Conference paper
Feasibility of non-linear simulation for Field II using an angular spectrum approach
Simulation of non-linear fields is most often restricted to single element, circularly symmetric sources, which is not used in clinical scanning. To obtain a general and valuable simulation, array transducers of any geometry with any excitation, focusing, and apodization should be modeled. Field II is restricted to simulate these for the linear case and the purpose of this paper is to develop a general frame work for extending it to non-linear simulation.
The extension to the non-linear domain is made by using the angular spectrum approach (ASA), where the field is calculated in a plane close to the transducer surface. This calculation is performed using Field II and, thus, includes modeling array transducers of any geometry with any excitation, focusing, and apodization.
The propagation in the linear or non-linear medium is then performed using the angular spectrum approach. The first step in deriving this procedure is to find the accuracy of the approach for linear propagation, where the result can be validated using Field II simulations. The ASA calculations are carried out by 3D fast Fourier transform using Matlab, where lambda=2 is chosen as the spatial sampling rate to reduce aliasing errors.
Zero-padding is applied to enlarge the source plane to a (4N - 1) times (4N - 1) matrix to overcome artifacts in terms of the circular convolution. The source plane covering an area of 9 times 9 mm2 with N = 61 samples along both side, is 0.05 mm away from a 5 MHz planar piston transducer, which is simulated by Field II.
To determine the accuracy, different sampling intervals and zero-paddings are compared and the errors are calculated with Field II as a reference. It can be seen that zero-padding with 4N - 1 and lambda=2 sampling can both reduce the errors from 25.7% to 12.9% for the near-field and from 18.1% to 5.8% for the far-field, and improve the price of an increase in computation time.
The angular spectrum approach in combination with Field II opens for- - the possibility of simulating the non-linear acoustic propagation for any kind of array transducers.
| Language: | English |
|---|---|
| Publisher: | IEEE |
| Year: | 2008 |
| Pages: | 1314-1317 |
| Proceedings: | 2008 IEEE International Ultrasonics Symposium |
| Series: | I E E E International Ultrasonics Symposium. Proceedings |
| ISBN: | 1424424283 , 9781424424283 , 1424424801 and 9781424424801 |
| ISSN: | 15513025 and 10510117 |
| Types: | Conference paper |
| DOI: | 10.1109/ULTSYM.2008.0318 |
| ORCIDs: | Jensen, Jørgen Arendt |
3D FFT Computational modeling Convolution Fast Fourier transforms Field II nonlinear simulation Geometry Mathematical model Matlab Pistons Sampling methods Solid modeling Transducers Transmission line matrix methods angular spectrum approach bioacoustics biomedical ultrasonics distance 0.05 mm fast Fourier transform fast Fourier transforms frequency 5 MHz nonlinear acoustic propagation nonlinear acoustics nonlinear medium propagation physics computing planar piston transducer size 9 mm transducer array apodization transducer array excitation transducer array focusing transducer array geometry transducer array modeling ultrasonic imaging ultrasonic propagation ultrasonic transducer arrays
