Comparison of three different techniques in parotid gland tumors using three dimensional conformal radiation therapy

Introduction:
Background: Radiotherapy of parotid tumors is achieved by different radiotherapy techniques. So they deliver the dose to organs at risk such as contralateral parotid, temporal lobe & spinal cord. The consequences of high dose to OARs are xerostomia, Temporal lobe necrosis and loss of hearing.
Purpose: The aim of this study was to compare different treatment techniques for parotid gland tumors using three different techniques to find the optimal technique which demonstrates sufficient target coverage and preserving of surrounding normal tissue at 3DCRT treatment of parotid cancer
Materials and Methods:
The CT-scans of ten parotid patients were used. The target volume and OARs were contoured and after 3D dose distribution and using of dose-volume histogram (DVH), three different plans were done and were compared: A. Ipsilateral oblique wedge photon 6MV pair with bolus
B. Photons, 3-fields AP(wedge), PA(wedge), lateral(open), C. Mixed beam: 6MV photon ipsilateral oblique wedge pair & 14Mev electron with bolus (1:4)
Results:
Target coverage was suitable for techniques B and C. Technique c showed the best homogeneity and conformity index at target volume. The dose to OARs was lower than other techniques. On other hand, technique A demonstrated ineligible homogeneity within PTV & the higher dose to OARs than other techniques.
 
Conclusion:
mixed beam: 6MV photon ipsilateral oblique wedge pair & 14Mev electron with bolus is an optimal treatment plan for treatment of parotid cancer patients in such way than other techniques.