Description
1. (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.
2. (1 p) What is meant by vignetting in radiographic imaging and what are the
effects of this artifact?
3. (0.5 p) What determines the highest energy of x-ray photons emitted from an xray tube? What determines the energy spectrum of the x-ray photons?
4. (1 p) Compare characteristic radiation and bremsstrahlung radiation. What are
their similarities and differences?
5. (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
6. (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?
7. (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?