

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Changyul Cheon

Seoul National University

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Youngwoo Kwon

Seoul National University

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Yong-Kweon Kim

Seoul National University

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Jeonghoon Yoon

Seoul National University

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Jung-Mu Kim

Chonbuk National University

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Dong Hoon Oh

Seoul National University

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Sungjoon Cho

Seoul National University

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Kihyun Kwon

Seoul National University

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Sungkyu Lim

Seoul National University

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