Simultaneous MRI Acquisition of Blood Volume, Blood Flow

同时采集反映大脑活动不同方面的互补功能血流动力学指标将是功能性脑成像研究的一个有价值的工具，可提供增强的检测能力和改进的数据解释。因此，提出了一种新的MRI技术，该技术能够主要基于与脑激活相关的脑血容量、血流量和血氧的变化来实现三种血液动力学图像的同时采集。具体而言，反转恢复脉冲序列已被设计成在单次扫描中测量VASO（血管空间占用）、ASL（动脉自旋标记）灌注和BOLD（血氧水平依赖性）信号。分析了该序列的MR信号特征，并优化了图像参数，以便同时采集这些功能图像。新技术的可行性和有效性进行了评估，脑激活实验与视觉刺激范式。对健康志愿者的实验表明，与单独收集这些功能图像的传统技术相比，该技术提供了有效的图像采集，从而提高了每单位时间的对比度噪声比（CNR）。此外，它被证明，所提出的技术是能够被利用在事件相关的功能磁共振成像实验，具有潜在的优势，获得准确的瞬态信息的激活诱导的血流动力学反应。

Simultaneous acquisition of complementary functional hemodynamic indices reflecting different aspects of brain activity would be a valuable tool for functional brain imaging studies offering enhanced detection power and improved data interpretation. As such, a new MRI technique is presented that is able to achieve concurrent acquisition of three hemodynamic images based primarily on the changes of cerebral blood volume, blood flow and blood oxygenation, respectively, associated with brain activation. Specifically, an inversion recovery pulse sequence has been designed to measure VASO (vascular space occupancy), ASL (arterial spin labeling) perfusion, and BOLD (blood-oxygenation level dependent) signals in a single scan. The MR signal characteristics in this sequence were analyzed, and image parameters were optimized for the simultaneous acquisition of these functional images. The feasibility and efficacy of the new technique were assessed by brain activation experiments with visual stimulation paradigms. Experiments on healthy volunteers showed that this technique provided efficient image acquisition and thus higher contrast-to-noise ratio (CNR) per unit time, compared with conventional techniques collecting these functional images separately. In addition, it was demonstrated that the proposed technique was able to be utilized in event-related functional MRI experiments, with potential advantages of obtaining accurate transient information of the activation-induced hemodynamic responses.