1. The brachytherapy advanced example Susanna Guatelli (CERN/INFN)
Geant4 Users Workshop
CERN 14th November 2002

2. Brachytherapy
Radioactive sources deliver therapeutic doses near tumors, while preserving surrounding healthy tissues
Brachytherapy is a medical therapy used for cancer treatment
Interstitial brachytherapy
prostate
I-125
Endocavitary brachytherapy
uterus, vagina, lungs
Ir-192 source
Superficial brachytherapy
skin
Leipzig Applicator

3. approximate dose calculation the source is approximated to a point
Software characteristics
for brachytherapy
precision
reproduction of the real geometry and tissues (CT )
calculation speed
simple to use ( for hospitals !)
Calculation of dose delivered to tissue
All the tissues are approximated
to water
Analytical calculation methods
Commercial software available
es.: Variseed V 7, Prowes
Disadvantages
approximate dose calculation
density insensitive
the source is approximated to a point
Advantage
high speed dose calculation

4. Project software for dose calculation
3D dose distribution calculation
Isodose curves
Simulation
Geant4
Analysis
AIDA/Anaphe
Monte Carlo method
Accurate physical process simulation
Test to guarantee the quality of the software
Precision
Real geometry reproduction
Accurate description of the geometry
Possibility to interface the sofware to CT
Graphical visualization + user interface
Dose distribution analysis ( eg. isodose curves )
Simple to use
Use in hospitals
Parallelisation
Access to calculation distributed resources
Calculation speed
Expansive to new functionalities
Public access
Other user requirements

5. Development of the project
Sofware planning and
development
Tests
Test from a microscopic point of view (on e- ranges)
Test the dose distribution of the interstitial source Isoseed I-125
Experimental mesurements
functionalities
design
Software Process
(USDP )
Brachytherapic Application
Dose distribution calculation
Isodose curves
in different brachytherapic techniques
Results and future
Technology Transfer

6. Design of the brachytherapy example
run
Primary Particles
physics
Energy deposit
detector
analysis
visualization
geometry and materials
event
User Interfaces

7. Comparison with the protocol data
Software tests
Test of Geant4 e- electromagnetic processes
Microscopic test
e- CSDA range simulations for different absorber
materials
Comparison of different physical models
(Standard/Low Energy)
Comparison with protocol data (Report ICRU 37)
CSDA range
Test of the dose distribution
of Bebig-Isoseed I-125
dose distribution 2
Comparison with the protocol data

8. CSDA range test design
Primary particles
Physics
Range
Detector

9. Test: CSDA range e- delivered from the centre of the box
Range = distance between the origin and the point where the kinetic energy of e- is zero
Beryllium
Max step fixed
No secondary particles
No energy loss fluctuations
No multiple scattering
Geant4 packages
Low Energy / Standard

10. Materials of interest to medical physics
Test results
Materials
Beryllium
Berillium
elements
Materials of interest to medical physics
Beryllium
Aluminum
Gold
Lead
Uranium
Water
Soft tissue
Muscle
Bone
Geant4 packages
Low Energy / Standard simulate ranges with good accuracy
(~ %)

11. Dose distribution test design
Primary particles
Physics
Energy deposit
Detector

12. Dose distribution test
Bebig Isoseed I-125 at the center of the phantom
Source composition structure
Geometry
Random generation point and direction in the radionuclide,
Decay gamma energy spectrum
Primary particles
Cut in range= 100 mm
electromagnetic processes for e+, e-, gamma
E (keV)
Prob.
27.4
0.784
31.4
0.17
35.5
0.046
Physics
Track geometry and dose calculation geometry are separated (voxels = 1 mm3)
CPU Optimisation
2D histogram: energy deposit in the plane containing the source
analysis dose

13. Dose distribution resultsmm
simulation
TG43
The simulation results are NOT in agreement
with protocol data

14. Protocol data Performed with dosimeters LiF Lif wide range of use
Low spatial resolution
Critical measurements (delicate methodology of use of Lif)
Measurement in plexiglass
Measurements performed in water
Better spatial resolution(~ 0.5 mm)
Disadvantage : reduced range of use in comparison with LiF
Experimental measurement of dose distribution with the use of films
misura diretta

15. Experimental measurements
d = 3.1+/- 0.2 mm
Optimisation of the experimental set-up
film
dose measurements of a single source characterised by
different exposure time (2, 9 , 12, 30 minutes)
Water phantom
The measurements disagree
with the protocol data
and agree with Geant4
simulation
Experimental
measurements
protocol MC
protocol

16. Consequences Experimental measurements results
The results of this work would
affect strongly the clinical activity
In depth studies will be performed

17. Generalisation of the software
Functionality
3D dose distribution
Isodose curves
Choice of the materials of the phantom
Graphical visualisation
Possibility to interface the system to CT
source composition
geometry, materials, spectrum
Abstract Factory
Use of abstract classes
Radioactive source definition thanks to the design pattern: Abstract Factory
Generalisation +
Specific aspects of the source
Parametrisation of the volumes in the geometry
Parametrisation function: volume material
Interface to CT
Simulation result: energy deposit
Analysis: dose distribution and isodose curves
Dosimetry

18. Interstitial brachytherapy
Results:
Interstitial brachytherapy
Source Bebig Isoseed I-125
0.16 mGy =100%
isodose curves
The results can be generalised to more sources located in the phantom

19. Endocavitary brachytherapy Superficial brachytherapy
Results:
Endocavitary brachytherapy
Source MicroSelectron-HDR
Results:
Superficial brachytherapy
Leipzig Applicator

20. Parallelisation and distributed calculation
Speed is a fundamental requirement for software used in clinical practice
MC simulations were never used until now in clinical practice due to the long calculation time
Intermediate system between applications and GRID
Parallelisation
Access to distributed computing resources
First results:
factor ~30 increase in speed
(conference Siena 2002)
Possibility to run the brachytherapy example simulation + analysis via web?
Look at A. Mantero Thesis

21. Results of my simulation
Technology
Transfer
Particle physics software aids space and medicine
Geant4 is a showcase example of technology transfer from particle
physics to other fields such as space and medical science […].
CERN Courier, June 2002
Results of my simulation

22. Conclusions Software In collaboration with
3D dose calculation
Accurate simulation of physics
Realistic experimental configuration
Possibility to interface the system to CT
Applicable to all brachytherapic techniques
Exstensive
GRID compatible
New and original
Unità Operativa di Fisica Sanitaria, Savona
IT Division, CERN
Geant4 collaboration
Anaphe team
INFN
In collaboration with
Example of collaboration between different environments:
Hospital activities and High Energy physics