In vivo functional human imaging using photoacoustic microscopy: response to ischemic and thermal stimuli
We report results of two in vivo functional human imaging experiments using photoacoustic microscopy. In Experiment 1, the hemodynamic response to an ischemic event was measured. The palm of a volunteer was imaged and a single cross-section was monitored while periodic arterial occlusions were administered using a blood pressure cuff wrapped around the upper arm and inflated to ~280 mmHg. Significant relative decreases in oxygen saturation (sO_2) and total hemoglobin (HbT) were observed during periods of ischemia. Upon release of the occlusion, significant relative increases in sO_2 and HbT due to post-occlusive reactive hyperemia were recorded. Experiment 2 explored the vascular response to a local, external thermal stimulus. Thermal hyperemia is a common physiological phenomenon and thermoregulation function in which blood flow to the skin is increased to more efficiently exchange heat with the ambient environment. The forearm of a volunteer was imaged and a single cross-section was monitored while the imaged surface was exposed to an elevated temperature of ~46°C. Due to thermal hyperemia, relative increases in sO_2 and HbT were measured as the temperature of the surface was raised. These results may contribute as clinically relevant measures of vascular functioning for detection and assessment of vascular related diseases.
Additional Information© 2010 Society of Photo-Optical Instrumentation Engineers (SPIE). This research was supported by National Institutes of Health grants R01 EB000712, 5 T32 AR07284, R01 EB008085, R01 CA113453901, and U54 CA136398. LW acknowledges financial interest in Endra Inc., which, however, did not support this research.
Published - 75640Z.pdf