Module 2: Basic Instrumentation Flashcards
The Ultrasound systems converts the mechanical sound waves from the patient and converts them to what?
Electrical information
The converted voltages are processed by the machine to do what?
Reconstruct an image from the reflectors in the body
Once the voltages are processed by the machines to reconstruct an image from the reflectors in the body. What happens?
The voltages are stored and converted once again into the image we see on the monitor
What is the process for basic instrumentation?
- Tech
- Beam former
- Signal processor
- Image processor
- Display
What is the process for beam formers?
- Tech
- Transducer
- Amplifier
- ADC’s
- Echo delays
- Sum
- Signal processors
What is the other alternative process for beam former?
- Pulsed
- Pulse delay
- T/R
- Amplifiers
- ADC
- Echo delays
- Sum
- To signal processors
Digitizations of the voltage is crucial to maintain what?
The integrity of the data through the system
The process of digitizations involves what?
Converting the voltage into a binary number which is more stable
Digitizations can occur before or after what?
The echo delay in the beam former but the preferences is before to stabilize the signal early on
Signal processing involves what two steps?
- ADC
- The receiver
What is the function of the receiver?
It’s function is to process the returned echoes as analog voltages in preparation for display
There are five separate steps for the receiver preparing images for display. What are they?
- Amplification
- Compensation
- Compression
- Rejection
- Demodulation (includes rectification and smoothing)
Rac cd
Why must we use amplification for images?
Returning echos are weak and must be amplified if they are to make it through the circulatory of the machine
We further control the amount of amplification to do what?
To satisfy the need to brighten or darken the image
What is the control for amplification? and how is it expressed?
The control is the GAIN and is expressed in decibels typically in the range of 60 - 100dB
What are the two reasons why we need to use compensation for images?
- Sound attenuates as it travels and thus there is a need to compensate for it
- Similar signals from reflectors should have the same brightness regardless of how deep you image the reflector
What is the control for the compensation control?
TGC is the control responsible and is expressed in dB with a range of around 60dB
TGC can also be called what?
DGC
TGC usually operates in what increments?
1cm increments and can correct for the main bang artifact and attenuation in the far field
What is the compression control? And what is it used for?
The compression control is known as dynamic range, and it is the process of decreasing the difference between the smallest (reject level) and largest (saturation) amplitudes and is expressed in decibels
What is logarithmic amplification?
Where the gain is applied exponentially as a function of the input signal level and the result is the compression of the dynamic range
What is the rejection function also known as?
Threshold or suppression
What is the rejection control used for?
To eliminate or suppress low level echoes that may represent noise and therefore, improve the signal to noise ratio
What does rejection control help with?
Reduce the dynamic range and may or may not be operator controlled
What is the demodulation?
The process which converts the radio frequency (RF) signal into a video signal for monitor display
Demodulation is the two stage process that includes what?
- Rectification
- Smoothing
Rectification turns all negative portions of the signal into what?
Positive ones
What is the basic instrumentation path?
- TX
- Beam former
- Signal processor
- Image processor
- Display
What is the image processing path?
- From signal processor
- Scan converter
- Pre processor
- Memory
- Post processor
- DAC
- To display
What is scan conversion?
A simple function of the scan converter is to write the vertical acquired ultrasound data horizontally to memory
The Scan converter or memory of a analog scan converter is similar to what?
CRT except that the phosphor face is replaced with a wafer or silicon called the dielectric matrix
For analog scan converters electrons emitted by the filament, pass through what?
The deflection plates and strike the silicon wafer leaving a negative charge proportional to the amplitude of the signal strengths
The electron beam of the analog converter moves across what?
Dielectric matrix in what is called a raster format
What is pre- processing?
Simply any processing of the wave signal before it is transferred and stored to memory
For preprocessing different ultrasound machines offer what?
Different processing
What are some pre- processing functions?
- Receiver functions
- Maps
- Interpolation
- Edge enhancement
- Write zoom
- Persistence
Rip mew
Maps are “curves” applied to what?
The shades of gray to accentuate different levels
The purpose of maps is to do what?
Enhance the visualization of certain aspects of the image
In preprocessing it has become apparent that there is a gap present between scan lines in the image, how do we correct for this?
Interpolation is used, which averages pixel grey scale values to fill in information where non exists.
What does Interpolation do in terms of appearance of pre- processing?
Improve the appearance but the trade off is “what is real”
Too much interpolation could do what?
Misrepresent the image
What is edge enhancement?
- Another tool to improve the look of the image
- It will sharpen the boundaries to make them more distinguishable and help make measurements more precise
What is a “kernel”?
Applied to the pixels to sharpen the boundaries to make them look more distinguishable
What is write zoom?
Expands the image before storage in the memory
What is the benefit of Write zoom for the sonographer?
The region of interest is adjustable by sonographer
What is ROI (region of interest)?
The box that occurs when we press zoom
What is the advantage of ROI?
Is that the ROI is rescanned and additional scan lines are added which increases spatial resolution, detailed and pixel ratio
What is persistence?
Takes data from several ultrasound frames and averages them before displaying the image to improve the signal to noise ratio
What is persistence also known as?
Frame average
What is the biggest negative portion of persistence?
Frame rate drops
Over use or “sampling” over time will decrease what?
The temporal resolution so the rate of movement must be small otherwise blurring occurs.
Because of the decrease of temporal resolution, persistence is not used for what?
- Echo
- Obstetrics
What is post processing?
An processing that occurs after the information has been stored into memory
Some examples of post processing include what?
- Measuring
- Annotations
- Post- processing curves
- Read zoom
- Color doppler mapping
- Angle correction
- B-Color (coloured 2-D)
crab map
What is the post processing curves function?
Curves can be applied to a frozen image and is the assignment of the display intensity (brightness) to a digital value
What is an example of an operator controlled function that is accomplished in the DAC?
Curves that are applied to a frozen image and is the assignment of display intensity
In terms of curves, how does each model vary?
Vary by the manufacturer
What is the most commonly used probe for Curves?
Linear curve
What is read zoom?
Post processing function that magnifies a frozen image by reassigning the pixel size.
What is an disadvantage of read zoom?
There is a decrease in resolution
What is the B colour function?
Uses various colour schemes from oranges to purples to blues.
Why would we use B colour?
It may help improve the contrast resolution of the image
What is the DAC (digital analog converter)?
The function that reconverts the digital information into voltage signal
Label the image
Label the image
Label the basic instrumentation pathway
Label the beam former pathway
Label the beam former pathway
Label the image processing pathway
