PULSED ESR MICROSCOPE

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 这一子项目包括开发和建造以脉冲模式工作的ESR显微镜。ESR显微镜在概念上类似于众所周知的磁共振成像(MRI)系统。主要的区别是用于测量的自旋类型(核磁共振中的电子与质子)和图像分辨率(微米与毫米)。因此，大多数与生物相关的样品必须掺杂或标记稳定的自由基，以便于ESR测量(类似于光学显微镜中的染料)。此外，样品的典型尺寸必须不超过1-2毫米。当与光学显微镜相结合时，脉冲ESR显微镜可以成为生物科学中的一种有价值的工具。扩散张量、氧气浓度、弛豫时间(T1，T2)和ESR线型等空间分辨参数可以揭示模型和活系统中的大量信息，这些信息是光学方法无法获得的。在过去，人们曾尝试将核磁共振和光学显微镜相结合，但由于核磁共振的分辨率有限(~10微米)和成本较高，成功有限。ESR显微镜的灵敏度更高，可以获得与光学方法相当的分辨率(~1微米)的磁共振图像，而且成本要低得多(在核磁共振显微镜中，简单的电磁铁与大的超导磁)。我们已经构建了脉冲ESR显微镜的初步原型。该系统由自制的6~17 GHz脉冲微波桥、脉冲梯度驱动器、系统控制和数据采集计算机、脉冲成像探头(谐振器+梯度线圈)组成。在16 GHz下演示了分辨率为3×3×8微米的三维ESR图像。进一步发展到更高的频率9UP到~60 GHz，将有助于达到所需的亚微米图像分辨率。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This subproject involves the development and construction of an ESR microscope operating at pulsed mode. The ESR microscope is conceptually similar to the well known Magnetic Resonance Imaging (MRI) system. The main differences are with the type of spins used for the measurements (electron vs. protons in MRI), and the image resolution (microns vs. mm). Consequently, most biologically-related samples must be doped or labelled with stable radicals to facilitate the ESR measurement (similar to dyes in optical microscopy). Furthermore, the samples must be with a typical size of no more than 1-2 mm. When combined with optical microscopy, the pulsed ESR microscope can be a valuable tool in bio-science. Spatially resolved parameters such as diffusion tensor, O2 concentration, relaxation times (T1, T2), and the ESR lineshape can reveal a wealth of information in model and live systems, inaccessible by optical methods. In the past attempts has been made to combine NMR and optical microscopy, but with limited success due to the limited resolution of NMR (~10 microns) and its high cost. The ESR microscope, which is much more sensitive, should achieve magnetic resonance images with resolution comparable to optical method (~ 1 micron), and at much lower cost (simple electromagnet vs. large superconducting magnetic in NMR microscopy).We have constructed an initial prototype of the pulsed ESR microscope. The system is made of a home-built 6-17 GHz pulsed microwave bridge, a pulsed gradient driver, a computer for system control and data acquisition, and a pulsed imaging probe (resonator+ gradient coils). Three dimensional ESR images with a resolution of 3x3x8 microns were demonstrated at 16 GHz. Further progress to higher frequencies 9up to ~60 GHz, would facilitate the required sub-micron image resolution.