Tang Yuqi, Wu Huaiyu, Klippel Paul, Zhang Bohua, Huang Hsiao-Ying Shadow, Jing Yun, Jiang Xiaoning, Yao Junjie
Department of Biomedical Engineering, Duke University, Durham, NC USA.
Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC USA.
Biomed Eng Lett. 2022 Feb 16;12(2):135-145. doi: 10.1007/s13534-022-00216-0. eCollection 2022 May.
Venous thromboembolism (VTE) is a condition in which blood clots form within the deep veins of the leg or pelvis to cause deep vein thrombosis. The optimal treatment of VTE is determined by thrombus properties such as the age, size, and chemical composition of the blood clots. The thrombus properties can be readily evaluated by using photoacoustic computed tomography (PACT), a hybrid imaging modality that combines the rich contrast of optical imaging and deep penetration of ultrasound imaging. With inherent sensitivity to endogenous chromophores such as hemoglobin, multispectral PACT can provide composition information and oxygenation level in the clots. However, conventional PACT of clots relies on external light illumination, which provides limited penetration depth due to strong optical scattering of intervening tissue. In our study, this depth limitation is overcome by using intravascular light delivery with a thin optical fiber. To demonstrate in vitro blood clot characterization, clots with different acuteness and oxygenation levels were placed underneath ten-centimeter-thick chicken breast tissue and imaged using multiple wavelengths. Acoustic frequency analysis was performed on the received PA channel signals, and oxygenation level was estimated using multispectral linear spectral unmixing. The results show that, with intravascular light delivery, clot oxygenation level can be accurately measured, and the clot age can thus be estimated. In addition, we found that retracted and unretracted clots had different acoustic frequency spectrum. While unretracted clots had stronger high frequency components, retracted clots had much higher low frequency components due to densely packed red blood cells. The PACT characterization of the clots was consistent with the histology results and mechanical tests.
静脉血栓栓塞症（VTE）是一种血液凝块在腿部或骨盆的深静脉内形成从而导致深静脉血栓形成的病症。VTE的最佳治疗方法取决于血栓的特性，如血凝块的年龄、大小和化学成分。血栓特性可通过光声计算机断层扫描（PACT）轻松评估，这是一种将光学成像的丰富对比度和超声成像的深度穿透性相结合的混合成像方式。多光谱PACT对血红蛋白等内源性发色团具有固有敏感性，可提供血凝块中的成分信息和氧合水平。然而，传统的血凝块PACT依赖于外部光照射，由于中间组织的强烈光散射，其穿透深度有限。在我们的研究中，通过使用细光纤进行血管内光传输克服了这一深度限制。为了证明体外血凝块的特征，将具有不同急性程度和氧合水平的血凝块置于10厘米厚的鸡胸组织下方，并使用多个波长进行成像。对接收的光声通道信号进行声频分析，并使用多光谱线性光谱分解估计氧合水平。结果表明，通过血管内光传输，可以准确测量血凝块的氧合水平，从而估计血凝块的年龄。此外，我们发现回缩和未回缩的血凝块具有不同的声频谱。未回缩的血凝块具有更强的高频成分，而回缩的血凝块由于红细胞密集堆积而具有更高的低频成分。血凝块的PACT特征与组织学结果和力学测试一致。
