在本研究中，我們結合了預先極化技術以及超導量子干涉元件 ( Superconducting quantum interference device, SQUID ) 開發了大型低場核磁共振及核磁造影系統。系統主要由均勻磁場、預極化線圈、脈衝線圈、SQUID、及三個維度的梯度線圈所組成。為了抵銷地球磁場的雜訊，我們設計了一對抵銷地球磁場的線圈，並將系統放置於屏蔽屋之內，來降低環境雜訊對系統的影響。在磁共振訊號量測中，經由梯度磁場補償提高了系統磁場的均勻度後，並對內徑10公分接收線圈做最佳化。使400毫升去離子水樣品的磁共振訊號頻譜線寬可以從原本的15赫茲縮減到1赫茲，且訊雜比由21.14提高到340.6。在磁振造影量測中，我們對不同大小的水樣品進行二維平面造影，使用相位編碼、頻率編碼的造影方法，均能得到完整的樣品影像，驗證本系統的空間解析度可以達到5毫米 ; 在三維造影，我們成功將3cm厚的樣品成功切成6個切面，造影解析度也進一步提升至5mm x 5mm x 1cm。新系統的樣品量測範圍遠遠大於從舊系統的量測面積，從原本的內徑6公分圓面積擴大至內徑20公分的圓面積，增加未來使用低磁場系統來量測動物器官影像、人體腦部造影的可行性，且系統造價低，具有產業化的潛力。

In this work, we combine pre-polarization technology and superconducting quantum interference device (SQUID) to developed a large low-field nuclear magnetic resonance image system. The system consists of a uniform magnetic field ( B0 coil), the pre-polarization coil (BP coil), RF pulse coil (B1 coil), SQUID, and the gradient coil (Gx、Gy、Gz)composed of three dimensions. In order to offset the noise of Earth's magnetic field, we designed a pair of offset the Earth's magnetic field coil (Bc coil). The coils and SQUID are put inside a shielded house and shielded cylinder which were made of aluminum to reduce the surrounding noise. We apply three dimensional gradient field to cancel the field inhomogeneity in our lab to obtain a narrow linewidth of NMR spectrum at 1 Hz and Signal Noise Ratio (SNR) increased from 21.14 to 340.6. In magnetic resonance imaging, we measured water specimen of different sizes and the 2-dimensional image are obtained with a high image resolution of 5mm. The 3-dimensional image of water phantom are demonstrated with a imaging resolution of 5 mm × 5mm × 1cm. Our high-Tc SQUID based MRI system shows the feasibility for biomedical imaging.

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