A non-linear ultrasound imaging simulation
software should be capable of simulating the non-linear
fields for any kind of transducer, focusing, apodization, and
attenuation. At present, a major issue is the overlong simulation
time of the non-linear software. An Angular Spectrum
Approach (ASA) using a quasi-linear approximation for solving
the Westervelt equation can simulate the second harmonic
pressure at any distance. Therefore, it shortens the execution
time compared with the operator splitting method. The purpose
of this paper is to implement the monochromatic solution for
the second harmonic component based on ASA and Field II,
and to compare with results from the simulation program
Abersim. A linear array transducer with a center frequency
of 4 MHz and 64 active elements is used as the transmitting
source. The initial plane is 5 mm away from the transducer
surface, and the fundamental pressure is calculated by Field II.
The second harmonic pressure in k-space along the propagating
direction is calculated as an auto-convolution of the fundamental
pressure multiplied by an exponential propagating coefficient.
In this case, the second harmonic pressure can be calculated
using ASA for any plane parallel to the initial plane. In the
focal plane (elevation-lateral) at 60 mm from the transducer
surface, calculated by ASA, the RMS errors for the fundamental
component are 2.66% referred to Field II and 4.28% referred
to Abersim. For the second harmonic component, the RMS
error is 0.91% referred to Abersim.
|Title of host publication||Proceedings of IEEE International Ultrasonics Symposium|
|Conference||2010 IEEE International Ultrasonics Symposium|
|City||San Diego, California|
|Period||11/10/10 → 14/10/10|
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