Agostino TARTARI - International Centre for Theoretical...
Transcript of Agostino TARTARI - International Centre for Theoretical...
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Demands and needs of alternate X ray sources based on DMP devices: the proposals for a
Plasma Focus based brachytheraphy approach
Agostino TARTARIDepartment of PhysicsUniversity of Ferrara
Plasma Focus Italian informal network: present situation
University of Ferrara (Department of Physics)
ENEA (National Board for Energy), CR Brasimone
University of Bologna (Nuclear Engineering Laboratory)
ASSING spa factories
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Work in progress
Radio-surgery probe for interstitial brachytheraphy
A straightforward, rough and cheap DAS device for spectra and doses monitoring
X-ray spectrometers with cylindrically and spherically curved crystalsJoint venture EchoPulse (USA) - "Kurchatov" Moscow, Russia
Cauchois-Johansson based spectrograph Manufactured by the Russian Research Institute “Kurchatov” Supplied by EchoPulse, Inc. Springfield (USA)Not suitable for routinely monitoring
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Pulsed X rays Sources for Interstitial Radio-surgery(I.O.R.T.)
Plasma Focus facility: PF1 in Ferrara Investigation and simulations:
Electron Impact Ionization (formula CTB, i.e. Casnati-Tartari-Baraldi)
EGS4 up dating with our data sets (Coherent, anomalous scattering and CTB)
Final goal
Setting up of electron-pipe lines (φ < 5 mm)
Interstitial radio-surgery of small tumours
Requirements
Legislation and policy NO neutronsEffectiveness High dose-rateHealth tissue prevention (Enclosed small masses) raysAccessibility Brachytherapy
Low energy X
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)( 2DG DneS βα +−=
Cell survival following irradiation.
S surviving fraction of cells that were irradiatedn number of dose fractions towards the entire treatment dose,D dose per fraction, [Gy]α linear component of cell killing [Gy–1]β quadratic component of cell killing representing sub lethal damage,
[Gy–2]G dose rate effect on repair of sub lethal damage.
Radiobiological needs and modeling
v When the filling gas is H, from the pinch region we can exploit three main sources:w Soft X-ray from the plasmoid region (the “pinch”)w Proton beams (forward)w Relativistic electron beams REB (strongly back warded)u Contaminants
THE DOSE IS RELEASED IN SOME TENS OF NANOSECONDS: very high dose rate and fractioning
FESEABILITY of a REB-PF based X-Ray sources
X - Ray
REB
PROTONS
Interstitial radio surgery (brachyteraphy) proposal based on PF devices
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FERRARA Plasma Focus with REB scattering chamber
The dosimeters based differential absorption spectrometer (DAS) and related mathematics
M1 M2 ----------------------- Mn
t1 t2 ----------------- -tn
∫ −=max
0
)()()(1)(E tE
enM dEeEEEIktT µµ T = A(E,t) • I(E)
(TM = Mi/Mo)
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Spectrum unfolding
•
=
)(...
)(
),(...),(.........
),(...),(
)(...
)(
pO
1O
pn1n
p111
nM
1M
EI
EI
ExAExA
ExAExA
k1
xT
xT
In matrix algebra and after a suitable energy binning
( ) ( )( )∑
µ= =µ−
k
1iij xE
jjenk eEEExA
Usually p>n the solution presents a family of possible Io(Ej) vectors and - due to noise - results highly ill-conditioned.
5,0
6,5
8,0
9,5
11,0
12,5
14,0
15,5
17,0
18,5
20,0
21,5
23,0
2,6E-01
1,1E+00
1,8E+00
2,6E+00
3,4E+00
0,0E+00
2,0E+00
4,0E+00
6,0E+00
8,0E+00
1,0E+01
1,2E+01
1,4E+01
1,6E+01
A (E
,t)
E (keV)
t (g/
cm2)
1,4E+01 -1 ,6 E+0 1
1,2E+01 -1 ,4 E+0 1
1,0E+01 -1 ,2 E+0 1
8,0E+00 -1 ,0 E+0 1
6,0E+00 -8 ,0 E+0 0
4,0E+00 -6 ,0 E+0 0
2,0E+00 -4 ,0 E+0 0
0,0E+00 -2 ,0 E+0 0
A special formalism based on least –square solution is carried out
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2
2
2
2
2minminmin meascalcmeas TTTAIr −=−=
The solution can be expressed as sum of two vectors
OLS III +=)
I is the measured instrumental fluence and Io is a solution satisfying the condition
AIo = 0
Our approach
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Some segmentation Spectrometer support
The spectrometer
REB: scattering chamber and spectrometer holder
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DAS (Differential Absorption Spectrometry) and spectra evaluation
Spectra retrieval from transmission Spectra simulation from EGS4 with
the Casnati-Tartari-Baraldi formula
X ray emission by 30 keV electron impact on Cu
0
0.06
0.12
0.18
0.24
0 5 10 15 20 25 30E (keV)
I (a.
u.)
Explt
EGS4
Transmission T for REB sources
0
0.02
0.04
0.06
0.08
1 2 3 4 5 6 7 8 9 10 11 12 13
dosimetri
I/Io
5 8
11 14 17 20 23
0.26351.054
1.84452.635
3.4255
0.001
0.01
0.1
1
10
100
A(E,t)
E (keV)
t (g/cm2)
SPEDOS Response Function
1-20-1-1-0-2--1-3--2
90° (a)
0,0E+00
5,0E-04
1,0E-03
1,5E-03
2,0E-03
2,5E-03
0 10 20 30 40 50 60
Energia (keV)
I/I0
(a.u
.)
90° (b)
0,0E+00
4,0E-05
8,0E-05
1,2E-04
1,6E-04
2,0E-04
2,4E-04
15 20 25 30 35 40 45 50
Energia (keV)
I/I0
(a.u
.)
0° (a)
0,0E+00
5,0E-04
1,0E-03
1,5E-03
2,0E-03
2,5E-03
0 10 20 30 40 50
Energia (keV)
(a.u
.)
0° (b)
0,0E+00
4,0E-05
8,0E-05
1,2E-04
1,6E-04
2,0E-04
2,4E-04
15 20 25 30 35 40 45 50
Energia (keV)
(a.u
.)
Lateral ad forward observation
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REB – W target collision observation
REB position (a)
0,0E+00
5,0E-04
1,0E-03
1,5E-03
2,0E-03
2,5E-03
0 10 20 30 40 50 60
Energia (keV)
I/I0
(a.u
.)
REB position (b)
0,0E+00
4,0E-05
8,0E-05
1,2E-04
1,6E-04
2,0E-04
2,4E-04
15 20 25 30 35 40 45 50
Energia (keV)
I/I0
(a.u
.)
X ray production simulation: characteristic and continuous components
The exact knowledge of characteristic X rays production by electron impact.was pursued by using the well known Casnati Tartari Baraldi (CTB) formula [J. Phys. B 15 (1982) 155 and J. Phys B 16 (1983) 505];The continuous X rays component was obtained by the usual Bremsstrahlung impact procedure of the EGS4 Monte Carlo code;Simulated spectra were obtained and a comparison was made between DAS and EGS4+CTB resultsDue to the large uncertainties of matrix results from DAS data, comparison is difficult
Our (CTB).. Explt
Our (CTB).. Explt
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SimulationsK-X ray production
0.00E+00
5.00E-04
1.00E-03
1.50E-03
2.00E-03
2.50E-03
0 2 4 6 8 10 12 14 16 18
U (=T/Ek)a.
u. Serie1
K-Xray production
0.0E+00
5.0E-04
1.0E-03
1.5E-03
2.0E-03
2.5E-03
0 5 10 15 20 25 30 35
Ek (keV)
Inte
nsity
(a.u
.)
Calculated T=28 keVExptl
UU
EIRan
K
ooKK
ln2
ψϕσ
=
Electron impact ionization
U=T/EK
K-XRF= ωΚσΚFe
Cu
MoCd
DAS (Differential Absorption Spectrometry)
Spectra retrieval from transmission Spectra simulation from EGS4 with
the Casnati-Tartari-Baraldi formula
X ray emission by 30 keV electron impact on Cu
0
0.06
0.12
0.18
0.24
0 5 10 15 20 25 30E (keV)
I (a.
u.)
Explt
EGS4
Transmission T for REB sources
0
0.02
0.04
0.06
0.08
1 2 3 4 5 6 7 8 9 10 11 12 13
dosimetri
I/Io
5 8
11 14 17 20 23
0.26351.054
1.84452.635
3.4255
0.001
0.01
0.1
1
10
100
A(E,t)
E (keV)
t (g/cm2)
SPEDOS Response Function
1-20-1-1-0-2--1-3--2
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L-shell ionisation by electron impact
L-shell ionization like a K-shell ionizationMax at 28-30 keVMax for L-shell ionization of W - AuThe optimum choice is for a W and Au target
W L-Xray production
0.00E+00
5.00E-04
1.00E-03
1.50E-03
2.00E-03
2.50E-03
0 10 20 30 40 50 60 70 80 90 100T (keV)
a.u.
FOLLOWING PHOTOIONISATION AT ENERGY OF 59.54 KEV
TARTARI A, BARALDI C, CASNATI E, DA RE A, FERNANDEZ JE and TAIOLI S
J Phys B: At Mol Opt Phys 36 (2003) 843
Yb
0.0E+00
3.0E-03
6.0E-03
9.0E-03
1.2E-02
1.5E-02
5 6 7 8 9 10 11
E (keV)
Cou
nt ra
te (s
-1)
60°90°120°
0.6
0.7
0.8
0.9
1
1.1
50 60 70 80 90 100 110 120 130
Angle (degrees)
(L/L
)(L
/L)6
0°
Our Yb
Our Hf
Our Ta
Our W
Our Pb
Pb- Ertugrul1996Pb Kahlon1991Pb-Seven2002
ON THE ANGULAR DEPENDENCE OF L X-RAY PRODUCTION CROSS SECTIONS
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Assessment of spectra component
Dual energy hypothesis
X-ray Fraction EnergyComponent (keV)
L-X rays 0.35 8.9Bremsstrahlung 0.65 25.0Total 1.00
Measured spectrum
0
20
40
60
0 10 20 30 40 50 60E [keV]
Io(E
) [a.
u.]
validationsWater attenuation
1.00E-17
1.00E-12
1.00E-07
1.00E-02
1.00E+03
0 0.01 0.02 0.03 0.04 0.05 0.06
E (MeV)
I (a.
u.)
Incident
1 mm
3 mm
5 mm
1 cm
5 cm
The spectrum attenuation and corresponding dose calculation in water confirm the hypothesized dual component:The dose falls off as the third power similarly to those found in the literature for this spectra composition;The dose deposition concerns a vanishing sphere with the core mainly interested.
A
BDose along a sphere radius
0.0E+00
5.0E-03
1.0E-02
1.5E-02
2.0E-02
2.5E-02
3.0E-02
3.5E-02
4.0E-02
0 10 20 30 40 50 60Radius (mm)
Dose
(a.u
.)
8.9 keV
25 keV
100 keV
Synergism
Absorption in water and
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Dose considerations and comparisons
Present proposal
Dose in TLD at 5 mm: 4.5 Gy/shot;
tshot =30 ns
Dose rate 1.5E+08 Gy/s
Other comparable literature:Curry et al, IEEE Tr Pl Sc 28
(2000) 122 (Food sterilization at 220 kV
Bremsstrahlung X rays)Dose rate = 3.3E+07 Gy/s
Beatty et al, Med Phys 23 (1996) 53Skull interstizial radiosurgery
(continuous 40 kV BremsstrahlungX rays from electron probe)
Dose rate = 5.0E-02 Gy/s
ConclusionsThe X ray production mainly deals with a peak at 10 keV energy plus a continuous up to about 40 keV.
The energy is imparted to a sphere of about 0.5-1 cm radius plus a shadowing surrounding vanishing at 1-2 cm.
The energy (dose) is imparted in about 30E-9 seconds. This high dose rate and fractioning may results in a very high radio-biologic effectivenessWith a moderate repetition rate (0.1 – 1 Hz) a dose rate in water of about 100 cGy/min may be foreseen similarly to those of the actual continuous miniature X ray device [Med. Phys. 23 (1996) 53-62]
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