Assessment of parotid gland dose changes during head and neck cancer radiotherapy using daily megavoltage computed tomography and deformable image registration

作者：Lee Choonik^*; Langen Katja M; Lu Weiguo; Haimerl Jason; Schnarr Eric; Ruchala Kenneth J; Olivera Gustavo H; Meeks Sanford L; Kupelian Patrick A; Shellenberger Thomas D; Manon Rafael R

来源：International Journal of Radiation Oncology, Biology, Physics, 2008, 71(5): 1563-1571.

DOI：10.1016/j.ijrobp.2008.04.013

• head-and-neck cancer
• anatomic changes
• deformable image registration
• parotid gland dose

Purpose: To analyze changes in parotid gland dose resulting from anatomic changes throughout a course of radiotherapy in a cohort of head-and-neck cancer patients.
Methods and Materials: The study population consisted of 10 head-and-neck cancer patients treated definitively with intensity-modulated radiotherapy on a helical tomotherapy unit. A total of 330 daily megavoltage computed tomography images were retrospectively processed through a deformable image registration algorithm to be registered to the planning kilovoltage computed tomography images. The process resulted in deformed parotid contours and voxel mappings for both daily and accumulated dose-volume histogram calculations. The daily and cumulative dose deviations from the original treatment plan were analyzed. Correlations between dosimetric variations and anatomic changes were investigated.
Results: The daily parotid mean dose of the 10 patients differed from the plan dose by an average of 15%. At the end of the treatment, 3 of the 10 patients were estimated to have received a greater than 10% higher mean parotid dose than in the original plan (range, 13-42%), whereas the remaining 7 patients received doses that differed by less than 10% (range, -6-8%). The dose difference was correlated with a migration of the parotids toward the high-dose region.
Conclusions: The use of deformable image registration techniques and daily megavoltage computed tomography imaging makes it possible to calculate daily and accumulated dose-volume histograms. Significant dose variations were observed as result of interfractional anatomic changes. These techniques enable the implementation of dose-adaptive radiotherapy.

• 出版日期2008-8-1