1. True or False a) In medical x-ray imaging, photon noise is the dominant sourc
ID: 3279821 • Letter: 1
Question
1. True or False
a) In medical x-ray imaging, photon noise is the dominant source of noise.
b) In medical x-ray imaging, signal can be considered only as the number of x-ray photons detected by the detector and it is not related to the x-ray intensity map from the x-ray source.
c) The ability of differentiating two materials in an x-ray image depends on the contrast-to-noise ratio of the two materials in the x-ray image.
d) For a given x-ray imaging system with a fixed x-ray source to detector distance, the x-ray source penumbral blur will decrease when the object is placed closer to the detector.
Explanation / Answer
a). In a good medical imaging system, quantum noise ( photon noise), which is unavoidable is the dominant source of noise.
b). It also depends on the intensity.
c). Yes. it depends on how well your ratio is.
d).A greater distance between the source and the object will reduce geometric unsharpness. However, the intensity of the source decreases as the distance increases. Therefore, the source should be placed only as far away as necessary to control the penumbra. If the test object is placed in direct contact with the detector (like is often done in film radiograph) the following formula can be used that takes into account the material thickness instead of the object-to-detector distance.
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