FOIL ACTIVATION TECHNIQUE-A TOOL FOR THE EVALUATION OF PHOTO-NEUTRON DOSE IN RADIOTHERAPY.

Treatment of cancer is carried out using photon beams from high-energy medical linear accelerators. Photo-neutrons are also produced as an unwanted by product in the process of dose delivery to the cancer patients during their radiation treatments. In the present study, photo-neutron dose equivalents (both thermal and fast components) per unit delivered gamma-photon dose were measured at different depths, as function of distances from iso-centre in patient plane, field sizes, wedge angles and at LINAC head for a 15-MV medical linear accelerator model Elekta Precise using multi-foil activation technique. The neutron dose equivalents determined for the above-mentioned parameters were found to be lower (<0.05%) in comparison with the therapeutic photon dose delivered and within the prescribed limits recommended by the national regulatory authority.

PERFORMANCE OF BARC NEUTRON PERSONAL DOSEMETER IN EURADOS INTERCOMPARISON EXERCISE IC2017N - A LESSON LEARNT.

Bhabha Atomic Research Centre (BARC) conducts fast neutron personnel monitoring service to radiation workers involved in reactors, accelerators, spent fuel processing plants, oil-well industries, etc., using CR-39 detector based dosemeter. In this study, performance of the BARC fast neutron personnel dosemeter has been checked through EURADOS intercomparison exercise for simulated workplace neutron fields. The overall performance of the dosemeter in the lower dose equivalent (≤ 5 mSv) was found to be acceptable as per ISO-14146. The performance (ratio of estimated to reference dose equivalent) of the dosemeter in the higher dose equivalent (12 mSv) was found to be in the range of 0.48-0.44 and not satisfactory as per the ISO-14146 criteria for any dosimetry service. Based on this performance, a new imaging system was developed and performance of the dosemeters were improved and found to be acceptable (within ±20%) as per ISO.