What are the differences (disadvantages and advantages) between LINACS and Cobalt-60 machines e.g. doserate?
 Sketch the main components of a linear accelerator.
 Describe the theory of beam production and the part each component plays in the production of a clincally useful beam:
· Klystrons & Magnetron
· Electron Gun
· Accelerator Waveguide
· Bending Magnet
· Flattening Filter
· Collimation (primary & secondary)
· Monitor Ionisation Chambers
· Wedges (physical/flying/dynamic)
 What changes are made to change the Linac from photon to electron mode?
 What are the differences between the Varian 600C and the Siemens KD2?
Orthovoltage (Conventional) X-ray Machines
 Describe the operation of a standard therapy x-ray machine.
 What is the purpose of the beryllium window (how thick)?
 How is most of the energy lost?
 Describe how and why full wave rectification of the high voltage supply is necessary.
 Sketch the radiation spectrum seen, with and without the effect of target filtration and additional filtration.
 Explain the need for external filters.
 What materials are used?
 Why do applicators for x-rays (>150kVp) have a closed perspex end?
 What is the ‘Heel Effect’?
 Sketch depth dose curves for 300, 100 and 50kV x-rays.
 What are the approximate 90% depths for low and medium energies?
 Sketch a free air ionisation chamber set-up.
 What is the definition of exposure?
 How does this affect the design of the free-air ionisation chamber?
 What thickness of surrounding air is required at 200kV? 300kV?
 Sketch a simple thimble chamber.
 What is the air equivalent wall?
 What is the calibration chain for ionisation chambers at your training hospital?
 Describe the consistency checks using Strontium-90.
Photon/Electron Interactions & Depth Dose Characteristics
 Describe the main photon interaction processes, their energy and atomic number dependence and threshold for domination using a graph.
 Describe the main electron interaction processes.
 Sketch depth dose curves and isodose distributions for kilovoltage, megavoltage and electron beams.
 What is the ‘rule of thumb’ describing the relationship between dMAX and the photon/electron energy?
 What are the advantages in terms of treatment planning of each of these types of radiation?
Exposure, Absorbed Dose and Air Kerma
 Give the definitions and units of each of the above quantities.
 How are the three related?
 What calculations must be made to change dose in air to dose in water?
 Sketch graphs indicating the differences at increasing energy for bone and tissue.
 Under what conditions can air kerma and dose be considered identical, when not?
 What is intracavity brachytherapy?
 What are the advantages of this type of treatment?
 Describe the properties of an ideal source and relate to currently used Cs-137 & Ra-226.
 What are the advantages of afterloading brachytherapy devices?
 What are the approximate dose rates for LDR, MDR & HDR afterloading systems?
 What are biological effects of using a LDR or MDR machine?
 Describe the Selectron suite and afterloading machine (plus applicators) at your training hospital.
 What radiation protection devices are in place?
 What is the purpose of catheterisation?
 What are the anatomical origins and geometrical positions of points A & B in the Manchester system?
 What are the dose limits to the rectal and bladder points?
 What are the major features of the Paris system of dosimetry (9 Rules)?
 How does this differ from the Manchester system?
 What are the properties of Ir-192?
 In dose calculations what are the basal doserate, the reference doserate and the treatment volume.
 What is the effective length of the hairpin taken to be?
Unsealed Source Therapy
 What are the properties of I-131?
 How is it used therapeutically?
 What are the administered activities for ablation and overactive thyroid treatment?
 Describe the procedure in each case.
QA Procedures (Megavoltage)
 List the daily checks performed and the tolerances for each result.
 What additional checks are performed weekly?
 List the checks performed monthly on the Linac (8).
 What codes of practice are used?
 Describe the experimental set-up including the field size, MU, build-up material, tolerances, etc. for each check.
 What is the definition of TMR?
QA Procedures (Kilovoltage)
 What is the code of practice relating to kilovoltage output measurements?
 How has this changed since the previous document?
 How are the three energy ranges categorised?
 Describe the procedure for checking the output reading.
 What is the backscatter factor?
 What corrections must be applied to the instrument reading? After multiplication by chamber calibration factor, mass absorption coefficient, ratio water/air, etc.
 What are the differences between the measurement/calculation made for outputs at 90, 135 and 300kV?
 What other QC procedures might be carried out on the kilovoltage unit (5)?
 Describe the calibration chain for ionisation chambers & dosemeters.
 Describe the procedure for consistency checks with Sr-90.
 Briefly describe QC checks performed on the Selectron.