RADIATION PROTECTION IN RADIOTHERAPY

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RADIATION PROTECTION IN RADIOTHERAPY
IAEA Training Material on Radiation Protection in
Radiotherapy

• Part 12 Quality Assurance
• PRACTICAL EXERCISE

IAEA Post Graduate Educational Course Radiation
Protection and Safe Use of Radiation Sources
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Objectives

• To be familiar with the concepts of Quality
  Assurance as a multidisciplinary activity and its
  interrelation with radiation protection in
  radiotherapy.
• To be familiar with Quality Assurance procedures
  as a tool for reviewing and assessing the overall
  effectiveness of a radiation protection program.
• To be able to understand the need for and role of
  specific tests in the context of quality control
  and be able to identify appropriate national and
  international protocols for this task
• To be aware of the need for involvement of
  professionals in a quality assurance program and
  for radiation protection

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Part 12 Quality Assurance
IAEA Training Material on Radiation Protection in
Radiotherapy

• Practical 2 Check X Ray light field coincidence
  for a megavoltage treatment unit

IAEA Post Graduate Educational Course Radiation
Protection and Safe Use of Radiation Sources
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Geometry

• Must work for
• all collimators
• different field sizes
• different SSDs
• gantry and collimator angles
• blocks

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X Ray light field co-incidence

• Also applicable to 60-Co gamma rays
• Also applicable to some diagnostic equipment
• If treatment set-ups are mostly fixed distance
  and aligned to marks on the skin, this is one of
  the most important factors for successful
  treatment.

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Contents Objective

• Appreciate the importance of X Ray/ /light field
  coincidence checks
• Use a simple test based on film to check
  coincidence

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What Minimum Equipment is Needed?

• Radiographic film
• Pen, ruler

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Set-up

• Place slab phantom at desired distance
• Place pre-packaged film on top and secure with
  tape
• Mark the light field outline using
• pressure and a pen
• radio-opaque objects
• Use appropriate build up to remove electron
  contamination

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Film with marks
Tape to secure the film
Mark beam geometry
Marks for light field
Package labeled
Slab phantom
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Comments

• If no pre-packaged film is available, one can use
  a film cassette from the X Ray department
• Suitable radio opaque objects are screws,
  washers, .

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Typical film

• Marked with pen - shows thin white lines where
  emulsion has been squeezed
• Test two fields at the same time
• Arrow marks Gun/Target direction
• Can verify field collimator readouts
• Important to label film directly after
  developing it

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Technique using pin pricks
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Repeat as necessary for

• Different SSDs
• Different field sizes
• Different gantry angles
• Blocks
• MLC

Courtesy Elekta
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Questions?

• Lets get started...