study of the fragmentation of carbon ions for medical applications
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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 - PowerPoint PPT PresentationTRANSCRIPT
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Study of the fragmentation of Carbon ions for medical applications
Protons (hadrons in general)especially suitable for deep-sited
tumors (brain, neck base, prostate)and fat people
Giovanni De LellisNapoli University
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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
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Carbon beam
Same energy deposit profile as protons but with larger energy loss per unit length
one ionization every ~ 10nm
(DNA helix ~ 2nm)
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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
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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
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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 ionsLexan: = 1.15 g/cm3 and electron density = 3.6 x 1023/cm3
e.g. Water 3.3 x 1023/cm3
Cell structure
LE
XA
N
LE
XA
N
LE
XA
N
R0 R1 R2
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.)
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Carbon exposure at HIMAC (NIRS-Chiba)
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C ions angular spectrum
Slope X
Slo
pe
Y
slope X
(3 )
slope Y
(3 )
P1-0.150 ±0.004
-0.003 ±0.005
P2-0.017 ±0.004
-0.002 ±0.005
P3 0.134 ±0.004
-0.001 ±0.005
3.4 cm2 scanning in each sheet (all sheets scanned)
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Vertex reconstructionAbout 2300 vertices analyzed
C
3 cm
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Impact parameter distribution
Hydrogen tracks Helium tracks
µm µm
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Track volume: sum of the areas of the clusters belonging to the track
BG, mip
Z > 1
p
Upstream sheet
Downstream sheet(about 5 cm)
p Z > 2
one sheet – R0 type one sheet – R1 type
Downstream sheet(about 5 cm)
Upstream sheet
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R0 vs R1 and R1 vs R2 scatter plot
H
He
He
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Charge identification
Z = 2
Z = 3
Z = 4
5 R1 VS 5 R2 (2 cm) 10 R1 VS 10 R2 (4 cm)
15 R1 VS 15 R2 (6 cm)
20 R1 VS 20 R2 (8 cm)
Z = 4
Z = 3
Z = 2
Z = 5
Z = 6
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Charge separation
Journal of Instrumentation 2 (2007) P06004
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Charge distribution of secondary particlescharge reconstruction efficiency
Inefficiency Charge = 0Charge efficiency = (2848-27)/2848 =
99.1±0.2%
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Carbon interaction
Bragg peak
Contamination at the % level
Track multiplicity
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Angular distribution of secondary particlesElastic scattering Hydrogen
Helium
large angle (a few percent)
Lithium
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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
( 1) 2330 150
( 2) 1060 100
( 3) 1650 120
z mbarn
z mbarn
z mbarn
Toshito et al.
Toshito et al.Toshito et al.
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Interaction length for different secondary ions
14.0 1.2H mm 14.0 1.2H mm
14.0 1.2H mm
14.0 1.2H mm 19.3 2.3He mm
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Very preliminary• 8Be He + He (10-16 s) • Q value 90 keV
8( ) 225 50C Be mbarn
(rad)
He
He
Real event
He-proton opening angle
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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 measurementPossible improvements
•Improve the identification capability for short tracks•Measure the momentum for isotope discrimination•Extend the energy range for cross-section measurements