All-optical generation and detection of acoustic waves for intravascular ultrasound and photoacoustic imaging

The combination of intravascular ultrasound (IVUS) and photoacoustic (IVPA) imaging has been a potentially effective tool for detection of atherosclerotic plaques. Its clinical applications, however, have been hindered by several factors, including the lack of a cost-effective solution for a disposable scanhead. In this study, we propose a new scanhead design for IVUS/IVPA imaging. Specifically, the design is based on optical generation and detection of acoustic waves for both imaging modalities. No electronic components and conventional piezoelectric materials are used and the design is suitable for one-time, disposable use. The all-optical IVUS/IVPA imaging scanhead consists of an optical fiber with an axicon tip for excitation, and a microring for acoustic detection. Using a single firing of laser pulse, an ultrasound (US) signal can be generated and transmitted by the scanhead and a photoacoustic (PA) signal from the object can be induced. It has been tested on a grid phantom. The -6dB spatial resolution for lateral and axial direction were estimated at 305μm and 169μm. In our study, US and PA signals are separated by time delays and a subband imaging technique. In addition, mass production is possible with the adoption of the nanoimprint technique for fabrication. Therefore, this design has the potential to be a useful clinical tool for atherosclerosis diagnosis in the future.