Title: MONTE CARLO RADIATION DOSE SIMULATIONS AND DOSIMETRY COMPARISON OF THE MODEL 6711 AND 9011 125I BRACHYTHERAPY SOURCES
1MONTE CARLO RADIATION DOSE SIMULATIONS AND
DOSIMETRY COMPARISON OF THE MODEL 6711 AND 9011
125I BRACHYTHERAPY SOURCES
Mark J. Rivard Department of Radiation Oncology,
Tufts Medical Center, Boston, Massachusetts 02111
Med. Phys. 36 (2), February 2009
2BACKGROUND
- 6711125I seed model
- Smaller sources allows smaller diameter needles
- Lower incidence of healthy-tissue complications
3INTRODUCTION
- TRUS guided prostate implantation
- 125I seed (6711 Model)
- Sources placed with needles into prostate
- Results in swelling
- Minimized by small diameter needles
- New model 9011 125I seed
- Oncura GE Healthcare (Arlington Heights, IL)
4PURPOSE OF THE STUDY
- Study and determine dosimetry parameters of the
new 125I 9011 model - Treatment planning
- Clinical implementation
5MATERIALS AND METHOD
A. Source Characteristics
6B. Radiation Transport code
7B. Radiation Transport code
- MCNP 5 with EPDL97 (LLNL report)
- 20 cm radius liquid water phantom
- Coordinate system origin located at the center of
the capsule - Photon transport MODE P
- Tallies
- Track length estimator (F6)
- Cell energy fluence (f4)
- 1 keV energy cutoff
- 2 x 109 photon histories
-
8Coordinates system in MCNP
9TG 43U Dose Calculation Formalism
According to TG 43, the dose distribution around
a cylindrical symmetric brachytherapy source is
defined by the following equation.
10C. UNCERTAINITY ANALYIS
11III. RESULTS AND DISCUSSION
III. A. Dose rate constant
Recommended value 0.965 cGy h-1 U-1
12III. B. Dose rate constant
13III. C. Anisotropy function
14III. C. Anisotropy function
15IV. D. DOSE RATE TABLE
16CONCLUSION
- Monte Carlo simulations of dose rate
distributions - Model 6711 and 9011 125I sources
- Similar trends and dose falloff characteristics
- Determine the TG-43 brachytherapy dosimetry
parameters - Needed for clinical brachytherapy treatment
planning - Two source models dose rate difference are 2
- Require separate data entry into treatment
planning systems
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