الفهرس 
Evaluation study of different hypofractionated radiotherapy techniques
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Abstract
Radiotherapy treatment became more accurate with the modern technology development of the multileaf collimator (MLC) design, which plays an important role in the treatment plan, of the linear accelerators. The aim of this study is to assess the impact of MLC widths (10 and 5 mm) on the plan quality for prostate cancer patients. Additionally, to investigate the influence of MLC energy mode (MLC agility flattened beam (FB), MLC agility free flattening filter (FFF), and MLCi2) on the radio-therapeutic plan for patients receiving hypo-fractionated radiotherapy. Various dosimetric parameters (Monitor Units (MUs), treatment delivery times, conformity, and homogeneity indices) for the whole prostate gland (PTVp) and to the pelvic nodes (PTVn) have been assessed to evaluate plan quality. Two different radiotherapy techniques (volumetric-modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT)) have been considered in this study. In total, 60 treatment plans were generated on MONACO planning system of Elekta, using two machines Synergy and VERSA HD from Elekta. According to the plans, the prostate gland (PTVp) and the lymph nodes (PTVn) received 60 Gy (3Gy per fraction) and 44 Gy (2.2 Gy per fraction) respectively in 20 fractions. For each design of MLCs, VMAT and IMRT plans were performed separately with the same arrangement (arcs and beams) , constraints, and optimization parameters to evaluate the plan quality difference. Plans were accepted to cover PTVs at least by 95% of the prescribed dose. Critical structures and PTVs evaluated based on dosevolume histogram (DVH) data with the same dosimetric parameters to compare between the treatment plans. For VMAT technique, we found that the homogeneity index (HI) for PTVp was improved for agility FB ( 0.09) and agility FFF (0.095) than MLCi2 (0.11)