National Chiao Tung University, Department of Electrical Engineering, Hsinchu, Taiwan.
J Biomed Opt. 2012 Jun;17(6):061210. doi: 10.1117/1.JBO.17.6.061210.
The specificity of the hemodynamic response function (HRF) is determined spatially by the vascular architecture and temporally by the evolution of hemodynamic changes. Here, we used functional photoacoustic microscopy (fPAM) to investigate single cerebral blood vessels of rats after left forepaw stimulation. In this system, we analyzed the spatiotemporal evolution of the HRFs of the total hemoglobin concentration (HbT), cerebral blood volume (CBV), and hemoglobin oxygen saturation (SO(2)). Changes in specific cerebral vessels corresponding to various electrical stimulation intensities and durations were bilaterally imaged with 36 × 65-μm(2) spatial resolution. Stimulation intensities of 1, 2, 6, and 10 mA were applied for periods of 5 or 15 s. Our results show that the relative functional changes in HbT, CBV, and SO(2) are highly dependent not only on the intensity of the stimulation, but also on its duration. Additionally, the duration of the stimulation has a strong influence on the spatiotemporal characteristics of the HRF as shorter stimuli elicit responses only in the local vasculature (smaller arterioles), whereas longer stimuli lead to greater vascular supply and drainage. This study suggests that the current fPAM system is reliable for studying relative cerebral hemodynamic changes, as well as for offering new insights into the dynamics of functional cerebral hemodynamic changes in small animals.
血流动力学反应函数（HRF）的特异性在空间上由血管结构决定，在时间上由血流动力学变化的演变决定。在这里，我们使用功能光声显微镜（fPAM）来研究大鼠左前爪刺激后的单个脑血管。在该系统中，我们分析了总血红蛋白浓度（HbT）、脑血容量（CBV）和血红蛋白氧饱和度（SO(2)）的 HRF 的时空演变。使用 36×65-μm(2)的空间分辨率对对应于各种电刺激强度和持续时间的特定脑血管的变化进行双侧成像。施加 1、2、6 和 10 mA 的刺激强度持续 5 或 15 s。我们的结果表明，HbT、CBV 和 SO(2)的相对功能变化不仅取决于刺激的强度，还取决于其持续时间。此外，刺激的持续时间对 HRF 的时空特征有很强的影响，因为较短的刺激仅在局部血管（较小的动脉）中引起反应，而较长的刺激则导致更大的血管供应和引流。这项研究表明，当前的 fPAM 系统可可靠地用于研究相对脑血流动力学变化，并为小动物功能性脑血流动力学变化的动态提供新的见解。
