RADIOFREQUENCE (RF) PULSE DEVELOPMENT AND DESIGN FOR HIGH FIELD MRI

高场 MRI 射频 (RF) 脉冲开发和设计

• 批准号: 7957223
• 负责人: GERALD B MATSON
• 金额: $ 1.1万
• 依托单位: NORTHERN CALIFORNIA INSTITUTE/RES/EDU
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7957223
• 关键词: Algorithms; Computer Retrieval of Information on Scientific Projects Database; Computer software; Development; Frequencies; Funding; Grant; Graph; Image; Immunity; Institution; Length; Magnetic Resonance Imaging; Methods; Neurodegenerative Disorders; Operative Surgical Procedures; Phase; Physiologic pulse; Positioning Attribute; Predisposition; Research; Research Personnel; Resources; Simulate; Slice; Source; System; Tissues; United States National Institutes of Health; Weight; base; design; improved; research study; simulation; software development; voltage

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Overview: The promise of improved MRI results at high field strength is compromised by the difficulties encountered at high field, including: i) Non-uniform excitation, due to the non-uniform B1 field inherent at high field. Typically, the non-uniform excitation produces non-uniform tissue contrast, although other deleterious effects can be produced as well. ii) Large susceptibility gradients, which can distort slice positions unless large slice-select gradients are used. However, the limited RF power available on high field systems severely limits the gradient strength that can be used for T2-weighted images. The specific aims propose the further development and refinement of two new RF pulse designs to ameliorate these deleterious effects. In addition, further development of software for simulating MRI experiments is proposed to aid in effective implementation of these new RF pulses into suitably re-designed MRI experiments. Specific aim 1: Pulses with immunity to B1 inhomogeneity. The new B1-insensitive design is based on optimized concatenations of rectangular pulses applied along different axes in the rotating frame, where the optimization is for both uniform tip and immunity to resonance offset. The design focuses on excitation pulses, but includes extension of the method to spin echo and inversion pulses. Specific aim 2: Lowered peak voltage spin echo frequency-selective pulses. The new, lowered peak voltage design method consists of concatenation of conventional, frequency-selective pulses with gradients of alternating sign. The design includes spoiler gradients incorporated into the spin echo pulse to shorten the overall length of the pulse. Operation of these pulses in inhomogeneous B1 fields is also considered. Specific aim 3: Further development of MRI simulation software with inclusion of "inadvertent" magnetization transfer (MT) effects. The further development builds on software already developed for MP RAGE MRI experiments, and will include extended phase graph (EPG) algorithms to cover a wide range of MRI experiments. These simulations will aid in effective implementation of the new RF pulses, and avoid deleterious MT effects. A further use of these simulations is expected to be in the optimization of MRI sequences for 4.0 Tesla.

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 概述：高场在高场遇到的困难，包括：i）非均匀激发，这是由于高场固有的非均匀B1场而遭受的，包括：i）不均匀的激发。 通常，尽管也可以产生其他有害作用，但不均匀的激发会产生非均匀的组织对比。 ii）较大的敏感性梯度，除非使用大切片选择梯度，否则会扭曲切片位置。 但是，高场系统上可用的有限的RF功率严重限制了可用于T2加权图像的梯度强度。该特定目的提出了两种新的RF脉冲设计的进一步开发和完善，以改善这些有害效果。 此外，提出了进一步开发用于模拟MRI实验的软件，以有助于有效实施这些新的RF脉冲，以适当重新设计的MRI实验。 特定目标1：对B1不均匀性免疫的脉冲。 新的B1不敏感设计基于沿旋转框架中不同轴施加的矩形脉冲的优化串联，其中优化是针对均匀的尖端和免疫力以抵消均匀的。 该设计的重点是激发脉冲，但包括旋转回声和反转脉冲方法的扩展。 特定目标2：降低峰值电压自旋频率选择性脉冲。 新的，降低的峰值电压设计方法包括传统的频率选择脉冲与交替符号梯度的串联。该设计包括将扰流板梯度纳入自旋回波脉冲中，以缩短脉冲的整体长度。 还考虑了这些脉冲在不均匀B1场中的操作。 特定目标3：进一步开发MRI模拟软件，其中包括“无意”磁化转移（MT）效应。 进一步的开发基于已经为MP RAGE MRI实验开发的软件，并将包括扩展相位图（EPG）算法以涵盖广泛的MRI实验。 这些模拟将有助于有效实施新的RF脉冲，并避免有害的MT效应。 这些模拟的进一步使用预计将在4.0特斯拉的MRI序列优化中。