medical linear accelerators are one of the most widespread methods for cancer treatment. despite their advantages, unwanted photoneutrons are produced by high energy linacs. this photoneutrons are as undesired doses to patients and a significant problem for radiation protection of the staffs and patients. photoneutrons radiological risk must be evaluated because of their high let and range.in o...

The treatment delivery time of intensity-modulated radiation therapy (IMRT) with a multileaf collimator (MLC) is generally longer than that of conventional radiotherapy. In theory, removing the flattening filter from the treatment head may reduce the beam-on time by enhancing the output dose rate, and then reduce the treatment delivery time. And in practice, there is a possibility of delivering...

Dosimetry protocols for external beam radiotherapy currently in use, such as the IAEA TRS-398 and AAPM TG-51, were written for conventional linear accelerators. In these accelerators, a flattening filter is used to produce a beam which is uniform at water depths where the ionization chamber is used to measure the absorbed dose. Recently, clinical linacs have been implemented without the flatten...

This is an author produced version of a paper published in Medical Physics. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. "Prediction of stopping-power ratios in flattening-filter free beams." Abstract 25 Purpose: In recent years, there has been an increasing interest in flattening-filter free (FFF) beams. However, since the ...

Objective We aimed to compare the dosimetric characteristics of 6-MV flattening filter mode (FF) and filter-free (FFF) volumetric-modulated arc therapy (VMAT) plans in preoperative radiotherapy for rectal cancer using an Edge linear accelerator. Methods Two-arc FF-VMAT FFF-VMAT were generated 15 patients with Philips Pinnacle treatment planning system (version 9.10). The homogeneity index, conf...