Evaluation and comparison of dose distributions for nasopharyngeal carcinoma patients treated by Jaws-Only IMRT technique and by 3D-CRT technique at Dong Nai General Hospital

Abstract

The goal of radiation therapy is twofold: maximize the possibility of destroy malignant cells while minimizing the damage to healthy tissue. The introduction of intensity modulated radiation therapy (IMRT) technique has brought improvements in this goal. Multi-leaf collimator (MLC) is a useful tool for IMRT. However, the use of MLC is not necessarily mandatory. The Panther Treatment Planning System version 4.6, Prowess Inc., enables the implementation of this technique for accelerator without MLC (the socalled Jaws-Only IMRT technique). This study aims to evaluate the results of application of Jaws-only IMRT technique for nasopharyngeal carcinoma patients at Dong Nai general hospital. Twenty five patients were randomly selected for this study. For each patient, two plans were generated: 3D-CRT (Three-Dimensional Radiation Treatment) and JO-IMRT. The dose distributions, dose-volume histograms (DVH), conformity indexes (COIN), homogeneity indexes (HI) were used to compare between these two plans and find out the best plan. Pretreatment verifications were performed for all patients' plans using ion chamber (Farmer Type Chamber FC65-P, IBA), detector array (MapCHECK2, Sun Nuclear Corporation and Octavius 4D 1500, PTW). The average deviation between measurement and calculation for point dose was 2.3±1.1 %, within limit dose constraint. For detector array measurements, the gamma index with 3 % dose difference and 3 mm was higher than 95 %. The results showed that the JO-IMRT technique had generated better dose distribution in the target volume and reduced dose to healthy tissues compared to 3D-CRT.

Assessment of the Dosimetric Index from IMRT and Rapid arc Plan for Oropharyngeal Cancer with Simultaneous Integrated Boost (SIB) Technique in Combination with EUD-based NTCP and TCP Radiobiological Models

“…The maximum dose for the brain stem and spinal cord [33,34] and the mean dose for the parotids [35][36][37][38] were not statistically significant for either 7-field or 9-field IMRT (p > 0.05). The NTCP [39], effective volume, EUD, and NTID of the brainstem, spinal cord, and parotids were also not statistically significant (p > 0.05). The mean dose, NTCP, effective volume, EUD, and NTID of both parotids were not statistically significant (p > 0.05).…”