3.4 Perform relative dose measurements in external beam radiotherapy and relate to absolute dose

Recommended Items of Training

Dosimeter related issues
a. Gain an understanding of the appropriate use of dosimeters for relative dose measurements. Summarize this use.
b. Gain an understanding of factors influencing a dose measurement under non-reference conditions. Summarize your findings.

Phantom related issues
c. Gain an understanding of the requirements for dosimeters and phantom material & design for measurements in phantoms .
d. Explain correction factors required for non water-equivalent phantom materials (difference for photons and electrons).

Auxiliary related issues
e. Gain familiarity and high level skills with the operation of a water phantom system including knowledge of statistical analysis, correction facilities, ancillary functions that may be provided with the system.
f. Gain an understanding of the design criteria and purpose of common dosimetric accessories such as intercomparison jigs or blocks, calibration blocks and their correct usage. By practical use develop skills to use appropriately and efficiently.

TPS related issues
g. Determine at least the following items in a water phantom at regular intervals:

  • Percentage depth dose
  • Beam profiles: open, blocked, wedged fields
  • scatter factors (collimator scatter, phantom scatter)

h. Determine the following items regularly (if used) in solid and water phantoms (using different dosimetry equipment):

  • Wedge (physical and dynamic) output factors
  • Total scatter factors
  • Collimator scatter and phantom scatter factors
  • Compensator factors
  • Electron cutout factors
  • Tray transmission factors

i. Perform measurements with film (if available) in a solid phantom.
j. Analyse the uncertainty of the dose measurements.

k. Perform procedures under examination conditions with qualified ROMPs

Training, Evidence and Notes

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