高溫超導表面線圈於磁振造影中之特性與研究

Abstract

高溫超導表面線圈是為了增加核磁共振造影的敏感度而設計出來的，由螺旋形的釔鋇銅氧薄膜共振器以及2×2 cm2 的鋁酸鑭基座所構成。 為使質子在3 Tesla下有更好的造影效果，並求知敏感度的差異性，我們使用釔鋇銅氧薄膜為共振器，比較高溫超導薄膜共振器與傳統銅電路板共振器，高溫超導薄膜共振器的訊雜比有顯著的提高，在128×128像素，金桔與斑馬魚的訊雜比增益分別為3.46與2.8倍，我們也將此結果與理論預估值討論與比較。 此外我們以玻璃纖維材質(G10)，針對3 Tesla磁振造影系統設計製作了一個低溫恆溫器(Dewar)量測架構並且使用了商業化的高溫超導帶材來製作直徑20 cm的超導帶表面線圈。以葡萄柚為待測樣品，造影像素為128×128，常溫下的銅表面線圈與77 K下的超導帶表面線圈，得到的訊雜比增益為2.8倍。葡萄柚為待測樣品，造影像素為512×512，常溫下的銀帶表面線圈與77 K下的超導帶表面線圈，我們得到訊雜比增益為2.17倍

The HTS superconducting surface receiver coil composed a spiral YBa2Cu3O7-y thin film resonator on a 2×2 cm2 LaAlO3 substrate is designed to enhance the sensitivity of the nuclear magnetic resonance imager. For better performance YBCO resonator is optimized to the resonance imager frequency of the proton at 3 Tesla. To evaluate the sensitivity, the spin echo images coupled to the HTS resonator is presented and compared with images obtained from the copper surface resonator fabricated from the printed circuit board. An improvement of the signal-to-noise (SNR) ratio was achieved for YBCO thin film resonator over a conventional copper resonator. The SNR gain was 3.46 and 2.8 for calamondin and zebra fish at 128×128 pixels respectively. These results are discussed and compared with the theoretical calculation in the gain of SNR ratio. We designed a G10 glass fiber cryostat to be fit in Brüker 3T MRI system and used commercialized Bi2Sr2Ca2Cu3O tape to fabricate a HTS coil with a diameter of 20 cm . A SNR gain about 2.8 can be obtained from the HTS tape coil over a conventional copper surface coil in grapefruit at 128×128 pixels. A SNR gain about 2.17 can be obtained from the HTS tape coil over a silver surface coil in grapefruit at 512×512 pixels.