Shape of phased array Doppler ultrasound sample volumes

Some of the methods used to reduce estimation errors make use of simplified models of the Doppler sample volume (SV). However, these models do not accurately take into account the SV's shape and pressure distribution. The SV can be accurately simulated through the inclusion of a Doppler time gate to a B-mode simulation based on the underlying physics of ultrasound propagation and reception from a linear phased array transducer, including the effects of focusing and attenuation. A commercial diagnostic B-mode/Doppler ultrasound system was simulated to produce four SVs at different axial depths and lengths. It was found that every SV's axial length was larger than the theoretical length used in its design. The further the SV was away from a focal depth, the greater its size in that dimension. The pressure distribution was not symmetrical about the center of the SV, but rather skewed towards the transducer.