CEREBRAL BLOOD VOLUME MAPPING IN HUMANS AT 7T WITH HYPEROXIC CONTRAST

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 增加氧气的吸入部分(FIO2和GT；0.21)已经在许多研究中表明 基于血液在T2*加权图像中产生正对比度增强 氧合依赖(BOLD)效应。最近，有研究表明，脑血容量 (CBV)可以通过测量短历元期间3T时EPI中的信号变化来准确计算 (&lt；6分钟)轻度高氧。通常，以这种方式获取的图像的空间分辨率较低 (约4x4x6 mm)，因为需要：(A)高对比度噪声比(CNR)，因为 组织信号变化通常很小，并且(B)高时间分辨率以平均信号 T2*加权EPI的固有波动。超高场强(&gt；7T)可以增强 本实验的CNR是由于与场强相反的非线性增加所致， 潜在地允许显著提高空间分辨率。然而，表现出高- 在7T时，使用EPI进行分辨率CBV实验是困难的，原因有很多。几何学 空气-组织界面附近由于B0不均匀造成的失真和信号丢失非常严重 7T的问题。更重要的是，用这种方法量化CBV需要 大胆的对比主要是血管内的。由于7T时的静脉血有10毫秒的T2*； 需要小于标准EPI的短回声时间(TE&lt；9 ms)和读出长度 即使在高带宽和部分傅里叶(PF)编码的情况下，也可以产生序列。 此外，由于切片轮廓的原因，使用2D方法获取薄片是困难的 不完美。为了解决这些问题，我们正在调查使用高分辨率 (1x1x2 Mm)稳态采集部分傅里叶编码分段3D EPI 7T时基于高氧的CBV图。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Increasing the inspired fraction of oxygen (FiO2>0.21) has been shown in numerous studies to produce positive contrast enhancement in T2*-weighted images based on the blood oxygenation-dependent (BOLD) effect. Recently, it has been shown that cerebral blood volume (CBV) can be accurately calculated by measuring signal changes in EPI at 3T during short epochs (<6min) of mild hyperoxia. Typically, images acquired in this fashion have low spatial resolution (approximately 4x4x6mm) because of the need for: (a) high contrast-to-noise ratio (CNR), since tissue signal changes are typically small, and (b) high temporal resolution to average the signal fluctuations inherent to heavily T2*-weighted EPI. Ultra-high field strengths (>7T) can enhance the CNR of this experiment due to the nonlinear increase in BOLD contrast with field strength, potentially allowing for significantly increased spatial resolution. However, performing a high- resolution CBV experiment using EPI is difficult at 7T for a number of reasons. Geometric distortions and signal dropout due to B0 inhomogeneity near air-tissue interfaces are substantial problems at 7T. Even more significantly, quantifying CBV with this method requires that the BOLD contrast be primarily intravascular. Since venous blood at 7T has a T2*<10ms, a short echo time (TE<9 ms) and readout length are required that are less than standard EPI sequences can produce even at high bandwidth and with partial-Fourier (PF) encoding. Furthermore, acquiring thin slices using a 2D approach is difficult to do due to slice profile imperfections. To address these problems, we are investigating the use of high resolution (1x1x2mm) steady-state acquisition partial-Fourier encoded segmented 3D EPI for hyperoxia-based CBV maps at 7T.