Comparison between 3D-CRT and Modulated Techniques for Head-and-Neck and Breast

摘要

Objective: Knowing that the most important steps related to planning systems and the success of IMRT is the optimization process, the objective of this work was to reach an optimal intensity pattern through cost functions by comparing the 3D-CRT technique and the IMRT technique for carcinomas of the head and neck and breast. The results obtained in the passage between these two techniques have shown good results for the treatment of these tumors and a great advantage in the optimization to avoid OAR. Materials and methods: To fulfill the objective proposed in this work for the head and neck plan, a SIB with a prescribed dose of 70 Gy for PTV1 and 56 Gy for PTV2 given in 35 fractions was used. In the breast plan with a prescribed dose of 50.4 Gy for PTV and 58.8 Gy for PTV boost delivered in 28 fractions. 6 MV and 10 MV photons were used for an Elekta Synergy linear accelerator, equipped with an MLC. Monaco was used as a TPS system. The Elekta iViewGT panel was used as the matrix for 2D quality control. The analysis of the data was done using the conformality index (CI) and the heterogeneity index (HI). A tolerance limit was proposed for quality control over 85% according to the hospital protocol. Results: Head and neck: The 3D technique and the 3 modulated techniques were able to meet the dose limit for PTV1 of D95%≥66.5 Gy and the dose for PTV2 of D95%≥ 53.2 Gy. The CI values for Step and Shoot and dMLC were the best for the PTV, as well as for the OARs such as the medulla and parotid. The PTV2d95 (Gy) of all techniques successfully exceeds the limit value of 53.2 Gy greatly satisfying the optimal intensity pattern using IMRT showing that the modulated techniques have better performance in these types of carcinomas. Breast: An acceptable plan with double-arch VMAT was achieved for the increase in dose coverage for 95% PTV (55.9 Gy) with 57.2 Gy. A difference of the four techniques was not significant in the spinal cord. The objective of this work is established w