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改善对于增强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，由于人体生理限制，利用强梯度和高磁场强度来提高速度和SNR面临着迫在眉睫的限制。我们提出了一种新技术，称为并行激励，是基于一个并行发射系统，该系统由多个发射线圈与相应的RF脉冲合成器和放大器，以及脉冲设计方法，体现了编排RF场时空变化的新概念，大大提高了激励和成像性能。具体计划目标包括：1）设计和构建原型MRI系统和线圈阵列，2）开发使用并行激励实现多重激励加速和翻转角均匀性改善的脉冲设计方法，以及3）开发基于并行激励的方法以减少RF功率吸收。我们将进一步开发基于2D或3D翻转角轮廓的新用途的高速成像应用，有和没有并行接收MRI。成功完成后，将建立两个功能齐全的系统（1.5T和3T），可以随时传播以进行进一步的应用开发，或在稍加修改后使用，以实现更高场强下的身体和头部成像，并有效管理SAR和翻转角问题。与此同时，将产生并传播有关并行激励的知识，这些知识将改变MRI中执行RF激励的方式，从而在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.