Next-Generation RF Coils with High-Permittivity Material for Improved Performance in MRI

 描述（由申请人提供）：越来越多的研究表明，在射频（RF）线圈和人体受试者周围的空间中仔细选择和布置高介电常数材料或高介电常数材料（HPM），可以显著提高磁共振成像（MRI）的质量和安全性。在战略用途中，这些材料通过位移电流的作用将RF线圈和患者周围空间中的无用电场能量转换为有用的磁场能量。这些位移电流是比单独的离散导线中的传导电流更分散的磁场源，并且可以比离散导线更靠近对象，从而在不损害安全性的情况下提高灵敏度。最终结果是接收时的SNR更高（在许多实验和模拟中约为40%），并且受试者在发射时吸收的RF能量明显更少。考虑到MRI的SNR受限性质，使用更高场强（包括寻找NbTi的替代品）的多项重大成本，以及HPM可用于所有现有扫描仪以立即提高SNR的事实，继续这项工作对于在现有和未来系统上推进MRI至关重要。 我们建议开发薄而坚固的HPM，以适应目前最先进的临床线圈中塑料线圈架所占据的空间，并将其集成到新的线圈设计中。因此，最终结果将不大于现有的临床线圈，并且传导线圈将不会远离受试者。初步的仿真和实验验证了该方法的可行性。考虑SNR和患者发热（SAR）的数值模拟将指导材料在所需特性和形状方面的设计。另外，将构建包含和不包含HPM的等同射频头部线圈，用于7T研究和3T临床系统。在两种场强下，将在多个临床相关方案中比较带和不带HPM的线圈的性能。还将性能与现有最先进的临床弹簧圈进行比较。我们预期在两种场强下，SNR将显著增加，SAR将显著降低。这项研究的成功完成将克服HPM实际常规使用的众多障碍，并使未来和现有MRI系统的SNR显著（约40%）增益成为可能。

 DESCRIPTION (provided by applicant): A growing number of studies show that the quality and safety of Magnetic Resonance Imaging (MRI) can be significantly improved with careful selection and arrangement of materials having a high electric permittivity, or High Permittivity Materials (HPMs) in the space around the radiofrequency (RF) coil and the human subject. With strategic use, these materials act to convert otherwise useless electric field energy in the space surrounding the RF coil and patient into useful magnetic field energy through the effects of displacement currents. These displacement currents are more distributed sources of magnetic fields than are the conductive currents in the discrete wires alone, and can be closer to the subject than the discrete wires improving the sensitivity without compromising safety. The net result is higher SNR (by about 40% in many experiments and simulations) in reception and significantly less RF energy absorbed by the subject in transmission. Given the SNR-limited nature of MRI, the multiple significant costs of going to ever-higher field strengths (including finding superconductive alternatives to NbTi), and the fact that HPMs can be used in all existing scanners for an immediate boost in SNR, pursuing this work is critical to the advancement of MRI on existing and future systems. We propose to develop thin, solid HPMs that will fit within the space that is currently occupied by the plastic coil formers in state-of-the-art clinical coils and integrate them into new coil designs. Thus, the final result will be no larger than existing clinical coils and the conducting coils will be no further from the subject. Preliminary simulation and experiments demonstrate the feasibility of this approach. Numerical simulations considering both SNR and patient heating (SAR) will guide the design of the materials both in terms of desired properties and shape. Otherwise equivalent RF head coils with and without the incorporation of HPMs will be constructed for use on 7T research and 3T clinical systems. The performance of coils with and without HPMs will be compared in a number of clinically relevant protocols at both field strengths. Performance will also be compared to existing state-of-the-art clinical coils. We expect significant gains in SNR and reduction in SAR at both field strengths. Successful completion of this research will overcome numerous obstacles to practical, routine use of HPMs and make significant (~40%) gains in SNR possible on both future and existing MRI systems.