Ultrasound Imaging Parts Flashcards
What are the ultrasound imaging parts? (7)
- transducer
- pulser
- beam former
- receiver
- memory
- display
- master synchronizer
What does the beam former do?
It is the “brain” – it controls the phasing of the transducer. It figures out the timing of everything
What does the pulser do?
It’s the “braun” – it creates the voltage needed to excite crystals & make the pulse. It tells memory & receiver that contact has been made with the probe
Other names for the pulser voltage? (6)
Acoustic power, output power, transmit, output, energy output, output gain
Does pulser voltage have bioeffects?
Yes – always use the lowest power possible
What does the receiver do?
Preps information from signals that return to the probe then eventually displays them on the monitor
What are the operations of the receiver?
Amplification
Compensation
Compression
Demodulation
Rejection
What is another name for amplification?
Receiver gain
What is amplification/receiver gain?
Small voltages are boosted and made stronger.
What is the result of increasing amplification/receiver gain?
The image’s overall echogenicity is increased
What is preamplification?
The process of improving the signal quality before it’s amplified. Large spikes are clipped and very weak signals are amplified
Where is the preamplifier?
Between the transducer and amplifier
What are the synonyms for compensation? (4)
- Swept gain
- Time gain compensation (TGC)
- Depth gain compensation (DGC)
- Line gain compensation (LGC)
What does compensation do?
It compensates for attenuation because of depth for uniform echogenicity
What are the synonyms for compression? (2)
- Log compression
- Dynamic range
What is the relationship between dynamic range and compression?
Inversely related – compression/log compression are ACTIONS on the dynamic range
What is dynamic range?
the range of amplitudes in the signal
What is compression?
The ratio of the greatest to smallest amplitudes that can be handled by the US machine
What happens when you increase dynamic range (DR)?
Increase dynamic range
Increase shades of grey
Decrease contrast
Increase contrast resolution
Smoother image
What happens when you increase compression?
Increase compression
Decrease dynamic range
Decrease shades of grey
Decrease contrast resolution
More contrast!
When would you want to drop dynamic range/increase compression?
When you need more contrast between two structures
Ex: cysts
What is demodulation?
The process of changing voltages to another form more suitable for display
What are the 2 parts of demodulation?
- Rectification
- Smoothing
What is rectification?
Turning negative signals to positive signals
What is smoothing?
Averaging the signals to remove “bumps” of voltage signal
What are the synonyms for rejection? (4)
- Suppression
- Threshold
- Filter
- Wall filter
What is rejection/suppression/filter/threshold?
The process of eliminating small voltage amplitudes
What is the purpose of suppression?
To reduce noise in spectral and clutter in color doppler
Which one of the receiver’s operations is not user adjustable?
Demodulation
What is the synonym for scan converter?
Memory
What does the scan converter/memory do?
Stores information coming from the receiver
What are the two ways to store data?
- Analog
- Digital
What are the elements of digital scan converters? (2)
- Pixels
- Bits
What is a pixel?
Picture element – the smallest building block of digital pictures
What is a bit?
Binary digit – the smallest amount of computer memory
What determines a pixel’s shade of grey?
The number of bits it has
What is contrast resolution?
The ability to show various shades of grey
What is pre-processing?
Manipulating the image data before storage in the scan converter. This happens before freezing the image
What are synonyms for write zoom?
RES (regional expansion selection), write zoom, HD
What does RES/write zoom/HD do to the image?
It takes the ROI, rescans it, and this image has more scan lines and pixel density, leading to better spatial resolution
Is RES/write zoom/HD pre or post processing?
Pre-processing
Synonyms for persistence? (2)
Temporal compounding and temporal averaging
What is persistence/temporal averaging/temporal compounding?
Purposely slowing the frame rate down with frame averaging to see a smoother image
When is it a good time to use persistence?
When we’re scanning bigger organs that don’t move too much
When should we turn persistence off?
When we’re scanning anything that moves quickly – echo
What is fill-in interpolation?
When the machine fills in missing pixels by using pixel averaging due to scan line divergence
What image formats use fill-in interpolation?
- Sector
- Blunted sector
What is post-processing?
The manipulation of image data after storing in scan converter
What are the synonyms for read zoom?
Read magnification, MAG, ZOOM
Is read zoom/mag/zoom pre or post processing?
Post-processing
What are the 2 synonyms for display?
- TV monitor
- Cathode ray tube (CRT)
What are the 3 types of displays?
- Interlaced display
- Noninterlaced display/progressive scan
- High res monitors/HD displays
How do interlaced displays work?
Made up of 525 horizontal lines – odd ones are written first & then even
Disadvantage of interlaced displays?
Eye strain, especially for moving objects
How to progressive scan/noninterlaced displays work?
Lines are written in sequence using raster scan
What is the advantage of progressive scans?
Less eye strain
How many horizontal lines do HD displays have?
1000+ lines
What is the advantage of HD displays?
More lines + more pixels = better spatial resolution
What are the two monitor controls that can also be found on printers?
Brightness & contrast
What are the 5 ways to record & archive images?
- multi-image camera
- laser printer
- thermal printer
- color thermal printer
- strip charts
Which archiving system(s) use photographic emulsion film?
Multi-image camera & laser printer
Which archiving system(s) use heat sensitive paper?
Thermal printers & color thermal printers
Which archiving system uses strips of paper to record info?
Strip charts
Advantages of multi-image camera for archiving?
Good spatial resolution
Disadvantage of multi-image cameras for archiving? (2)
Photographic film needs storage space
Retrieval problems
Advantages of laser printers? (3)
Good spatial & grey-scale resolution
More images on 1 sheet of film can save costs
Film develops automatically which can save time and labor costs
Disadvantages of laser printers? (2)
Storage & retrieval problems (like multi-image cameras)
Printing systems are expensive
Advantages of thermal printers? (2)
Portable & variable costs
Disadvantages of thermal printers? (2)
Unstable archival storage
Spatial & image resolution aren’t as good as film
Advantage of color thermal printers?
Full size color images
Disadvantage of color thermal printers
Desktop printers – not portable
What are strip charts used for?
M-mode & spectral doppler information
Fetal non-stress tests
Advantages of strip charts? (2)
Portable
Low-cost supplies
What are the two types of magnetic recording devices?
- Videotape casettes
- Fiber optics
Advantages of videotape cassettes? (2)
- images can be recorded in real time
- can be erased & written over
Disadvantages of videotape cassettes? (2)
- Magnetic tape becomes unstable overtime
- Europe & Asia have different formats
What are the two types of digital format storage options?
- Magneto-optical disc
- PACS/DIN/IMACS
How do magneto-optical discs save images digitally?
They combine read/write capabilities of magnetic technology with storage capabilities of optical media
What are the advantages of magneto-optical discs?
Think of them as hard drives/CD roms - more stable than VHS
Info can be saved, deleted, rewritten
What do PACS/DIN/IMACS stand for?
Picture archiving & communications system
Digital imaging network
Image management acquisition control system
What does the local area network (LAN) do for PACS?
Links together acquisition, display, archiving, and hard copy components
Advantages of PACS/DIN/IMACS? (4)
- Teleradiology
- Reduced necessity for different hard copy devices
- Lower film costs
- Lower time to retrieve images
Disadvantages of PACS/DIN/IMACS? (4)
- Complex
- Expensive
- Can be limited in spatial resolution
- Reduced accuracy –> less time on scan since it’s sent right away
What are on the axes of A-mode?
X-axis: depth
Y-axis: amplitude
What are on the axes of M-mode?
X-axis: time
Y-axis: depth & if there is motion or not
What are on the axes of B-mode?
X-axis: depth
Y-axis: none
Z-axis: amplitude/brightness
What are the 4 display modes in imaging?
- A-mode
- B-mode
- M-mode
- 3D
What is temporal resolution?
Resolution relating to time
What factors affect temporal resolution? (4)
- Line density
- Sector angle
- Multiple focal zones
- Imaging depth
What is the relationship between penetration depth, focal zones, and lines per frame?
Depth x # Focal zones x Lines per frame </= 77,000
