Ul Banna Hasan, Mitchell Benjamin, Chen Stephen, Palko Joel
Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26505, USA.
School of Medicine, West Virginia University, Morgantown, WV 26505, USA.
Bioengineering (Basel). 2023 Jun 6;10(6):689. doi: 10.3390/bioengineering10060689.
Imaging of the ocular vasculature can provide new insights into the pathophysiology of ocular diseases. This study proposes a novel high-frequency super-resolution ultrasound localization microscopy (SRULM) technique and evaluates its ability to measure in vivo perfusion changes in the rat eye at elevated intraocular pressure (IOP). A 38.4 MHz center frequency linear array transducer on a VisualSonics Vevo F2 imaging platform was used to collect high frame rate (1 kHz) radiofrequency data of the posterior rat eye following systemic microbubble contrast injection. Following clutter and spatiotemporal non-local means filtering, individual microbubbles were localized and tracked. The microbubble tracks were accumulated over 10,000 frames to generate vascular images quantifying perfusion velocity and direction. Experiments were performed using physiologic relevant controlled flow states for algorithm validation and subsequently performed in vivo on the rat eye at 10 mm Hg IOP increments from 10 to 60 mm Hg. The posterior vasculature of the rat eye, including the ophthalmic artery, long posterior ciliary arteries and their branches, central retinal artery and retinal arterioles and venules were successfully visualized, and velocities quantified at each IOP level. Significant reductions in arterial flow were measured as IOP was elevated. High-frequency SRULM can be used to visualize and quantify the perfusion velocity of the rat eye in both the retrobulbar and intraocular vasculature simultaneously. The ability to detect ocular perfusion changes throughout the depth of the eye may help elucidate the role ischemia has in the pathophysiology of ocular diseases such as glaucoma.
眼部血管成像能够为眼部疾病的病理生理学提供新的见解。本研究提出了一种新型高频超分辨率超声定位显微镜（SRULM）技术，并评估其在眼内压（IOP）升高时测量大鼠眼部体内灌注变化的能力。在VisualSonics Vevo F2成像平台上，使用中心频率为38.4 MHz的线性阵列换能器，在全身注射微泡造影剂后，采集大鼠眼后部的高帧率（1 kHz）射频数据。经过杂波和时空非局部均值滤波后，对单个微泡进行定位和跟踪。微泡轨迹在10000帧上进行累积，以生成量化灌注速度和方向的血管图像。使用生理相关的可控血流状态进行实验以验证算法，随后在大鼠眼上进行体内实验，眼内压以10 mmHg的增量从10 mmHg升高到60 mmHg。成功可视化了大鼠眼的后部血管系统，包括眼动脉、睫状后长动脉及其分支、视网膜中央动脉以及视网膜小动脉和小静脉，并在每个眼内压水平量化了速度。随着眼内压升高，测量到动脉血流显著减少。高频SRULM可用于同时可视化和量化大鼠眼后段和眼内血管系统的灌注速度。在整个眼深度检测眼部灌注变化的能力可能有助于阐明缺血在青光眼等眼部疾病病理生理学中的作用。
