Calculation of pulsed wave phantom data for arteria femoralis

This phantom is used for calculating RF data as measured from arteria femoralis in the upper leg. The phantom generates a number of files for particular time instances. The scatterers are then propagated between pulses according to the Womersley model mentioned in Jensen (1996) thereby generating a three-dimensional, pulsed model of the flow in the femoral artery. Note, that all the scatterer position files are generated before the simulation of the fields take place. For a pulse repetition frequency of 5 kHz, 5000 files are generated per second of simulation time, so a large amount of data is involved here.

The scatterer position files are then used during simulation for generating one RF signal for each pulse emission. These files can then be used for doing either spectral analysis as shown below or for estimating the profile in the artery.

The simulation is made so multiple workstations can work on the problem automatically at the same time, as long as they have access to the same directory. This is done by looking at which RF files that have been generated. The first one not simulated is reserved by the program by writing a dummy file, and then doing the simulation. Multiple workstations can then work simultaneously on the problem and generate a solution quickly. This has been done for the data show below, where 5 workstations automatically coordinated their simulations.

The resulting spectogram for the simulation is:

Spectrogram from arteria femoralis.

The m-files can be found at:

The routine field.m initializes the field system, and should be modified to point to the directory holding the Field II code and m-files. The routine make_sct.m is then called to make the file for the scatterers in the phantom. The script sim_pw_multi.m is then called. Here the field simulation is performed and the data is stored in RF-files; one for each RF-line done. The script show_data.m is used for making the pulsed wave spectrogram by demodulating the data and calling sonogram.m.

References:

Jørgen Arendt Jensen: "Estimation of Blood Velocities Using Ultrasound, A Signal Processing Approach", Cambridge University Press, 1996.