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