Piecewise-linear approximation for improved accuracy in near-field ultrasound simulation
Computer simulation is an important tool for the design of phased array ultrasonic systems. FIELD II, which determines the two-way temporal response of a transducer at a point in space, is the current de facto standard for ultrasound simulation tools . However, our laboratory has recently described  a complementary tool, entitled DELFI, which is optimized for prediction of spatial responses at a single instant in time. This tool makes use of an analytical approach by defining the impulse response as delta functions or sums of unit step or unit ramp functions. Here we have modified this original DELFI tool, removing any far-field assumptions, to achieve a significant increase in accuracy for near-field applications, with only a slight loss in computational efficiency. For applications requiring a spatial response at a single instant in time, new DELFI is roughly 110 times faster than FIELD-triangles for similar amounts of error and 9 times more accurate than original DELFI at a computational cost factor of 1.3. For spatio-temporal applications, new DELFI has about the same computational efficiency as FIELD-triangles for similar amounts of error and is 9.3 times more accurate than original DELFI at a computational cost factor of 1.5. © 2006 IEEE.