Analysis of Radiation Dose Distribution Inhomogenity Effects in Gamma Knife Radiosurgery using Geant4

Öz

The Monte Carlo method is widely used in the Gamma Knife dose distribution calculations. In this study, Monte-Carlo simulation with Geant4 was applied to determine Leksell Gamma Knife dose distribution for homogeneous solid water and heterogeneous brain phantoms, and primarily focused on the differences arising from the effects of inhomogeneity. The relative dose graphs were displayed for different collimator diameters. The dose values from the maximal interval regions were determined and compared. It seen that when the collimator size was 4mm, the mean maximum relative dose point was at 47mm for water phantom and at 44mm for the brain. The difference found was about 6.38%. The differences among the results determined for water and brain were ranged from 2 to 17%. As a result, the inhomogeneity effect should be considered in dose calculation in Gamma Knife planning system.

Anahtar Kelimeler

• Radiosurgery
• gamma knife
• γ-rays
• inhomogeneity
• brain

Kaynakça

1. [1] Leksell, L., "The stereotaxic method and radiosurgery of the brain". Acta Chir Scand, 102:316–319, (1951).
2. [2] Elekta "Leksell GammaPlan Instructions for use for version 4.0-Target Series". Elekta, Geneva (1996).
3. [3] Solberg, T., DeMacro, J., Holly, F., Smathers, J. and DeSalles A., "Monte Carlo treatment planning for stereotactic radiosurgery". Radioth and Onco 49:73–84, (1998).
4. [4] Xiong, W., Huang, D., Lee, L., Feng, J., Morris, K., Calugaru, E., Burman, E., Li, J. and Ma C-M., ''Implementation of Monte Carlo simulations for the gamma knife system. First European workshop on Monte Carlo Treatment Planning.'' In: Journal of Physics: Conference Series 74, 2023, (2007).
5. [5] ICRU Report 62 Prescribing, Recording and Reporting Photo Beam Therapy (Supplement to ICRU Report 50), Bethesda, MD, (1999).
6. [6] Xiaowei, L., Chunxiang Z Simulation of dose distribution irradiation by the Leksell Gamma unit. Phys Med Biol 44: 441–445, (1999).
7. [7] Al-Dweri, F.M.O., Lallena, A.M., Vilches, M., A simplified model of the source channel of the Leksell GammaKnife tested with PENELOPE. Phys Med Biol 49:2687–2703 .
8. [8] Al-Dweri, F.M.O., Lallena, A.M., A simplified model of the source channel of the Leksell Gamma Knife: testing multisource configurations with PENELOPE. Phys Med Biol 49:3441–3453, (2004).

9. [9] Cheung, J.Y.C., Yu, K.N., Ho, R.Y.C., Stereotactic doseplanning system used in Leksell Gamma Knife model-B: EGS4 Monte Carlo versus GafChromic films MD-55. Appl Radiat Isot 53:427–430, (2000).
10. [10]https://physics.nist.gov/cgibin/Star/compos.pl?refer=ap&matno=276
11. [11] https://physics.nist.gov/cgibin/Star/compos.pl?matno=123
12. [12] Li, J.S., Ma, C.M., A method to reduce the statistical uncertainty caused by high-energy cutoffs in Monte Carlo treatment planning. J Phys Conf Ser (2008)102:.
13. [13] Bertolino, N., "Experimental validation of Monte Carlo simulation of Leksell Gamma Knife Perfexion stereotactic radiosurgery system". PhD Thesis, Università Degli Studi Di Milano (2009).
14. [14] Moskvin, V., Timmerman, R., DesRosiers, C., et al. Monte carlo simulation of the Leksell Gamma Knife: II. Effects of heterogeneous versus homogeneous media for stereotactic radiosurgery. Phys Med Biol 49:4879–95, (2004).
15. [15] Moskvin, V., DesRosiers, C., Papiez, L., et al. Monte Carlo simulation of the Leksell Gamma Knife: I. Source modelling and calculations in homogeneous media. Phys Med Biol, 47:1995–2011, (2002).
16. [16] Cheung, J.Y.C., Yu, K.N., Ho, R.T.K. and Yu, C., Monte Carlo calculated output factors of a Leksell Gamma Knife unit. Phys Med Biol, 44:N247–N249, (1999).
17. [17] Cheung, J.Y.C., Yu, K.N., Yu, C.P., Ho, R.T.K., Monte Carlo calculation of single-beam dose profiles used in a gamma knife treatment planning system. Med Phys 25:1673–1675, (1998).
18. [18] Cheung, J.Y., Yu, K.N., Ho, R.T., Yu, C.P., Monte Carlo calculations and GafChromic film measurements for plugged collimator helmets of Leksell Gamma Knife unit. Med Phys 26:1252–1256, (1999).
19. [19] AAPM Task Group 21 A protocol for the determination of absorbed dose from high-energy photon and electron beams. Med. Phys, 10:741–771 (1983).
20. [20] Cuttone, G., Mongelli, V., Romano, F., Russo, G., Sabini M Geant4 based simulation of the Leksell Gamma Knife for treatment planning validations. In: 14th Geant4 Users and Collaboration Workshop. Catania, Italy, (2009).