An integrated magnetic resonance plant imager for mobile use in greenhouse and field
An integrated magnetic resonance plant imager for mobile use in greenhouse and field
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DOI：
10.1016/j.jmr.2020.106879
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发表时间：
2021-01-07
影响因子：
2.2
通讯作者：
Windt, Carel W.
中科院分区：
文献类型：
--
作者：
Meixner, Marco;Kochs, Johannes;Windt, Carel W.
在这个贡献中，我们展示了一个移动的，集成的MR植物成像仪，可以由一个人处理并在现场使用。关键是它的建设是一个小而轻的梯度放大器，专门为我们的磁铁，梯度线圈和所需的脉冲序列的要求的组合量身定制。为了对树枝和茎部进行成像，使用了一个开放的c形永磁体。在磁体的设计中，优先考虑极隙宽度、重量轻和坚固性，而不是均匀性和场强。为了克服短T-2*的不利影响，采用多自旋回波成像，利用短回波时间和高光谱宽度。为了在这些限制条件下实现微观分辨率，需要由强而快速的梯度放大器驱动的快速开关场梯度。虽然小型光谱仪和射频放大器很容易获得，但目前还没有合适的小型梯度放大器或其设计。因此，我们在传统电流控制AB放大器设计的基础上构建了一个小型的3通道梯度放大器，使用便宜且知名的部件。完成的装置重5公斤，能够提供持续时间为60毫秒的40 A梯度脉冲。所有组件都安装在铝制手推车上，成像装置重45公斤，小到可以装进一辆汽车。我们首先展示了该设备成像定量含水量和T-2的移动性和实用性，首先是果园中的一棵苹果树；第二张是温室里春天冲洗叶子时山毛榉树的照片。后者的实验连续运行了62天，获得了6000多张图像。(C) 2020德国德国工程技术股份有限公司Elsevier Inc.出版。
In this contribution we demonstrate a mobile, integrated MR plant imager that can be handled by one single person and used in the field. Key to the construction of it was a small and lightweight gradient amplifier, specifically tailored to our combination of magnet, gradient coils and the requirements of the desired pulse sequences.To allow imaging of branches and stems, an open C-shaped permanent magnet was used. In the design of the magnet, pole gap width, low weight and robustness were prioritized over homogeneity and field strength. To overcome the adverse effects of short T-2*, multi-spin echo imaging was employed, using short echo times and high spectral widths. To achieve microscopic resolution under these constraints requires fast switching field gradients, driven by strong and fast gradient amplifiers. While small-scale spectrometers and RF amplifiers are readily available, appropriate small-scale gradient amplifiers or designs thereof currently are not. We thus constructed a small, 3-channel gradient amplifier on the basis of a conventional current-controlled AB amplifier design, using cheap and well-known parts. The finished device weighs 5 kg and is capable of delivering 40 A gradient pulses of >6 ms in duration.With all components built onto an aluminum hand trolley, the imaging setup weighs 45 kg and is small enough to fit into a car. We demonstrate the mobility and utility of the device imaging quantitative water content and T-2, first of an apple tree in an orchard; second, of a beech tree during spring leaf flushing in a greenhouse. The latter experiment ran for a continuous period of 62 days, acquiring more than 6000 images. (C) 2020 Forschungszentrum Julich GmbH. Published by Elsevier Inc.