Gradient-Free Quantitative MRI using a Combination of B1-Selective Excitation and Fingerprinting

项目摘要 磁共振成像(MRI)是最重要的医学成像方式之一，因为它具有 能够检测和确定全身病变的特征。然而，核磁共振成像的使用受到其严重限制 昂贵的硬件、复杂的选址要求和典型的质量图像，这些都需要很高的技能 放射科医生需要解读。该项目提出了一种全新的MRI编码方法，可以实现 实质上更便宜和更多的fl可扩展的定量核磁共振扫描仪。 如今，绝大多数MRI扫描使用两种主要方法进行编码：B0梯度 以及使用接收器线圈阵列的并行成像。B0梯度占据了fi直径的很大一部分。 声音大，会引起周围神经刺激，影响病人的舒适性；它们的持续时间相对较长 由于线圈的高电感，开关时间；它们需要庞大的冷却系统和定制的AM- Plifier；它们很昂贵，相当于临床扫描仪成本的25-30%；而且它们必须小心 根据扫描仪的B0磁铁进行设计和定制。B0梯度编码还受到空间误差的影响，这是由于 伴随项，随着B0fi焊接强度的降低而增加，并将限制新兴的性能 便携和低成本的核磁共振系统。并行成像通过区分以下位置的信号来实现扫描加速 空间距离大，但不能单独对完整的图像进行编码。虽然有些人提出了第三类 在使用射频发射(B1+)梯度的编码方法中，到目前为止描述的方法都没有 由于其性能的实际限制、严格的硬件要求，已被转化为临床使用 图像对比度缺乏fl灵活性。 该项目将开发和验证基于并行的第四种根本新的MRI编码方法 使用由无线RF线圈单元产生的B1+选择性脉冲的传输，所述无线RF线圈单元具有线圈上放大器fi 射频发射和接收，以及由MR Finger启发的采集和重建过程- 打印(MRF)。这种新的方法，章动和指纹选择性编码(Senf)，完全 消除了对B0渐变的需要，并与多种磁铁设计和fl灵活交流兼容。 问答策略。与以前的B1+成像方法不同，SERF对空间变化没有严格的要求 在射频梯度fi场上，这使得fl系统设计变得灵活，并且相同的线圈可以用于空间能量计。 编码和信号接收。此外，与因复杂的自旋动力学而导致的错误相反， 通过RF编码，Senf利用这些动力学优势来区分定量组织参数。 该项目的成功完成将使新一代更便宜、更容易获得、更模块化的 和维护较低的MRI扫描仪，其量化输出可以更直接地与疾病和 组织状态。

Project Summary Magnetic Resonance Imaging (MRI) is one of the most important medical imaging modalities because of its ability to detect and characterize lesions throughout the body. However, access to MRI is severely limited by its expensive hardware, complex siting requirements and typically-qualitative images, which require highly skilled radiologists to interpret. This project proposes a fundamentally new way to encode MRI that could enable sub- stantially cheaper and more flexible quantitative MRI scanners. Today the overwhelming majority of MRI scans are encoded using two primary methods: B0 gradients and parallel imaging using an array of receiver coils. B0 gradients take up a significant fraction of the bore diam- eter; 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 am- plifiers; they are expensive, representing 25-30% of the cost of a clinical scanner; and they must be carefully designed and customized to a scanner's B0 magnet. 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. Parallel imaging enables scan acceleration by differentiating signals across large spatial distances, but cannot encode complete images on its own. While some have proposed a third class of encoding methods using radiofrequency transmit (B1+) gradients, none of the methods described to date have been translated into clinical use because of practical limits on their performance, stringent hardware requirements and lack of flexibility in image contrast. This project will develop and validate a fourth, fundamentally new way to encode MRI based on parallel transmission using B1+-selective pulses produced by wireless RF coil units with on-coil amplifiers that perform RF transmission and reception, combined with an acquisition and reconstruction process inspired by MR Finger- printing (MRF). This new method, Selective Encoding through Nutation and Fingerprinting (SENF), completely eliminates the need for B0 gradients and is compatible with a wide range of magnet designs and flexible ac- quisition strategies. Unlike previous B1+ imaging methods, SENF places no strict spatial variation requirements on the RF gradient fields, which enables flexible system design, and the same coils can be used for spatial en- coding and signal reception. Furthermore, instead of suffering from errors due to complex spin dynamics during RF encoding, SENF leverages those dynamics to its advantage to differentiate quantitative tissue parameters. Successful completion of this project will enable a new generation of cheaper, more accessible, more modular, and lower-maintenance MRI scanners with quantitative outputs that can be more directly related to disease and tissue states.