Background: This Study Evaluate two state of Art techniques, Rapid Arc and large-field sliding window IMRT in terms of dosimetric end points and delivery time for head and neck cancer. Materials and Methods: 22 patients with head and neck cancer were selected for a planning comparative study. All patients went to CT-simulation in supine position. PTVs were delineated for two dose level of prescription 70 Gy to the boost-PTV70Gy and 54 Gy to the elective-PTV54Gy in 35 equal fraction/day. Simultaneous Integrated Boost (SIB) technique plan was generated for all patients and optimized with both techniques, Rapid Arc and IMRT with similar planning objectives. Dose of all plans of both techniques were calculated for 6MV photon using AAA implemented in Eclipse treatment planning system (10.0.39) with calculating grid size of 2.5 mm. Results: Comparison of Rapid Arc and IMRT plans in every patient showed significantly higher conformity index (CI95%) (p = 0.021) and sparing of the all OARs with Rapid Arc. The average homogeneity Index (HI95%) of lower prescribed dose target PTV54Gy which is in proximity to Higher dose prescribed target PTV70Gy was improved significantly with rapid Arc (p = 0.0001). D1% of spinal cord dose reduced significantly (p = 0.047) with Rapid Arc and the average mean dose of both left-parotid (21.26 ± 8.5 Gy), right-parotid (22.37 ± 7.44 Gy) were received lesser than with IMRT (22.78 ± 11.2 Gy and 24.1 ± 7.96 Gy) respectively. A significantly less monitor unit (MU) was required to deliver the plan (p < 0.00001) with significantly lesser treatment time (p < 0.00001). Conclusion: Rapid Arc technique was superior to IMRT in sparing the OARs without compromising target coverage and delivered the plan with lesser monitor unit and treatment time.

The aim of this study was to evaluate the impact of conformity index in the unified dosimetry index (UDI) score for two different planning techniques namely intensity-modulated radiotherapy (IMRT) and Rapid Arc. Rapid Arc and IMRT plans of 57 patients were evaluated and compared using UDI score which incorporates four indices. To determine the impact of conformity index on the IMRT and Rapid Arc plans, UDI at conformity index one of all plan (UDIunit_CI) score was calculated by assuming conformity index is equal to one. Mean and standard deviations of all indices were calculated. Rapid Arc technique plans of different treatment sites of all patients scored lesser UDI than IMRT plans, and the conformity index of Rapid Arc plan was significantly better than IMRT plan. The average dose gradient, homogeneity, coverage, and conformity index of all sites with Rapid Arc plans were 0.212 ± 0.05, 1.123 ± 0.03, 0.959 ± 0.03, and 1.056 ± 0.09; with IMRT plans were 0.190 ± 0.05, 1.113 ± 0.04, 0.950 ± 0.04, and 1.172 ± 0.16, respectively. UDI score value with actual conformity index of Rapid Arc and IMRT plans differed significantly (P < 0.001). However, UDIunit_CI score values with assumed conformity index equal to one did not differ significantly (P = 0.528). In the comparison of IMRT and Rapid Arc plans using the UDI score, the impact of conformity index was significant.

Background:Radiotherapy plays an important role in the management of cancer. Although the improved technologies increase therapeutic index, different delivery techniques deliver different dose pattern to the healthy tissue within and outside treatment volume.Objective:The objective of this study was to evaluate the low, intermediate, and high dose to healthy tissue within and outside the treatment volume and to find the relation between tumor volume and various doses received healthy tissue volume.Materials and Methods:A total of 150 patients were included. For all patients, planning computed tomography images were acquired. Tumors, critical structures, and healthy tissue volumes at different regions were delineated. Two sets of plans, one with volumetric-modulated arc therapy and another with intensity-modulated radiation therapy (IMRT) were created, optimized for 6 MV photons and dose was calculated. Dosimetry results for tumor, organs at risks (OARs), and healthy tissue from both the techniques were evaluated and compared.Results:Tumor coverage and dose to OARs was significantly better with volumetric-modulated arc therapy (VMAT). Volume of healthy tissue received high-dose within the treatment volume as well as volume of healthy tissue received low and intermediate-dose out of treatment volume were significantly (P < 0.002) lesser with VMAT. Besides, the results showed that as the tumor volume increased, the various dose received healthy tissue volume also increased.Conclusions:VMAT plan can reduce the risk of secondary malignancy while treating different sites of cancer. VMAT is the most appropriate technique than IMRT, especially in the treatment of large tumor volume. Special attention has to be given, especially while treating women and children.