High-speed intravascular photoacoustic imaging with blood flushing

Intravascular photoacoustic imaging (IVPA) can obtain specific inflammation information and lipid composition in vivo, which is a new method for the diagnosis of atherosclerotic plaques. Numerous IVPA systems have been proposed and pushed towards clinical application. But imaging speed hinders their final clinical translation, considering necessary blood flush or balloon blood blockage operations during the intravascular intervention. In this study, we developed a high-speed IVPA system based on a 1064 nm pulsed laser, with the imaging speed of 60 round/second, about twice speed of the fastest IVPA system. In this system, a 0.9 mm outer diameter catheter was used for simultaneous IVPA and IVUS imaging. A plastic tube with an outer diameter of 1.3 mm was wrapped on the outside of the imaging catheter for protection and blood flushing channels. Firstly, the capability of high-speed imaging was verified by the imaging of a manually moving metal needle. Photoacoustic and ultrasonic images of the needle were obtained. No artifacts were found during the real-time imaging of the needle, which was unavoidable in the low-speed imaging system. Then, an artery excised from abdominal aorta of a New Zealand rabbit was sealed and a certain frequency of flowing water was injected from the one end to simulate the pulsation of blood vessels with a frequency of about 4.5 Hz, which was a typical heart rate of a rabbit. The high-speed IVPA-US imaging of pulsed blood vessels was successfully performed, which proved the feasibility of the system in vivo and even further clinical application.