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Myocardial infarctions are most often caused by the so-called vulnerable plaques, usually featured as non-obstructive lesions with a lipid-rich necrotic core, thin-cap fibroatheroma, and large plaque size. The identification and quantification of these characteristics are the keys to evaluate plaque vulnerability. However, single modality intravascular methods, such as intravascular ultrasound, optical coherence tomography and photoacoustic, can hardly achieve all the comprehensive information to satisfy clinical needs. In this paper, for the first time, we developed a novel multi-spectral intravascular tri-modality (MS-IVTM) imaging system, which can perform 360° continuous rotation and pull-backing with a 0.9-mm miniature catheter and achieve simultaneous acquisition of both morphological characteristics and pathological compositions. Intravascular tri-modality imaging demonstrates the ability of our MS-IVTM system to provide macroscopic and microscopic structural information of the vessel wall, with identity and quantification of lipids with multi-wavelength excitation. This study offers clinicians and researchers a novel imaging tool to facilitate the accurate diagnosis of vulnerable atherosclerotic plaques. It also has the potential of clinical translations to help better identify and evaluate high-risk plaques during coronary interventions.

The rupture of atherosclerotic plaques is the leading cause of acute coronary events. The detection of lipid content and its distribution within the plaques is critical for identifying vulnerable plaques that are prone to rupture [1]. Intravascular spectroscopic photoacoustic technology is capable of imaging the composition and structure of atherosclerotic plaques [2, 3]. To achieve accurate spectroscopic IVPA imaging, an ns-pulsed, wavelength tunable laser [e.g., optical parameter oscillator (OPO) laser] is critical. However, in previously reported IVPA systems, laser pulse energy in the order of mJ was usually required to produce decent photoacoustic signals, so the choices of laser sources were usually limited to OPO lasers of a pulse repetition rate of 10–20 Hz. The B-scan rate at a single wavelength with such lasers was 0.05–0.1 f/s (assuming 200 A-lines/B-scan); for spectroscopic imaging, the image acquisition would take several times longer. Overall, the imaging speed is becoming one of the major challenges for translating IVPA into clinical applications [4, 5]. In this study, a catheter of 0.9 mm in diameter with a novel quasi-focusing light illumination scheme is designed and developed, smaller than the critical size of 1 mm required for clinical translation. With this design, the laser fluence in the targeted imaging region was increased, which produced detectable signals with laser energy as low as ~30 μJ/pulse. As a result, a 1-kHz-repetition-rate, ns-pulsed optical parametric oscillator (OPO) laser was able to be utilized to achieve high-speed IVPA imaging, working at both the 1.2 and 1.7 μm spectral bands for lipid detection. Specifically, a B-scan acquisition rate of 5 Hz was achieved, ~100-fold faster than conventional IVPA systems operating at the similar tunable range. With the system, multi-wavelength (five wavelengths) spectroscopic IVPA imaging of both a lipid-mimicking phantom and peri-adventitial adipose tissue from a porcine vessel was demonstrated at both the 1.2 and 1.7 μm spectral bands. The significantly improved imaging speed, together with the reduced catheter size and multi-wavelength spectroscopic imaging ability, suggests that the developed high-speed IVPA technology is of great potential to be further translated for in vivo applications.

Photoacoustic imaging is a novel hybrid medical imaging technology. It uniquely combines the advantages of optical absorption contrast with ultrasonic resolution for in vivo imaging as deep as 5-7 centimeters. Here we will discuss some technology development pursued in our lab towards clinical translations.

Based on on-line detection technology of computer, combined with process control theory, the roll diameter detection process quality control system is designed; meanwhile the roll diameter automatic detection, data acquisition, analysis, process as well as statistical process control of the process is realized. For the part of software, adopting the theory of statistical process control, the software employs JSP procedure code to designing system, so as to realize automatically collect database data of process quality control system, on-line analysis control of computer and process function for abnormal. For the part of hardware, the roll automatic detection device is researched and designed. Adopting Minitab software and the research data are applied to analyze the measurement system, thereby to verify the reliability, thus that measurement system meets measurement standard can be determined, through on-line analysis to determine the accuracy of the monitoring system. The result shows that the designed automatic detection system has good accuracy and reliability.