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362 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Signals returning from transducer are extremely _____.
The receiver boosts them, and prepares them for ______. |
weak
display |
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* Know "order" of the receiver
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1. amplification
2 . compensation 3.compression 4.demodulation 5.rejection |
alphabetical order
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Purpose of amplification?
Aka? |
increases the strength in the RECEIVER
receiver gain |
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Amplification changes the brightness of the?
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Entire image
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Purpose of compensation?
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Create UNIFORM BRIGHTNESS from top to bottom
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Time gain compensation (TGC),
Depth compensation (DGC), and Swept gain... are AKA? |
Compensation
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What controls gray scale?
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Compression
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Compression decreases the ______ of the signals.
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Dynamic range
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Purpose of Demodulation?
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CHANGES THE SIGNALS FORM to one suitable for tv display
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Rectification?
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CORRECTS or ELIMINATES negative voltages
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We use _______ to eliminate LOW LEVEL noise in our images.
(Does not effect?) |
Rejection
Bright echos |
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Contrast agents are Aka?
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Micro bubbles (of gas entrapped in a shell)
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When the image is too bright due to high output, what resoluton degrades?
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Lateral and longitudinal resolution
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Minimizing patient exposure is Aka?
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ALARA
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* Why are harmonics created?
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Because sound travels faster in compressions than rarefactions
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* Harmonic frequency is created by what behavior?
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Non linear behavior
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* The harmonic frequency is ______ the transmitted frequency
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Twice
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* Harmonics are multiples of the ______ frequency.
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transducer frequency
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* Harmonics are created in the ______.
(Not the _____!) |
in the TISSUES
(not the transducer) |
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A form of harmonic imaging where positive and negative pulses are transmitted down each scan line?
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Pulse inversion harmonic imaging
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Pulse inversion harmonic imaging degrades what?
improves what? |
degrades temporal resolution
improves spatial resolution |
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Pulse inversion harmonics requires what type of transducers?
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wide - bandwidth or broadband transducers
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The more pixels per inch (pixel density) the greater detail in image. This is called?
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Spatial or detail resolution
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The smallest element of a digital picture?
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A pixel
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A microprocessor converts image data into numbers (Aka _____?) then processed into an image.
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Digital image data
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* Spatial resolution detail is related to the _______ ?
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Number of lines per frame
(More lines the better) |
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The more bits per pixel, the more shades of gray, and better _________?
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The contrast resolution
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* What is the number of shades that can be represented by 10 bits?
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1024
(Multiply 2 by itself 10 times. 2x2x2x2x2x2x2x2x2x2=1024) |
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A group of 8 bits is a ?
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Byte
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* Post processing is performed on ______ images?
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Frozen images
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* Fill in interpolation is done _____processing.
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Pre processing
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Fill in interpolation improves _____, especially for _____ parts of the image.
The edges of a circular structure will be ___________? |
Image detail (spatial resolution)
especially for deeper parts edges will be better defined |
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* Spatial compounding is in ______ transducers only.
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Phased array
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* Persistence is Aka ______?
Provides a _____ of past images that is added to current image. |
Temporal averaging
Provides a HISTORY |
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* Edge enhancement purpose is to ___________ between different medium/tissues.
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Emphasize the boundary
(distinguish interfaces) |
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* Which component of US machine processes info with WIDEST (greatest/highest) dynamic range?
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Pick the component earliest in the imaging chain.
(ie, the transducer being the beginning.) |
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* Which component of US machine has the NARROWEST (smallest/lowest) dynamic range?
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Pick the last in imaging chain
(ie, display or storage device) |
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* Computer disks and video tape are 2 examples of what kind of media?
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Magnetic media
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Pulsatile flow results from?
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Cardiac contraction
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Phasic flow results from?
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Respiration
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* Turbulent flow is Aka?
Has what type of flow pattern? |
Spectral broading
Rotational/swirling pattern. (Vortex, hurricane) |
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Spectral broading is associated with ______ pathology...
and _______ velocities. |
cardiovascular pathology
and increased velocities |
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Reynolds number is a unitless # indicating if turbulent flow is present.
** Is 2,400 considered turbulent?** |
Yes.
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* Where is Kinetic energy the maximum?
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At the maximum stenosis
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*Where is Pressure Energy the lowest?
*Known as what principle? |
At the maximum stenosis
Bernoulli's principle |
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* What is it called when:
The total fluid energy (blood flowing) at one location DIFFERS from total fluid energy at another location. |
Energy gradient
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Increased hematocrit or hemoglobin (polycythemia or erythrocytosis) causes ______ blood viscosity.
Anemia causes blood to be thinner and causes _______ blood viscosity. |
Increased
Decreased |
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Viscosity units?
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Poise
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* Rbc's speed up, slow down (velocity changes) when passing through ________.
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A stenosis
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Stenosis:
* What are the 3 factors that determine resistance? |
1. Radius of lumen (most important)
2. Length of stenosis 3. Viscosity of fluid |
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* When a patient is supine, there is no colum of blood pressing on vessels, therefore the hydrostatic pressure is ______ at ______ locations.
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ZERO at ALL locations.
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* During inspiration, pressure in ABD cavity increases:
Venous flow in legs _________. Pressure in THORAX decreases: Venous return to heart _______. |
Decreases
Increases |
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* What does Sonographer need to know to accurately determine Velocity?
(2 things) |
The angle between directions of flow
and The sound beam. |
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* Doppler shift equation?
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* What does Doppler measure?
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Velocity.
*(not speed)* |
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Doppler frequency depends on direction.
* The magnitude of shift depends upon the ______ of the angle, between the sound beam and the _______. |
Cosine
Direction of motion. |
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* Most accurate angle to doppler = 100% true velocity?
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0 degrees
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* (Normally) What MHz transducer used to perform doppler study?
* What MHz with DOPPLER SHIFT? |
Norm: 2 to 10 MHz (Megahertz)
Shift: 20 to 20,000 Hz (Hertz) |
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Doppler shift is the difference between ________ and ________ frequencies.
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received and transmitted frequency
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Typical values in doppler shift (clinical studies):
____ to ____ and is _________. |
20Hz to 20kHz
AUDIBLE |
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Non-coherent processing is used with which doppler?
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Uni-directional
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Phase quadrature processing is used in which doppler?
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Bi-directional
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Which doppler requires headohones, speakers, or display that can represent flow towards and away from transducer.
(Above and below baseline) |
Bi-directional
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*Number of crystals in continuous wave doppler?
*And the advantages? (4) |
2 crystals
1. No damping 2. Narrow bandwidth 3. Easier detecting small doppler shifts 4. Able to measure very high velocities |
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Pulse wave doppler:
How many crystals? Advantage? |
One crystal
Advantage: sample volume or gate (range resolution, range specificity, range ambiguity) |
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Simultaneous imaging and doppler is known as:
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Duplex Ultrasound
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* Eliminating aliasing improves the ability to measure the maximum ________ with doppler.
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Velocity
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There are ways to eliminate unwanted aliasing but,
* _______ _______ makes unwanted aliasing, only APPEAR to have vanished. |
Baseline shift ( using 0 )
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* What component of US machine exposes patient to greatest risk?
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The transducer
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* Portions of tissue that are BRIGHTNESS THAT SURROUNDING tissues, or
tissues that appear brighter than normal ? |
Hyperechoic
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* Portions of an image that are not as bright (or less than) surrounding tissues,
or tissues that appear less bright than normal? |
Hypoechoic
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Without echos, echo free?
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Anaechoic
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Equal echo brightness?
(Same shades of gray) |
Isoechoic
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A tissue or structure that has similar echo characteristics throughout?
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Homogeneous
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A variety of different echo characteristics within the tissue?
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Heyerogeneous
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* 90 degree angle cosine = ?
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Zero
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How does a SMALL sample volume (gate) effect doppler spectrum?
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Larger, clean envelopes
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How does a LARGE sample volume (gate) effect doppler spectrum?
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Smaller envelopes, with spectral broading (fill in)
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* What helps rid Aliasing?
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Zero baseline shift
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* Nyquist limit equation?
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kHz=PRF/2
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* Eliminating Aliasing improves the ability to measure the _______?
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Maximum velocity with doppler
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* Aliasing is more likely to occur with
(high or low) frequency transducers? |
High
(Low is desirable for pulsed doppler) |
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* If transducer frequency is doubled, doppler shift is _______?
If transducer frequency is halved, doppler shift is _______? |
Doubled
Halved |
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* What is the gray scale on a doppler spectrum?
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The # of RBC'S traveling in that velocity,
and amplitude of the reflection |
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Color doppler reports ________ velocities.
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Average/mean
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* There is NO doppler shift at ____ degrees.
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90 degrees
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B. Right to left
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A. Left to right
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* What single control has the greatest effect on color doppler?
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Jet size
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* Doppler packets Aka __________,
are multiple pulses needed to determine Velocity. *Advantage? |
Ensemble length
MORE pulses, greater velocity accuracy! |
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* Spectral doppler (pulsed and cw) measures ________ velocity.
* Color flow measures ________ velocity. |
Peak
Mean |
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Why is there no color in this vessel?
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#1 disadvantage to color power mode (energy mode) doppler?
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Flash artifact
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* Fast Fourier Transform (FFT)
is a form of "spectral analysis" - aka processing doppler signals) for what type of doppler? |
Pulsed and CW doppler
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* Autocorrection or correlation function
is a form of spectral analysis for what type of doppler? *It is slightly *less accurate, but substantially ______ than FFT. |
Color flow doppler
faster |
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* Steering the sound beam further away from ____ degrees, and closer to ____ degrees,
increases the __________. |
Doppler shift, color flow
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What can be done to fix this?
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Increase the scale (Aka increase *PRF)
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What can be done to fix this?
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Decrease color doppler gain
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The phenomenon where high velocities appear negative is called?
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Aliasing
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The frequency at which aliasing occurs is called?
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Nyquist limit
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Doppler shift produces information about?
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Velocity
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True or false
Only pulsed wave doppler exams have a sample volume? |
True
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C. 2.2 kHz
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*What feature does pulsed wave doppler have that CW doppler doesn't?
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Pulsed wave has a RECEIVE GATE THAT IS ADJUSTED by Sonographer.
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What is the difference between speed and velocity?
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Speed has only magnitude.
Velocity has magnitude and direction. |
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What is the typical range of doppler shift found in diagnostic imaging?
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20Hz to 20kHz (audible)
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The area of interrogation in a pulsed doppler exam is called?
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Sample volume
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What angle will doppler shift be at a maximum?
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0 or 180 degrees
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What angle will doppler shift be at a minimum?
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90 degrees
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5 causes of artifacts?
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Reverberation appear as "ping pong" btwn 2 reflectors.
Usually are _______ and _________. |
Multiple and equally spaced.
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What type artifact?
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Reverberation
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What type of artifact?
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Comet tail, ring down.
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Ring down appears as?
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Single, long, solid hyperechoic line..
Parallel to sound beam. |
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* Shadowing occurs when structure has _______ than usual attenuation.
*and appears? |
higher
anechoic/hypoechoic |
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What type of artifact?
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Edge shadow
OR Shadow by refraction |
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Edge shadow OR shadowing by refraction is:
Refraction at the edge of a _______ structure. |
Circular structure
(Such as testes) |
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A hyperechoic region appearing beneath a structure with ABNORMALLY LOW attenuation?
(Foreground color) |
Enhancement
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With enhancement, do the correct # of anatomic structures appear on the image?
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Yes!
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A normal GB has _____ attenuation.
A GB stone has _____ attenuation. |
Low
High |
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With mirror artifact, the artifact is always _______ than the real anatomy.
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Deeper
(Equally spaced/distance from mirror) |
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What artifact is:
Ultrasound system ASSUMES that sound travels directly to a reflector and back to transducer? |
Mirror image
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Propagation speed errors (range error artifact) appear as a _______?
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Step off, split, or cut.
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The correct # of reflectors, but wrong depth is what artifact?
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Propagation speed error
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When the propagation speed (error) is greater/faster than 1540 m/s, the reflector will be placed too _______ on the display.
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Shallow
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When the propagation speed (error) is LESS than 1540 m/s, the reflector will be placed too _______ on the display.
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Deep
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* What fixes artifacts?
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Change the view
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What artifact:
Cannot identity artifact from true anatomy from single static image. (appears side by side with true anatomy) |
Refraction artifact
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Side lobe artifacts degrade _______ resolution.
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Lateral
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What fixes (grating) side lobes?
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Apodization and Subdicing
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* Slice thickness artifact is Aka? (2)
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Partial volume artifact
Section thickness artifact |
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Slice thickness artifact makes cystic structures appear?
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Filled in
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* How do you fix Slice thickness artifact?
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Fixed with a 1 1/2 dimensional array transducer
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* Generally, linear array transducers have poor ________ resolution.
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Elevational
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* Acustic speckle is a ______ appearance in the _____ part of the picture.
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Grainy
Shallow |
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Acustic speckle is created by ________ effects.
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Interference effects
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*How do you cure Range ambiguity artifact?
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Lower the PRF
(make image deeper) |
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What artifact places the artifact too Shallow on the image?
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Range ambiguity
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* Color flash aka "ghosting" is eliminated by?
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US knob called "wall filter" or "high pass filter"
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Wall filters are used to reject?
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Clutter/speckle
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Turn off wall filter
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Mirror. Found in ______ only.
Happens when ______ is too high. |
Doppler only
Doppler gain too high |
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Quality Assurance:
*A phantom is an ______ standard. |
OBJECTIVE STANDARD
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* Propagation speed thru soft tissue?
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1540 m/s
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* Downfall of the AIUM 100mm, water filled phantom test?
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Cannot evaluate gray scale
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What phantom mimics soft tissue and can evaluate gray scale?
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Tissue equivalent phantom
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Doppler phantoms are used to evaluate _____ kinds of dopplers.
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ALL kinds of doppler
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* 2 types of doppler phantom equipment?
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Vibrating string
and Moving belt |
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Performance Measures:
* Minimum sensitivity? |
TGC set flat, increasing the gain
until deep pin is visualized. |
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Performance Measures:
* Normal sensitivity? |
Gain setting where ALL THE PINS are visualized.
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Performance Measures:
*Sensitivity? |
Adjustments to make an object go from fully bright to scarcely visable.
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What helps eliminate the DEAD ZONE?
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Acustic standoff pad,
Gel pack, or IV bag. |
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* A family member can be used to interpet, but never
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Consent
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True or false:
Patient may revoke consent at any time. |
True
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* Patients who feel out of control and most vulnerable are?
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Sick and old
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* Hydrophone measures the ______ in a sound beam.
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Pressure
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* Calorimeter tells us the total ______ of the beam.
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energy/heat gain
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* Thermocouple tells us the _______ of the sound beam at ______ locations.
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Intensity
SPECIFIC LOCATIONS |
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* The science of identifying and measuring characteristics of an ultrasound field, which are especially relevant to its potential for producing biological effects, is?
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Dosimetry
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* The Food and Drug Administration REGULATES system and ______ outputs.
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transducer
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*What is the AIUM bioeffect intensity limit? (*SPTA*)
Focused and unfocused? |
Focused: 1W/cm2 (1000 mW/cm2)
Unfocused: 100mW/cm2 |
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* Highest output intensities are used with _____?
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Pulsed Doppler
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* Lowest output intensities are with ______?
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Gray scale imaging
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* Study techniques for biologic effects:
The strongest conclusions are made when mechanistic and emprical approaches are in _______ with each other? |
Agreement with each other
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True or false:
There is no evidence that vibration harms tissues. |
True
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* The biggest absorber in the body is ______.
Therefore temperature elevation is _________. |
Bone
More likely |
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* SPTA is related to?
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Tissue heating
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* Temperature elevation in fetal soft tissue is considered of greater harm than adults.
Therefore fetal soft tissues adjacent to ______ are of greater concern. |
Bone
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* Any exam that causes a temperature elevation greater than ________ is considered potentially harmful to a fetus.
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41 degrees C
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Is thermal index of 2 means that a temperature elevation of 2 degrees centigrade ____ occur.
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MAY
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* 3 thermal index's:
#1 TIS? |
Thermal index in soft tissue
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* 3 thermal index's:
#2 TIB? |
Thermal index where bone is at the beams focus
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* 3 thermal index's:
#3 TIC? |
Thermal index where cranial bone is near the skin surface (near field)
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* What type of beam is more likely to cause temperature elevation in tissues?
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Unfocused
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* Mechanical index is higher and more likely to produce cavitation with ____? (2)
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Peak rarefaction pressure
and lower frequency |
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* Peak rarefaction pressure has what effect on microbubbles?
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Expands the bubble
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* Where in the body is the most likely site for cavitation and why?
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LUNG
because has gas bubbles |
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Bubbles do not burst in what type of cavitation?
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Stable
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Bubbles that expand during peak rarefactions and the bubbles burst is known as what type of cavitation?
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Transient (or normal) cavitation
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What type of cavitation has highly localized violent effects such as enormous pressures and colossal temperatures?
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Transient
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Cavitation measures the pressure of ultrasound pulses, therefore the units are?
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Pascals
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* The AIUM says 2 general concepts regarding bioeffects:
#1 In vitro (in glass) studies: results are ______. #2 Although results are important scientifically, studies which claim direct clinical significance should be viewed _________? |
Real.
With caution. |
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* AIUM States that diagnostic ultrasound should be performed when the potential benefits outweigh the ______.
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Risks
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* The ALARA principal required to produce optimal images is to use _______ output power and ______ receiver gain.
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Minimum output power and
Highest receiver gain. |
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* What component of an ultrasound machine exposes the patient to greatest risk?
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Transducer
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The greatest risk from a cracked transducer housing is ______?
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Electrical shock
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What sound parameter is determined only by the medium?
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Propagation speed
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* Propagation speed through tendon is about?
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1850 m/s
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* Propagation speed through bone is about?
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2000-4000 m/s
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The range of frequencies in a pulse is: ?
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Bandwidth
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The maximum cyclical change in a quantity is known as?
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Amplitude
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The # of images displayed per second in real time imaging is?
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Frame Rate
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* Trapezoidal shape = ?
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Vector image (from linear)
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Dynamic apature helps ______ resolution?
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Lateral
(apature aka face of transducer ) |
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Common causes for propagation speed error (range equation)
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Fat and fluid
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