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

tartari@fe.infn.it

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

1

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

2

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

3

)( 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

4

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)

5

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

2

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

6

Some segmentation Spectrometer support

The spectrometer

REB: scattering chamber and spectrometer holder

7

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

9

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

10

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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