Prompt gamma measurements for the verification of dose deposition in proton therapy. Contents. Two Proton Beam Facilities for Therapy and Research

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1 Prompt gamma measurements for the verification of dose deposition in proton therapy Two Proton Beam Facilities for Therapy and Research Ion Beam Facilities in Korea 1. Proton therapy facility at National Caner Center Jong-Won Kim National Cancer Center, Korea H. Kubo, T. Tanimori Department of Physics, Kyoto University, Japan 2. Neutron therapy facility at Korea Cancer Center Hospital 2002 July: Contract with IBA 2003 Jun: Start building construct 2005 Feb: Start installation i 2006 Dec: Accept 1 st gantry room 2007 Mar 19: Treat the first patient Contents 1. Gamma production by proton beam 2. Prompt gamma detection techniques 2.1 A collimation method 2.2 A pinhole camera method 2.3 Compton camera method 3. Monte Carlo simulation studies for prompt gamma imaging 4. Concluding remarks Necessity of Proton Range Localization X-ray Proton Clinical data show significant decrease in tumor control (>5%) when tumor dose decreased by 4-5%. Therefore significant portion of CTV cannot fall outside high dose region more than once in fractionated course of radiation L. Vehey UCSF Uncertainty in range calculation based on X-ray X CT

2 1. Gamma production by proton bombardment on tissue nuclei Photo of irradiated PMMA sample E. Testa et al., Monitoring the Bragg peak location of 73 MeV/u carbon ions by means of prompt γ-ray measurements, Applied Phys. Lett. (2008) Gamma lines by proton interaction with organic nuclei E (MeV) Transition Reaction Mean Life (s) B g.s. 12 C(p,x) 10 B C(p,x) 10 C(ε) 10 B O(p,x) 10 B F g.s. 16 O( 3 He,p) 18 F* B B C(p,x) 10 B O(p,x) 10 B F g.s. 16 O( 3 He,p) 18 F* N N N(p,p*) 14 N* C g.s. 12 C(p,x) 11 C B g.s. 12 C(p,x) 11 B N g.s. 14 N(p,p*) 14 N O(p,x) 14 N O O O(p,p*) 16 O Ca g.s. 40 Ca(p,p*) 40 Ca C g.s. 12 C(p,p*) 12 C N(p,x) 12 C O(p,x) 12 C B g.s. 12 C(p,2p) 11 B N(p,x) 11 B N g.s. 14 N(p,p*) 14 N O(p,x) 14 N O g.s. 16 O(p,x) 15 O < O g.s. 16 O(p,p*) 16 O O g.s. 16 O(p,p*) 16 O O g.s. 16 O(p,p*) 16 O C g.s. 12 C(p,p*) 12 C B. Kozlovsky et al., Astrophysics J., Suppl. Ser. 141 (2002) First suggestion of utilizing prompt gamma for range verification F. Stichelbaut, Y. Jongen, Verification of the Proton Beam Position in the Patient by the Detection of Prompt γ-rays Emission, PTCOG-39, 2003 Distributions with angular cuts (± Δθ) PET method to monitor the ranges of hadron therapy beams First suggestion (?): G.W. Bennett et al., Science 200 (1978) E p = 214 MeV (range=28.5 cm) Phantom size: 40 x 20 x 20 cm 3 GEANT 3.21 with hadronic model of Fluka Secondary γ : photons from n-capture and inelastic scattering Proton: 250 MeV D. Litzenberg et al., Med Phys. (1999) Institute of Nuclear and Hadron Physics, GSI, Germany Many publications for HI cases: e.g) F. Sommerer et al., Phys. Med. Biol. 54 (2009)

3 2. Prompt gamma detection techniques 2.1 Prompt gamma measurement using a multi-layer collimator Measurement at the experimental room of the NCC CsI(Tl) Comparisons of the depth dose distributions measured by the ionization chamber to the PGS (Prompt gamma scanner) measurements at three different proton energies of 100, 150, 200 MeV s. MCNPX (Ver e) FLUKA (Ver. 2003) G. Seo, MS. thesis, mm x 30 mm Angular span: 90±α C. Min, C. Kim, M. Youn, J. Kim, App. Phys. Letts. 89 (2006) Analysis of prompt gamma measurements Effects of with and without paraffin shielding CsI(Tl) 2 MeV 4 MeV 6 MeV The gamma-count distributions vs. depth with different minimum gamma energies The gamma-energy spectrum measured at three different locations adjacent to the Bragg peak at the proton energy of 100 MeV. (The inset is the energy calibration for the MCA.) The gamma-count distributions versus depth with and without paraffin shielding plates surrounding the outside of the PGS

4 Measurements at the therapy beam line of the NCC Prompt gamma measurement for an ATOM phantom using mono-energetic beams 1.05 Relative prompt gammas (normalized) mm 90 mm Range: 7.0 cm A single scattering, field radius=2 cm Set-up at the horizontal fixed beam line of the NCC Depth in ATOM phantom (mm) ATOM phantom Bone density: 1.6 g/cc Composition: C(37%), O(35%), Ca(15%), H(4.8%), P(2.9%), Mg(6.2%) 2.2 A pinhole Camera Method Measurement results with a pinhole camera Prompt gamma distributions by the pinhole camera calculated with GEANT Prompt gamma measured at a proton beam energy of MeV Measurement with 50-MeV proton beam using MC50 cyclotron at Korea Cancer Center Hospital Shielding thickness estimation for a 50 MeV proton beam with GEANT3 D. Kim, H. Yim, J. Kim, submitted to J. of Korean Physical Soc. June, 2009 Peak variation: 0.5 mm / MeV

5 ' Anode 2.8 mm Cathode Substrate 2 mm 2.3 Compton camera method 1) SPECT 2) Compton cameras of two types solid or gas Collimator GEANT simulation for electron-tracking Compton camera Compton camera measurement simulation of 90 emitted gammas Photon Energy E: ~ < 300 kev Compton camera E: 200 ~ 2000 kev B. Kang, J. Kim, IEEE Nucl. Sci GEANT simulation results for electron-tracking Compton camera Reconstruction resolution MeV γ-rays Compton scattering PCB detector Compton camera measurements of prompt gammas by a group of Kyoto University e - Pixellated CsI(Tl) Estimated resolution of reconstruction relative to the location of gamma emission. Reconstruction resolution vs. detector performance 5 cm 16x16 multianode photomultiplier cos φ = m ec ( ), Eo = Er ' + Er Eo cos 2 m c e Ee α = 1 2 E, E e+ 2mec γ Ee Water phantom Size 20x20x40 cm 3 TPC Size 5x3x5(h) cm 3 Gas Ar:C 2H 6=90:10 Electron drift velocity 4 cm/ms No of anode/cathode channels 25/15 Pitch of electrode 2 mm electron de/e 30% CsI (Tl) Pixel size 2 x 2 mm 2 No of channels 16x20 gamma de/e 7% Measurements of prompt gamma spectra and background neutrons at RCNP of Osaka University (July, 2008) Prompt gamma image measurement at the proton therapy center of Tsukuba University (Jan. 2009)

6 Set-up for prompt gamma image measurement with Compton camera at Tsukuba proton therapy center GSO Energy Spectrum RCNP experiment Tsukuba experiment Prompt gamma images analyzed for different energy ranges :Location of Bragg peak Counts (a. u.) Energy range: kev (± 2xFWHM) proton Monte Carlo simulation of prompt gamma imaging for a 200 MeV proton beam (1σ σ): 11 mm Beam size (1 Avg. beam current: 30 pa Beam time: 14 hours ~100 Gy Iteration 39cm image fusion 109 events proton Counts (a. u.) 254 events Energy range: kev (± 2xFWHM) proton Counts (a. u.) Energy range: kev (± 2xFWHM) 98 events By K. Ueno and S. Kurosawa of Kyoto University

7 Passage to improve detection efficiency of electron-tracking Compton camera 3. MC simulation studies for prompt gamma imaging Monte Carlo simulation study on a photodiode array detector Current efficiency of electron tracking type: 10-5 with Gas volume of 10 x 10 x 10 cm (Efficiency by solid scatter: 10-2 ) Use of different gas: Ar CF 4 Increase gas pressure: 1 atm 2 atm Improvement of 3D tracking algorithm of Compton scattered election MCNPX, LA150 and ENDF/BVI libraries C. Min et al., J. of Korean Phys. Soc. (2008) Monte Carlo calculations on prompt gamma emission from biological tissues Concluding remarks MCNPX calculations at MD Anderson Cancer Center 1. Prompt gamma appears to be a promising modality of proton range verification considering its capability of on-time monitoring with therapy and good correlation with proton dose distribution. 2. Prompt gamma measurement using collimation system can be a viable tool for the verification of proton range especially for the scanning beams. J. Polf et al., Prompt gamma emission from biological tissues during proton irradiation: a preliminary study, Phys. Med. Biol. 54 (2009) 3. Electron-tracking Compton camera can be a tool for prompt gamma imaging with improvement in detection efficiency to its full potential.

8 Acknowledgements Seoul National University, Department of Physics D. Kim, Ph.D student Kyoto University, Department of Physics S. Kurosawa, Ph.D student K. Ueno, Ph.D student Thank you for your attention!