Intensity-modulated radiation therapy (IMRT) is believed to be one of the best radiation treatment techniques. IMRT is able to deliver fatal doses of radiation to the tumor region with minimal exposure of critical organs. It is essential to have a comprehensive quality assurance program to assure precision and accuracy in treatment, due to the character of IMRT. We applied quality assurance technique to the Eclipse treatment planning system and sought to determine its effectiveness in patient treatment planning. An acrylic phantom, film, and an ionization chamber were used in this study.
Purpose:This study compared 3 dimensional conformal radiation therapy (3DCRT) to intensity modulated radiation therapy (IMRT) in parotid glands sparing in head and neck cancers.
Materials and Methods:Planning target volume (PTV) was outlined on each CT slice. The dose of 50.4 Gy was prescribed to the PTV with the conventional fraction, 5 fractions per week. We also outlined spinal cord and both parotid glands. With Eclipse 3 dimensional planning system, 3DCRT and IMRT planning were done.
Results :After plan optimization, PTV dose distribution was evaluated with dose volume histogram. The 90% isodose curve covered almost all of PTV for both techniques. Maximum and median dose for spinal cord were 36.8 Gy and 34.2 Gy in 3DCRT, 39.9 GY and 37.5 Gy in IMRT. For parotid glands, mean and median dose were 33.6 Gy and 37.6 Gy in 3DCRT, 24.9 Gy and 24.5 Gy in IMRT.
Conclusion :For the non-pharyngeal head and neck cancers, 3DCRT was cost effective radiation modality in prevention radiation therapy induced xerostomia.