Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712, USA.
Ultrasonics. 2012 Mar;52(3):435-41. doi: 10.1016/j.ultras.2011.10.005. Epub 2011 Oct 18.
The structure, composition and mechanics of carotid artery are good indicators of early progressive atherosclerotic lesions. The combination of three imaging modalities (ultrasound, strain rate and photoacoustic imaging) which could provide corroborative information about the named arterial properties could enhance the characterization of intimal xanthoma.
The experiments were performed using a New Zealand white rabbit model of atherosclerosis. The aorta excised from an atherosclerotic rabbit was scanned ex vivo using the three imaging techniques: (1) ultrasound imaging of the longitudinal section: standard ultrasound B-mode (74Hz frame rate); (2) strain rate imaging: the artery was flushed with blood and a 1.5Hz physiologic pulsation was induced, while the ultrasound data were recorded at higher frame rate (296Hz); (3) photoacoustic imaging: the artery was irradiated with nanosecond pulsed laser light of low fluence in the 1210-1230nm wavelength range and the photoacoustic data was recorded at 10Hz frame rate. Post processing algorithms based on cross-correlation and optical absorption variation were implemented to derive strain rate and spectroscopic photoacoustic images, respectively.
Based on the spatio-temporal variation in displacement of different regions within the arterial wall, strain rate imaging reveals differences in tissue mechanical properties. Additionally, spectroscopic photoacoustic imaging can spatially resolve the optical absorption properties of arterial tissue and identify the location of lipid pools.
The study demonstrates that ultrasound, strain rate and photoacoustic imaging can be used to simultaneously evaluate the structure, the mechanics and the composition of atherosclerotic lesions to improve the assessment of plaque vulnerability.
颈动脉的结构、组成和力学特性是早期进行性动脉粥样硬化病变的良好指标。结合三种成像模式（超声、应变速率和光声成像）可以提供关于动脉特性的补充信息，从而增强对内膜黄色瘤的特征描述。
使用新西兰兔动脉粥样硬化模型进行实验。从动脉粥样硬化兔中取出的主动脉在体外用三种成像技术进行扫描：（1）超声纵向截面成像：标准超声 B 模式（74Hz 帧率）；（2）应变速率成像：用血液冲洗动脉，同时诱导 1.5Hz 的生理脉动，记录更高帧率（296Hz）的超声数据；（3）光声成像：用低能量纳秒脉冲激光照射动脉，在 1210-1230nm 波长范围内，记录光声数据的帧率为 10Hz。基于互相关和光吸收变化的后处理算法，分别得到应变速率和光谱光声图像。
基于动脉壁内不同区域位移的时空变化，应变速率成像揭示了组织力学特性的差异。此外，光谱光声成像可以空间分辨动脉组织的光吸收特性，并识别脂质池的位置。
该研究表明，超声、应变速率和光声成像可用于同时评估动脉粥样硬化病变的结构、力学和组成，以改善斑块易损性的评估。
