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An Improved Deterministic 3D Dose Calculation for Radiation Therapy Application


M Huang

M Huang*, K Manalo, Georgia Insitute of Technology, Atlanta,A Dhabaan, Emory University Radiation Oncology, Atlanta, W Bolch, Univ Florida, Gainesville, FL,C Lee, National Cancer Insitute, MD, G Sjoden, Georgia Institute of Technology, Atlanta

SU-E-T-532 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose
Here we present a Hybrid Deterministic-Monte Carlo dose calculation algorithm, EDK-Sn, in a parallel computation environment, for rapid whole body dose calculation. This method adapts the Varian Clinac head model.

Method and Materials
Current treatment planning dose calculation algorithm poses two major challenges: inhomogeneity correction for small field and out-of-field secondary organ dose calculation inaccuracy. Currently, full physics Monte Carlo calculations have been regarded as a 'gold standard' for dose assessment of in field inhomogeneity correction and out of field Organ at Risk assessment. However, traditional Monte Carlo calculations require very long computation times, and also demonstrate large statistical errors for out-of-field dose. Deterministic transport dose calculation resolves the above issues without statistical inaccuracies; one example is the AcurosXB dose calculation engine adapted by Varian medical systems. We developed a hybrid deterministic-Monte Carlo 3D dose calculation for 3D whole body organ dose calculation. The Varian Clinac iX Linear Accelerator at Georgia Tech has been modeled from IAEA phase space into deterministic dose transport modeling, and performed calculations with the Linear Boltzmann equation in discrete ordinates (Sn) system using PENTRAN deterministic dose solver to obtain 3D photon fluence in the 3D space with 16 discrete energy bins, 4000 angles and in 3D space for whole body phantom organ dose. We then apply a quaternion rotation based on pre-calculated MCNP electron dose kernels that have been calculated in a high performance computing environment to obtain organ doses.

Results
This deterministic transport calculation method has been validated to be faster than full Monte Carlo, with comparable accuracy and differences under 10% for different organ dose calculations. The hybrid transport method for accessing organ doses also demonstrated minimized statistical errors.

Conclusion
Our hybrid EDK-Sn method has been validated for assessing organ doses for radiotherapy.


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