Research On High-speed Intravascular Photoacoustic System

Although the diagnosis and treatment of cardiovascular disease have been progressing in recent years,acute cardiovascular events are still the leading killer of human health.Fundamental clinical studies have shown that the damage of coronary atherosclerotic plaques is the main cause of acute cardiovascular events,and its in vivo research mainly relies on intravascular imaging technology.However,these existing clinical imaging techniques such as intravascular ultrasound and optical coherence tomography can only provide structural information of the tissue,and cannot effectively identify important functional information such as the composition of plaques.Emerging photoacoustic imaging technology utilizes the light absorption specificity of the tissue to provide both structural and functional information of the tissue,and has broad prospects for its clinical application.In view of this,this article conducts research on the intravascular photoacoustic imaging technique,the main contents are as follows:(1)Designed a IVPA-US imaging system.First,joint photoacoustic and ultrasound imaging methods complement each other due to their unique advantages.Secondly,the design of the imaging catheter is optimized by reducing the outer diameter of the catheter to 0.9mm,which meets the requirements for clinical methods intervening in blood vessels and can realize full-field imaging.Finally,the system can be controlled by the combination of upper and lower computer,which can improve the system’s real-time control and ensure the flexibility of the system.(2)The high-speed imaging solution is proposed.The production/consumption model is adopted in the LabVIEW data acquisition module program to realize the parallel work of acquisition and storage,which greatly improves the data collection efficiency.The imaging scan of uniformly distributed wires in rotating status is performed at a high rotation speed of 30 revolutions per second.The results showed that the imaging position of the wires was consistent with the acquisition position,which confirms the feasibility of the scheme.(3)Image denoising algorithm research.A morphological image denoising algorithm based on threshold segmentation is proposed.From the results of hair filament and blade photoacoustic image processing,it can be seen that this algorithm can well filter out the impulse noise in the image,and after processing,the standard deviation of the image increases accordingly,and the image quality is significantly improved.(4)The system imaging capability is verified.We verified the system imaging capability by conducting the test of resolution of the system and signal-to-noise ratio by using a wire and a black tape.The result shows that the vertical resolution of the system is as high as 40.2μm,and the maximum signal-to-noise ratio is 58.6dB,which can meet the needs of inside human body research.In addition,the samples of the blood vessels with lipid composition were obtained,and then the samples were imaged to obtain two-dimensional,three-dimensional photoacoustic and ultrasound images of test bodies.The recognition ability of the chemical components of plaques was fully demonstrated by the contrast between the photoacoustic and the ultrasound image of butter signal.In this study,a high-speed intravascular photoacoustic imaging scheme was proposed while ensuring high resolution and small probes,and it has drastically promoted the resolution of two core issues:the large size of the imaging catheter and the slow imaging speed in photoacoustic imaging technology.It also provides an important basis for the development of photoacoustic imaging technology,and it is expected to be of great help for early detection and early diagnosis of cardiovascular diseases.