Ultrasound Beamformer

Program

FocusInstall.exe - Ultrasound Beamformer
- Written by Kevin Aylward B.Sc.

This program calculates data associated with medical imaging ultrasound
beamformers, such as what delays, apodization (gaussian amplitude weightings) and
when are they required to focus sound at
specific depths. It was written a while back, so uses a hlp file format not directly
supported on Windows 7/ Vista. However, you can download a fix from MS.

Technical Notes

Number of Elements

The number of elements for a given focal depth is determined from the following equations:

Linear Array:

Beamwidth = Pitch

Aperture = Number of elements × Pitch

Number of elements = 1.22 Velocity × Focal distance ÷ Beamwidth ÷ Frequency ÷ Aperture

Convex Array:

Beamwidth = Pitch × (Radius + Focal Distance) ÷ Radius

Aperture = 1.22 Velocity × Focal distance ÷ Beamwidth ÷ Frequency ÷ Beamwidth

Angle = arccos(1 - 0.5 × Aperture × Aperture ÷ Radius ÷ Radius)

Number of elements = Angle × Radius ÷ Pitch

Differential Beam Delay

The delay difference of the beam is given by the following equations:

X = element number × Pitch

depth = Focal distance

Linear Array:

delta distance = depth - sqrt(depth×depth-2×depth×X×sin(beam_angle)+X×X)

delta time = delta distance ÷ velocity

Convex Array:

k = sqrt(depth×depth+radius×radius+2×depth×radius×cos(beam_angle))

psi = asin(depth/k×sin(beam_angle))

theta = X/radius - psi;

delta distance = dept - sqrt(k×k+radius×radius-2× k×radius×cos(theta));

Annular Arrays:

The beam angle is the beam angle swept out per scan line of the sector.

Aperture = 1.22 × velocity / frequency / beam angle

The nearest average diameter to the required aperture is selected from the list of element rings