Kamberger R, Göbel-Guéniot K, Gerlach J, Gruschke O G, Hennig J, LeVan P, Haas C, Korvink J G
BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany.
BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Germany; Medical Physics, Department of Radiology, Medical Center - University of Freiburg, Germany.
Magn Reson Imaging. 2018 Oct;52:24-32. doi: 10.1016/j.mri.2018.05.010. Epub 2018 May 29.
MR in microscopy can non-invasively image the morphology of living tissue, which is of particular interest in studying the mammalian brain. Many studies use live animals for basic research on brain functions, disease pathogenesis, and drug development. However, in vitro systems are on the rise, due to advantages such as the absence of a blood-brain barrier, predictable pharmacokinetics, and reduced ethical restrictions. Hence, they present an inexpensive and adequate technique to answer scientific questions and to perform drug screenings. Some publications report the use of acute brain slices for MR microscopy studies, but these only permit single measurements over several hours. Repetitive MR measurements in longitudinal studies demand an MR-compatible setup which allows cultivation for several days or weeks, and hence properly functioning in vitro systems. Organotypic hippocampal slice cultures (OHSC) are a well-established and robust in vitro system which still exhibits most histological hallmarks of the hippocampal network in vivo. An MR compatible incubation platform is introduced in which OHSC are cultivated according to the interface method following Stoppini et al. In this cultivation method a tissue slice is placed onto a membrane with nutrition medium underneath and a gas atmosphere above, where the air-tissue interface perpendicular to the B field induces strong artefacts. We introduce a handling protocol that suppresses these artefacts and increases signal quality significantly to acquire high resolution images of tissue slices. An additional challenge is the lack of available of MR microscopy equipment suitable for small animal scanners. A Lenz lens with an attached capacitor can dramatically increase the SNR in these cases, and wirelessly bring the detection system in close proximity to the sample without compromising the OHSC system through the introduction of wired detectors. The resultant signal gain is demonstrated by imaging a PFA-fixed brain slice with a 72 mm diameter volume coil without a Lenz lens, and with a broadband and a self-resonant Lenz lens. In our setting, the self-resonant Lenz lens increases the SNR 10-fold over using the volume coil only.
显微镜磁共振成像（MR）能够对活体组织的形态进行非侵入性成像，这在研究哺乳动物大脑方面具有特别的意义。许多研究使用活体动物进行脑功能、疾病发病机制和药物开发的基础研究。然而，由于诸如不存在血脑屏障、药代动力学可预测以及伦理限制减少等优点，体外系统正在兴起。因此，它们提供了一种廉价且合适的技术来回答科学问题并进行药物筛选。一些出版物报道了将急性脑切片用于MR显微镜研究，但这些研究仅允许在数小时内进行单次测量。纵向研究中的重复性MR测量需要一个与MR兼容的装置，该装置允许培养数天或数周，从而使体外系统正常运行。器官型海马切片培养（OHSC）是一种成熟且强大的体外系统，它仍然展现出体内海马网络的大多数组织学特征。本文介绍了一种与MR兼容的孵育平台，其中OHSC按照Stoppini等人的界面法进行培养。在这种培养方法中，将组织切片放置在下方有营养培养基且上方有气体氛围的膜上，垂直于B场的气 - 组织界面会产生强烈的伪影。我们引入了一种处理方案，该方案可抑制这些伪影并显著提高信号质量，以获取组织切片的高分辨率图像。另一个挑战是缺乏适用于小动物扫描仪的MR显微镜设备。在这些情况下，带有附加电容器的伦兹透镜可以显著提高信噪比，并且通过引入有线探测器不会对OHSC系统造成影响，从而将检测系统无线地靠近样品。通过使用直径为72毫米的体线圈，在不使用伦兹透镜、使用宽带伦兹透镜和自谐振伦兹透镜的情况下对经多聚甲醛固定的脑切片进行成像，展示了由此产生的信号增益。在我们的设置中，自谐振伦兹透镜使信噪比相对于仅使用体线圈时提高了10倍。
