Field II Tutorial Help
Field II Tutorial Help
TRANSDUCER PARAMETERS
(see Figure 1 for dimension definitions)
These parameters describe the physical dimensions of the transducer.
See the above figure for clarification.
number of elements: Number
of elements in the lateral dimension of the transducer. (see figure
above)
kerf: The spacing between the elements
in the lateral dimension given in millimeters.
width: The width of an individual element
given in millimeters.
height: The height of an individual element
given in millimeters..
focal point: The point in space
in front of the transducer face at which the sound field constructively
converges. The axes are (lateral, elevation, axial).
The center of the transducer face is defined as (0,0,0). The axial
location is referred to as the focal depth.
center frequency: Center
frequency of the transmitted pulse given in MHz.
fractional bandwidth: This
is the fraction of the center frequency that represents the width of the
pulse at the half power (-6 dB) point. (e.g. for a pulse w/ a center
frequency of 7.5 MHz, it would have a 50% frac. Bandwidth if the half power
pulse width was 3.75 MHz.)
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CALCULATE MENU
Field calculates the ultrasound field of your choice - either the Transmitted
pressure field (TX), or the Transmit/Recieve (TX/RX) pressure field.
The TX/RX pressure field provides an ultrasound image of the point targets
that have been specified under the target
characteristics menu. After these calculations
are performed, more options will appear under the Plot menu (e.g. pressure
field plots, lateral beamplots, and axial waveform plots).
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PLOT MENU
After the transducer has been defined and appropriate calculations
have been performed (using the calculate menu),
the GUI will generate several plots of your calculated fields. These
include image formats of the space/time domain and the K-space domain (for
TX/RX fields), as well as lateral beamplots and plots of slices take
in either the axial or lateral dimensions.
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GENERAL SETTINGS
Define the sampling frequency and sound speed of the medium.
sampling frequency: Frequency
at which echoes are received.
sound speed: The speed of sound
propagation through the medium.
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SAVE MENU
Save current plot.
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TARGET TYPE
AND CHARACTERISTICS
Describes the location of point targets in the axial/lateral plane
of the transducer, such that when you compute the TX/RX Field Image, you
will obtain an image of these points. These points can be either
structured,
diffuse,
or a combination of the two.
Structured
Parameters Parameter specification for evenly distributed
point targets with a fixed amplitude, which represent a structured target
medium. (see Figure 1 for dimension definitions)
number of axial points:
the number of point targets that will be placed along the axis of the transducer.
They are automatically centered around the focal point of the transducer.
Dist b/t axial points:
the distance between each point target on the transducer axis. They are
automatically centered around the focal point of the transducer.
axial distance from focal
point: Axial position for the center of the point targets with
respect to the axial focal point of the transducer. A value of 0
is at the transducer's defined axial focal point.
number of lateral points:
the number of point targets that will be placed along the lateral dimension
of the transducer. They are automatically centered around each axial point
target location.
Dist b/t lateral points:
the distance between each point target laterally. . They are automatically
centered around each axial point target location.
lateral distance from
focal point: Lateral position for the center of the point targets with
respect to the lateral focal point of the transducer. A value of
0 is at the transducer's defined lateral focal point.
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Diffuse Parameters
Parameter specification for randomly distributed, random
amplitude point targets, which represent a diffuse scattering medium. (see
Figure
1 for dimension definitions)
NOTE: SIMULATIONS WITH DIFFUSE SCATTERING CAN TAKE A VERY LONG
TIME TO RUN - MAKE SURE YOU PAY ATTENTION TO THE ROI SIZE, BOTH LATERALLY
AND AXIALLY - IN ADDITION, TO DECREASE RUNTIME TRY DECREASING SCATTERER
DENSITY
Diffuse ROI Size: Axial size
of region containing randomly distributed scatterers, centered on the focal
position of the transducer. The lateral size is determined from the
lateral
roi range, specified under Image Size.
Diameter of Cyst: Diameter of
circle centered on the focal point that is devoid of scatterers.
This simulates a cyst in vivo, which would not exhibit appreciable
scattering.
Diffuse Scatterer Density:
Number
of scatterers (point targets) per resolution volume. The resolution
volume is determined by the pulse length axially, and lambda Z/D laterally.
Amplitude Ratio: Ratio of
the maximum amplitude of the structured scatterers to the maximum amplitude
of the diffuse scatterers. The diffuse scatterers have a random amplitude
(from 0 to 1), whereas the structured scatterers all have the same amplitude.
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IMAGE SIZE
(see Figure 1 for dimension definitions)
Determines the lateral extent and spacing between lines (TX/RX)
or hydrophones (TX) of the calculation to be performed. This region
is centered around the lateral focal point.
lateral ROI range: Defines
the lateral Region of Interest over which Field performs its calculation.
lateral increment: Step
size to use for calculations in the lateral plane.
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EXCITATION PULSE
(see Figure 1 for dimension definitions)
Define the type of excitation pulse that is used, along with its characteristics.
pulse type: Choose
between a delta function, sine wave, or a square wave.
center frequency:
Center frequency of the excitation pulse.
number of cycles:
Number of cycles of the excitation pulse. Default value is 1.
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