Superheated emulsions and track etch detectors for photoneutron measurements

This paper describes the criteria behind the selection of neutron detection techniques for photoneutron dosimetry as well as the methods adopted to obtain dosimetric readouts. The work was conducted within the framework of Working Group 9 (WG9 Radiation Protection Dosimetry in Medicine), coordinated by the European Radiation Dosimetry Group (EURADOS). WG9 research aims at estimating the risk of second cancer induction due to radiation therapy. Therefore, a comprehensive experimental programme was devised to measure doses received by non-target organs-at-risk (OAR) during radiation therapy. The techniques described in this work were selected and used for the neutron dosimetric assessment during in-phantom simulations of clinical prostate radiotherapy treatments, carried out in three European facilities. Non-conformal standard fields were used as a common reference between different facilities.Performing neutron measurements near linacs is a complex task, because of the intense pulsed photon primary field. Therefore, photon insensitive dosimeters such as superheated emulsions (SE) and solid state nuclear track detectors (SSNTD) were chosen. Their readout procedures were carefully assessed. Methods were developed to count the large number of tracks and bubbles in SE. These are described in detail in the present work, along with a brief introduction to the detector physics.