IMPOLGRID Polar-type grid for ultrasound images

IMPOLGRID returns a polar-type (fan-type) grid expressed in Cartesian coordinates. This is the "natural" grid (before scan-conversion) used when beamforming signals obtained with a cardiac phased array or a convex array.

Contents



Syntax

[X,Z] = IMPOLGRID(SIZ,ZMAX,WIDTH,PARAM) returns the X,Z coordinates of the fan-type grid of size SIZ and angular width WIDTH (in rad) for a phased array described by PARAM. The maximal Z (maximal depth) is ZMAX.

[X,Z] = IMPOLGRID(SIZ,ZMAX,PARAM) returns the X,Z coordinates of the fan-type grid of size SIZ and angular width WIDTH (in rad) for a convex array described by PARAM. For a convex array, PARAM.radius is not Inf. The maximal Z (maximal depth) is ZMAX.

[X,Z,Z0] = IMPOLGRID(...) also returns the z-coordinate of the grid origin. Note that X0 = 0.

Units: X,Z,Z0 are in m. WIDTH must be in rad.

PARAM is a structure which must contain the following fields:

  1. PARAM.pitch: pitch of the linear array (in m, required)
  2. PARAM.Nelements: number of elements in the transducer array, (required)
  3. PARAM.radius: radius of curvature (in m, default = Inf, linear array)



Example #1: Low-resolution grids (for clarity purpose)

This example shows how polar-type grid look like for a phased array or convex array.

Choose a 2.7-MHz 64-element cardiac phased array with GETPARAM.

param = getparam('P4-2v');

Create a 60-degrees wide polar-type 20-by-20 grid.

[x,z] = impolgrid([20 20],10e-2,pi/3,param);

Display the grid.

plot(x*1e2,z*1e2,'ko','MarkerFaceColor','k')
xlabel('[cm]')
ylabel('[cm]')
axis equal ij tight
title('A polar-type grid for a cardiac phased-array')

Now choose a 3.6-MHz 128-element curved linear array.

param = getparam('C5-2v');

Create a polar-type 20-by-20 grid.

[x,z] = impolgrid([20 20],10e-2,param);

Display the grid.

plot(x*1e2,z*1e2,'ko','MarkerFaceColor','k')
xlabel('[cm]')
ylabel('[cm]')
axis equal ij tight
title('A polar-type grid for a curved array')



Example #2: A focused pressure field with a phased-array

This example shows how to simulate a pressure field on a polar-type grid.

Choose a 2.7-MHz 64-element cardiac phased array with GETPARAM.

param = getparam('P4-2v');

Define a focus position.

xf = 2e-2; zf = 5e-2;

Calculate the transmit delays with TXDELAY.

txdel = txdelay(xf,zf,param);

Create a 60-degrees wide 10-cm deep 100-by-50 grid with IMPOLGRID.

[x,z] = impolgrid([100 50],10e-2,pi/3,param);

Simulate the RMS pressure field with PFIELD.

P = pfield(x,z,txdel,param);

Display a scatter plot of the pressure field.

scatter(x(:)*1e2,z(:)*1e2,5,20*log10(P(:)/max(P(:))),'filled')
colormap jet
caxis([-20 0])
c = colorbar;
c.YTickLabel{end} = '0 dB';
axis equal ij tight
xlabel('[cm]')
ylabel('[cm]')

Display the pressure field.

pcolor(x*1e2,z*1e2,20*log10(P/max(P(:))))
shading interp
colormap hot
axis equal ij tight
xlabel('[cm]')
ylabel('[cm]')
caxis([-20 0])
c = colorbar;
c.YTickLabel{end} = '0 dB';



See also

das, dasmtx, pfield



About the author

Damien Garcia, Eng., Ph.D.
INSERM researcher
Creatis, University of Lyon, France

websites: BioméCardio, MUST



Date modified