A DECOUPLED COIL DETECTOR ARRAY FOR FAST IMAGE ACQUISITION IN MAGNETIC-RESONANCE-IMAGING
A DECOUPLED COIL DETECTOR ARRAY FOR FAST IMAGE ACQUISITION IN MAGNETIC-RESONANCE-IMAGING
复制标题
DOI：
10.1118/1.596723
复制
发表时间：
1991-03-01
期刊：
影响因子：
3.8
通讯作者：
NAVON, G
中科院分区：
文献类型：
--
作者：
KWIAT, D;EINAV, S;NAVON, G
本文研究了一种磁共振成像（MRI）方法，即将物体置于均匀磁场下，并通过对物体周围的线圈探测器阵列中收集的数据应用逆源程序获得图像。由于磁偶极子在每个体素内的进动，每个线圈中的感应电流取决于磁偶极子频率和强度的特性，以及它与线圈的距离、线圈在空间中的方向和线圈的电学性质。通过计算线圈探测器阵列上的感应电流信号，建立了一组信号与被测物体结构之间的关系。然后，线性关系可以用矩阵表示，对这个矩阵求逆将产生物体的图像。在该方法中必须考虑的重要问题是信噪比和相邻线圈之间的耦合。这些问题的解决将为核磁共振瞬时图像的获取提供一种新的方法，而无需进行梯度切换编码。提出了一种通用的线圈解耦算法，并采用快速采样代替滤波，以同时降低噪声和数值舍入误差。灵敏度考虑了所需线圈的数量及其与线圈半径和信噪比的关系。计算机仿真验证了该方法的可行性。针对使用大量线圈同时记录信号所涉及的问题，本文提出了一种改进的多线圈记录方法，将其与传统的具有读取和相位梯度的周波法相结合，形成一种新的磁共振成像方法。在组合方法中，不存在相位编码梯度。只有一个切片选择梯度，后面跟着一个读梯度。代替相位编码梯度，使用的是等量的线圈。现在线圈的数量大大减少了。该方法建议在单个回声时间内拍摄单个切片图像，并且仅使用128个线圈即可实现128 x 128分辨率。该方法的适用性基于探测器（线圈和电缆）的成功解耦程序以及具有宽动态范围的高精度，高增益，低噪声放大器的可用性。
A method for magnetic resonance imaging (MRI) is investigated here, whereby an object is put under a homogeneous magnetic field, and the image is obtained by applying inverse source procedures to the data collected in an array of coil detectors surrounding the object. The induced current in each coil due to the precession of the magnetic dipole in each voxel depends on the characteristics of both the magnetic dipole frequency and strength, together with its distance from the coil, the coil direction in space, and the electrical properties of the coils. By calculating the induced current signals over an array of coil detectors, a relationship is established between the set of signals and the structure of the body under investigation. The linear relation can then be represented in matrix notation, and inversion of this matrix will produce an image of the body. Important problems which must be considered in the proposed method are signal-to-noise ratio (SNR) and coupling between adjacent coils. Solutions to these problems will provide a new method for obtaining an instantaneous image by NMR, with no need for gradient switching for encoding. A general algorithm for decoupling of the coils is presented and fast sampling of the signal, instead of filtering, is used in order to reduce both noise and numerical roundoff errors at the same time. Sensitivity considerations are made with respect to the number of coils that is required and its connection with coil radius and SNR. A computer simulation demonstrates the feasibility of this new modality. Based on the solutions presented here for the problems involved in the use of a large number of coils for a simultaneous recording of the signal, an improved method of multicoil recording is suggested, whereby it is combined with the conventional zeugmatographic method with read and phase gradients, to result in a novel method of magnetic resonance imaging. In the combined method, there are no phase-encoding gradients. Only a single slice-selecting gradient, to be followed by a single read-gradient. Instead of phase-encoding gradients, use is made of an equivalent number of coils. The number of coils now is reduced significantly. This method suggests a single slice image taken within a single echo time, and where a 128 x 128 resolution is possible with only 128 coils. The applicability of the method is based on a successful decoupling procedure for the detectors (coils and cables) and the availability of highly accurate, high-gain, low-noise amplifiers with a broad dynamic range.