Non Standard Hadronic Therapy vs. Highly Conformal Gamma Therapy based on the Use of the Compton Gamma Back Scattering Source to be Developed within the Project ELI-NP

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Non Standard Hadronic Therapy vs. Highly
Conformal Gamma Therapy based on the Use of the
Compton Gamma Back Scattering Source to be
Developed within the Project ELI-NP

• Radu A. Vasilache1, Nicolae Verga2, Andreea
  Groza3, Agavni Surmeian3, Constantin Diplasu3,
  Mihai Ganciu3
• 1Canberra Packard Central Europe GmbH,
  Bucharest2Coltea Clinical Hospital, Radiotherapy
  Clinic, Bucharest3INFPLR, Bucharest Magurele

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Contents

• Introduction state of the art in radiation
  therapy
• Hadron beam therapy is possible to do it with
  beams generated by high power lasers?
• Alternatives proposed

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State of the art in radiotherapy

• External radiation

Gamma and electron beams, up to 21 MV, usually 6
MV High conformality IMRT, IGRT, IMAT, VMAT.
Not so simple dosimetry, but highly
standardised Need for hiperfractions (like,
e.g., in GammaKnife Cyberknife) Difficult
complicated treatment planing system rather
complicated dosimetry QC tools to check the
treatment plan output
Hadron beams (protons and carbon ions) Higher
conformality than for photons (courtesy of the
Bragg peak) The need to spread the Bragg peak
leads to cumbersome and extremely expensive
facilities Unstandardised dosimetry, at least
for the moment
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State of the art in radiotherapy

• Brachytherapy and metabolic radiotherapy

Brachytherapy (intracavitary radiotherapy) still
used with a good degree of succes Metabolic
radiotherapy the use of beta / alpha emitters
bonded to molecules that are metabolized in the
tumor, therefore, practically the entire dose is
deposited in the affected area.
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Using high power lasers for radiation therapy
1. Proton therapy - very difficult to realise
at this stage (very short pulse, with rather low
repetition rate, very difficult to mount a
gantry, thus very difficult to spread the Bragg
peak) - other competitive technologies (like the
dielectric wall accelerators from
CPAC/Accuray/Tomo) will be available sooner than
any practical solutions with lasers see
www.cpac.pro/index.html
2. Classical photon therapy are there any
gains from using high power laser technologies?
YES! The use of Compton backscaterred photons for
RT have been proposed as long back as
1996 Weeks, Litvinenko Madey, Compton
backscattering process and radiotherapy Med.
Phys.24 (3), 1997
3. Non-standard hadron therapy using the
Compton backscattered beam to induce photonuclear
reactions and obtain low life time alpha or
neutron emitters, that could be injected directly
into the tumour
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Advantages of RT with Compton backscattered
photons

• Energy distribution

Weeks et al., Med.Phys. 24 (3) 1997
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Advantages of RT with Compton backscattered
photons

• Beam focusing

Weeks et al., Med.Phys. 24 (3) 1997
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Advantages of RT with Compton backscattered
photons

• Energy dispersion

Weeks et al., Med.Phys. 24 (3) 1997
Using an appropriate collimator / gantry the
energy spread is significantly reduced
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How to do it, which are the challenges

• Many others also identified this line of
  experiment with focus being on diagnostic use of
  the backscattered Compton radiation
• Problems to be dealt
• convolution of energy, angles, polarisation
• luminosity loss, energy shift, jitter as effect
  of the collision angle
• Focalisation loss as an hourglass effect

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Solutions

• Wormser
• compact electron ring e bunches with a high rep
  rate
• laser system with similar high freq. and large
  average power coupled to a high finesse
  Fabry-Perot resonator

• Our proposal
• high power laser
• electron storage ring with a line for the
  extraction and re-insertion of electrons
• Mobile gantry with fixed collimator and MLC

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Solutions
Wormser
Our solution
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Some source characteristics

• Weeks in 1997 the RT with backscattered Compton
  was out of reach due to the needed photon beam
  intensity 1012 /s

now 1013 /s is achievable with the ELI source

• Energy 1-30 MeV
• Natural energy spread 2-3 (see Weeks MC
  calculations)
• Possibility of collimation down to 0,1

Beam spot at the IP the order of 10ths microns,
divergence at the IP few mrads !!!! (Also
Weeks) By comparison, the smallest pencil beam
available now is from Cyberknife, at it is only
slightly sub-milimetric in diameter, with a much
higher divergence
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What to achieve in the end
Images from www.accuray.com
Non-isocentric gantry movement
Avoiding critical organs through hairlike beams
Hyperfractionation (Barrow Neurological Inst.)
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Advantages Summary

• Proton therapy very difficult to be realised in
  the foreseeable future
• Compton backscattered photons for RT
• The distribution of energies is centered on high
  energies, whereas classical LINACs give photon
  beams centered on lower energies new method
  would give higher penetration, dose depth
  profiles more uniform
• Very low divergence, hair like beams
  possibility to achieve very high conformality (at
  present only Cyberknife delivers pencil beams,
  but with normal LINAC divergence)
• Possibility to obtain quasi-monoenergetic beams,
  which significantly eases treatment planning,
  dosimetry and QC
• Continuously tunable energy (whereas classical
  LINACs offer 2 or 3 photon energies), which, for
  the first time, offers the possibility for IEMRT
• By using an electron storage ring, the electrons
  are recuperated and re-used for Compton
  generation
• The most important can be realised within a
  reasonable time frame this is evolution, not
  revolution

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