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Microwave ablation system design to study the effects of coaxial antenna on in-vitro animal tissue
(2014-01-01)
Chaichanyut, M.
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Lertprasert, P.
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Tungjitkusolmun, S.
This paper presents a novel low cost microwave ablation system design to study the effects of coaxial antenna on In Vitro animal tissues. The system utilizes a high-voltage power supply so that the magnetron can generate a microwave field continuously, and its output power can be adjusted from 10 - 80 W at frequency of 2.45GHz. We control output microwave power level by using control the magnetron power supply, which it is an important part of a microwave heating system. Power control of the magnetron’s power supply is desired for microwave heating to enhance performance and to provide system flexibility. The high frequency switching technique in the power supply control is costly and complicated. In another way, pulsing the output power of the magnetron can be simply realized with TRIAC, but in that case the magnetron does not operate continuously. The proposed circuit is a simple one with TRIAC. The power control is achieved by controlling the triggering events at appropriate phase angle of the household 220V. Experimental protocol was composed by a radiation system and a thermometry system. Coaxial antenna works at 2.45 GHz, power apply during experiments was 10W×8min; 20W×4min; 40W×2min and 80W×1min. Thermal sensors were placed next to the antenna at 1mm., a large number of experiments on porcine liver are carried out, the temperature distribution within the liver are measured and illustrated, for cases of different injected microwave power and ablation time. In addition, the ablation areas in cases of different input microwave powers are measured also. All these results indicate the potential validity of this system on medical treatment of liver cancer of human body.
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The modeling techniques for analyses of electromagnetic distributions and reflection coefficients for microwave ablation
(2014-01-01)
Chaichanyut, M.
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Lertprasert, P.
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Tungjitkusolmun, S.
many advantages of microwave ablation over the other ablative therapies in the field of liver tumor ablation have driven researchers to develop innovative interstitial microwave antennas to effectively treat deep seated, nonresectable hepatic tumors. A new coaxial antenna for microwave ablation therapies has been proposed in this research paper. Three dimensional Finite Element Method (FEM) has been used to design the results of the proposed antenna. Objective metrics for assessing the characteristics of helix antennas for microwave ablation by analyzing the electromagnetic field distributions and reflection coefficients for efficiency of antenna has been specified and verified for the proposed antenna, at frequency of 2.45GHz. Our simulation results, Relative permittivity at 2.45 GHz during thermal ablation. Accumulated ablation times noted on each figure to identify temporal variations. Values tended to drop quickly in all cases when temperatures reached 100 °C and continued to drop as temperature was maintained and the tissue became more dehydrated. Changes were irreversible as tissue returned to baseline temperatures. We designs the antenna matching obtained at 2.45 GHz. During thermal ablation, the reflection coefficients it can be noted that the antenna resonance shifts toward higher frequencies and the electric field distribution at the near field region changing follow the temperature variations in tumor tissue.
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Experimental studies on power control microwave ablation in vitro animal tissues with microwave percutaneous coagulator
(2013-12-01)
Chaichanyut, M.
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Lertprasert, P.
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Tungjitkusolmun, S.
Microwave coagulation therapy (MCT) has been used mainly for the treatment of small-size tumors. The operating frequency is 2450 MHz for the present MCT. In this paper, we analyzed the heating characteristics (temperature distributions patterns, lesion on size and etc.) of an applicator composed of thin microwave antenna. The configurations of thin microwave monopole antennas were considered: Coaxial Quarter Conductor Antennas (CQCA). Experimental protocol was composed by a radiation system and a thermometry system. We apply the microwave power during experiments was 10W, 20W, 40W and 80W which microwave power all case will vary the duration time for ablation were 60s 120s 240s and 480s respectively; Thermal sensors were placed next to the antenna at 1mm, a large number of experiments on porcine liver are carried out, the temperature distribution within the liver are measured and illustrated, for cases of different injected microwave power and ablation time. From our experimental results, if we considered the region where temperature exceeds 50°C, the threshold for successful hepatic ablation. The CQCA has lesion size was larger, with a lesion width of approximately 20 mm. In addition, the ablation areas in cases of different input microwave powers are measured also. All these results indicate the potential validity of this system on medical treatment of liver cancer of human body. © 2013 IEEE.
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Bone mineral density and bone mineral content estimation using low-cost x-ray detector
(2007-12-01)
Chuaychunu, N.
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Pititheerapab, Y.
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Chanwimalueang, T.
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Lertprasert, P.
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Pintavirooj, C.
This paper presented a design of a low-cost x-ray-detector using CMOS camera with an application on bone mineral content estimation. The main components consist of CMOS camera, optical lens, and image intensifier screen. CMOS camera offers various advantages including miniature-sized, low power consumption and cost effective. To apply the CMOS camera as x-ray detector, x-ray-to-visible light convector is required. Our key component of x-ray-to-visible light converter is intensifier screen. The application of x-ray detector for bone mineral density (BMD) and bone mineral content (BMC) is also given in this paper. The concept of dual energy x-ray is adopted to estimate the BMD on the finger bone. To compute BMC from BMD, the area of the bone is required. The concept of aative contour is applied to estimate the finger-bone area. ©2007 IEEE.
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Comparison temperature distribution between microwave and radio-frequency ablation probe in hepatic cancer
(2007-01-01)
Chaichanyut, M.
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Tungjitkusolmun, S.
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Potejanasaja, I.
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Lertprasert, P.
This paper presents three-dimensional finite element analyses of hepatic cancer ablation. The analyses performed in this paper are composed of two systems. In the first system, the simulation was microwave ablation by using open-tip monopole antenna. We analyses microwave ablation at frequency of 2.45GHz. Additional simulations of radiofrequency ablation by using monopolar probe. All simulations, we studied and compared the characteristics of the electric field and temperature distributions between monopole antenna and monopolar probe. From the simulation results, the electric field distribution of open-tip monopole was a wide electric field distribution while the electric field distribution of monopolar has a narrower. The temperature distribution has distributed same with electric field distribution. The temperature distribution of open-tip monopole was larger when compared with monopolar probe.
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Length effect of metal-tip monopole antenna to temperature distributions for microwave ablation
(2007-01-01)
Chaichanyut, M.
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Lertprasert, P.
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Phonphruksa, P.
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Tungjitkusolmun, S.
This paper present three-dimensional finite element analyses of hepatic cancer. We studied the characteristics of metal-tip monopole (MTM) antennas for microwave ablation by analyzing the length effect of metal at the antenna tip. We analyses microwave ablation at frequency of 2.45GHz.The length of metallic tip (ht) are varied so as to observe the effect on the temperature distribution. Simulations the length of metallic tip are 1mm, 2mm and 4 mm. From the simulation results, we considered the hepatic cancer region where temperature exceeds 50 °C. The lengths of metallic tip are 1 mm, 2 mm and 4mm had similar temperature distribution profiles and the maximum temperature occurred around the tips of the antennas. In case the length of metallic tip is 4mm, the temperature distribution was widest and induced the highest temperature in cancer tissue. In addition, the temperature distribution was narrowly shaped along the length in regions the shaft body of the antenna. For case the length of metallic tip is 2 mm, the temperature had minimum in cancer tissue and can be minimum ablation cancer tissue (17.34cm<sup>3</sup>). For case the length of metallic tip is 1 mm, this case can be maximum ablation cancer tissue (18.67cm<sup>3</sup>).
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Improved-resolution x-ray array detector applied for SART fanbeam
(2006-12-01)
Angsuwatanakul, T.
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Chanwimalueang, T.
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Pintavirooj, C.
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Sangworasil, M.
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Lertprasert, P.
In this paper, we investigate the design and construction of improved-resolution x-ray detector. Our detector is an array of photo-transistors coated with gadolinium based phosphor similar that used in the x-ray cassettes and used in advanced medical CT detector. The x-ray array detector module consists of two main part: the detector frontend and data acquisition system. The detector frontend includes preamplifying, low-pass filter. The data acquisition system is served to convert the signal in to digital form and forward it to personnel computer. The application of the detector as a CT detector shows a promising result. © 2006 IEEE.
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Finite element analyses for a study of hepatic cancer tissue destruction using monopolar and bipolar radio-frequency ablation
(2005-11-28)
Tungjitkusolmun, S.
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Boontaram, A.
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Lertprasert, P.
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Krairiksh, M.
This paper presents three-dimensional finite element analyses of radio-frequency hepatic tumor ablation. The analyses performed in this paper are composed of two systems. In the first system, the simulation was of monopolar ablation (one needle), while the second system was the simulation of bipolar ablation (two needles). We performed a preliminary study of thermal and electrical distributions of both systems. Additional simulations of bipolar ablation were performed to investigate the effect of spacing distance between two needle electrodes (2 cm, 3 cm, 4 cm, and 5 cm). The ablation duration used in all cases was 10 min, and the controlled maximum temperature was set to 90°C. From the results, the electric field in monopolar ablation appeared to be distributed uniformly between the electrode and the ground surface, but the electric field in bipolar ablation was focused in the regions between the two electrodes. For bipolar ablation, when the distances between the electrodes were 2 cm and 3 cm, the lesion created was contiguous and covered the areas surrounding both electrodes. However, when the distances between the electrodes were 4 cm and 5 cm, the lesions created were not contiguous and shaped similar to performing two monopolar ablation operations.
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Finite element method for analyses of magnetic and electric field distributions of monopole antennas in liver tissue
(2004-12-01)
Tungjitkusolmun, S.
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Chaichanyut, M.
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Lertprasert, P.
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Krairiksh, M.
This paper presents three-dimensional finite element analyses of microwave ablation. We studied the characteristics of various monopole antennas for microwave ablation by analyzing the magnetic and electric field distributions at frequency of 2.45GHz. Four configurations of monopole antennas were considered: open-tip, dielectric-tip, metal-tip and slot antennas. From the simulation results, the open-tip antenna had a small amount of magnetic field distribution at the tip, while the dielectric-tip antenna had virtually no magnetic field distribution at the tip. The metal-tip and slot antennas had continuons magnetic field distribution extending from the tip. The electric field distribution of open-tip, dielectric-tip, and metal-tip monopole antennas were similar, while the electric field distribution of slot antenna was maximized at the tip, but covered a narrower region along the length of the antenna. © 2004 IEEE.

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