Susil Robert C, Yeung Christopher J, Atalar Ergin
Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Magn Reson Med. 2003 Aug;50(2):383-90. doi: 10.1002/mrm.10506.
The design and application of an intravascular extended sensitivity (IVES) MRI antenna is described. The device is a loopless antenna design that incorporates both an insulating, dielectric coating and a winding of the antenna whip into a helical shape. Because this antenna produces a broad region of high SNR and also allows for imaging near the tip of the device, it is useful for imaging long, luminal structures. To elucidate the design and function of this device, the effects of both insulation and antenna winding were characterized by theoretical and experimental studies. Insulation broadens the longitudinal region over which images can be collected (i.e., along the lumen of a vessel) by increasing the resonant pole length. Antenna winding, conversely, allows for imaging closer to the tip of the antenna by decreasing the resonant pole length. Over a longitudinal region of 20 cm, the IVES imaging antenna described here produces a system SNR of approximately 40,000/r (mL(-1)Hz(1/2)), where r is the radial distance from the antenna axis in centimeters. As opposed to microcoil antenna designs, these antennas do not require exact positioning and allow for imaging over broad tissue regions. While focusing on the design of the IVES antenna, this work also serves to enhance our overall understanding of the properties and behavior of the loopless antenna design.
本文描述了一种血管内扩展灵敏度（IVES）磁共振成像（MRI）天线的设计与应用。该装置采用无环天线设计，将绝缘介电涂层与天线鞭状绕组整合为螺旋形状。由于这种天线能产生一个较宽的高信噪比区域，并且还能在装置尖端附近进行成像，因此对长腔结构成像很有用。为了阐明该装置的设计和功能，通过理论和实验研究对绝缘和天线绕组的影响进行了表征。绝缘通过增加谐振极长度，拓宽了可采集图像的纵向区域（即沿血管腔）。相反，天线绕组通过减小谐振极长度，使得能够在更靠近天线尖端的位置进行成像。在20厘米的纵向区域内，这里描述的IVES成像天线产生的系统信噪比约为(40,000/r)（(mL^{-1}Hz^{1/2})），其中(r)是以厘米为单位，从天线轴的径向距离。与微线圈天线设计不同，这些天线不需要精确的定位，并且能够在较宽的组织区域进行成像。在专注于IVES天线设计的同时，这项工作也有助于增强我们对无环天线设计特性和行为的整体理解。
