Description
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(0.5 p) For the following changes in an x-ray imaging system indicate the effect on subject contrast (i.e. increase, decrease or no effect):
– increase in patient thickness, – increase in kVp,
– reduction in field of view of the detector
– use of a high atomic number contrast agent.
Provide a brief explanation for each of your answers.
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(1 p) What is meant by vignetting in radiographic imaging and what are the effects of this artifact?
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(0.5 p) What determines the highest energy of x-ray photons emitted from an x-ray tube? What determines the energy spectrum of the x-ray photons?
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(1 p) Compare characteristic radiation and bremsstrahlung radiation. What are their similarities and differences?
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(1 p) Using relativistic equations, determine the speed of an electron that is accelerated across a 120 kV potential in the X-Ray tube.
From Einstein’s theory of relativity, we know that the (relativistic) mass of a particle is given by
= #$ ) where , is the rest mass of the particle, v is the speed of the particle, and c is the
%&’(*)
speed of light.
The kinetic energy of a particle is the difference in energy between the moving particle and the stationary particle.
= −,= 1−,1
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(1 p) If 80% of x-ray photons of a certain energy pass through a slab of material, what percentage passes through a slab of the material which is twice as thick as the original slab?
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(1 p) A chest radiograph is 36cm×43cm. If we want to preserve all the detail in the image, to a spatial resolution 5mm−1, how many pixels would be required? What will be the size of the image, if quantization were performed on 256 gray levels?
