Magnetic Resonance Tomography for 3-D Water-Bearing Structures Using a Loop Array Layout

Magnetic resonance tomography (MRT) is a technique that is used in the 2-D or 3-D detection and imaging of subsurface water-bearing structures based on the principle of surface nuclear magnetic resonance. Currently, the research and application of 3-D MRT is still limited by low measurement efficiency and image resolution. In this paper, a new loop array layout that consists of a coincident transmitting (Tx) and receiving (Rx) loop and an array of Rx loops is proposed to achieve high-efficiency MRT data acquisition and 3-D imaging. A number of water-bearing structures with various shapes (X, L, + and S models) are simulated based on the forward modeling of separated Tx and Rx loops with arbitrary geometries and topographies. Using the complex QT inversion scheme, images of these structures produced by 3-D MRT with the loop array layout are examined. The numerical simulation experiment shows that in low noise conditions, the water content distribution pattern obtained by inversion can reflect the fine details of the water-bearing structure, and an accurate relaxation time (T₂*) is provided. As the noise level increases, 3-D MRT images gradually become blurry. Nevertheless, increasing the number of Rx loop arrays can significantly improve the image resolution. Finally, the feasibility of practical applications of 3-D MRT with the loop array layout and feasible methods of improving measurement are discussed.