Parallel Excitation for High-Speed and High-Field MRI

描述(由申请人提供)：扫描速度和信噪比的提高对于提高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方面。然而，由于人类生理的限制，以强梯度和高磁场强度提高速度和信噪比面临着迫在眉睫的限制。我们提出了一种称为并行激励的新技术，它基于由多个发射线圈以及相应的射频脉冲合成器和放大器组成的并行发射系统以及脉冲设计方法，该脉冲设计方法体现了协调射频场时空变化的新概念，以显著提高激发和成像性能。具体的项目目标包括1)设计和建造MRI系统和线圈阵列的原型，2)开发使用并行激励来实现多倍激励加速和翻转角度均匀度的脉冲设计方法，以及3)开发基于并行激励的降低射频功率吸收的方法。我们将进一步开发基于2D或3D翻转角度轮廓的新用途的高速成像应用，包括并行接收和不并行接收MRI。在成功完成后，将建立两个功能齐全的系统(1.5T和3T)，可以很容易地传播，用于进一步的应用开发，或经过轻微修改，以实现更高场强的身体和头部成像，并有效地处理SAR和翻转角度问题。同时，将产生和传播大量关于并行激励的知识，这些知识将改变在MRI中执行RF激励的方式，在MRI系统仪器、RF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.