Application of deformable image registration in adaptive radiotherapy for lung cancer

Objective: To evaluate the effect of different methods of deformable image registration on the dose evaluation in adaptive radiotherapy for lung cancer. Methods: By using Raystation Ver 4.5 treatment planning system platform, two algorithms (Hybrid-and Biomechanics-based deformable image registration) and two orders (CT images before and during radiotherapy as reference images) were adopted. Four deformable image registration methods were utilized to calculate the accumulative dose. Eleven patients of lung cancer received adaptive radiotherapy for 35.0-61.6 Gy were recruited. The mean doses of lung, heart and GTV and the D₉₈ and D₂ of GTV were statistically compared using four methods. Results: With the four deformable image registration methods, the standard deviation of the mean lung dose of 11 lung cancer patients was ranged from 0.07 to 0.70 Gy, 0.01 to 0.79 Gy for the mean heart dose, 0.01 to 2.23 Gy for the mean GTV dose, 0.02 to 6.51 Gy for the D₉₈ of GTV and 0.01 to 0.97 Gy for the D₂ of GTV, respectively. Conclusion: The selection of deformable image registration method causes uncertainty to the calculation of accumulative dose during adaptive radiotherapy for lung cancer. (authors)