電子式SQUID梯度計應用於生物磁場測量

• Main Authors: Hsu S C, 徐士君
• Other Authors: Yang H C
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/14817855528940244282

碩士 === 國立臺灣師範大學 === 光電科技研究所 === 92 === ABSTRACT We set up 1st-order electronic high-Tc SQUID gradiometer system to measure the magnetocardiography (MCG) of small animals in moderate magnetically shielded environment. The 1st-order gradiometer system consists of two high-Tc rf SQUID. Because the low frequency noise is not reduced sufficiently by the magnetically shielded room or 1st-order gradiometer, therefore we use a feedback system to reduce the external noise level leaking into the shielded room. This is an active compensation technique for improving the performance of SQUID gradiometer in a μ-metal magnetically shielded room. Active compensation system is established by canceling the magnetic field inside the magnetically shielded room detected by the reference SQUID magnetometer. The reference sensor is used to feed a current through coils surrounding the room. The noise field inside the room is then eliminated. We used the active compensation for magnetic field in the vertical direction in the magnetically shielded room. We also used the low-pass filter with the cut off frequency at 44 Hz to filter out the high frequency noise, the high-pass filter with the cut off frequency at 0.1 Hz is used to suppress the low frequency fluctuation and the 60 Hz notch filter to reduce the power line interference. In the experimental process, we mount the small animal on the X-Y translation bed which is controlled by a computer. In this way, we can move the test object between scanning points fast and locate the object accurately. The noise measured by the 1st-order gradiometer MCG system in the moderate magnetically shielded room was about 1 pT above 1 Hz. Therefore, we can perform MCG measurements of rabbits in the moderate shielded environment. A two dimensional MCG mapping of healthy and hypercholesterolemic rabbits were obtained. The results are discussed.