Little Callum D, Colchester Richard J, Noimark Sacha, Manmathan Gavin, Finlay Malcolm C, Desjardins Adrien E, Rakhit Roby D
Department of Cardiovascular Medicine, Royal Free NHS Foundation Trust, London, United Kingdom.
Wellcome-Engineering & Physical Sciences Research Council (EPSRC) Centre for Interventional and Surgical Sciences, London, United Kingdom.
Front Cardiovasc Med. 2020 Oct 14;7:525530. doi: 10.3389/fcvm.2020.525530. eCollection 2020.
Conventional intravascular ultrasound (IVUS) devices use piezoelectric transducers to electrically generate and receive US. With this paradigm, there are numerous challenges that restrict improvements in image quality. First, with miniaturization of the transducers to reduce device size, it can be challenging to achieve the sensitivities and bandwidths required for large tissue penetration depths and high spatial resolution. Second, complexities associated with manufacturing miniaturized electronic transducers can have significant cost implications. Third, with increasing interest in molecular characterization of tissue , it has been challenging to incorporate optical elements for multimodality imaging with photoacoustics (PA) or near-infrared spectroscopy (NIRS) whilst maintaining the lateral dimensions suitable for intracoronary imaging. Optical Ultrasound (OpUS) is a new paradigm for intracoronary imaging. US is generated at the surface of a fiber optic transducer via the photoacoustic effect. Pulsed or modulated light is absorbed in an engineered coating on the fiber surface and converted to thermal energy. The subsequent temperature rise leads to a pressure rise within the coating, which results in a propagating ultrasound wave. US reflections from imaged structures are received with optical interferometry. With OpUS, high bandwidths (31.5 MHz) and pressures (21.5 MPa) have enabled imaging with axial resolutions better than 50 μm and at depths >20 mm. These values challenge those of conventional 40 MHz IVUS technology and show great potential for future clinical application. Recently developed nanocomposite coating materials, that are highly transmissive at light wavelengths used for PA and NIRS light, can facilitate multimodality imaging, thereby enabling molecular characterization.
传统的血管内超声（IVUS）设备使用压电换能器来电产生和接收超声。在这种模式下，存在许多限制图像质量提升的挑战。首先，随着换能器的小型化以减小设备尺寸，要实现大组织穿透深度和高空间分辨率所需的灵敏度和带宽可能具有挑战性。其次，与制造小型化电子换能器相关的复杂性可能会带来巨大的成本影响。第三，随着对组织分子表征的兴趣增加，在保持适合冠状动脉内成像的横向尺寸的同时，将光学元件与光声（PA）或近红外光谱（NIRS）结合用于多模态成像一直具有挑战性。光学超声（OpUS）是一种用于冠状动脉内成像的新模式。超声通过光声效应在光纤换能器表面产生。脉冲或调制光被吸收在光纤表面的工程涂层中并转化为热能。随后的温度升高导致涂层内压力升高，从而产生传播的超声波。来自成像结构的超声反射通过光学干涉测量法接收。借助OpUS，高带宽（31.5 MHz）和压力（21.5 MPa）已实现轴向分辨率优于50μm且深度>20 mm的成像。这些值对传统的40 MHz IVUS技术构成挑战，并显示出未来临床应用的巨大潜力。最近开发的纳米复合涂层材料在用于PA和NIRS光的光波长下具有高透射率，可促进多模态成像，从而实现分子表征。
