Wavelength agile photoacoustic microscopy for video-rate functional imaging

[133153]脉冲光声显微镜技术是一种很有前途的技术，它依赖于脉冲光激发和超声检测。精细的组织微血管的活体图像，包括单个毛细血管，已经获得了良好的对比度基于光学吸收而不是反射。生理变化可以改变光吸收的波长依赖性，使功能性PAM （fPAM）在多波长的光激发下成为可能。fPAM在肿瘤微血管的氧合研究和小动物模型的脑活动监测方面受到了相当大的关注。fPAM的一个主要限制是成像速度。虽然单波长图像可以快速获取，但多波长图像的获取时间过长。因此，传统的fPAM不能产生快速动态事件的功能图像（例如，胚胎心脏发育中的血氧）。传统脉冲激光器的波长调谐缓慢，使得无法获得视频速率的fPAM图像。有希望的初步研究表明，基于受激拉曼散射的多色光源可以实现高速fPAM。这个提议的基本假设是波长敏捷性可以彻底改变fPAM的能力。pi建议开发这种紧凑的光源，在不到1毫秒的时间内切换波长，这代表了传统激光器切换速度的1000倍提高。这种波长敏捷源为实现视频速率fPAM提供了必要的突破。他们进一步建议将我们的高速fPAM系统与他们现有的光学相干层析成像（OCT）系统结合起来。该组合系统将以视频帧率提供微血管和周围组织的高分辨率结构和功能图像。

1133153BumaPhotoacoustic microscopy (PAM) is a promising technique that relies on pulsed optical excitation and ultrasonic detection. Exquisite in vivo images of tissue microvasculature, including individual capillaries, have been obtained with excellent contrast based on optical absorption rather than reflectance. Physiological changes can alter the wavelength dependence of optical absorption, making functional PAM (fPAM) possible with optical excitation at multiple wavelengths. fPAM has received considerable interest for oxygenation studies of tumor microvasculature and monitoring brain activity in small animal models. A major limitation of fPAM is imaging speed. Although single-wavelength images can be acquired quickly, multi-wavelength images require excessively long acquisition times. Therefore, conventional fPAM cannot produce functional images of fast dynamical events (e.g. blood oxygenation in a developing embryonic heart). The slow wavelength tuning of conventional pulsed lasers makes it impossible to obtain video-rate fPAM images. Promising preliminary studies suggest that high speed fPAM is possible with a multicolor optical source based on stimulated Raman scattering. The fundamental hypothesis of this proposal is that wavelength agility can revolutionize the capabilities of fPAM. The PIs propose to develop this compact source to switch wavelengths in less than 1 millisecond, representing a 1000-fold improvement in switching speed over conventional lasers. This wavelength agile source provides the breakthrough necessary to realize video-rate fPAM. They further propose to combine our high speed fPAM system with their existing optical coherence tomography (OCT) system. This combined system will provide high resolution structural and functional images of both microvasculature and surrounding tissue at video frame rates.