Open-source software and hardware tools for local B0 field control

项目摘要/摘要 多线圈(MC)垫片阵列已成为改善MRI图像质量的一种很有前途的灵活工具。 放置在身体附近的小的、独立驱动的环路阵列提供了一种有效的方式来生成 可快速切换的磁场偏移量(ΔB0)，可成形以提供有用的内部磁场分布 尸体。MC阵列最初是为动态可切换的、高空间阶数的B0填隙而提出的 主体到零静态背景B0场的特定于对象的扰动。改进的垫片减少了 回波平面成像中的几何失真(广泛用于功能和扩散磁共振成像)和线条加宽 在磁共振光谱学中。然而，在过去的几年中，MC阵列的新用途已经被提出， 包括补充空间编码、改进的脂肪抑制、缩放成像和减小翻转角度 (B1)不均质性。这种多样化且不断增长的方法--我们将其归类为本地现场控制-- 利用MC阵列的两个核心特性：(1)非正交ΔB0基集生成场分布的能力 不能用线性渐变创建的；以及(2)快速更新填补电流而不会导致 手工艺品。 不幸的是，MC当地的田间控制研究一直进展缓慢，无法扩展到少数几个地点。 仪器和控制软件的可获得性有限。具有动态特性的商用填补放大器 交换能力很少，而现有的交换能力对于大多数应用来说都是成本高昂的 (&gt；1000美元/频道)。同时，目前还没有现成的软件来控制垫片放大器和 与扫描仪主机接口。此外，还缺乏使用凸集的软件工具 优化以有效地解决定制局部场控制的垫片电流幅度。我们会崩溃的 这些进入壁垒是通过开发名为Effect(自动化灵活域)的开源资源来实现的 编码和控制工具包)。我们将改进和传播我们之前验证的低成本(100美元- 150个/声道)，可扩展到声道的低压填补放大器。我们还将升级和打包 用于处理B0场图和计算最佳垫片电流的图形用户界面(GUI)。图形用户界面 将被模块化，以允许用户插入他们自己的定制垫片优化工具。最后，我们将创造 图形用户界面和扫描仪主机之间的无缝接口，以改进工作流程。 已经有10多个研究小组与我们联系，要求使用我们的开源填隙放大器。 然而，还需要做进一步的工作，为传播做好硬件和软件准备。的目标是 这个项目是将我们的原型转换成健壮的、用户可扩展的工具，这些工具被打包并记录下来。 为了加快传播速度，我们将为多达10个研究小组提供免费的32声道放大器设置 充电。用户还可以免费下载原理图并自行制作电路板。

Project Summary/Abstract Multi-coil (MC) shim arrays have emerged as a promising and flexible tool for improving MRI image quality. Arrays of small, independently-driven loops placed close to the body provide an efficient way to generate rapidly-switchable magnetic field offsets (ΔB0) that can be shaped to provide useful field profiles inside the body. MC arrays were originally proposed for dynamically-switchable, high spatial order “B0 shimming” in the body to null subject-specific perturbations of the static background B0 field. The improved shimming reduces geometric distortion in echo planar imaging (widely used for functional and diffusion MRI) and line broadening in MR spectroscopy. However, in the past few years, a surge of new uses for MC arrays have been proposed, including supplementary spatial encoding, improved lipid suppression, zoomed imaging, and reduced flip angle (B1+) inhomogeneity. This diverse and growing set of methods – which we classify as local field control – exploit two core features of MC arrays: (1) the ability of non-orthogonal ΔB0 basis sets to generate field profiles that can not be created with linear gradients; and (2) the ability to rapidly update shim currents without causing artifacts. Unfortunately, MC local field control research has been slow to spread beyond a small handful of sites due to limited availability of instrumentation as well as control software. Commercial shim amplifiers with dynamic switching capability are rare, and those that do exist are cost-prohibitive for most applications (>$1,000/channel). At the same time, there is no readily-available software for controlling shim amplifiers and interfacing with the scanner host computer. Moreover, there is a lack of software tools using convex optimization to efficiently solve for shim current amplitudes for tailored local field control. We will break down these barriers to entry by developing an open-source resource called AFFECT (Automated Flexible Field Encoding and Control Toolkit). We will refine and disseminate our previously-validated low-cost ($100- 150/channel), low-voltage shim amplifier that is scalable up to 64-channels. We will also upgrade and package a graphical-user-interface (GUI) used to process B0 field maps and compute optimal shim currents. The GUI will be made modular to allow users to plug in their own custom shim optimization tools. Finally, we will create a seamless interface between the GUI and the scanner host computer to improve workflow. More than 10 research groups have already contacted us asking to use our open-source shim amplifiers. However, further work is required to prepare both the hardware and software for dissemination. The goal of this project is to translate our prototypes into robust, user-extensible tools that are packaged and documented. To expedite dissemination, we will provide up to 10 research groups with 32-channel amplifier setups free of charge. Users will also be free to download schematics and fabricate the circuit boards on their own.