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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 

 

© Kevin Aylward 2013

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Website last modified 27th April 2013

www.kevinaylward.co.uk