1. Basic concept of Monte Carlo for
transport particle in Matter I
SOUTHEAST ASIAN CONGRESS FOR
MEDICAL PHYSICS (SEACOMP)
POST CONGRESS WORKSHOP ON
MONTE CARLO APPLICATIONS IN
RADIOTHERAPY
Manila, November 21-24, 2011
Freddy

2. Basic Idea of Using Radiation
Source Object
Detector

3. Particle Transport
Source:
Object: Detector:
-Type of Radiation
- Physical Aspect: - Diagnose  Imaging
-Quality  energy
- Geometry & Material - Therapy Verification
-Quantity  number
- Biological and chemical Aspects
-Geometry of source

4. Interaction?
 Macroscopic View
−µ (E)x
I = I 0e
I0 , E µ ( E), x

5. Interaction (cont.)
Only for
monoenergetic
narrow beam
with 1D object
Eabsorb = E * ( I 0 − I )
−µ ( E ) x
= E * I 0 (1 − e )

6. Interaction (cont.)
 Polyenergetic Narrow-Beam with 1D Object
Eabsorb = ∫ I 0 ( E )(1 − e −µ (E)x
)d E

7. Interaction (cont.)
 Microscopic View: Neutron
Photon
Electron

8. Microscopic View  Modern Physics
 Interaction:
– Each Particle
– Type of Particle:
 Photon
 Electron
 Positron
 Neutron
– Energy
– Matter of Medium

9. Differences between “Electron” and
“Photon”
 Mass
E = p c +E
2 2 2 2
o
– Energy:
h
p= Eo = mo c 2
c
hλ
 Photon:
E= mo = 0
c2 2
 Electron:
E = p c + (511 keV )
2 2
E = Ek + 511 keV

10. Interaction between Photon and
Matter

11. Photon

12. Table of Interaction
interaction Atomic Nucleus Electric field
electron of the nucleus
Energy loss
100% Fotoelectric Photonuclear Pair
Effect reactions production
0%<∆
E < 100% Compton - -
Effect
≈
0% Coherent - -
Scattering

13. Photoelectric(1)

14. Photoelectric (2)
E = 0.1 MeV Z 4 −3
Z n −m
τ =ρ Eγ (cm 2 / Atom) τ =ρ Eγ (cm 2 / Atom)
A A
•n  4.6 if E > 3 MeV
•m  1, If E > 5 MeV

15. Photoelectric (3)
The Distribution of scatter angle of Electron

16. Effect Compton (1)

17. Ee-
hν
φ
Compton efek (2) θ
hν’
Photon (θ) Electron (φ)

18. Pair Production (1)

19. γ  e- + e+
γ + e-  e- + e- + e+

20. Elastic Scatter
 Characteristic of this interaction:
 Photon only change in direction but not in its energy
 Distribution
of the angle of scatter Photon
 Matter and Energy

21. Photonuclear
 (γ,p)
 (γ,n)

22. The Resume
Dependence of Energy Z Z
Type of interaction σ cm2/atom cm2/g
Photoelectric Effect E-3.5 Z4 to Z5 Z3 to Z4
Compton Effect E-0.5 to E-1 Z ≈
independent
Pair Production E1 to ln E Z2 Z

23. Cross Section

24. Interaction between Electron and
Matter

25. Interaction’s Type (1)
http://www.microscopy.ethz.ch/interactions.htm
http://www4.nau.edu/microanalysis/Microprobe/Interact-Effects.html

26. Interaction’s Type (2)

27. Interaction’s Type (3)
Sumber: Heinrich, 1981

28. Bremsstrahlung
 Photon Energy: Continue 0  Ek, Where Ek = Kinetic
energy of electron
 If Ek < 100 keV, Photon will be scatter with the scatter
angle 90° of the initial direction of electron. For
higher Ek  the direction of scatter photon = the
initial direction of electron

29. STOPPING POWER
 For Thick Matter:

30. STOPPING POWER
• Collision stopping power ↓ as Z ↑

31. Feynmann Diagram (1)

32. Feynmann
Diagram (2)