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Study of the fragmentation of Carbon ions for medical applications

Study of the fragmentation of Carbon ions for medical applications. Giovanni De Lellis Napoli University. Protons (hadrons in general) especially suitable for deep-sited tumors (brain, neck base, prostate) and fat people. Dose modulation. From the overlap of close peaks

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Study of the fragmentation of Carbon ions for medical applications

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  1. Study of the fragmentation of Carbon ions for medical applications Giovanni De Lellis Napoli University Protons (hadrons in general) especially suitable for deep-sited tumors (brain, neck base, prostate) and fat people

  2. Dose modulation From the overlap of close peaks (close energies), a conformational profile is obtained The patient is rotated so to avoid a long exposure time of the healthy tissues Size of the sick part

  3. Carbon beam Same energy deposit profile as protons but with larger energy loss per unit length one ionization every ~ 10nm (DNA helix ~ 2nm)

  4. Charge and mass measurement • Density of energy along the track path Z2 • Multiple scattering or magnetic field provides either p or p • From the combined measurement, we can get p and the mass A,Z Open issues • Knowledge of the Carbon cross-section with human tissues • In particular the exclusive cross-section in the different channels so to predict the detailed irradiation of the neighboring tissues  optimization of the therapy with higher effectiveness

  5. Facilities in Europe • Typically joint beam (physicists) and therapeutic (biological, medical) facilities. • In Europe, a high energy (few hundred MeV/nucleon) carbon beam is at GSI, Darmstadt, Germany • In Italy (Pavia, close to Milan) the CNAO under construction, starting on 2009 • Proton centers more numerous • In Italy (linked with INFN) one proton center operative in Catania, Sicily

  6. R0 R1 R2 LEXAN LEXAN LEXAN Exposure of an ECC to 400 Mev/u Carbon ions ECC structure: 219 OPERA-like emulsions and 219 Lexan sheets 1 mm thick (73 consecutive “cells”) exposed to 400 Mev/u Carbon ions Lexan:  = 1.15 g/cm3 and electron density = 3.6 x 1023/cm3 e.g. Water 3.3 x 1023/cm3 Cell structure R0: sheet normally developed after the exposure R1: sheet refreshed after the exposure (3 days, 300C, 98% R.H.) R2: sheet refreshed after the exposure (3 days, 380C, 98% R.H.)

  7. Carbon exposure at HIMAC (NIRS-Chiba)

  8. C ions angular spectrum Slope Y Slope X 3.4 cm2 scanning in each sheet (all sheets scanned)

  9. Vertex reconstructionAbout 2300 vertices analyzed C 3 cm

  10. Impact parameter distribution Helium tracks Hydrogen tracks µm µm

  11. Track volume: sum of the areas of the clusters belonging to the track one sheet – R0 type one sheet – R1 type Z > 2  BG, mip p Z > 1 Upstream sheet Upstream sheet p Downstream sheet (about 5 cm) Downstream sheet (about 5 cm)

  12. R0 vs R1 and R1 vs R2 scatter plot He He H

  13. Charge identification 5 R1 VS 5 R2 (2 cm) 10 R1 VS 10 R2 (4 cm) Z = 4 Z = 3 Z = 2 20 R1 VS 20 R2 (8 cm) 15 R1 VS 15 R2 (6 cm) Z = 5 Z = 3 Z = 6 Z = 4 Z = 2

  14. Charge separation Journal of Instrumentation 2 (2007) P06004

  15. Charge distribution of secondary particlescharge reconstruction efficiency Inefficiency Charge = 0 Charge efficiency = (2848-27)/2848 = 99.1±0.2%

  16. Carbon interaction Track multiplicity Bragg peak Contamination at the % level

  17. Hydrogen Angular distribution of secondary particles Elastic scattering large angle (a few percent) Lithium Helium

  18. Cross-section measurement • A volume of about 24cm3 was analyzed • 2306 interaction vertices found (475 elastic) • The number of events with maximal charge as Lithium (z = 3) is 183, as beryllium (z = 2) is 118, as Boron (z = 1) is 258 Toshito et al. Toshito et al. Toshito et al.

  19. Interaction length for different secondary ions

  20. He-proton opening angle Very preliminary • 8Be  He + He (10-16 s) • Q value 90 keV He  He Real event  (rad)

  21. Conclusions • The charge separation capability is about 5 sigma for protons and helium already with less than 10 plates where other detectors fail • The separation between boron and carbon requires 30 plates to reach 2.5 sigma • Emulsions provide unprecedented results in the light ion identification • Preliminary results cross-section measurement Possible improvements • Improve the identification capability for short tracks • Measure the momentum for isotope discrimination • Extend the energy range for cross-section measurements

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