Survey of photoneutron emitted from 6MV, 10MV, and 15MV medical LINAC using nuclear track detection

Abstract

Background: Medical linear accelerators (LINAC) can produce unwanted photoneutrons that might cause tissue damage or cancer in other organs. The efficient techniques and detectors are importantly required to detect these harmful neutrons. Objectives: This study aimed to measure photoneutrons produced from medical LINAC of 6, 10, and 15 megavolts (MV). Materials and methods: Nuclear track detector (CR-39 detectors) were employed to quantify the number of neutrons from LINACs. The X-ray energies, doses, and radiation techniques were varied to compare the number of neutrons. The photoneutron productions inside the LINAC room were also examined. Results: The results showed that there were no neutrons from medical LINAC 6 MV, whereas photoneutrons could be detected from 10 and 15 MV LINAC. Radiotherapeutic techniques with moving multi-leaf collimator (MLC) produced higher photoneutron than techniques without using MLC. The neutrons were detected on the walls of the LINAC room. Conclusion: X-ray energy greater than 10 MeV generated undesired photoneutrons that can penetrate the shielding and increase the patient dose. For the safety of staff to re-enter the treatment room, delaying time should be considered for the neutron decay process