Contents

1. 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

2. 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

3. 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

4. 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.

5. 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

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

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

9. 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

10. 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

11. 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 Solutions

12. Solutions Four mirrors Fabry Perot cavity Electron beam dump Electron Storage ring Collision point Electron beam pipe Collision point Laser beam Linac +RF gun Wormser Our solution

13. 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

14. 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.)

15. 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

16. Danke schön! Merci beaucoup! Grazie mille! Děkuji ! Dakujem! Dziękuję! Köszönöm szépen ! Большое спасибо! Дякую! Дзякуй! Много благодаря! Xвала! Falemenderit shumë! Рахмет! ...and,for all the others: どうも有り難うございました ! THANK YOU! Don’t shoot the piano player, he does what he can…