Real-time chirp-coded imaging with a programmable ultrasound biomicroscope.

Ultrasound biomicroscopy (UBM) of mice can provide a testing ground for new imaging strategies. The UBM system presented in this paper facilitates the development of imaging and measurement methods with programmable design, arbitrary waveform coding, broad bandwidth (2-80 MHz), digital filtering, programmable processing, RF data acquisition, multithread/multicore real-time display, and rapid mechanical scanning (<or=170 frames/s). To demonstrate the capacities of the UBM system, chirp (1.28, 2.56, and 5.12 micros durations) sequences with matched filter analysis are implemented in real time. Chirp and conventional impulse imaging (31 and 46 MHz center frequencies) of a wire phantom at fast sectorial scanning (0.7 degrees ms(-1), 20 frames/s one-way image rate) are compared. Axial and lateral resolutions at the focus with chirps approach impulse imaging resolutions. Chirps yield 10-15 dB gain in SNR and a 2-3 mm gain in imaging depth. Real-time impulse and chirp-coded imaging (at 10-5 frames/s) are demonstrated in the mouse, in vivo. The system's open structure favors test and implementation of new sequences.