An FPGA-Based Backend System for Intravascular Photoacoustic and Ultrasound Imaging

Abstract

The integration of intravascular ultrasound (IVUS) and intravascular photoacoustic (IVPA) imaging produces an imaging modality with high sensitivity and specificity which is particularly needed in interventional cardiology. Conventional side-looking IVUS imaging with a single-element ultrasound (US) transducer lacks forward-viewing capability, which limits the application of this imaging mode in intravascular intervention guidance, Doppler-based flow measurement, and visualization of nearly or totally blocked arteries. For both side-looking and forward-looking imaging, the necessity to mechanically scan the US transducer limits the imaging frame rate, and therefore array-based solutions are desired. In this paper, we present a low-cost, compact, high-speed, and programmable imaging system based on a field-programmable gate array (FPGA) suitable for dual-mode forward-looking IVUS/IVPA imaging. The system has 16 US transmit and receive channels and functions in multiple modes including interleaved photoacoustic (PA) and US imaging, hardware-based high-frame-rate US imaging, software-driven US imaging, and velocity measurement. The system is implemented in the register-transfer level, and the central system controller is implemented as a finite state machine. The system was tested with a capacitive micromachined ultrasonic transducer (CMUT) array. A 170-frames-per-second (FPS) US imaging frame rate is achieved in the hardware-based high-frame-rate US imaging mode while the interleaved PA and US imaging mode operates at a 60-FPS US and a laser-limited 20-FPS PA imaging frame rate. The performance of the system benefits from the flexibility and efficiency provided by low-level implementation. The resulting system provides a convenient backend platform for research and clinical IVPA and IVUS imaging.

Design, Development, and Multi-Characterization of an Integrated Clinical Transrectal Ultrasound and Photoacoustic Device for Human Prostate Imaging

“…For the space-constrained TRUSPA imaging, a curvilinear ultrasound array consisting of 128 or 196 elements is desired to generate prostate images with higher quality and a wider field-of-view, for example in conventional TRUS prostate imaging. Although this and previous studies demonstrated the high PA sensitivity of CMUTs [ 26 , 27 ], the unavailability of curvilinear CMUT arrays limit their use for developing a wide field-of-view clinical-grade TRUSPA device. This limitation also extends for emerging piezoelectric micromachined ultrasound transducer (PMUT) arrays, which recently showed good experimental results for deep-tissue photoacoustic imaging applications [ 28 , 29 ].…”

Investigation on Design Theory and Performance Analysis of Vacuum Capacitive Micromachined Ultrasonic Transducer

“…Its design and investigation are of great significance. Vacuum CMUT can be widely used in many fields such as intravascular ultrasound detection [ 11 ], intravascular photoacoustic imaging [ 12 ], tissue harmonic imaging [ 13 ], high-intensity focused ultrasound therapy [ 14 ], and liquid flow velocity measurement [ 15 ].…”

“…As an acoustic–electric conversion element, the CMUT’s working efficiency is characterized by its performance parameters such as transmission sound pressure, reception sensitivity, and fractional bandwidth [ 12 ]. In the design process, it is necessary to optimize the structural parameters that affect these performances to improve the efficiency of the CMUT.…”

CMOS-integrated biosensor circuits and systems : FMCW radar sensor for noncontact multimodal vital signs monitoring and coherent photoacoustic sensor for non-invasive in vivo sensing and imaging

“…It also needs to be mentioned that FPGA can now support efficient backend processing for US imaging or PA imaging in a configurable and convenient way [113].…”

“…20 (a) demonstrates the PA/US system's schematic where the FPGA is used to control the laser, and the imaging process is achieved by the FPGA backend, where the system is implemented in the register-transfer level. The FPGA, ADC board, and CMU sensing front-end used in the system are demonstrated in Fig.2.20(b)[113].…”