新型高温超导磁共振线圈设计建构及其生物医学应用

As the development in biomedicine and clinical diagnosis, both higher spatial and temporal resolutions are expected to observe fine details of the structure. However, as the imaging resolution goes higher, signal-to-noise ratio (SNR) will become the limiting factor for accurate quantitative MR microscopy, such as molecular imaging. Hence, the image quality is a very important issue with the need of high resolution imaging in biomedicine field. Recently, high-temperature superconducting (HTS) radio-frequency (RF) coil has been proposed as a promisingly useful tool to investigate the tissue microscopy with high resolution due to its zero-resistance characteristic for MR probe design. In this project, we have 4 phases in three years: 1. Build a high temperature superconducting coil in the different MRI field (3T, 7T and 9.4T) and design the prototype dewars. 2. Build a electromagnetic model to optimize the high temperature superconducting coil 3.Develop a temperature-stable cryostat for the high temperature superconducting coil 4. Using the high temperature superconducting coil for in vivo applications Since the HTS material has to be immersed in liquid-nitrogen to keep its superconducting status, the first anticipated problem will be the performance of the Dewar, to provide the thermal-isolation between the liquid-nitrogen and the air. The second anticipated obstacle will be the maintenance of the animal's life during 90 minutes scan time under such cold temperature. Some of the possible solutions to this problem are to design the Dewar without any gap to leak the liquid-nitrogen, to add a vacuum layer to prevent the heat conducing and to use special thermal-isolated material other than G10 fiber-glass. Besides the HTS RF coil and the Dewar, we also need a automatic supplement system that can maintain the quantity of the liquid-nitrogen during the acceptable time (>1 hr~1.5 hr) for the stability of image quality. The third potential problem is to monitor the vital signs of samples by the physiological monitoring system inside the platform. In the past, we have successfully worked on the rat MRI platform with physiological signal monitoring.Biomedical applications, including dynamic enhancement cancer study, stem cell tracking and molecular imaging with targeted contrast agent for preclinical cancer applications will be applied to demonstrate its advantages in three years. With this imaging platform in the differrnt strength of MRI, MR capacity could be leveraged to another high level for probing the fundamental biological processes in vivo.

随生医科技蓬勃发展，临床诊断上的发展期盼有先进的磁共振造影技术来实时获得细微的组织结构，因此影像讯杂比是个非常重要的研究议题。医学影像研究已进入分子影像时代，对于影像讯杂比的需求是越来越高，然而传统线圈却会受到讯杂比的限制。使用电阻极低的高温超导材料可大幅提升线圈质量并成为线圈制备发展趋势。我们前期工作显示带状超导线在线圈几何形狀的选择上弹性大，制作便利，并能实现大幅提高影像讯杂比。本课题拟在我们前期工作基础上，搭建高温超导线圈以及真空低温平台并在3T、7T及9.4 T不同场强小动物磁共振成像系统中进行生物医学性能评价，以期在磁共振线圈研发的基础研究及应用转化方面取得技术突破。课题将从传统的结构性影像到先进的分子影像应用中开拓高温超导线圈在不同磁场磁共振成像仪中的生物医学应用，具有重大的科学意义和临床转化应用价值。

随生医科技蓬勃发展，临床诊断上的发展期盼有先进的磁共振造影技术来实时获得细微的组织结构，因此影像信噪比是个非常重要的研究议题。使用电阻极低的高温超导材料可大幅提升线圈质量和图像信噪比成为线圈制备发展趋势。本课题在项目基金的资助下已经完成了对高温超导线圈的建立以及初步低温平台的构建，以超导材料Bi2Sr2Ca2Cu3Ox (Bi-2223)为基础建立了直径为40mm的高温超导线圈，并将其与直径为35mm的商用相控阵线圈进行比较。通过高温超导线圈采集到的图像，其图像信噪比可提高近3.84倍。本课题组随后将高温超导应用于氢氟双调频接收线圈的设计制作，采用Bi-2223超导带，制作高温超导磁共振氢氟双调频接收线圈, 该实验采用不同浓度的样品，样品浓度分别为20 mM，10 mM， 5 mM，2.5 mM，信噪比分别为220.181，111.091，43.427，17.437，利用高温超导技术对于信噪比的提升作用，更好的获得氟元素的磁共振信号，解决氟元素信号弱、探测灵敏度低等难题，为含氟探针的生物应用提供技术可行性。同时本课题构建了核磁共振造影射频线圈冷却装置，该装置结构简单，通过与射频线圈热接触的方式，提高了制冷效率，可以将冷却时间缩短至40分钟左右，使图像噪声降低，信噪比提高，进而达到高影像分辨率。