NOVEL APPROACHES TO LOW-COST MRI
NOVEL APPROACHES TO LOW-COST MRI
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DOI：
10.1002/mrm.1910300211
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发表时间：
1993-08-01
影响因子：
3.3
通讯作者：
CONOLLY, S
中科院分区：
文献类型：
--
作者：
MACOVSKI, A;CONOLLY, S
本文提出了一种结合的投机性的方法，一些与早期的工作和一些显然是新颖的，这显示出很大的希望，在提供一类新的MRI机器，将大大降低成本。与现有的MRI相比，这类MRI将具有优点和缺点，而且成本低。缺点包括明显不能执行经典光谱学，以及在选择性激发领域的灵活性有限。其优点包括对不均匀性和敏感性问题的基本免疫力，能够创建为特定解剖相关应用而设计的广泛类别的机器，能够设计开放式机器以供医生访问，以及改进的高速成像能力。通用的所有提出的方法是一个脉冲偏振场和振荡读出偏置场。脉冲场最初使磁矩极化。由于它在读出操作期间不开启，因此其具有可忽略的均匀性要求，因为场幅度的变化将仅仅遮蔽图像强度。在读出期间，使用相对低的磁场。为了能够使用相对不均匀的电磁场，使用具有零平均值的振荡场。这防止了由于与不均匀性相关联的频率误差而导致的相位误差的任何长期积累。因此，平均偏置频率将仅由偏置场的频率而不是幅度来确定。三种方法进行了描述，都包括上述功能。前两个涉及在实验室框架中成像，而第三个涉及在旋转框架中成像。第二种方法不需要RF激励，第三种方法使用RF激励和梯度信号。描述了切片选择的一些方法。
This paper presents a combination of speculative approaches, some related to earlier work and some apparently novel, which show great promise in providing a new class of MRI machines that would be considerably less expensive. This class would have advantages and disadvantages as compared to existing MRI, over and above that of low cost. The disadvantages include the apparent inability to perform classic spectroscopy, and limited flexibility in the area of selective excitation. The advantages include a fundamental immunity to inhomogeneity and susceptibility problems, the ability to create a wide class of machines that are designed for specific anatomy related applications, the ability to design open machines for physician access, and improved capability for high speed imaging. Generic to all of the methods presented are a pulsed polarizing field and an oscillatory read-out bias field. The pulsed field initially polarizes the magnetic moments. Since it is not on during the readout operation it has negligible homogeneity requirements since changes in the field amplitude will merely shade the image intensity. During readout a relatively low blas field is used. To enable the use of a relatively inhomogeneous blas field, an oscillatory field is used that has a zero average value. This prevents any long-term buildup of phase errors due to a frequency error associated with inhomogeneity. Thus the average bias frequency will be determined solely by the frequency rather than the amplitude of the bias field. Three methods are described, all including the above features. The first two involve imaging in the laboratory frame, while the third involves imaging in the rotating frame. The second approach requires no RF excitation and the third approach uses RF blas and gradient signals. Some approaches to slice selection are described.