The Design And Research Of Multi- Modality Intravascular Imaging Catheter Based On Photoacoustic Technique

Cardiovascular disease has become the leading cause of death in China. The latest statistics shows that cardiovascular disease is ranked at the first place, accounting for 44.8% of the deaths for rural residents, and 41.9% for urban residents. The rupture of vulnerable plaques is the major cause of acute cardiovascular disease. The existing intravascular imaging techniques such as intravascular ultrasound (IVUS) and intravascular optical coherence tomography (IVOCT) can only provide the structure information of the vulnerable plaque, which is unable to evaluate the plaque vulnerability. In contrast, intravascular photoacoustic spectroscopy demonstrates the capability of imaging the atherosclerotic plaque composition with higher sensitivity and specificity, allowing for identifying the vulnerable plaques accurately. Therefore, the development of multi-modal vascular imaging techniques that combines the advantages from the three technologies mentioned is expected to provide comprehensively clinical information of the plaque pathologic features, including structure and function characteristics.The imaging catheter is the key fact that influences the imaging quality of intravascular interventional imaging technology. Firstly, this work analyzes the advantages and disadvantages of the existing intravascular imaging catheters. Secondly, a multi-modality photoacoustic vascular imaging catheter is proposed and simulated. Thirdly, both optical and acoustic features of the multi-modality photoacoustic vascular imaging catheter were studied. At last, the multi-modality imaging catheter was fabricated, and its performance was tested.We designed and fabricated a catheter of 9 mm in diameter for intravascular multi-modality imaging, which is smaller than the critical size of 1 mm required for the clinical translation. A quasi-focusing photoacoustic excitation scheme was used in the catheter, high signal-to-noise ratio IVPA signals were generated from stents and lipids with a laser energy as low as ～30μJ/pulse. As a result, this design enable the use of an optical parametric oscillator laser low-energy and high-repetition rate for high-speed spectroscopic IVPA imaging at both the 1.2-μm and 1.7-μm spectral bands for lipid detection. IVPA image with a 1-kHz A-line rate was achieved for each wavelength. Furthermore, intravascular ultrasound imaging and intravascular OCT imaging can be achieved simultaneously. The resolution of ultrasound imaging is estimated to be 100μm, and the lateral resolution of OCT imaging is identified at 19.3μm, respectively. The multi-modality imaging was performed in the conduit of phantoms and animals isolated samples, which proves the possibility to detect lipid by the catheter.