Gradient Arrays for High Performance Extended FOV MRI

描述（由申请人提供）： 本计画将设计、建构及评估一种新颖的梯度阵列系统，以应用于磁共振影像的延伸视野成像。梯度设计包括纵向和横向梯度的新重复，以创建多个非相邻成像区域。在所施加的场梯度为线性的区域中执行成像。正如麦克斯韦对（由具有交流电的两个同轴线圈组成）可以用于生成Z梯度以在一个区域上执行成像，麦克斯韦三元组（由具有交流电的三个线圈组成）可以用于在线性场变化的2个非连续区域上执行图像采集，从而提高成像效率。为了从非线性场变化的中心区域采集图像数据，需要与第一阵列重叠的第二麦克斯韦阵列，使得第二阵列的线性区域定位在第一阵列的中心非线性I区域上。将以类似的方式设计用于多区域成像的横向梯度阵列。 在R21阶段，我们将使用数值方法和计算机模拟来研究这种梯度阵列的设计和预测性能，包括效率，转换速率，均匀性和功率要求作为电流分布的函数。我们还将研究梯度重叠，发射和接收RF线圈，以及脉冲序列设计的问题，以获得连续的成像区域。在R33阶段，我们将使用R21阶段的设计来构建原型插入梯度系统和多区域成像所需的RF线圈。我们将在生产的各个阶段测试梯度阵列和RF线圈。我们还将构建一个全身复合梯度阵列，并进行详细的神经刺激研究。这种新颖的设计将允许完全利用所有现有的高性能脉冲序列。它还将允许开发新的脉冲序列，这些脉冲序列利用完整的硬件功能同时获得更高的梯度性能、更大的成像视野和更少的神经刺激。

DESCRIPTION (provided by applicant): This project will design, construct, and evaluate a prototype novel gradient array system for extended field of view imaging in magnetic resonance imaging. The gradient design consists of novel repetitions of the longitudinal and transverse gradients to create multiple non-adjacent imaging regions. Imaging is performed in the regions where the applied field gradients are linear. Just as the Maxwell pair (composed of two coaxial coils with alternating currents) can be used to generate a Z-gradient to perform imaging over one region, a Maxwell triplet (composed of three coils with alternating currents) might be used to perform image acquisition over 2 non-contiguous regions of linear field variation and thereby improve imaging efficiency. To acquire image data from the central region of non-linear field variation requires a 2nd Maxwell array which overlaps with the first array such that the linear region(s) of the 2nd array are positioned over the central non-linear I region of the first array. Transverse gradient arrays for multiple region imaging will be designed in a similar manner. In the R21 phase we will use numerical methods and computer simulations to investigate the design and predict the performance of such gradient arrays, including efficiency, slew rate, homogeneity, and power requirements as a function of current distribution. We will also study the issues of gradient overlap, transmit and receive RF coils, and pulse sequence design to obtain contiguous imaging regions. In the R33 phase, we will use the designs from the R21 phase to construct a prototype insert gradient system and the RF coils required for multiple region imaging. We will test the gradient arrays and RF coils at various stages of production. We will also construct a whole-body composite gradient array and perform detailed nerve stimulation studies. This novel design will allow complete utilization of all existing high performance pulse sequences. It will also allow the development of new pulse sequences that utilize the complete hardware capabilities to simultaneously attain increased gradient performance, increased imaging field of view, and decreased nerve stimulation.