Diagnostic Imaging of Cerebral Blood Flow with MRI

脑血流成像（CBF）是一种诊断评估痴呆、中风和癫痫患者的有力技术。 一种称为动脉自旋标记MRI的技术已经证明了在没有放射性或注射的情况下提供高质量CBF图像的能力。 然而，由于患者运动的破坏性影响，用于对抗这些运动影响的快速回波平面成像技术的图像质量差，以及无法在合理的检查周期内从整个大脑获取图像，这种技术的进步受到限制。 申请人提出通过改进新颖的背景抑制方法来克服这些限制。多个反转脉冲将用于在图像采集之前降低不感兴趣的信号的强度。 这种方法可以将运动相关误差减少100倍，同时保留CBF信号。 由于运动相关误差的显著减少，可以采用上级3D快速自旋回波成像方法，以在6分钟内提供来自全脑的CBF图像，其灵敏度是早期方法的两倍。 我们建议通过以下方式实现这种方法的潜力：1。优化用于背景抑制的RF脉冲的设计，以最大限度地减少CBF信号损失和大脑顶部和底部附近的系统误差。 2.使用非线性最小化策略来优化反转的定时，以便实现理想的背景抑制3.开发一种用于脑组织T1定量的策略，该策略将与3D快速自旋回波序列兼容，并且对脑脊液（CSF）的存在不敏感。CBF测量需要TI测量，但可能被体素中的少量CSF污染。 4.测量背景抑制序列的效率。效率将作为标记平面位置的函数进行测量，以指导后续应用的参数选择。 5.在正常对照和痴呆患者中测量优化的CBF成像方法的重测信度，并将其与未抑制的方法进行比较。 这些信息是设计和解释诊断测试，药物评价和其他研究采用CBF MRI所需要的。这些发展将使动脉自旋标记的可靠CBF成像成为诊断成像的广泛适用技术。

Imaging of Cerebral Blood Flow (CBF) is a powerful technique for the diagnostic evaluation of patients with dementia, stroke and epilepsy. A technique known as Arterial Spin Labeling MRI has demonstrated the ability to provide high quality images of CBF without radioactivity or injection. The advancement of this technique has been limited, however, by the destructive effects of patient motion, the poor image quality of the fast, echoplanar imaging technique used to combat these motion effects, and the inability to acquire images from the entire brain in a reasonable exam period. The applicants propose to overcome these limitations by refining a novel background suppression approach. Multiple inversion pulses will be used to reduce the intensity of uninteresting signals prior to image acquisition. This approach can reduce motion-related errors by a factor of 100 while preserving the CBF signal. Because of the dramatic reduction in motion-related errors, a superior, 3D fast spin echo imaging approach can be employed to provide CBF images from the whole brain in under 6 minutes with twice the sensitivity of earlier approaches. We propose to realize this potential of this approach by: 1. Optimizing the design of the RF pulses used for background suppression to minimize CBF signal loss and systematic errors near the top and bottom of the brain. 2. Using a nonlinear minimization strategy to optimize the timing of the inversions so as to achieve ideal background suppression 3. Developing a strategy for T1 quantification of brain tissue that will be compatible with the 3D fast spin echo sequence and which will be insensitive to the presence of cerebrospinal fluid(CSF). TI measurement is required for CBF measurement but can be contaminated by small amounts of CSF in the voxel. 4. Measuring the efficiency of the background suppressed sequences. Efficiency will be measured as a function of labeling plane location to guide the choice of parameters for subsequent applications. 5. Measuring the test-retest reliability of the optimized CBF imaging method in normal controls and patients with dementia and comparing it to unsuppressed methods. This information is needed for the design and interpretation of diagnostic tests, pharmaceutical evaluations and other studies employing CBF MRI. These developments will make reliable CBF imaging by Arterial Spin Labeling a widely applicable technique for diagnostic imaging.