-
Piezoelectric crystal
- rigid man made ceramic
- part of the piezoelectric effect
-
Time Gain Compensation
A method of increasing amplification of the signal with depth to compensate for loss caused by attenuation
-
Dynamic Range
a measure of the span of signal magnitudes that can be represented or processed by the various components of a system
-
Gain
methos of increaing amplification of the overall gain
-
B-mode
- 2D/ real time
- two dimensional grey scale imaging in real time
-
m-mode
is udes in echocardiography and displays of an echo structure such as a heart valve (depth v. time)
-
Color Doppler
visualization of presence, characteristics and direction of blood flow
-
Spectral Doppler
allows us to qualify velocities and characteristics of blood flow in a specific location
-
State the range equation and apply it to the production of sonographic images.
- · Depth into tissue= velocity of sound in tissue x time between sent and
- received divided by 2
- ·D=cT/2
- ·D: distance c:1540 m/s T: pulse echo round trip 13 microseconds= 1
- centimeter
- · Looks at time elapsed, for echo to return to the transducer, determines
- the depth of echo signal on display
-
Describe the component parts of an ultrasound
machine.
- -Timer (clock)
- -Tansmitter (voltage pulse, generator)
- -Tx (transducer)---patient----back to Tx
- · Receiver (computer)-processes electrical voltage signal detected by
- crystal
- ·Display—maybe storage
-
What types of procedures are the different types of transducers used for?
- -Sector: Needle placement, cardiac, ABD, liver,
- spleen, kidney, pelvis
- -Linear: Vascular, small parts, carotid, testicle,
- thyroid
- -Curvilinear: OB, ABD, GYN, TV
- -Radial: endoscopic, intercavity, TV, TR,
- intervascular, CAD
-
Characterize transducers by image shape/configuration,
frequency, footprint.
- -Sector: pie shape:2.0/5.0 :small
- -Linear: rectangular:7.0/up :large
- -Curvilinear: broadened pie:3.0/5.0 :large
- -Radial: wagon wheel:14.0/20.0 (TV-5.0/7.0) :very
- small
-
Ampllification
- overall gain
- uniformly amplifies all returning voltage signal
-
Compensation
- TGC
- variable amplification, based on distance of echo to transducer
-
Compression
- log compression, grey scale, dynamic range
- adjust for attenuation of sound tissue. Allows uniform display of similar tissue at any depth. Proportional decrese in signal amplitude. Without losing min and max signals
-
demodulation/ rectification
- no knob
- goes from AC to DC changing signal shape
- rectification (AC>DC)
-
rejection
- Doppler wall filter
- eliminates the weak signals and keeps the rest. Minimizes background nois and wall motion artifacts
-
Plug flow
- blood is going the same velocity in the vessel
- large/ medium diameter vessels (AO, femoral, ECA (face) and common iliac)
- Triphasic (bidirectional)
- High resistance vascular bed
-
Parabolic Flow
- Laminar flow/ layered flow
- majority of arteries in the body
- Low resistance
-
Identify 5 ways to reduce or eliminate aliasing from the display
- -decrease tx frequency
- -lower baseline
- -increase velocity range
- -increase PRF
- -switch to CW, because it is not see
-
Describe how yo recognize aliasing on PW spectral displays and color Doppler displays:
- -Spectral the wave forms will be filled in instead of empty
- -Color borrows colors for other color bar
-
Describe why and how aliasing occurs
- Aliasing is when blood velocities peak over the
- range of velocities given or blood changes directions
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