Technology for Portable MRI

描述（由申请人提供）：磁共振成像（MRI）自30多年前问世以来，一直是检测和诊断神经系统疾病和损伤的无可争议的护理标准。然而，MRI扫描仪的成本、重量、尺寸和维护需求通常阻碍了它们在一些可能需求最大的地方的使用，包括急诊科、神经重症监护病房（icu）、手术室、运动场、战场、农村医疗站点和救护车。事实上，目前还没有真正便携式的“即时”核磁共振成像系统，尽管有几个研究小组试图将核磁共振成像扫描仪组件小型化和简化。需要一种新的方法来制造这样一种真正便携式的、负担得起的脑部扫描仪，这里称之为“便携式脑部扫描仪”（PBS）。然而，使传统扫描仪便携的问题不仅在于需要一个大而高度均匀的磁场（需要使用多吨磁铁和低温设备），而且还在于可切换梯度编码场的重量和功耗要求（额外的重量和高达2兆瓦的峰值功率）。在这项工作中，我们完善了我们的概念验证原型PBS，并在试点临床测试中，验证了它是一种低成本的，可以放置在几乎任何地方的即时护理MRI扫描仪。我们采用一种方法，使磁体的磁场均匀性要求放宽约1000倍。这使得一个轻量级的，永磁体设计，没有冷冻或电力消耗。我们的大脑磁铁原型只有45公斤重。与传统成像梯度相比，我们通过旋转头部周围的非均匀磁场，利用磁体的场不均匀性，以广义的方式对信号进行空间调制，从而实现图像编码，并消除了重的、消耗功率的梯度线圈。其中，以主磁体的场不均匀性作为编码场，将图像重构为迭代逆问题。这种设计“一石二鸟”，因为它既简化了磁铁，又消除了梯度线圈

DESCRIPTION (provided by applicant): Magnetic Resonance Imaging (MRI) has been the undisputed standard of care for the detection and diagnosis of neurological disorders and injuries since its inception over 3 decades ago. The cost, weight, size, and maintenance needs of MRI scanners, however, typically precludes their use in some locations with perhaps the greatest need - including Emergency Departments, Neurological Intensive Care Units (ICUs), surgical suites, sports fields, battlefields, rural healthcare sites, and ambulances. Indeed, no truly portable, "point-of-care" MRI system currently exists, despite attempts by several groups to miniaturize and simplify MRI scanner components. A new approach is needed to create such a truly portable, affordable brain scanner, referred to here as the "Portable Brain Scanner" (PBS). The problem, however, with rendering conventional scanners portable is not only the requirement for a large, highly homogeneous magnetic field (necessitating the use of multi ton magnets and cryogenic apparatus), but also, the weight and power consumption requirements of switchable gradient encoding fields (an additional ton of weight and up to 2 MW of peak power). In this work, we refine our proof-of-concept prototype PBS and, in pilot clinical testing, validate it as a low cost, point-of-care MRI scanner that can be sited almost anywhere. We employ an approach whereby the magnet's field homogeneity requirements are relaxed approximately 1000 fold. This allows a lightweight, permanent magnet design with no cryogens or power consumption. Our prototype brain magnet weighs just 45kg. We achieve image encoding and eliminate the heavy, power consuming gradient coil, by rotating this inhomogeneous field around the head using the magnet's field inhomogeneity to spatially modulate the signal in a generalized fashion compared to what is done with conventional imaging gradients. Specifically, the field inhomogeneities of the main magnet serve as the encoding field, and the image is reconstructed as an iterative inverse problem. This design "kills two birds with one stone", in that it both simplifies the magnet and eliminates the gradient coil - resulting in a truly "point-of-care" brain MRI scanner. We further refine this design by adding truly parallel reception, to improve spatial encoding, as well as by adding TRASE encoding for the third dimension. Preliminary clinical evaluation of this prototype will be performed on a cohort of patients with mild-to-moderate hemorrhagic brain injury in the Emergency Department, and in stable peri-operative patients with structural lesions in the Neurological Intensive Care Unit.