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Ch 28 Physics
Ch 28 physics
Question | Answer |
---|---|
What are the 2 principle characteristics of medical imaging? | spatial and contrast resolution |
What is spatial resolution usually described as? | the size of an object that can be viewed |
What is spatial frequency expressed in? | line pairs/millimeter |
As the spatial frequency becomes ______, the object becomes smaller. | larger |
The liver, kidneys, and brain have a ______ spatial frequency. | low |
What limits the spatial resolution? also in CH 26 | pixels |
An imaging system with a _________ spatial frequency has better _______ ____________. | higher, spatial resolution |
When calculating the Spatial frequency, you have to double the spatial resolution and then divide by the reciporal. Pg 450! | read pg 450! |
The ability of an imaging system to render objects of different sizes onto an image is? | modulation transfer function MTF |
The ideal imaging system would have a MTF equal to ______. | one |
Objects with _______ spatial frequency are more difficult to image. | higher |
How many pixels are required to form a line pair? | 2 |
A _______ _________ test tool is used to measure the blur of the increased spatial resolution. | bar pattern |
______ increases when 2 screens are used. | MTF |
What is contrast resolution? | ability to distinguish many shades of gray from black and white |
How many shades of gray can the human eye visualize? | 30 |
The number of gray shades that an image can reproduce? | dynamic range |
What is the dynamic range in digital imaging identified by? | bit capacity of each pixel |
What modality has the highest dynamic range? | mammo |
What is contrast resolution limited by? | noise or SNR |
When using digital imaging, __________ is constant, so a higher ________ can be used to reduce patient dosage. | contrast, kVp |
What is the purpose of the Contrast Detail curve? | shows when an objects contrast is high, small objects can be imaged; when it is low, large objects can be imaged |
________ influences spaital resolution while ______ influences contrast resolution. | MTF, SNR |
In screen-film radiology, what controls the spatial resolution? | focal spot size |
In digital imaging, what controls the spatial resolution? | pixel size |
When should a film be repeated? | never! Unless the entire body part is clipped |
The possibility of x-ray interacting with the image receptor is termed? Also is related to the absorption coefficient and to the SF of the signal.... ppt | Detective Quantum Efficiency |
What does the term DQE stand for? | Detective Quantum Efficiency |
The _______ is the portion of the image forming x-ray that represents the anatomy. | signal |
____ limits contrast resolution. | noise |