The Challenge of Delivering
Proton Therapy in England
Dr R.MacKay
Director Christie medical Physics and
Engineering
The Christie NHS Foundation Trust
Future Accelerator Technology
The Christie NHS Foundation Trust
Challenge- What challenge?
• We know that the proton has a fundamentally
advantageous dose distribution
• Prescribed list of indications
• We have an estimated number of patients that fit
the indications
• We have guidance on the technology required
• We have a number of international centres to
learn from
• We have a number of commercial suppliers
keen to work in the UK
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Challenge- What challenge?
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•
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We know that the proton has a fundamentally advantageous dose
distribution
–
Yes but x-ray radiotherapy has moved on
Prescribed list of indications
–
Yes but they are all very complex
We have an estimated number of patients that fit the indications
–
Yes but will they all be referred
We have guidance on the technology required
–
Yes but the technology changes very quickly
We have a number of international centres to learn from
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And a number of projects that are struggling
We have a number of commercial suppliers keen to work in the UK
–
Who like using litigation when they do not get awarded
contracts
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Conformal Therapy
•Source: ProCure Training and Development Center
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IMRT
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Protons vs IMRT
• Source -PSI Winter School
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Technology – Scanning
• http://www.varian.com.br/euit/oncology/proton/active_scanning.html
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Technology – Passive scattering
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Scanning - Advantages
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Conformality – IMPT
No compensator
Limited use of collimator
Treatment planning (theoretically)
Less treatment modes
• Tony Lomax, PSI
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Scanning - Problems
• Commercial solutions
- Spot size
- Availability
- Robustness
• Treatment planning systems
• Time per beam?
• Movement!!!!!
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Throughput
• University of Florida
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Model Overview
• Aims:
• Quantitative throughput estimates
• Study sensitivity of system to key parameters
• Methodology:
• All code written in MATLAB.
• Monte-Carlo approach.
• Patients selected at random from the patient mix,
and tracked through the treatment process.
• Large number of independent days modelled to
characterise the system.
• Limitations of the model:
• Assumes centre is running at full capacity
• Does not model commissioning
• Does not model equipment downtime
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Modelled Process
flow
Yellow stages:
Duration is defined by
the model inputs.
Green stage:
Duration depends on
the status of the other
treatment rooms.
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Sensitivity: Number of rooms
• Adding extra rooms:
+ Increases throughput only if system is unsaturated
Results shown
for beam
– Increases mean time waiting for the beam
Fractions per day v No. of rooms
switch time of
2 minutes
Wait time per beam v No. of rooms
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Sensitivity: Beam switch time
• Reducing the beam switch time:
+ Increases throughput
+ Reduces mean time waiting for the beam
Fractions per day v No. of rooms
Wait time per beam v No. of rooms
3 mins
0 mins
1 mins
2 mins
2 mins
3 mins
1 mins
0 mins
The Christie NHS Foundation Trust
Sensitivity: Patient setup time
• Reducing patient setup times:
+ Increases throughput only if system is unsaturated
– Increases mean time waiting for the beam
Fractions per day v No. of rooms
Wait time per beam v No. of rooms
Setup times
reduced by half
Setup times
reduced by half
Standard
setup times
Standard
setup times
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Benchmarking
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Summary: Key results
1.
Adding extra rooms:
+ Increases throughput only if system is unsaturated
– Increases mean time waiting for the beam
2.
Minimising the beam switch time and beam on time:
+ Increases throughput
+ Reduces mean time waiting for the beam
3.
Reducing patient setup times:
+ Increases throughput only if system is unsaturated
– Increases mean time waiting for the beam
4.
Changing from a 1-accelerator to a 2-accelerator system:
+ Increases throughput
+ Reduces mean time waiting for the beam
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Safety
• Safety is about delivering the correct dose
distribution!
• Why should that be more difficult for proton
therapy as compared to radiotherapy
the planning process
the verification process
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Heterogeneity
• Inhomogeneity
• Shifts the range
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Effect of dose bone inhomogeneity
• In radiotherapy we can use CT scans to
calculate relative electron density
• For protons we need proton stopping power
from proton CT
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Overcoming The Challenge
• Excellent planning of facilities
• Excellent partnerships with industry
• Strong clinical physics
-Rapid development of clinical technology
• Engagement of expertise from the broader proton
community
- Accelerator expertise
- Detector expertise
- Monte Carlo expertise
• Strong international collaboration
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