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的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 大量研究表明，增加吸入氧气分数（FiO 2>0.21）， 在基于血液的T2* 加权图像中产生正对比度增强 氧合依赖性（BOLD）效应。 最近，研究表明， (CBV)可以通过测量短时期内3 T下EPI的信号变化来精确计算 （<6 min）轻度高氧。 通常，以这种方式获取的图像具有低空间分辨率 （约4x 4x 6 mm），因为需要：（a）高对比度噪声比（CNR），因为 组织信号变化通常较小，以及（B）高时间分辨率以平均信号 T2* 加权EPI固有的波动。 超高场强（> 7 T）可以增强 该实验的CNR由于BOLD对比度随场强的非线性增加， 潜在地允许显著增加的空间分辨率。 然而，执行高- 由于多种原因，使用EPI的分辨率CBV实验在7 T下是困难的。 几何 由于空气-组织界面附近的B 0不均匀性而导致的失真和信号丢失是相当大的 7 T的问题。 甚至更重要的是，用这种方法定量CBV需要 BOLD造影剂主要是血管内的。 由于7 T下静脉血的T2*<10 ms， 需要短回波时间（TE<9 ms）和小于标准EPI的读出长度 甚至在高带宽和部分傅立叶（PF）编码下也可以产生这样的序列。 此外，由于切片轮廓，使用2D方法采集薄切片是困难的 不完美 为了解决这些问题，我们正在研究使用高分辨率 （1x 1x 2 mm）稳态采集部分傅立叶编码分段3D EPI， 7 T下基于高氧的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.