Part I Trial Papers


Completed past papers

  1. February 2005 paper

Trial papers

  1. pseudo-Trial Paper 1
  2. pseudo-Trial Paper 2
  3. marked physics papers
  • Question 1

1. A deep lobe of parotid tumour is to be treated with radiation therapy treatment. Describe each of the following treatment techniques with particular attention to the limitations and possible solutions:
(a) fixed field electrons (3 marks)
(b) MV photons (3 marks)
(c) electron/photon mix (4 marks)

  • Question 2

2. Dosimetry for IMRT is routinely undertaken.
(a) Indentify 2 types of dosimeter commonly used for this application (2 marks)
(b) Describe the physical principles upon which the above dosimeters operate and the advatages and disadvantages of these dosimeters. (6 marks)
(c) Comment on the statement that "if this type of dosimetry is required with a linac that has been properly commisioned, perhaps the initial commissioning was a waste of time". (2 marks)

  • Question 3

3. Cobalt machines are still commonly used in external beam radiation therapy throughout the second and third worlds.
a) Draw a schematic diagrams of a cobalt machine describing its safety features (2 marks)
b) Draw a schematic diagram of the field definition system detailing its performance. (2 marks)
c) Describe the benefits of using cobalt machine with a 100cm, rather than 60cm isocetric mounting. (2 marks)
d) describe how dose is controlled and delivered by the cobalt machine. (2 marks)
e) what are the advantages that make the cobalt so attractive to its users. (2 marks)

  • Question 4.

The photons used in clinical radiotherapy can interact with matter in several ways.
a) Photoelectric Effect: describe the major disadvantage of this interaction and how it arises. (2 marks)
b) Compton Scattering: describe how bone can absorb more dose while still having a lower Compton Scattering effect in the MV range (2 marks)
c) Pair Production: describe in detail pair production and where it is most useful. (4 marks)
d) there are two other lesser known effects - Coherent Scattering and Triplet Production - give a brief description of these two processes. (2 marks)

  • Question 5.

a) Define the terms “Brachytherapy” and "Unsealed source". (2 marks)
b) Using the example of Iodine, describe the properties that make it ideal for its range of uses in Clinical Radiotherapy. (3 marks)
c) Describe the benefits and difficulties arising if the Iodine isotopes were substituted in the range of uses you have described above. (3 marks)
d) describe the management of a staff member who has ingested radioactive iodine (2 marks)

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