Objectives: To evaluate and compare dose distribution between IMRT and VMAT plan in radiotherapy for head and neck cancer using TrueBeam STx accelerator. Subjects and methods: CT imaging of head and neck cancer’s patients treated with VMAT on the TrueBeam STx accelerator was used to replan using IMRT technique in TPS Eclipse . | Journal of military pharmaco-medicine no1-2019 EVALUATE DOSE DISTRIBUTION OF IMRT AND VMAT TECHNIQUE IN RADIOTHERAPY FOR HEAD AND NECK CANCER USING TRUEBEAM STX LINEAR ACCELERATOR Pham Hong Lam1; Nguyen Thi Van Anh2; Pham Quang Trung2 SUMMARY Objectives: To evaluate and compare dose distribution between IMRT and VMAT plan in radiotherapy for head and neck cancer using TrueBeam STx accelerator. Subjects and methods: CT imaging of head and neck cancer’s patients treated with VMAT on the TrueBeam STx accelerator was used to replan using IMRT technique in TPS Eclipse . Conformity index, gradient index and homogeneity index were used to compare plan quality and dose distribution at planning target volume, organs at risk. Results: The dose distribution on planning target volume of IMRT technique based on CI100 - Paddick, HIRTOG index ( ± , ± ) gave the same value as the VMAT technique ( ± 0, 44, ± ). Maximum doses on organs at risk such as spinal cord, brainstem, and mandible received from IMRT technique were a little lower than the doses from VMAT technique. Conclusion: The IMRT technique is equivalent to the VMAT based on coverage, ability to focus dose on the planning target volume and the ability to spare dose to critical organs. Both the IMRT and VMAT technique on the TrueBeam STx Linac can be selected to treat head and neck cancer patients in 108 Military Central Hospital. * Keywords: Head and neck cancer; IMRT; VMAT; Conformity index; Homogeneity index; Gradient index. INTRODUCTION Radiation therapy is one of the main modalities for cancer treatment. The linear accelerator (Linac) is an indispensable device and it is the most basic component of an external radiotherapy. Especially, radiation therapy plays an important role in head and neck cancer treatment. The biggest difficulty with the treatment of head and neck cancer by radiotherapy is that it has a large number of critical organs near treatment volume. Organs at risk
