Neutron contamination in conventional 3DCRT treatment and step and shoot IMRT technique using 10 mv photon beam

Abstract

Introduction Linear accelerator is a device that can able to generate high energy photon from 4 MV to 25 MV, and these beams are used for radiation therapy. There are different treatment techniques using now a days to deliver radiation externally but most common is 3DCRT (3D conformal radiotherapy) and Intensity modulated radiation therapy. The major issue arises using photon beam having energy ∼10 MV and above is the productions of secondary neutron which can maximize the patient absorb doses. Purpose The aim of the study is to evaluate 3D conformal radiation therapy and step and shoot intensity modulated radiation therapy (ssIMRT) techniques for less neutron contamination that lead to minimum patient exposure from neutrons. Material and methods For this purpose five treatment plan of breast were made on both 3DCRT and ssIMRT using 10MV photon. Linear accelerator Elekta Synergy is used to deliver these plans and for measuring neutrons dose in primary beam, a portable, Ludlum neutron detector is used which is placed on patient’s couch. Results Obtained data shows that the mean values with standard error for each technique was found to be 14.56 mSv ± 0.38 and 25.07 mSv ± 1.2 for 3D CRT and ssIMRT, respectively. Mean difference between two techniques for neutron contamination was found to be 10.5 mSv. Conclusion It can be concluded from the study that contamination of neutrons increases by a factor of 10.5 when we move from 3D CRT to ssIMRT. This is because of increase no. of MUs that are being used in ssIMRT. Although ssIMRT therapy provides better plan optimization for target than 3DCTR but contains greater neutron contamination.