MAGNETIC RESONANCE IMAGING OF SLOW FLUID FLOW

描述：(改编自申请表)申请人的长期 目标是开发和表征磁共振成像(MRI) 这些技术将对组织血流进行成像，并最终提供 对它的定量测量。目前的目标是继续 稳态自由进动(SSFP)磁共振成像方法的发展首先，一个 方法将在理论上开发，然后编程为 分光计。然后对其流量灵敏度进行测量。这些技术 待开发和表征的是1)丢失脉冲SSFP(MP-SSFP)，2)a MP-SSFP的三维(3D)傅立叶版本，其中速度是 3)移动参考系(MRF)技术。第一 已开发的MP-SSFP方法及其慢流(mm/S) 在流动模型中表现出敏感度。智能交通系统的质变 已经观察到信号强度作为灌注率的函数在 离体兔肾脏灌流。然而，来自的大背景信号 这种方法中的静态组织对来自流动的信号进行量化 血腥难忍。3D MP-SSFP技术将提供一种定量的 图像的每个体素的速度谱，从而分离出 信号的静态分量，同时提供 流量的定量测量。磁流变液技术将被用于 用非零均值测量速度分布。这项技术 测量的信号仅来自移动速度接近于 磁流变液。的速度分布的平均值和宽度 磁流变液是敏感的，可以调整。流量敏感度将为 以使用逐渐增加的复杂性的流动幻影为特征的。 然后，将在隔离的灌流兔身上评估MRI技术 肾脏。体外肾脏具有真实的生物流动，但其 灌流可以很容易地控制。然后将对核磁共振技术进行测试 在三个活体模型中：a)兔肾，b)兔肌肉，既快又快 在各种电刺激下的缓慢抽动，以及c)兔脑 在这种情况下，光化学诱导的皮质灌注缺陷 由毛细管端阻塞形成。灌注量的标准测量(按 微球和/或Rb)在肾脏、脑和骨骼区域 兔子模型中的肌肉将与MRI获得的肌肉进行比较。 核磁共振方法的最后测试将确定 离体灌流兔肾内血流对观察到的MRI有贡献 信号。这将通过药理学和机械学来完成 操纵。

DESCRIPTION: (Adapted from the application) The applicant's long term objectives are to develop and characterize Magnetic Resonance Imaging (MRI) techniques that will image tissue perfusion, and ultimately, provide a quantitative measure of it. The immediate aim is to continue the development of Steady State Free Precession (SSFP) MRI methods. First, a method will be theoretically developed and then programmed into a spectrometer. Then its flow sensitivity will be measured. The techniques to be developed and characterized are 1) Missing Pulse SSFP (MP-SSFP), 2) a three dimensional (3D) Fourier version of MP-SSFP where velocity is the third dimension and 3) a moving reference frame (MRF) technique. The first method, MP-SSFP, has already been developed and its slow flow (mm/s) sensitivity demonstrated in flow phantoms. Qualitative changes in its signal intensity have been observed as a function of perfusion rate in the isolated perfused rabbit kidney. However, the large background signal from static tissue in this method makes quantitation of the signal from flowing blood difficult. The 3D MP-SSFP technique will provide a quantitative velocity spectrum for each voxel of the image, thus separating out the static component of the signal and at the same time providing a quantitative measure of the flow. The MRF technique will be used to measure velocity distributions with a non-zero mean. The technique measures signal only from material moving with a speed near that of the MRF. Both the mean and width of the distribution of speeds to which the MRF is sensitive can be adjusted. The flow sensitivity will be characterized by using flow phantoms of gradually increasing complexity. Then the MRI techniques will be evaluated in isolated perfused rabbit kidneys. The in-vitro kidney has realistic biological flow, but its perfusion can be readily controlled. The MRI technique will then be tested in three in-vivo models: a) rabbit kidney, b) rabbit muscle, both fast and slow twitch under a variety of electrical stimulations, and c) rabbit brain in which a photochemically induced cortical perfusion defect has been created by end-capillary block. Standard measurements of the perfusion (by microspheres and/or rubidium) in regions of the kidney, brain and skeletal muscle in the rabbit models will be compared with those obtained with MRI. The last tests of a MRI method will be to determine which components of the flow in the isolated perfused rabbit kidney contribute to the observed MRI signal. This will be accomplished by pharmacological and mechanical manipulation.