RF Encoding for Gradient-Free MRI

用于无梯度 MRI 的射频编码

基本信息

批准号：
10380178
负责人：
William A Grissom
金额：
$ 36.01万
依托单位：
VANDERBILT UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-15 至 2023-01-01
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10380178
关键词：
3-Dimensional Address Algorithms Amplifiers Brain imaging Clinical Custom Data Development Dimensions Frequencies Generations Goals Heating Human Image Individual Intuition Length Location Loudness MRI Scans Magnetic Resonance Imaging Magnetism Methods Noise Patients Performance Peripheral Nerve Stimulation Peripheral Nerves Phase Physiologic pulse Plant Roots Process Protocols documentation Rotation Safety Scanning Signal Transduction Slice System Techniques Technology Three-Dimensional Imaging Time Tissues Translating Translations Work base commercialization compliance behavior contrast imaging cost human imaging image reconstruction imaging modality imaging system improved in vivo in vivo imaging innovation magnetic field neuroimaging portability pre-clinical radio frequency success transmission process

3-Dimensional Address Algorithms Amplifiers Brain imaging Clinical Custom Data Development Dimensions Frequencies Generations Goals Heating Human Image Individual Intuition Length Location Loudness MRI Scans Magnetic Resonance Imaging Magnetism Methods Noise Patients Performance Peripheral Nerve Stimulation Peripheral Nerves Phase Physiologic pulse Plant Roots Process Protocols documentation Rotation Safety Scanning Signal Transduction Slice System Techniques Technology Three-Dimensional Imaging Time Tissues Translating Translations Work base commercialization compliance behavior contrast imaging cost human imaging image reconstruction imaging modality imaging system improved in vivo in vivo imaging innovation magnetic field neuroimaging portability pre-clinical radio frequency success transmission process

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项目摘要

Project Summary The goal of this project is to translate RF encoding methods developed in an R21 project to human imaging, by implementing them on a very low ﬁeld human MRI scanner. Its successful completion will enable silent, low-cost and more portable MRI systems, leading to a substantial reduction in the cost of imaging and improved patient compliance and comfort. In conventional MRI, a received signal is localized to its spatial location of origin based on its temporal frequency, which is controlled using magnetic ﬁelds that are parallel to the main (B0) ﬁeld of the scanner and vary linearly across space. There are many problems with these B0 gradient ﬁelds: they are loud and induce peripheral nerve stimulation, compromising patient comfort; they have relatively long switching times due to the high inductance of the coils; they require bulky cooling systems and customized ampliﬁers; and they are expen- sive, representing 25-30% of the cost of a clinical scanner. B0 gradient encoding also suffers from spatial errors due to concomitant terms, which increase with decreasing B0 ﬁeld strength and will limit the performance of emerging portable and low-cost MRI systems. A potential solution to these problems is to replace B0 gradients with RF gradients, which are silent and low-cost. Unfortunately, in spite of its potential RF gradient encoding has not yet become a clinical or commercial success. This is largely due to the fact that no existing RF gradient encoding method offers the orthogonality between contrast development and spatial encoding that is enjoyed by B0 gradients, or a straightforward path to convert existing B0 gradient-based MRI scans to use RF encoding. The methods developed in this project are the ﬁrst to meet these requirements, and will thus be the ﬁrst truly viable RF gradient-based imaging methods. The central innovation of this project is to use the Bloch-Siegert (BS) shift to spatially encode the MRI signal. As with B0 gradients, this encoding mechanism is based on the application of phase shifts to magnetization directly in the transverse plane, and therefore does not modulate the magnitude of the transverse magnetization, leaving image contrast unaffected by spatial encoding. The ﬁrst Aim of the project is to develop array and solenoid RF gradient coils and associated RF hardware to enable 2D and 3D Cartesian brain imaging on a human 0.0475 Tesla MRI scanner, including strategies for simultaneous RF transmission and reception to enable frequency encoding by BS shift. The second Aim is to develop and implement RF-encoded pulse sequences for brain imaging based on the BS shift, leveraging key developments from the R21 phase of the project including swept RF pulses for phase encoding, a theoretical basis and pulse sequence for BS frequency encoding, and RF pulses for RF gradient-based slice-selective excitation and slice-encoding. The third Aim is to develop image reconstructions and evaluate the encoding methods in human brain imaging. Successful completion of these Aims will establish the ﬁrst viable fully RF-encoded human imaging system and pave the way for commercialization and clinical use.

项目摘要该项目的目的是将RF在R21项目中开发的RF编码方法转换为人类成像，通过在非常低的人类MRI扫描仪上实施它们。它的成功完成将使沉默，低成本以及更多的便携式MRI系统，导致成像成本和改善患者的成本大大降低合规性和舒适性。在常规MRI中，基于其临时性频率，使用平行于扫描仪的主（B0）字段的磁场控制。跨空间线性变化。这些B0梯度领域有很多问题：它们响亮而影响力周围神经刺激，损害患者的舒适感；由于他们的切换时间相对较长线圈的高电感；他们需要笨重的冷却系统和定制的放大器；他们是eppen- Sive，占临床扫描仪成本的25-30％。 B0梯度编码还遭受空间错误由于术语的术语，随着B0场强度的降低而增加，将限制新兴便携式和低成本MRI系统。解决这些问题的潜在解决方案是替换B0梯度带有RF梯度，它们是无声且低成本的。不幸的是，尽管有潜在的RF梯度编码尚未成为临床或商业上的成功。这主要是由于没有现有的RF梯度编码方法提供了对比度开发与空间编码之间的正交性 B0梯度，或将现有的基于B0梯度的MRI扫描转换为使用RF编码的直接路径。这该项目中开发的方法是满足这些要求的第一个，因此将是第一个真正可行的基于RF梯度的成像方法。该项目的中心创新是使用Bloch-Siegert（BS）移动进行空间编码MRI 信号。与B0梯度一样，这种编码机制基于相移的应用到磁化直接在横向平面中，因此不会调节横向磁化的大小，留下不受空间编码影响的图像对比度。该项目的第一个目的是开发阵列和螺线管 RF梯度线圈和相关的RF硬件，以启用2D和3D笛卡尔大脑成像在人体上0.0475 特斯拉MRI扫描仪，包括简单RF传输和接收的策略以实现频率通过BS Shift编码。第二个目的是为大脑开发和实施RF编码的脉冲序列基于BS偏移的成像，利用项目的R21阶段的关键发展，包括RF 相位编码的脉冲，BS频率编码的理论基础和脉冲序列以及RF脉冲的脉冲基于RF梯度的切片选择性兴奋和切片编码。第三个目的是开发图像重建并评估人脑成像中的编码方法。这些目标的成功完成将建立第一个可行的完全由RF编码的人类成像系统为商业化和临床使用铺平了道路。