1. Radiation Shielding for
Megavoltage Photon Therapy
Machines
RADIATION
PROTECTION
1
Daryoush
khoramian

2. 2
The International Agency for Research on
Cancer(IARC) recently estimated that 7.6
million deaths worldwide were due to cancer
with 12.7 million new cases per year being
reported worldwide
Breast cancer in females and lung cancer in
males are the most frequently diagnosed cancers
( Freddie Bray et al 2011)
 Approximately 50% of all cancer patients will
receive radiation therapyradiation therapy during their course of
illness ( Basker et al 2012 )

3. Basic principles
 The purpose of radiation shielding :
To limit radiation exposures to members of the
public and employees to an acceptable level. (
NCRP report no.151 )
Areas
Uncontrolled areas  1 mSv/yr
Controlled areas  5 mSv/yr
NCRP,2007
NCRP,2007
3

4. The purpose of radiation shielding :
To reduce the effective equivalent dose from a linear accelerator to a point
outside the room to a sufficiently low level.
4
In radiation therapy rooms

5.  Workload
 Use factor
 Occupancy factor
Use factor
Walls 1/4
Floor 1/2
Ceiling 1/4 or 1/2
T
Full occupancy
Work areas, offices,
nurses’ stations
1
Partial occupancy
Corridors, restrooms, ..
1/4
Occasional occupancy
Waiting rooms,
stairways, …
1/6
Or
1/16
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Barriers

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TVL in 16
MV
TVL in 16
MV

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 It’s toxic
 lead is not self supporting  needs to be held in place
 Relatively transparent to neutrons but decrease energy of neutrons by inelastic scattering

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Overall size
 The couch radius : 9’
 Back wall  end of couch : 21’
 22’×20’ clear area
 Height : 9’-10’

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Machine orientation
Parallel to
the maze
Orthogonal to
the maze Special design

22. 22
Maze vs. direct door
 Where the available space
is minimal
 Doors are Very heavy
( several tons )
 Very expensive
 In order to reduce the radiation dose near
the entrance
 Is a route for ventilation ducts and electrical
conduits

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Ducts

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Electrical cable

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Special Considerations

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Skyshine Radiations

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References :
1.Baskar, Rajamanickam, Lee, Kuo Ann, Yeo, Richard, & Yeoh, Kheng-Wei. (2012). Cancer
and radiation therapy: current advances and future directions. International journal of medical
sciences, 9(3), 193.
2.Biggs, Peter J. (2010). Radiation Shielding for Megavoltage Photon Therapy Machines:
Boston: sn.
3.Deye, James A, Rodgers, JE, Wu, RK, Biggs, PJ, McCall, RC, & McGinley, PH. (2005).
Structural Shielding Design and Evaluation from Megavoltage X-and Gamma-Ray Radiotherapy
Facilities. National Cancer Institute, Rockville, Maryland.
4.INTERNATIONAL ATOMIC ENERGY AGENCY, RADIATION PROTECTION IN THE
DESIGN OF RADIOTHERAPY FACILITIES, IAEA, Vienna (2005).
5.Khan, Faiz M, & Khan, FM. (2003). The physics of radiation therapy (Vol. 3): Lippincott
Williams & Wilkins Philadelphia.
6.Turner, James Edward, & Kelsey, Charles A. (1995). Atoms, radiation, and radiation
protection: Wiley New York.

28. Thank you
Any question ?