論文 - 高橋　英俊

平面型微小コイルを用いた局所高感度MRI

土肥 徹次, 高橋 英俊, 松本 潔, 下山 勲

生体医工学 （一般社団法人 日本生体医工学会）  47 （ 16 ） 484 - 493 2009年12月

共著, 査読有り,  ISSN  1347-443X

　概要を見る

In this study, we fabricated micro planar coils as a receiver for a high sensitive MRI (Magnetic Resonance Imaging). According to the calculation of the scale effect, the sensitivity of the coil increases with decrease of the diameter of the coil under the condition of fixed inductance. The micro planar coils of 5 and 20 mm in diameter were fabricated by using MEMS technology. The resistance and inductance of the 20 mm coil were 1.4 &Omega; and 1.15 &mu;H at 8.5 MHz, respectively. Those of the 5 mm coil were 2.0 &Omega; and 1.05 &mu;H, respectively. The MRI signal receivers were made by attaching the micro coils to the tip of acrylic pipes. The SNRs (Signal to Noise Ratio) of MR images of phantom were measured by the micro planar coils and the medical MRI coil of 200 mm in diameter. The SNRs of MR images taken by the micro planar coils were about 8 times as high as the MR image taken by the medical coil. MR images of an okra (<i>Abelmoschus esculentus</i>) were acquired by fabricated MRI signal receivers with the voxel size of 2.0 &times; 2.0 &times; 2.0 mm³ and 0.5 &times; 0.5 &times; 1.0 mm³. Since the sensitivity of micro planar coils was high, we were able to clearly observe inner structure of the okra.

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Sensitivity enhancement by micro Helmholtz resonator for ultrasonic distance sensor

A Suzuki, H Takahashi, E Iwase, K Matsumoto, I Shimoyama

TRANSDUCERS 2009-2009 International Solid-State Sensors, Actuators and …    1557 - 1560 2009年

　概要を見る

This paper reports on a micro Helmholtz resonator (HR) enhancing the sensitivity of an ultrasonic distance sensor. Attaching an HR to the sensor that consists of a piezoresistive cantilever microphone makes its sensitivity against ultrasonic wave higher. A HR of 600 μm height demonstrated a 17.5 times larger maximum amplitude of the cantilever vibration against single frequency wave. We also evaluated the dependence of the sensitivity on frequency and acoustic pressure. Our sensor was able to detect the distance of 0.5-6.0 m with the maximum error of 2.0%. ©2009 IEEE.

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Air pressure sensor for an insect wing

H Takahashi, K Matsumoto, I Shimoyama

Micro Electro Mechanical Systems, 2009. MEMS 2009. IEEE 22nd International … （IEEE）     825 - 828 2009年

ISSN  1084-6999

　概要を見る

This paper reports on an air pressure sensor for the measurement of the aerodynamic force on an insect wing. A piezoresistive cantilever was fabricated as a pressure sensor. The size of the cantilever was 250 mu m x 200 mu m x 0.3 mu m. The sensitivity to air pressure was 0.29 x 10(-3) Pa-1 below 2.0 kHz. By attaching the sensors on the prototype of an insect wing, pressure distribution over the surface were measured when the flow was both steady and unsteady.

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Local high sensitive MRI with a micro planar coil

T Dohi, H Takahashi, K Matsumoto, I Shimoyama

Transactions of Japanese Society for Medical and Biological Engineering 47 … 47 （ 6 ） 484 - 493 2009年

ISSN  1881-4379

　概要を見る

In this study, we fabricated micro planar coils as a receiver for a high sensitive MRI (Magnetic Resonance Imaging). According to the calculation of the scale effect, the sensitivity of the coil increases with decrease of the diameter of the coil under the condition of fixed inductance. The micro planar coils of 5 and 20 mm in diameter were fabricated by using MEMS technology. The resistance and inductance of the 20 mm coil were 1.4 Ω and 1.15 μH at 8.5 MHz, respectively. Those of the 5 mm coil were 2.0 Ω and 1.05 μH, respectively. The MRI signal receivers were made by attaching the micro coils to the tip of acrylic pipes. The SNRs (Signal to Noise Ratio) of MR images of phantom were measured by the micro planar coils and the medical MRI coil of 200 mm in diameter. The SNRs of MR images taken by the micro planar coils were about 8 times as high as the MR image taken by the medical coil. MR images of an okra (Abelmoschus esculentus) were acquired by fabricated MRI signal receivers with the voxel size of 2.0 × 2.0 × 2.0 mm3 and 0.5 × 0.5 × 1.0 mm3. Since the sensitivity of micro planar coils was high, we were able to clearly observe inner structure of the okra.

Air flow senser for an insect-like flapping wing

H Takahashi, E Iwase, K Matsumoto, I Shimoyama

2008 IEEE 21st International Conference on Micro Electro Mechanical Systems … （IEEE）     916 - 919 2008年

ISSN  1084-6999

　概要を見る

This paper reports on a thin piezoresistive cantilever for measuring air flow velocity around flapping wings. To measure the air flow velocity at a point of the wing directly, our sensor was attached to the leading edge of the wing. The sensor was designed to be I pin thick. Because of the scale effect, the influence of the inertial force was small during flow measurement. The sensor had the sensitivity of 0.56 - 0.96 - 10(-3) (m/s)(-2) as well as the directivity By using the micro flow sensor, we measured the perpendicular air flow velocity at the point of the leading edge of the wing.

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A micro planar coil for local high resolution magnetic resonance imaging

H Takahashi, T Dohi, K Matsumoto, I Shimoyama

2007 IEEE 20th International Conference on Micro Electro Mechanical Systems … （IEEE）     786 - 789 2007年

ISSN  1084-6999

　概要を見る

This paper reports on a flexible micro planar coil for an MR (Magnetic Resonance) catheter. High resolution images can be obtained by using the MR catheter. Two types of coils of 5 mm and 20 mm in diameter were fabricated. Both of the coils were designed to have inductance of 1.0 mu H at 8.5 MHZ. The proto-type MR catheters were made by attaching the micro coils to the tip of acrylic pipes. In order to evaluate the MR catheters, the sensitive area and SNR (Signal to Noise Ratio) were measured. SNRs of the MR catheters were about three to eight times higher than that of a standard medical coil. Furthermore, we demonstrated that high resolution MR images can be achieved by using the MR catheters. MR images of a gumbo (Abelmoschus esculentus) were acquired with 0.5 x 0.5 x 1.0 mm(3) resolution. While clear MR images were not able to be taken by the standard medical coil due to its low SNR, we were able to observe the gumbo and distinguished its seeds one by one in the MR images taken by the MR catheters.