Investigation of the cerebral hemodynamic response function in single blood vessels by functional photoacoustic microscopy.
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.
National Chiao Tung University, Department of Electrical Engineering, Hsinchu, Taiwan.
Lun-De
LD
Liao
Chin-Teng
CT
Lin
Yen-Yu I
YY
Shih
Hsin-Yi
HY
Lai
Wan-Ting
WT
Zhao
Timothy Q
TQ
Duong
Jyh-Yeong
JY
Chang
You-Yin
YY
Chen
Meng-Lin
ML
Li
D000818:Animals; D001808:Blood Vessels / Q000473:pathology*; D001921:Brain / Q000473:pathology* / Q000502:physiology; D002560:Cerebrovascular Circulation; D006439:Hemodynamics / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007834:Lasers; D008297:Male; D033401:Microscopy, Acoustic / Q000379:methods*; D018613:Microscopy, Confocal / Q000379:methods; D015233:Models, Statistical; D010100:Oxygen / Q000378:metabolism; D061088:Photoacoustic Techniques / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D059629:Signal-To-Noise Ratio; D013997:Time Factors
D006454:Hemoglobins; D010100:Oxygen