Research Summary: Intravascular ultrasonic–photoacoustic (IVUP) endoscope with2.2-mm diameter cathet
Intravascular ultrasound (IVUS) imaging is extremely important for detection and characterization ofhigh-risk atherosclerotic plaques as well as gastrointestinal diseases. Recently, intravascular photoa-coustic (IVPA) imaging has been used to differentiate the composition of biological tissues with highoptical contrast and ultrasonic resolution. The combination of these imaging techniques could providemorphological information and molecular screening to characterize abnormal tissues, which would helpphysicians to ensure vital therapeutic value and prognostic significance for patients before commencingtherapy. In this study, integration of a high-frequency IVUS imaging catheter (45 MHz, single-element,unfocused, 0.7 mm in diameter) with a multi-mode optical fiber (0.6 mm in core diameter, 0.22 NA), anintegrated intravascular ultrasonic–photoacoustic (IVUP) imaging catheter, was developed to providespatial and functional information on light distribution in a turbid sample. Simultaneously, IVUS imag-ing was co-registered to IVPA imaging to construct 3D volumetric sample images. In a phantom study,a polyvinyl alcohol (PVA) tissue-mimicking arterial vessel phantom with indocyanine green (ICG) andmethylene blue (MB) inclusion was used to demonstrate the feasibility of mapping the biological dyes,which are used in cardiovascular and cancer diagnostics. For the ex vivo study, an excised sample of pigintestine with ICG was utilized to target the biomarkers present in the gastrointestinal tumors or theatherosclerotic plaques with the proposed hybrid technique. The results indicated that IVUP endoscopewith the 2.2-mm diameter catheter could be a useful tool for medical imaging.