Radiation Protection Considerations in
Proton Therapy Centre Design
Mark Hardy
Radiation Protection Advisor
Christie NHS Foundation Trust
Acknowledgments: Varian & Aurora
The Christie NHS Foundation Trust
Overview
• What’s the problem with protons?
• Designing a proton centre
• Calculations
• Design criteria
• Usage assumptions
• Sources of radiation
• Christie design
• Results
The Christie NHS Foundation Trust
What’s the problem?
The Christie NHS Foundation Trust
Proton interactions
 Stopping
 Scattering
 Nuclear
Shielding calculations
• Inputs:
• Design criteria
• Usage assumptions
• Radiation source information
• Design including ducting
• Primary calculations Monte-Carlo: Aurora
• Empirical secondary calculations : Varian
The Christie NHS Foundation Trust
Shielding calculations
• Inputs:
• Design criteria
• Usage assumptions
• Radiation source information
• Design including ducting
• Primary calculations Monte-Carlo: Aurora
• Empirical secondary calculations : Varian
The Christie NHS Foundation Trust
What do we want to achieve?
<1mSv/yr public
<20mSv/yr staff
Keep dose as low as reasonably
practicable (ALARP)
Minimise number of controlled areas
The Christie NHS Foundation Trust
The Instantaneous Dose Rate issue
• IRR99 ACoP recommends keeping IDR<7.5µSv/h
• Scanning beam Proton treatment:
• Uses intermittent exposures (10% duty cycle)
• Uses range of energies for every patient
• Uses highest energy infrequently
• Planning to worst case IDR results in substantial
over-shielding
• Use annual doses
• Required to show method is equivalent to ACoP
The Christie NHS Foundation Trust
Shielding calculations
• Inputs:
• Design criteria
• Usage assumptions
• Radiation source information
• Design including ducting
• Primary calculations Monte-Carlo: Aurora
• Empirical secondary calculations : Varian
The Christie NHS Foundation Trust
Seeing into the future
• Technology:
• Scanning vs. scattering
• Improved patient throughput
• Clinical:
• More patients receiving hypofractionation (5-10Gy/#
rather than 2Gy/#)
• More patients - Extra room – +33%
• Change in patients groups treated
• Gantry angle mix change
• Energy mix change
• Effects different in different areas
The Christie NHS Foundation Trust
Shielding calculations
• Inputs:
• Design criteria
• Usage assumptions
• Radiation source information
• Design including ducting
• Primary calculations Monte-Carlo: Aurora
• Empirical secondary calculations : Varian
The Christie NHS Foundation Trust
Sources
The Christie NHS Foundation Trust
Shielding calculations
• Inputs:
• Design criteria
• Usage assumptions
• Radiation source information
• Design including ducting
• Primary calculations Monte-Carlo: Aurora
• Empirical secondary calculations : Varian
The Christie NHS Foundation Trust
Progress so far…
9th November 2015
The Christie NHS Foundation Trust
Thank you!
The Christie NHS Foundation Trust