Parallel Excitation for High-Speed and High-Field MRI

描述（由申请人提供）：提高扫描速度和信噪比对于增强MRI的疾病检测灵敏度至关重要，特别是在心脏，血管和神经功能应用中。然而，由于人体生理条件的限制，利用强梯度和强磁场来提高速度和信噪比面临着隐现的制约。我们提出了一种新的技术，称为并行激励，它基于一个由多个发射线圈组成的并行发射系统，该系统带有相应的射频脉冲合成器和放大器，以及脉冲设计方法，该方法体现了协调射频场时空变化的新概念，从而大大提高了激励和成像性能。具体的项目目标包括：1)设计和构建原型MRI系统和线圈阵列；2)开发使用并联激励实现多重激励加速和改善翻转角均匀性的脉冲设计方法；3)开发基于并联激励的方法以减少射频功率吸收。我们将进一步开发基于2D或3D翻转角度轮廓的高速成像应用，有或没有平行接收MRI。在成功完成后，将建立两个功能完备的系统（1.5T和3T），可以很容易地推广进一步的应用开发，或使用，稍加修改，使身体和头部成像在更高的场强下，有效地管理SAR和翻转角问题。同时，关于并行激励的知识体系将产生并传播，这将改变MRI中射频激励的执行方式，在MRI系统仪器、射频脉冲设计、脉冲序列优化和诊断成像机会方面产生新的方向。

DESCRIPTION (provided by applicant): Improvements in scan speed and signal-to-noise ratio are essential for enhancing disease detection sensitivities of MRI, especially in cardiac, vascular and neurofunctional applications. Improving speed and SNR with strong gradients and high magnetic field strength however faces looming constraints due to human physiological limits. We propose new technique, called parallel excitation, is based on a parallel transmit system that is composed of multiple transmit coils with corresponding RF pulse synthesizers and amplifiers, as well as pulse design methods that embody the novel concept of orchestrating RF field spatiotemporal variations for a substantial boost in excitation and imaging performance. The specific program aims include 1) design and build prototype MRI systems and coil arrays, 2) develop pulse design methods that use parallel excitation to achieve multi-fold excitation acceleration and flip-angle uniformity improvement, and 3) develop parallel excitation-based methods for reducing RF power absorption. We will further develop high-speed imaging applications based on the novel use of 2D or 3D flip-angle profiles, with and without parallel-receive MRI. Upon successful completion, two fully functioning systems (1.5T and 3T) will have been established that can be readily disseminated for further application development, or used, with slight modification, to enable body and head imaging at still higher field strengths with SAR and flip-angle issues effectively managed. Meanwhile, a body of knowledge on parallel excitation will have been generated and disseminated that changes the way RF excitation is performed in MRI, yielding new directions in MRI system instrumentation, RF pulse design, pulse sequence optimization, and diagnostic imaging opportunities.