Knobology Flashcards
What is the best way to optimize an ultrasound machine?
Read the user manual
What are presets for?
To optimize an image for the assumed scanning conditions
What do presets help avoid?
Bio effects
When using presets it is important to?
- Use the correct one for the type of exam
2. Make adjustments beyond the preset
What is important to know about transducer selection?
- The probe must be plugged in to select it
2. Never unplug an active plug (damage)
What is multihertz?
Numerical gauge on frequency selection.
(On phillips machines = res/gen/pen
What is harmonics?
When it is activated the machine sends out a frequency but receives double that frequency when the echos return.
(2Mz out, 4 MHz back in)
When should harmonics be used?
Whenever the penetration allows
What is Coded Harmonics?
Allows for excellent penetration with higher frequencies
What is transmit power?
The intensity of the ultrasound beam transmitted into the patient
Increasing the transmitted power (intensity) will change what?
- Decrease/improve the SNR (signal to noise ratio)
2. Enhance sensitivity
When you turn on your machine, what will the transmit power be set at?
100%
In what situation would you turn the power down?
When using doppler on a fetus because doppler puts out more power
What does Gain do?
It amplifies all of the returning echos during signal processing
What unit is gain expressed in?
Decibels
What is TGC?
A receiver gain that adjusts the echos according to time delay (or depth).
How does changing depth effect TGC?
You have to readjust, changing depth changes the TGC
What knobology uses the range equation?
TGC
Do Gain and TGC improve the SNR?
No
How is TGC expressed?
As a slope.
An increase in slope is an increase in amplification.
What is the golden rule of TGC’s?
Never move one at a time
What is lateral gain?
Found on cardiac equipment, used to compensate for side-to-side non-uniformities in brightness due to different pathways
How does lateral gain differ from TGC?
It alters echo intensities from individual scan lines on the periphery of the image
What does focus do?
It adjusts the depth of near field to improve the lateral resolution at the area of interest.
What happens if multiple foci are used for a larger field?
The frame rate is significantly reduced (takes more time = choppier image).
What is co-processing?
A means of helping reduce the impact of the reduction in frame rate
What does focus impact?
Frame rate.
It gives better resolution at multiple points.
(We don’t use on something moving)
What does depth do?
Ability to maximize the field of view, as depth changes the echo info is redistributed to fit the monitor.
What does depth influence?
Frame rate and line density since the speed of sound is constant.
What is line density?
The density of scan lines in an image (the sound going and coming back).
How does changing the depth effect line density?
An decrease in depth will increase the line density,
What happens at a large depth?
The lines are less dense (spread out) which equals less information because the machine “makes up info” to fill in the gaps.
What is dynamic range?
A form of compression that reduces the number of shades of grey to increase the contrast of the image.
What happens when Dynamic Range is reduced?
Weak echos and noise are removed
What is another name for Dynamic Range on other machines?
Compression
How many shades of grey does the machine have? How many can the human eye see?
256 machine
100 human eye
Why is it important to have dynamic range set properly?
If wrong, it can prevent the visualization of small low-contrast structures (decreases tissue differentiation).
What is the limit of dynamic range?
Bi-stable (black and white)
What is freeze?
Control that stops the transducer from sending out sound, the machine continually writes the last available frame to display
What does freeze eliminate?
Real time blurr from capturing a moving image
What is cineloop?
The systems memory allows for a number of frames to be saved until the image is frozen
What does cineloop allow?
Frame by frame analysis in order to select the best image
How many frames does a machine store with cineloop?
Hundreds
What is sector width?
The ability to reduce the field of view by firing fewer scan lines
What types of probes have the option of sector width?
Curved linear and echo
What does sector width effect?
Decreasing the sector width will:
- Decreases the area
- Improves line density (concentrates the sound)
- Improve frame rate (spatial resolution)
What is dual image?
The ability to split the screen when demonstrating certain anatomy or pathology
Why was dual image invented?
As a cost saving measure when images were on film
What is persistence?
Reduces noise by applying temporal averaging to individual pixels
How does the operator control persistence?
By selecting the number of frames being averaged so that the image is more consistent
How does increasing persistence effect frame rate?
Increasing persistence decreases the frame rate
When is persistence not used?
For cardiac applications because we want a high frame rate in order to see small movements.
What is an example of calculations available on the machine?
Specific OB measurements and calculations available in an OB preset
What is zoom?
Magnifies the image, there are two diff types of zoom
What is write zoom?
Magnifies the image before it is written to memory (the zoom before you freeze).
“Optical zoom = the good one”
What is read zoom?
Magnifies the image after the image is committed to the systems memory (after image is frozen)
“Digital zoom = bad quality”
What type of zoom improves resolution?
Write zoom (magnifies before freeze)
Resolution is lost with read zoom
What are maps?
A way of redistributing the shades of grey displayed so that emphasis is given to particular values (used to brighten low level echos but ignore echoes above a threshold or vice versa)
Can maps be applied after freeze?
Yes
What is video invert?
Used to detect subtle changes in echotexture, fluid can be seen as white and soft tissue as black.
Not common practice
What is image invert?
Image is inverted top to bottom or left to right by changing the horizontal/vertical orientation of the image on the diplay
When is image invert used?
For intervention.
For a biopsy the performing physician may prefer to see the needle coming from a specific angle
What are hidden functions?
Some applications maybe be hidden until times of need
What is an example of a hidden function?
Biopsy needle overlay (to assist with intervention)
What is pre-processing?
Any control that can be adjusted before the image is frozen (committed to memory).
What is post-processing?
Controls applied to the image after it is frozen
What control is both post and pre processing?
2 D Gain
What are the doppler controls?
- Gain
- Scale (PRF)
- Steer
- Invert
What is compound imaging?
A combination of beam steering and frame averaging that can improve SNR and help eliminate artifacts
What is another name for compound imaging? (On our machine?)
Sono CT
Why should compound imaging not be used all the time?
Some artifacts are useful in diagnosis so it is not helpful to always eliminate them.
(Kidney stone: we need to see the shadows)
What is panoramic imaging?
If an area of interest is larger than the transducer face, panoramic allows the system to store multiple frames of a sweep and display the entire area
