Creatis- Univesity of Lyon || NTNU || Technical University of Denmark

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Evaluation framework
A complete description of the probe/system settings is given here
Probe settings

We selected the Verasonics Vantage 256 platform and the linear L11-4v probe with the following characteristics:
  • Pitch: 0.30 mm;
  • Element width: 0.27 mm;
  • Element height: 5 mm;
  • Elevation focus: 20 mm;
  • Number of elements: 128;
  • Aperture: 38.4 mm.

Transmit pulse

In order to use the L11-4v probe as a λ-pitch array the transmit frequency should be around 5.13 MHz. The closest frequency allowed by the Verasonics Vantage system is 5.208 MHz, which is chosen as transmit frequency. The following parameters define the pulse:
  • Transmit frequency: 5.208 MHz;
  • Sampling frequency: 20.832 MHz;
  • Pulse bandwidth: 67%;
  • Transmit voltage: 30 V;
  • Excitation: 2.5 cycles.

Plane-wave sequence

We selected a f-number of 1.75. The corresponding angle span [-αmaxmax] covered by the plane-wave sequence is equal to αmax = 16°. The maximum number of plane-waves in the sequence is computed as N = L / (F.λ) = 75. We thus decided to transmit 75 steered plane waves regularly spaced between -αmax and αmax for the acquisition of each phantom, which corresponds to an angle increment of 0.43°.


Beamforming grid

The beamforming grid defines the set of points from which the participants will have to reconstruct their envelope image (image before log compression). The dimensions of this grid are defined by the physical properties of the probe. The width is computed as: width = (number of elements-1) . pitch = 38.1 mm. We fix the maximum depth to 50 mm. The resolution of the grid is dimensioned according to the probe settings. The axial space between two consecutive nodes of the grid is set to λ/4 which corresponds to 0.074 mm with a total of 609 lines. In order to be sufficiently accurate during the evaluation procedures, the lateral scan is set to λ/3 which corresponds to 0.098 mm with a total of 387 columns.


Simulation details

One of the guideline of the simulation was to generate synthetic phantoms with close properties as the ones from real acquisitions. To this end, the following points have been taking into account:
  • Pitch: 0.30 mm;
  • Element width: 0.27 mm;
  • Element height: 5 mm;
  • Elevation focus: 20 mm;
  • Number of elements: 128;
  • Aperture: 38.4 mm.
  • Transmit frequency: 5.208 MHz;
  • Sampling frequency: 20.832 MHz;
  • Pulse bandwidth: 67%;
  • Excitation: 2.5 cycles.
To be noted: because of the use of the elevation focus, a small delay of 0.2 mm along depth can be observed on the simulated phantom used to evaluate the performance on resolution and distorsion. Since this effect comes from the transmission scheme, it should not be compensated by the reconstructed algorithms.