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Sensitivity of NTCP parameter values against a change of dose calculation algorithm
Carsten Brink1, Martin Berg, Morten Nielsen
1Radiofysisk Laboratorium, Odense University Hospital, DK-5000 Odense, Denmark.
Medical Physics
|October 12, 2007
Summary
Changing radiation dose calculation algorithms significantly alters normal tissue complication probability (NTCP) parameters. Accurate NTCP modeling requires specifying the dose calculation algorithm used for radiation treatment planning.
Area of Science:
- Medical Physics
- Radiation Oncology
- Computational Biology
Background:
- Accurate normal tissue complication probability (NTCP) estimation is crucial for optimizing radiation treatment planning.
- Existing NTCP models rely on dose distributions, which can vary based on the dose calculation algorithm employed.
- Different algorithms introduce approximations, leading to discrepancies in predicted dose distributions.
Purpose of the Study:
- To investigate whether optimal NTCP parameter values change significantly when the dose calculation algorithm is altered.
- To assess the impact of switching from a pencil beam (PB) to a collapsed cone (CC) algorithm on NTCP parameter values.
Main Methods:
- Retrospective recalculation of treatment plans for 17 breast cancer patients using a collapsed cone (CC) algorithm.
- Comparison of NTCP estimates for radiation pneumonitis derived from CC and clinically used pencil beam (PB) algorithms.
- Fitting NTCP parameters for CC calculations to match NTCP values obtained from PB calculations.
Main Results:
- Significant shifts in NTCP parameter values were observed across three different models when changing the dose calculation algorithm.
- The magnitude of these shifts was comparable to the uncertainties associated with previously published parameter values.
- The study highlights the algorithm-dependent nature of NTCP parameter estimation.
Conclusions:
- The choice of dose calculation algorithm has a substantial impact on NTCP parameter values.
- It is essential to report the specific dose calculation algorithm used when publishing NTCP parameter estimates.
- Ensuring correct model application necessitates clear documentation of the applied dose calculation algorithm in radiation therapy planning.
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