Development of a High-Frequency Ophthalmic Real-Time Ultrasound Imaging System Based on a 20 MHz Annular-Array Transducer

Abstract

Abstract Ophthalmic ultrasound imaging is a widely used diagnostic method for examining ophthalmic diseases in the clinic. A single-element transducer is adopted in the traditional ophthalmic ultrasound imaging systems. Although full depth focusing can be achieved using a linear-array transducer, it is unsuitable for ophthalmic imaging due to its inability to be tightly coupled to the eyeball and its higher cost. Annular-array-based systems provide an alternative, striking a balance between image quality and cost. Here, we present a newly developed high-frequency ophthalmic real-time ultrasound imaging system based on an annular-array transducer. This system uses a custom-made five-element, 20 MHz annular-array transducer encapsulated in a stainless steel housing and mounted in a commercially available handheld mechanical probe designed specifically for clinical ophthalmic imaging. The system uses a printed circuit board scheme and FPGA as the core to complete the hardware system design and realize the ultrasonic echo signal processing and system timing management. Full depth dynamic focusing of each scanning beam was achieved by designing the transmit and receive beamforming. Combined with advanced integrated circuits, the miniaturization and low cost of the overall system are realized. Extensive tests, including hardware, wire phantom, and tissue mimicking phantom measurements, were conducted to demonstrate good performance of the system. The results showed that the designed system can effectively improve the imaging resolution and enhance the depth of field of the image, particularly reducing the blind area of the near-field. The results of the normal human eye test verified that the imaging results met the needs of clinical diagnosis and have a good clinical application prospect.