Transcript IAEA Training Material on Radiation Protection in Radiotherapy

IAEA Training Material on Radiation Protection in Radiotherapy
Radiation Protection in
Radiotherapy
Part 5
External Beam Radiotherapy
Lecture 2 (cont.): Equipment and safe design
4. Other EBT irradiation units
Betatron - not produced anymore
 Tomotherapy - discussed before in
IMRT
 Neutrons - beyond the scope of the
present course
 Gamma knife
 Protons
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Betatron
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Circular accelerator for
electrons
Change of magnetic
field with increasing
electron energy
Allows flexibility in
energy selection up to
50MeV
Beam currents and
therefore output is
typically low
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Gammaknife
Used for stereotactic brain irradiations
 201 sources of Co-60 around a patients
head - only sources which shall
contribute to the irradiation are
‘unplugged’
 alignment crucial
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Gamma knife head applicator
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Patient in gamma knife collimator head
(from Ertl et al. Phys. Med. Biol. 42 (1997) 2137)
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Protons
Positively charged particles - directly
ionizing radiation
 About 2000 times heavier than electrons
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less angular struggling
 more difficult to steer
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The lightest of heavy charged particles
(such as C, Ne, Si, Ar) used for
radiotherapy
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Comparison to other radiation types
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Passive Scanning
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Passive beam
delivery
system
Spread Out Bragg
Peak SOBP
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Active Scanning
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Present of Proton Radiotherapy
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23 proton radiotherapy facilities worldwide
(1998) - virtually all of them not dedicated
(and optimized!) for radiotherapy
About 25000 patients treated up to 1998
worldwide - nearly half for eye melanoma
At least 10 dedicated radiotherapy centres
planned...
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Tsukuba
Facility
Courtesy of
Hitachi
Rotating
Gantry
Cyclotron
Accelerator
Fixed Beam
delivery
system
Copyright © Hitachi, Ltd. 1999, All Rights Reserved.
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Rotating Gantry at Loma Linda
Proton Radiotherapy Centre
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Rotating Gantry - a large facility
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Protons
Potentially better dose distribution
 More expensive
 Often combined with basic research
(e.g. nuclear physics) or other
applications (e.g. radiation testing for
space applications) to be more cost
efficient
 Large facility required
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Where things may go:
Robotic Pencil Beam Delivery
Future concept
of radiotherapy
with ultimate
flexibility...
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5. Associated radiation equipment
required for radiotherapy
CT scanners
 Radiotherapy simulators
 For treatment planning systems refer to
part 10 of the course
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CT
scanner
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CT scanners
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Covered in the training course on diagnostic
radiology
Used in radiotherapy to acquire patient
information required for treatment planning
A CT scanner for radiotherapy should have:
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a flat couch top like the treatment units
a large bore to allow scanning patients in a variety of
treatment positions
high spatial accuracy
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Simulator
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Radiotherapy simulator
A diagnostic X Ray unit mimicking the
geometry of a treatment unit
 Diagnostic aspects covered in course of
diagnostic radiology
 Additional features:

field defining wires
 centre of field indication
 couch matches treatment couch
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Simulator control
Control screen
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Fluoroscopy
X Ray screen
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Radiotherapy
Simulator
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Simulator
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Many movement
options
Can be adjusted to
mimic treatment
units with different
focus to axis
distance
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Simulator control screen
Machine parameters
similar to linac
Varian Medical systems
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Another simulator
Huestis/Cascade simulator
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Summary
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There is a large variety of equipment
currently in use for external beam
radiotherapy
Generally, the design includes redundant
features which ensure that no unwanted
exposure can take place
Computer control becomes increasingly
important for the operation of equipment
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Where to Get More Information
Part 10
 Medical Physics Textbooks
 Manufacturers brochures and
webpages

VARIAN
 Siemens
 Elekta (including former Philips)
 Nucletron…
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Any questions?
Question:
When purchasing a new piece of equipment what
must be considered?
Acknowledgments
John Drew, Westmead Hospital, Sydney
 Patricia Ostwald, Newcastle Mater
Hospital
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