THE DOSIMETRIC EVALUATION ON PHOTON ENERGY EFFECT FOR CERVICAL CARCINOMA IN 3D-CRT, IMRT, AND VMAT PLANS

Abstract

In the previous time, 3D-CRT technique has been considered as the primary treatment for cervical cancer treatment. Nowadays, advanced techniques, IMRT and VMAT, are used to treat because of the dosimetric and clinical benefit over 3D-CRT technique. However, each of these technique generates difference outcomes. The purpose of this study was to investigate the dosimetric outcomes between 6 and 15 MV photon energies in each 4 fields box 3D-CRT, 9 fields IMRT, and 2 arcs VMAT plans of five advanced cervical cancers using parameters of D95%, TC, HI, CI, CN from PTV, V45 Gy and V50 Gy from OARs, NTID, MUs, beam on time, neutron dose as well as gamma dose contamination. The plans were performed on Eclipse TPS with the prescribed dose of 50.4 Gy/28F. The results showed that PTV received dose at least 50.4 Gy for all energies and techniques, while the OARs doses were lower than the tolerance limits except 3D-CRT technique. The IMRT and VMAT techniques showed the great similar PTV and OARs doses in both energy plans. The two energy IMRT and VMAT plans revealed percent volume of bladder, rectum and bowel reside in tolerance limit. However, the NTID, Mus, and beam on time in the 15 MV of all planning techniques provided better results than 6 MV plans. For radiation contamination during irradiation, the 15 MV plans presented the higher neutron dose in IMRT than 3D-CRT and VMAT, respectively due to the influence of gantry directions. While at 30s, 2mins, and 5mins after irradiation, the results were different because the outcomes relate to MUs results. Therefore, the neutron and gamma dose of VMAT were higher than 3D-CRT technique whereas IMRT delivered the highest neutron and gamma dose contamination. In conclusion, the 15 MV is recommended in 3D-CRT due to the better in CI and CN property. In contrast, the 6 MV energy is a good option for IMRT technique, since the same dosimetric parameters but 15 MV beams present neutron and gamma dose. For VMAT technique, both of photon energies are suitable to treat cervical cancer due to no significant difference in almost all outcome parameters between these two energies.