Simulation of ultrasound fields and systems

Calculation of ultrasound fields from medical transducers is often done by applying linear acoustics and using the Tupholme-Stepanishen method of calculation. Here the spatial impulse response is found and, together with the basic one-dimensional pulse, it is used to find both the emitted and pulse-echo field. The spatial impulse response has only been determined analytically for a few geometries and using apodization over the transducer surface generally makes it impossible to find the response analytically. A popular approach for finding the general field is thus to split the aperture into small sub-elements, and then sum the weighted response from each of these. A triangle is used here, and the field from a triangle has been derived. A new field program has been made written in C and interfaced to the Matlab environment through a set of M-files. A large number of transducers can be defined and their properties manipulated. The program can calculate all types of ultrasound fields, and can also be used for simulating B-mode and color flow images. Both the focusing and apodization can be set to be dynamic with respect to time, and it is, thus, possible to simulate images focused at different zones.
The code for the program is available free of charge on the web at the address: http://www.it.dtu.dk/~jaj/field/field.html.Versions are found for the PC (Windows 3.1, 95 and NT) and for HP, SUN, SGI, and DEC workstations. The current program is used both by a number of companies (e.g. GE, Siemens, B&K Ultrasound Systems A/S, 3D Inc.) and a number of universities (e.g. Duke University, University of Illinois, DTU)