Tumor and critical organ's dose arising from different radiotherapy techniques applied to parot

• 作 者: Mohammad Taghi Bahreyni Toossi AtefehVejdani Noghreiyan Hamid Gholamhosseinian Kazem Anvari
• 机 构: Medical Physics Research Center,Mashhad University of Medical Sciences,Mashhad,Iran
• 出 处: The 15th Asia-Oceania Congress of Medical Physics (AOCMP2015
• 发表日期: 2015年7期
• 关键词: Parotid gland tumor Radiotherapy T1D Rando phantom

　　Purpose:Parotid gland tumors account for 3%of head and neck tumors.Adjuvant radiotherapy is suggested for reducing the risk of high grade parotid tumors.The aim of the present study was to compare patients dose arising from different techniques applied to treat parotid gland tumors and suggest useful modification,to optimize organs dose.Methods:The target volume dose and OARs of three usual parotid gland parotid radiotherapy techniqueswere measured on a Rando phantom by TLDs.Tech1:mixed beam of 6 MV photons and 10 MeV electrons technique(weighting= 1:2)Tech2:Paired wedge 6 MV photon beams Tech3:Paired wedge 6 photon beams using MLC Then,measured doses were compared with corresponding values obtained from treatment planning calculations.Finally,the best technique was suggested with respect to tumor dose sufficiency and homogeneity,and organ at risks protection.Results:Tech2 and tech3,significantly improved the homogeneity in PTV(ΔD95%-5%=2.31,2.28,respectively).Tech3 was most effective factor in dose reduction tissues beyond target volume.Tech1 kept the lowest dose to oral cavity(1.9 Gy).PTV received at least 95%of the prescribed dose in all techniques.Based on the TRS-430 protocol,95%of the measured dose by TLD inner and outer of the field was in good agreement with the treatment planning system calculations,for three examined techniques.Conclusions:In the studied techniques,tech1 can be considered for protecting oral cavity and preventing xerostomia.Regarding target dose homogeneity,tech2 and tech3 are preferred as the optimal techniques; moreover,in reduction dose to structures adjacent target volume,tech3 was selected.It is suggested that,if a combination of the three techniques are replaced by one single technique,the critical structures surrounding the tumoral tissues are spared more efficiently,and the tumor volume receives sufficient and homogeneity dose.