Dynamic Range Flashcards
What is Dynamic Range?
A method of reporting the extent to which signals vary and can still produce accurate images
Units: dB
What does the term Threshold refer to in dynamic range?
Smallest signals that are accurately measured; minimum intensity which should be exceeded to get a certain change
What happens to signals below the threshold?
They are too weak and will not be recognized by the system and are tossed out
What is the Saturation Point?
Largest signals (max. intensity) that are accurately measured
What occurs to signals above the saturation point?
They are too strong and are read as the max. intensity value
How is Dynamic Range calculated?
(threshold) to (saturation point)
Define Contrast Resolution.
Ability to distinguish the different/adjacent reflectors and still produce similar echoes
What characterizes a Narrow Dynamic Range?
Limited choices; bistable (black and white)
High contrast
What characterizes a Wide Dynamic Range?
Many choices; gray scale imaging (possible due to digital scan converter)
Low contrast
What is Compression in the context of dynamic range?
Performed by the ultrasound machine to display the image; signal ranking remains the same, but the range is changed
How can a sonographer adjust the dynamic range?
Via Gray Scale Mapping
What are the components of an Ultrasound System?
Transducer, Receiver, Amplifier, Scan Converter, Display, Archive
Each component plays a vital role in the functioning of an ultrasound system.
What does a narrow dynamic range refer to in ultrasound imaging?
Fewer Shades, Few choices, Black and white (bistable)
A narrow dynamic range limits the variety of grayscale in the images.
What is the typical dynamic range of high contrast in ultrasound imaging?
100-120 dB
High contrast allows for better differentiation between various tissues.
What is the formula for calculating the dynamic range of a compressed signal?
Uncompressed signal - amount of compression = dynamic range of compressed signal
This formula helps assess the impact of compression on signal quality.
What does the term ‘low contrast resolution’ refer to?
60-100 dB
Low contrast resolution indicates a lower ability to distinguish between similar tissues.
What is the mathematical relationship involving decibels in ultrasound?
Decibels add or subtract
This relationship is crucial for understanding how dynamic ranges are affected by compression.
Fill in the blank: A dynamic range of _____ is considered low contrast.
40-50 dB
Low contrast ranges indicate limited differentiation in image quality.
What is the dynamic range of images that is always less than the display?
10-20 dB
This indicates that the quality of the captured image may not fully utilize the display capabilities.
What are the characteristics of a wide dynamic range in ultrasound?
More Shades, Many choices, Gray scale
A wide dynamic range enhances the ability to visualize subtle differences in tissue density.
What does high contrast resolution indicate?
High contrast, Wide dynamic range
High contrast resolution is essential for accurate diagnosis based on imaging.
What is the dynamic range for images that are low contrast?
20-30 dB
Low contrast images can make it difficult to differentiate between various tissues.
What is the typical dynamic range for compressed signals?
10-30 dB
Compressed signals often result in a loss of detail and contrast.
