Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA.
Ultrason Imaging. 2019 Sep;41(5):290-300. doi: 10.1177/0161734619862287. Epub 2019 Jul 19.
Peripheral artery disease is often asymptomatic, and various imaging and nonimaging techniques have been used for assessment and monitoring treatments. This study is designed to demonstrate the ability of photoacoustic imaging to noninvasively determine changes in tissue oxygenation that occur in mice's hind limb skeletal muscle as they age. Mice from two age cohorts were scanned bilaterally with a pulsed laser. The photoacoustic signal was unmixed to generate a parametric map of estimated oxygen saturation and then overlaid on grayscale ultrasound images. Tissue oxygenation measured in young and old mice was compared. Photoacoustic imaging visually and quantitatively showed the decrease in skeletal muscle oxygenation that occurs with age. Percent tissue oxygenation decreased from 30.2% to 3.5% ( < 0.05). This reduction corresponded to reduced fractional area of oxygenation, which decreased from 60.6% to 6.0% ( < 0.05). The change in oxygenation capacity of the still active vascular regions was insignificant ( > 0.05). Intrasubject, intra-, and interobserver comparisons showed low variability in measurements, exhibited by high regression and intraclass correlations exceeding 0.81 for all ages. The decrease in oxygenation detected by photoacoustic imaging paralleled the known oxygenation decrease observed in aging tissues, demonstrating that photoacoustic imaging can assess age-related changes in a mouse calf muscle. These intramuscular changes could potentially act as a strong diagnostic marker for peripheral artery disease. This study thus opens the doors for a novel, affordable, noninvasive method of evaluation free of radiation or exogenous material.
外周动脉疾病通常无症状，已经有多种成像和非成像技术被用于评估和监测治疗。本研究旨在展示光声成像技术能够无创地检测到随着年龄增长，小鼠后肢骨骼肌组织氧合变化的能力。来自两个年龄组的小鼠被双侧用脉冲激光扫描。光声信号被解混以生成估计氧饱和度的参数图，然后叠加在灰度超声图像上。比较了年轻和老年小鼠的组织氧合情况。光声成像在视觉和定量上都显示了随着年龄的增长，骨骼肌氧合的下降。组织氧饱和度从 30.2%下降到 3.5%（<0.05）。这种减少对应于氧合分数的减少，从 60.6%下降到 6.0%（<0.05）。仍处于活跃状态的血管区域的氧合能力变化不显著（>0.05）。在个体内、个体内和观察者之间的比较中，测量的变异性较低，所有年龄的回归和组内相关系数都超过 0.81。光声成像检测到的氧合减少与衰老组织中观察到的已知氧合减少相吻合，表明光声成像可以评估小鼠小腿肌肉的年龄相关变化。这些肌肉内的变化可能成为外周动脉疾病的一个强有力的诊断标志物。因此，本研究为一种新的、负担得起的、无创的评估方法开辟了道路，该方法无辐射或外源性物质。
