Measurement of blood flow velocity is key to understanding physiology and pathology in vivo. While most measurements are performed at the middle of the blood vessel, little research has been done on characterizing the instantaneous blood flow velocity distribution. This is mainly due to the lack of measurement technology with high spatial and temporal resolution. Here, we tackle this problem with our recently developed dual-wavelength line-scan third-harmonic generation (THG) imaging technology. Simultaneous acquisition of dual-wavelength THG line-scanning signals enables measurement of blood flow velocities at two radially symmetric positions in both venules and arterioles in mouse brain in vivo. Our results clearly show that the instantaneous blood flow velocity is not symmetric under general conditions.

基于光学多普勒效应的无创血流测量技术具有实时性、无需介质、非侵入式等性质, 在临床医疗等领域存在着极大价值与应用前景。目前光学无创血流测量技术主要有激光多普勒血流测量技术、光学相干层析多普勒成像技术和光声多普勒血流测量技术。对这3种技术进行了原理分析, 简述了其研究现状, 并对这些新型技术的未来和发展进行了展望。

激光散斑对比成像(LSCI)是一种以宽视场方式监测血流速度的非扫描光学成像技术。LSCI技术具有高时间-空间分辨率、快速实时成像、非接触式、仪器结构简单、无需造影剂等优势。本文简要介绍了LSCI的基本原理，概述了反射式LSCI和透射式LSCI两种结构，综述了LSCI在皮肤血流、大脑皮层和视网膜血流等生物医学应用中的最新研究进展，并对其发展前景做了进一步展望，为血流监测提供理论依据和实践指导。

Measurement of both oxygen saturation and blood flow in the retinal vessels has proved to give important information about the eye health and the onset of eye pathologies such as diabetic retinopathy. In this study, we present the implementation, on a commercially available fundus camera, of a retinal imager and a retina blood flow velocimeter. The retinal imager uses division of aperture to acquire nine wavelength-dependent sub-images of the retina. Careful consideration is taken to improve image transfer by measuring the optical properties of the fundus camera and modeling the optical train in Zemax. This part of the setup is calibrated with optical phantoms of known optical properties that are also used to build a lookup table (LUT) linking phantom optical properties to measured reflectance. The retina blood flow velocimeter relies on tracking clusters of erythrocytes and uses a fast acquisition camera attached to a zoom lens, with a green illumination LED-engine. Calibration is provided using a calibrated quartz capillary tube and human blood at a known flow rate. Optical properties of liquid phantoms are retrieved from measured reflectance using the LUT, and blood flow measurements in the retina are presented.