An Ideal Observer Approach to Beamforming

Many signal processing issues in ultrasonic imaging can be viewed as attempts to focus signal energy while preserving the diagnostic information they contain. We have been developing a task-based ideal-observer approach to signal processing with the goal of better understanding the factors that influence the transfer of diagnostic information and improving signal processing algorithms for optimal transfer. We treat the scattering medium as a Gaussian random field with non-uniform variance that encodes the properties necessary for accurate task performance. Using measured pointspread functions for a given system we propagate the scattering statistics through to various stages of the acquisition process along with acquisition noise. In this work we focus on the role of beamforming in this process. We consider the efficiency of information transfer by analyzing the ideal observer acting on individual receive elements and then considering different strategies for preserving diagnostic information in beamformed echo signals. Optimal beamforming strategies suggested by the analysis are approximated by applying spatial filtering techniques to fixedfocus echo data. These results are compared with a standard delay-and-sum beamformer.