Calculations of intensities for radiation force modeling with the software package FOCUS

Rapid calculations of the intensity are required for models of the radiation force generated by linear ultrasound phased arrays. To determine the computation times and numerical errors produced by two medical ultrasound simulation packages, namely, FIELD II and FOCUS, comparisons of the calculated pressures and intensities are performed using a simulated Vermon L5 phased array probe with 128 active elements. In these simulations, the array generates a fixed focus 25 mm from the array for a 5MHz excitation, and the pressure field is computed on a 133 × 133 × 261 rectilinear grid that is centered at the focus. Half wavelength sampling is employed in all three directions. In FIELD II, this calculation takes approximately 4 hours on a 64bit laptop running Linux, and in FOCUS, the same calculation takes less than 4 minutes on the same computer. The numerical errors are also much smaller with FOCUS. Details of the simulation approaches employed for this transducer model are presented, including selection of FIELD II and FOCUS simulation parameters and calculations of the reference pressure field for error evaluations.