Hüfken Thomas, Lobmeyer Tobias, Gahr Bernd, Bschorr Fabian, Speidel Tobias, Just Steffen, Rasche Volker
Department of internal Medicine II, Ulm University Medical Center, Ulm, Germany.
Core Facility Small Animal Imaging, Ulm University, Ulm, Germany.
Sci Rep. 2024 Oct 9;14(1):23583. doi: 10.1038/s41598-024-73271-5.
The spatial resolution in magnetic resonance imaging is mainly limited by low SNR, which is commonly addressed by long measurement times or dedicated hardware. In single digit micron resolutions, diffusion becomes a further limiting factor since depending on the gradient strength, the diffusion length of particles may approach the target resolutions. Spatial resolution improvement has been addressed by microscopy inserts comprising dedicated gradient systems and RF-coils, usually designed for NMR spectrometers that are often equipped with a deuterium lock for field drift compensations. The presented microscopy insert has been designed to provide single-digit micron resolutions on horizontal preclinical imaging systems utilizing their full imaging and user interface capabilities. The incorporated gradient provides an efficiency of 0.135 T/(m∙A) which in combination with the system's gradient amplifiers yields a maximum of 27 T/m. With the additional low noise amplifier added to the RF-path a three-fold SNR improvement could be achieved for small samples. Furthermore, a modified constant time imaging sequence was introduced to improve the capability of the setup for ultra-high-resolution imaging demonstrated on zebrafish embryos at different development stages with (9 μm)³ resolution.
磁共振成像中的空间分辨率主要受低信噪比限制，通常通过延长测量时间或使用专用硬件来解决。在个位数微米分辨率下，扩散成为另一个限制因素，因为根据梯度强度，粒子的扩散长度可能接近目标分辨率。通过包含专用梯度系统和射频线圈的显微镜插入件可以提高空间分辨率，这些插入件通常为核磁共振光谱仪设计，而核磁共振光谱仪通常配备有用于场漂移补偿的氘锁定装置。所展示的显微镜插入件旨在利用水平临床前成像系统的全部成像和用户界面功能，提供个位数微米分辨率。内置梯度的效率为0.135 T/(m∙A)，与系统的梯度放大器相结合，可产生高达27 T/m的磁场强度。通过在射频路径中添加额外的低噪声放大器，对于小样本可实现三倍的信噪比提升。此外，引入了一种改进的恒时成像序列，以提高该装置在不同发育阶段的斑马鱼胚胎上进行超高分辨率成像的能力，分辨率可达(9μm)³。
