Alsop D C, Connick T J, Mizsei G
Department of Radiology, University of Pennsylvania Medical Center, Philadelphia 19104-4283, USA.
Magn Reson Med. 1998 Jul;40(1):49-54. doi: 10.1002/mrm.1910400107.
Biological samples have a high dielectric constant that can shorten RF wavelengths by a factor of 8 relative to the vacuum. At high field strengths, finite wavelength effects within larger samples are the dominant cause of RF field nonuniformity. A coil design is presented that can reduce and even eliminate this inhomogeneity; 4-T images in phantoms and in the head of a normal volunteer are presented, which demonstrate improved homogeneity relative to a standard coil. This coil design should aid in realizing the potential advantages of imaging large samples at high field strengths.
生物样本具有较高的介电常数，相对于真空而言，其可使射频波长缩短8倍。在高场强下，较大样本内的有限波长效应是射频场不均匀性的主要原因。本文提出了一种可减少甚至消除这种不均匀性的线圈设计；展示了在体模和正常志愿者头部采集的4-T图像，与标准线圈相比，这些图像显示出更好的均匀性。这种线圈设计应有助于实现高场强下对大样本成像的潜在优势。
