Influence of dose distribution selected from different beam orientation for a nasopharyngeal carcinoma IMRT plan / 中国癌症杂志

ABSTRACT

Purpose:To evaluate the different dose distribution created by three different plans on a nasopharyngeal carcinoma case with simultaneous integrated boost intensity modulated radiation therapy (SIB-IMRT). Methods:we designed three different SIB-IMRT plans on a nasopharyngeal carcinoma case, one was from anterior direction of the head, 5 non-equally spaced fields, another was from posterior direction of the head, 5 non-equally spaced fields also, third was 5 equally spaced fields around the head. Each plan had its dose distribution to the target and main critical structures.Results:No significant difference of dose distribution to the target when comparing the previous three different IMRT plans. However, dose to the parotids delivered from 5-equally spacd was obviously lower than the other plans, dose to the optic chiasm was much lower created by the plan designed from the posterior direction of the head with 5 non-equally spacea field.Conclusions:For a nasopharyngeal carcinoma case, there is no significant difference of dose distribution to the target compared with three different 5-beam orientation SIB-IMRT plans. To protect parotids, we recommend designing a plan with equal beam direction around the head. When the target is very close to the optic chiasm, plauning from posterior direction of the head should be better.