Ronald E. Daigle

The Verasonics ultrasound system as a pedagogic tool in teaching wave propagation, scattering, beamforming, and signal processing concepts in physics and engineering.

The Verasonics ultrasound system is a highly programmable data acquisition and processing platform designed to facilitate development of new medical ultrasound imaging methods. In contrast to conventional commercial ultrasound systems, individual element digitized rf data are available to the developer. All beamforming and postprocessing are done in software, and both the hardwaredata acquisition sequence and the host computer processing flow are programmable by the user using a MATLABinterface. Because the system is designed to be highly flexible, it can also be useful as a practical tool in teaching acoustic wave physics, transducer and array design, and data processing concepts, using benchtop scale homemade acoustic and elastic media, including flow models. For script evaluation and testing, the Verasonics system includes a hardware simulator that uses a simple point scatterer numerical model to compute rf backscatter data. rf data can also be recorded during a hardware acquisition, and then reprocessed using different user‐developed algorithms for comparative study. Because the system is easy to learn, many fundamental concepts can be explored in a laboratory setting, using scattering media or custom transducers fabricated as part of the student experimental plan. The system enables sophisticated hands‐on experience with acoustics beyond the numerical world.

Arbitrary waveforms using a tri-state transmit pulser

Conventional hardware for arbitrary waveform formation uses Digital-to-Analog Converters (DAC) and linear amplifiers. Proposed here are methods for encoding a tri-state pulser to approximate arbitrary waveforms. Algorithms are evaluated by simulation and experiment using the Verasonics, Inc. Vantage research ultrasound system, which transmits with 4 ns edge resolution. Two problems were considered: 1) matching the waveform produced by an ideal DAC given a particular transducer, and 2) compensating for the impulse response of a given transducer to reproduce a signal. The problems require the transducer impulse response in one-way and two-way propagation geometries, estimated here in water using a hydrophone and the ATL L7-4 transducer. Within measured nonlinear propagation effects, error in these four scenarios for an LFM waveform was consistent with simulated performance. In another test, a Gaussian pulse is encoded for transducer compensation, and compared to equivalent-bandwidth monopulse excitation in planewave imaging on a phantom. Here, a pin-trailing pedestal artifact is reduced by 3 dB over a span equal to the peak resolution (FWHM).