Particle velocity measurements with macroscopic fluorescence imaging in lymph tissue mimicking microfluidic phantoms

Ultrasound poroelastography can quantify structural and mechanical properties of tissues such as stiffness, compressibility, and fluid flow rate. This novel ultrasound technique is being explored to detect tissue changes associated with lymphatic disease. We have constructed a macroscopic fluorescence imaging system to validate ultrasonic fluid flow measurements and to provide high resolution imaging of microfluidic phantoms. The optical imaging system is composed of a white light source, excitation and emission filters, and a camera with a zoom lens. The field of view can be adjusted from 100 mm x 75 mm to 10 mm x 7.5 mm. The microfluidic device is made of polydimethylsiloxane (PDMS) and has 9 channels, each 40 μm deep with widths ranging from 30 μm to 200 μm. A syringe pump was used to propel water containing 15 μm diameter fluorescent microspheres through the microchannels, with flow rates ranging from 0.5 μl/min to 10 μl/min. Video was captured at a rate of 25 frames/sec. The velocity of the microspheres in the microchannels was calculated using an algorithm that tracked the movement of the fluorescent microspheres. The imaging system was able to measure particle velocities ranging from 0.2 mm/sec to 10 mm/sec. The range of flow velocities of interest in lymph vessels is between 1 mm/sec to 10 mm/sec; therefore our imaging system is sufficient to measure particle velocity in phantoms modeling lymphatic flow.

超声孔隙弹性成像能够量化组织的结构和力学特性，例如硬度、可压缩性和流体流速。这种新型超声技术正在被探索用于检测与淋巴疾病相关的组织变化。我们构建了一个宏观荧光成像系统，以验证超声流体流速测量结果，并为微流体模型提供高分辨率成像。该光学成像系统由一个白色光源、激发和发射滤光片以及一个带有变焦镜头的相机组成。视野可从100毫米×75毫米调整到10毫米×7.5毫米。微流体装置由聚二甲基硅氧烷（PDMS）制成，有9个通道，每个通道深40微米，宽度从30微米到200微米不等。使用注射泵推动含有直径为15微米的荧光微球的水通过微通道，流速范围从0.5微升/分钟到10微升/分钟。视频以25帧/秒的速率采集。使用一种追踪荧光微球运动的算法计算微通道中微球的速度。该成像系统能够测量从0.2毫米/秒到10毫米/秒的粒子速度。淋巴管中感兴趣的流速范围在1毫米/秒到10毫米/秒之间；因此，我们的成像系统足以测量模拟淋巴流的模型中的粒子速度。