208 FEASIBILITY STUDY OF TULIP – A TURNING LINAC FOR PROTONTHERAPY

S103 can be tuned to resonantly excite nuclear transitions. Such cross-sections peak at several barn, even when considering Doppler broadening in room temperature targets. Future gamma beam facilities that exploit Compton backscattering of intense laser light on intense relativistic electron beams may provide gamma ray flux densities of the order of 1018 γcm-2s-1. Hence very compact targets can be used. Beam heating is manageable since most energy is deposited by secondary electrons outside the production target. Moreover, compared to Bremsstrahlung facilities, due to small energy width (ΔE/E < 0.1%), a much higher fraction of the gamma beam is “useful” for inducing resonant reactions. We discuss the prospects for the future production of radioisotopes of relatively high specific activity by photonuclear reactions with gamma beams by comparing achievable specific activities and total activities with state-of-the-art production in high flux reactors and charged particle induced reactions. The production of 195mPt is an illustrative example for (γ,γ’) photo-excitation reactions. According to the published photo-activation yields specific activities of the order of tens of GBq/mg (few Ci/mg) should be achievable with a gamma beam facility. Such 195mPt could serve for SPECT imaging of the distribution of trace amounts of Pt chemotherapeuticals or, due to the emission of Auger electrons, for combined radio-chemotherapy with such compounds. If moreover suitable doorway states are found that can be excited by strong transitions from the 1/2- ground state of 195Pt and that decay partially to the 13/2+ isomer, then resonant excitation with small bandwidth gamma beams would lead to even higher specific and total activities. Presently experiments are ongoing at the HIGS facility (Duke University) and Institut Laue Langevin (Grenoble) to identify the most promising doorway states. An interesting example for (γ,n) reactions is the transmutation of 226Ra to 225Ra and subsequent extraction of the 225Ac daughter to cover the demand for 225Ac/213Bi generators. 213Bi is promising for targeted alpha therapy, but the presently available quantities of 225 Ac (milked from stockpiled 229Th) do not allow clinical applications on larger scale. 225Ac can also be produced by 226Ra(p,2n) or 226Ra(γ,n)225Ra(-) reactions. However, the alpha radiotoxicity and dose rate by high energy gamma rays limit the amounts of 226Ra that can be easily handled. The high flux density of a gamma beam would increase the transmuted fraction by orders of magnitude, thus enabling the industrial production of the order of tens of GBq of 225Ac per day (Ci per day) while using relatively small 226Ra targets (few mg, i.e. few mCi). 208 FEASIBILITY STUDY OF TULIP - A TURNING LINAC FOR PROTONTHERAPY K.M. Kraus1, U. Amaldi2, M. Garlasche1, A. Degiovanni1, P.A. Posocco1, V. Rizzoglio1, P. Riboni1 1 TERA Foundation (IT) 2 CERN Clinical studies have shown that the presence of proton single room facilities spread on the territory and serving a population of about 1.5-2 million people is more advisable than the construction of multi-room

ICTR-PHE 2012 centers. The development of innovative solutions for the construction of compact machines is therefore crucial for the realization of such centers. In this framework, TERA Foundation (TErapia con Radiazioni Adroniche) has recently started the study of a new Cyclinac accelerator for a proton single room facility. TERA’s Cyclinac design foresees an accelerator complex where a high frequency linear accelerator is used as a booster for protons coming from a high current cyclotron. The standing wave Side Coupled Linac is composed of modular units powered by independently controlled klystrons. The particles final energy variation (obtained by amplitude and/or phase modulation of the klystrons signal) combined with computer control of the proton source allows for variations of the beam intensity at every pulse, thus making the Cyclinac suitable for implementing the spot scanning technique with tumor multipainting. The project TULIP (Turning LInac for Protontherapy) is an application of the Cyclinac concept to a proton single room facility, consisting of a high-gradient linac (about 35 MV/m) mounted on an isocentric gantry which rotates around the patient. This rotating linac can produce a fast cycling proton beam well suited for spot scanning, while the possibility to perform Distal Edge Tracking (DET) is also envisaged. In the framework of this project, current studies concern accelerator performance, beam features and mechanical design of the structure. Furthermore, the dynamic dose delivery given by the combination of fast energy variation and gantry rotation is under study, where the analysis on the employment of couch motion is also planned. The current design of TULIP features an RF frequency of 5.7 GHz (C-band). The linac is subdivided into two sections: section 1 from 35 to 80 MeV (fixed energy) and section 2 with variable beam energy from 80 to 210 MeV. The average accelerating gradients are about 2025 MV/m in section 1 and 32-38 MV/m in section 2, with a maximum surface electric field around 170 MV/m. The RF power needed is about 110 MW (peak power) in 2.5 μs pulses at a maximum repetition rate of 200 Hz. A collaboration has been established with the RF group of the CLIC project (Compact Linear Collider) at CERN in order to study the limitation of high gradient in structure performance and the RF circuit design of the machine. The design of a compact matching line between the two linac sections and of the transfer line from the linac to the patient with a momentum acceptance of ± 2% is also under study. The linac, which is less than 10 meters long, is fixed to the rotating gantry. Mechanical design is ongoing in order to optimize the mass (the total weight is just around 60-70 tons), to minimize deformations (deflections of the supporting beams are in the order of tens of μm) and to enhance the overall simplicity of operation. 209 MR SPECTROSCOPY IMAGING (MRSI) FOR GLIOBLASTOMA DOSE PAINTING WITH INTENSITY MODULATED RADIATION THERAPY COMPRISING SIMULTANEOUS INTEGRATED BOOST ON SPECIFIC TARGETS S. Ken1,2, L. Vieillevigne1, X. Franceries2, C. Supper1, J.A. Lotterie2,3, T. Filleron1, V. Lubrano2,3, I. Berry2,3,