Transcript IAEA Training Material on Radiation Protection in Radiotherapy

IAEA Training Material on Radiation Protection in Radiotherapy
RADIATION PROTECTION IN
RADIOTHERAPY
Part 12: Quality Assurance
PRACTICAL EXERCISE
IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources
Objectives
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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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IAEA Training Material on Radiation Protection in Radiotherapy
Part 12: Quality Assurance
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
Geometry
Must work for
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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
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Place slab phantom
at desired distance
Place pre-packaged
film on top and
secure with tape
Mark the light field
outline using
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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
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Courtesy Elekta
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Questions?
Let’s get started...
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