On Presentation of Optimal Treatment Plan in Radiotherapy of Parotid Cancer: A Comparison of Nine Techniques in Three Dimensional Conformal Radiation Therapy

Introduction:
Today, radiotherapy combined with surgery in the treatment of parotid tumors widely are used specially for high grade parotid tumors. One of concern and challenge issue of radiotherapy is that the treatment of these tumors with irregular surface due to the presence of external ear and region of different physical electron density (air cavities, dense bone, soft tissue). Therefore, offering an optimal treatment plan to the desired results in terms of dose distribution factors to adequate target coverage and protect critical structures surrounding OARs is so important.
This study aimed to achieve an optimal treatment plan using low-energy electrons, as well as different modes of electrons and photons will be considered. Also the effect of bolus to achieve the optimal treatment plan is performed.
Materials and Methods:
CT of parotid patients during 2012 to 2014 is used. Twelve patients were evaluated by TPS Core plan, 3D dose distribution and using of dose-volume histogram (DVH), nine techniques were evaluated: a.6MV photons, 3-fields AP(wedge), PA(wedge), lateral(open), b. unilateral 10 Mev electrons, c. unilateral 14 Mev electrons, d. Mixed beam technique using 6MV photon and 10 Mev electron(1:4 weighting), e. Mixed beam technique using 6MV photon and 14 Mev electron(1:4 weighting), f. unilateral 10 Mev electrons with bolus (0.5 cm bolus is used), g. unilateral 14 Mev electrons with bolus (0.5 cm bolus is used), h. Mixed beam technique using 6MV photon and 10 Mev electron (1:4 weighting) with Bolus (0.5 cm bolus is used), i. Mixed beam technique using 6MV photon and 14Mev electron (1:4 weighting) with Bolus (0.5 cm bolus is used)
Results:
Using of DVH to appraise, the dose to OARs are 0 for techniques 6MV photons, (3-fields), unilateral 10 Mev electrons with and without Bolus, unilateral 14 Mev electrons with & without Bolus
Conclusion:
The highest conformal and homogeneity index and near to 1 were for 6MV photons, 3-fields, unilateral 14 Mev electrons with and without Bolus, mixed beam technique using 6MV photon and 14 Mev electron with and without Bolus.