Integrated Multi-frequency Intravascular Ultrasound and Photoacoustic Imaging

大多数（50-60%）心脏性猝死是由易损斑块引起的急性冠状动脉内血栓形成的结果。血管造影是介入冠状动脉管腔成像的金标准，非常适合于识别血流受限病变，但现在人们认识到，导致死亡的后续心脏事件的很大一部分是由没有明显狭窄的易损斑块引起的。因此，人们对开发影像学方法来识别这些病变有着浓厚的兴趣，目的是改善介入手术（例如支架放置）的指导。血管内成像有可能检测到易损斑块，如果方法能够被设计出来检测1)这些危险病变表面的薄纤维帽和2)潜在的血栓性脂质池，这些脂质池被认为在破裂和血管阻塞中起主要作用。我们计划创建一种基于导管的成像方法，旨在检测和量化这两种特征。我们在微超声阵列、光声学和血管内超声（IVUS）换能器领域的技术专长将成为本文提出的新血管内技术的基础。本研究的具体目标是：1)开发一种基于双向2频导管的超声探头，其中换能器经过优化，可检测60至100 MHz范围内的薄纤维帽；2)将双频IVUS探头与适当的光纤技术相结合，在光谱的近红外区域输送脉冲或调制连续波激光能量，以进行脂质光声成像；3)量化超声和激光束分布，并对设备在幻影、离体冠状动脉样本和动物模型中的性能进行研究。这个项目的新颖之处在于，多频IVUS导管以前没有集成到血管内成像系统中，更不用说与光声结合了。因此，这项新技术将很好地指导干预措施，并协助有关易损斑块相关风险的关键决策。

The majority (50-60%) of sudden cardiac deaths are the result of acute intracoronary thrombosis arising from what are frequently referred to as vulnerable plaques. Angiography, the gold standard in interventional coronary artery lumen imaging, is well suited to identifying flow-limiting lesions but it is now recognized that a significant proportion of ensuing cardiac events resulting in fatalities arise from vulnerable plaques that do not have significant stenosis. There is therefore an intense interest in developing imaging methods to identify these lesions with the objective of improving guidance for interventional procedures (e.g. stent placements). Intravascular imaging has the potential to detect vulnerable plaque if methods can be devised to detect 1) the thin fibrous cap at the surface of these dangerous lesions and 2) the underlying thrombogenic lippid pools that are thought to play a major role in rupture and vessel blockage. We plan to create a catheter based imaging approach that is designed to detect and quantify both of these features. Our technical expertise in the areas of micro-ultrasound arrays, photoacoustics, and intravascular ultrasound (IVUS) transducers will be the basis for the new intravascular technologies proposed here. The specific objectives of this research are to: 1) develop a bidirectional 2 frequency catheter based ultrasound probe in which the transducer is optimized for detection of thin fibrous caps in the 60 to 100 MHz range, 2) combine the dual frequency IVUS probe with appropriate optical fibre technology for the delivery of pulsed or modulated continuous wave laser energy in the near infrared region of the spectrum to perform photoacoustic imaging of lipids, and 3) quantify ultrasound and laser beam distributions and perform studies of device performance in phantoms, ex vivo coronary artery samples, and in vivo in animal models. The novelty in this project is high in that multi-frequency IVUS catheters have not previously been integrated into intravascular imaging systems much less combined with photoacoustics. This new technology would thus be well positioned to guide interventions and assist in critical decision making regarding the risk associated with vulnerable plaque.