Acoustic stack for combined intravascular ultrasound and photoacoustic imaging.

Multimodal intravascular ultrasound and photoacoustic (IVUS/PA) imaging is a promising diagnostic tool for cardiovascular diseases like atherosclerosis. IVUS/PA catheters typically require two independent transducers due to different frequency requirements, potentially increasing the catheter size. To facilitate multimodal imaging within conventional catheter dimensions, we designed, fabricated, and characterized a dual-transducer acoustic stack where a low-frequency (LF) PA receiver sits as a matching layer for the high-frequency (HF) US transducer. While the HF transducer operates around 50 MHz, the LF receiver targets frequencies below 15 MHz to capture most of the PA energy from atherosclerotic plaque lipids. Simulation results reveal that this configuration could increase the sensitivity of the HF transducer by 3.54 dB while maintaining bandwidth. Phantom experiments with fabricated stacks showed improved performance for the US transducer, validating the enhanced sensitivity and bandwidth. Following improvements in stack fabrication, the proposed acoustic stack is a viable design that can significantly enhance diagnostic accuracy for atherosclerosis, providing high-resolution, multifrequency imaging within a compact catheter form factor.