Transcript CPT-Brunel-Nov09-part2 - Particle Physics Department

Cancer Therapy and Imaging
Rob Edgecock
STFC Rutherford Appleton Laboratory
Imaging and Dosimetry
• What else do we need to know for radiotherapy?
 Where the tumour is (exactly)
Imaging
 The structure of the patient
Imaging
 Optimum treatment
Treatment planning
 Correct dose is delivered
Dosimetry
Imaging
• Four main techniques
X-rays
Imaging
• Four main techniques
X-rays
More absorption by denser objects, e.g. bones
- appear lighter
Less absorption by less dense objects
- appear darker
Imaging
• Four main techniques
CT Scan: Computerised (Axial) Tomography
X-rays source and detector rotate
Thousands of images taken
3Dish image built by computer
Very common technique as very fast
Imaging
• Four main techniques
CT Scan: Computerised (Axial) Tomography
Much bigger dose
than X-rays!
Imaging
• Four main techniques
Molecular imaging: PET and SPECT
Load tumour/organ with radiopharmaceutical.
Detect products from decay.
Positron Emission Tomography
Single Photon Emission Computed Tomography
Imaging
• Four main techniques
PET Scan:
Most accurate tumour location
Not so good for surroundings
Imaging
• Four main techniques
SPECT: uses a gamma emitter directly
Gamma detectors rotate.
Make 2D images.
3D reconstructed offline.
Resolution not as good as
PET.
Imaging
• Four main techniques
MRI Scan: Magnetic Resonance Imaging
Magnetic field lines up atoms.
Different atoms absorb different RF frequencies.
Very good for soft tissues (exploits hydrogen in water).
Imaging
• Four main techniques are (sort of) complementary
• None is ideal
• Can lead to incorrectly defined margins
Results from 11 student
oncologists.
Areas inside lines would
be treated.
Imaging
• Situation is improved by combining techniques
• E.g. CT + PET
• Still significant room for improvement
Results from 11 student
oncologists.
Areas inside lines would
be treated.
Treatment Planning
• Takes images, etc
• Uses software to determine best treatment plan
• Best position, angle, no. of fields, energies, etc
• Depends on image quality, knowledge of tissue, etc
• Tumour motion
Timescale
Effect
Possible solution
Seconds
Breathing
Gating; averaging
Minutes
Patient motion
Markers
Day
Patient position; food & liquid Markers; re-scan
Week
“
“
“
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Markers; re-scan
• Reduced precision of beam delivery – larger area
Dosimetry
• Verify correct dose delivered to tumour
• ”In-vivo” dosimetry preferred.....but not actually in-vivo!
Wireless
Catheterdosimeter
dosimeter
Contributions from Particle Physics
• Improved accelerators for radiotherapy
 hard to improve on linacs for X-rays
 but..........
Laptop
1MeV electron
prototype
Big sister being tested
Contributions from Particle Physics
Fixed Field Alternating Gradient accelerator
Synchrotron-like
Cyclotron-like
• Combines features of cyclotrons and synchrotrons
• Interesting for X-ray radiotherapy
• But.....particularly interesting for hadron therapy.....
• .....plus particle physics, power generation, etc
Hadron Therapy
• Requirements
 Proton up to carbon beams; 250 MeV to 400MeV/u
 Rapid cycling: ~500-1000Hz
 Rapid energy variation from accelerator
 Gantries
 Reliability
 “Small” cost
 Small size
• Used currently:
 Cyclotrons: protons; SC understudy for carbon
 Synchrotrons: protons and carbon
Requirements
Cyclotron
Synchrotron
FFAG
Yes(ish)
Yes
Yes
Rapid cycling
Yes
No
Yes
Variable energy
No
Yes
Yes
Cost and size – S/C
Yes
No
Yes
Gantries
Yes
Yes
Yes
Reliability
Yes
No(ish)
Yes
Protons & carbon
• FFAGs very interesting
• Most interesting type – no machine ever built
• So we’ve built one – called EMMA
EMMA
EMMA = proof-of-principle machine
Electrons from
10 to 20MeV
Use ALICE as
injector
42 magnetic
“cells”
Built on 7
girders
EMMA
Works!
Full experimental programme
started.
First results published in Nature
Physics.
PAMELA
PAMELA
PAMELA
Recondensing cryocooler
Insulating vacuum chamber
Next step: prototyping of main components:
- ring magnets
40k Radiation shield
- RF cavities
Magnet support structure- extraction magnets
Positive funding signs
F
D
F
Magnets
40k Inner radiation shield
4k Helium vessel
Contributions from Particle Physics
• Improved PET imaging:
 better tumour location
 verification that treatment in correct place
ToF PET
• Standard PET:
Conventional
 best tumour locator
 but essentially 2D
Detector
 software required
 worse resolution &
long time
• ToF PET
 3D
 better image
& shorter time
Tomograph
Ring
Time-of-Flight
ToF PET
Phantom
(1:2:3 body:liver:tumor)
Conventional
1.2 ns
700 ps
500 ps
300 ps
• PP techniques being tried
• Target ~50ps, but v. difficult
Commercially
available
• Projects to improve other techniques underway
Achieved
Contributions from Particle Physics
• In-vivo dosimetry
 smaller device - possible to leave in?
 lower power consumption
 additional functionality at later date
Concept of in-vivo dosimetry
Radiation
Source
PWR
UNIT
RF
UNIT
RAD
UNIT
RF
receiver
Implantable micro unit
Contributions from Particle Physics
• In-vivo dosimetry
 smaller device - possible to leave in?
 lower power consumption
 additional functionality at later date
Radiation Sensor
Antenna
Silicon chip
Low power electronic
Thin film battery
on the back side
1000μm
Contributions from Particle Physics
• Data storage and analysis:
 creating framework for clinical data
 including long term follow-up
 help strengthen case
 provide info for improvements
• Patient modelling
 no two patients the same
 treatment planning includes modelling of beam
 PP techniques and codes being tried
 PP measurements of interactions for models
Conclusions
• Knowledge from PP being applied in various areas
• Strong priority in the UK
• One discussed here
• Cancer therapy
 data storage and analysis
 modelling
 detector development
 accelerator design