Patient-specific quality assurance for the treatment of intensity modality radiation therapy of nasopharyngeal carcinoma

Abstract

Nasopharyngeal carcinoma is the most common malignant tumor of the nasopharynx. The aim of this study was to assess and evaluate the significant of performing patient specific quality assurance (QA) for patients diagnosed with nasopharyngeal carcinoma treated with intensity modulated radiation therapy (IMRT). Ten pretreatment IMRT plans were selected for this study. The ten selected plans were treated with the split-field technique for intensity modulated radiation therapy planning using 10 MV beams with a prescribed dose total of 7000 cGy in 35 fractions. As a quality assurance protocol the two-dimensional ionization-chamber array was used. The study results showed agreement between the measured dose and the preplanned dose using the treatment planning system. All of the plans passed >95% gamma with the pixels within 4% distance to agreement (4 mm) for IMRT patient-specific QA. We concluded that IMRT has the ability to deliver a highly conformal dose distribution to the planned target volume while sparing the organs at risk. In addition, our results showed a very good agreement between the measured dose and the calculated dose which preceded it. Key words: Radiation therapy, intensity modulated radiation therapy verii¬cation plan, gamma index, nasopharyngeal carcinoma.