Neutron personal dosimetry using polyallyl diglycol carbonate (PADC): Current status, best practices and proposed research

The objective of this paper is to provide an overview of the current status in neutron personal dosimetry based on poly allyl diglycol carbonate (PADC), also commonly known by the commercial name CR-39, to summarize the best practices in the field, and to point future research directions. An overview of the fundamentals of the technique is given, including a discussion on the PADC material, main parameters and characteristics, practical considerations, dosimetry approaches, and relevant standards. This work also summarizes the best practices adopted by individual monitoring services (IMSs) and discusses the research needed to improve the performance of this type of neutron dosimetry technique, as well as the challenges that make progress difficult. This work is based on the knowledge and experience of several laboratories and investigators and is part of the activities of the European Radiation Dosimetry Group (EURADOS) Working Group 2 – Harmonization of Individual Monitoring in Europe (WG2)

Ultra-high dose rate dosimetry for pre-clinical experiments with mm-small proton fields.

PURPOSE To characterize an experimental setup for ultra-high dose rate (UHDR) proton irradiations, and to address the challenges of dosimetry in millimetre-small pencil proton beams. METHODS At the PSI Gantry 1, high-energy transmission pencil beams can be delivered to biological samples and detectors up to a maximum local dose rate of ∼9000 Gy/s. In the presented setup, a Faraday cup is used to measure the delivered number of protons up to ultra-high dose rates. The response of transmission ion-chambers, as well as of different field detectors, was characterized over a wide range of dose rates using the Faraday cup as reference. RESULTS The reproducibility of the delivered proton charge was better than 1 % in the proposed experimental setup. EBT3 films, Al2O3:C optically stimulated luminescence detectors and a PTW microDiamond were used to validate the predicted dose. Transmission ionization chambers showed significant volume ion-recombination (>30 % in the tested conditions) which can be parametrized as a function of the maximum proton current density. Over the considered range, EBT3 films, inorganic scintillator-based screens and the PTW microDiamond were demonstrated to be dose rate independent within ±3 %, ±1.8 % and ±1 %, respectively. CONCLUSIONS Faraday cups are versatile dosimetry instruments that can be used for dose estimation, field detector characterization and on-line dose verification for pre-clinical experiments in UHDR proton pencil beams. Among the tested detectors, the commercial PTW microDiamond was found to be a suitable option to measure real time the dosimetric properties of narrow pencil proton beams for dose rates up to 2.2 kGy/s

Membrane fluidity matters: Hyperthermia from the aspects of lipids and membranes

Hyperthermia is a promising treatment modality for cancer in combination both with radio- and chemotherapy. In spite of its great therapeutic potential, the underlying molecular mechanisms still remain to be clarified. Due to lipid imbalances and 'membrane defects' most of the tumour cells possess elevated membrane fluidity. However, further increasing membrane fluidity to sensitise to chemo-or radiotherapy could have some other effects. In fact, hyperfluidisation of cell membrane induced by membrane fluidiser initiates a stress response as the heat shock protein response, which may modulate positively or negatively apoptotic cell death. Overviewing some recent findings based on a technology allowing direct imaging of lipid rafts in live cells and lipidomics, novel aspects of the intimate relationship between the 'membrane stress' of tumour cells and the cellular heat shock response will be highlighted. Our findings lend support to both the importance of membrane remodelling and the release of lipid signals initiating stress protein response, which can operate in tandem to control the extent of the ultimate cellular thermosensitivity. Overall, we suggest that the fluidity variable of membranes should be used as an independent factor for predicting the efficacy of combinational cancer therapies

SU‐E‐T‐119: A Phenomenological Model of the Al2O3:C Optically Stimulated Luminescence Detector (OSLD) Fading

Purposes: To explain the causes of fading in the Al2O3:C optically stimulated luminescence detectors (OSLDs). Methods: A phenomenological band diagram model with three electron traps and two recombination centers was used to represent the entities that are related to the OSL of Al2O3 :C OSLDs. The electron traps consist of a shallow trap, the main dosimetric trap and a deep trap. The shallow trap is unstable at room temperature (activation energy of 1.03 eV). Both recombination centers are radiative, however, the OSL signal is due only to one of the recombination centers. This model was based on experimental data of the thermoluminescence, optical absorption and OSL of Al2O3:C. A system of differential equations representing the transport and storage of charge carriers during irradiation, relaxation and stimulation phases was solved numerically. The system of equations was solved at room temperature conditions (T = 295 K). Results: The simulated shape of the OSL decay curve was in good qualitative agreement with experimental data. The simulated dose response of the OSL signal was linear in the interval of doses investigated (up to 10 Gy). The simulated fading of the OSL signal occurred in the first 10 min elapsed since irradiation and then became stable. Conclusions: The fading behavior of the OSL signal of Al2O3:C OSLDs can be explained by the existence of a shallow trap that is unstable at room temperature

Optically stimulated luminescence in vivo dosimetry for radiotherapy: physical characterization and clinical measurements in (60)Co beams

A commercial optically stimulated luminescence (OSL) dosimetry system was investigated for in vivo dosimetry in radiation therapy. Dosimetric characteristics of InLight dot dosimeters and a microStar reader (Landauer Inc.) were tested in (60)Co beams. The reading uncertainty of a single dosimeter was 0.6%. The reproducibility of a set of dosimeters after a single irradiation was 1.6%, while in repeated irradiations of the same dosimeters it was found to be 3.5%. When OSL dosimeters were optically bleached between exposures, the reproducibility of repeated measurements improved to 1.0%. Dosimeters were calibrated for the entrance dose measurements and a full set of correction factors was determined. A pilot patient study that followed phantom validation testing included more than 100 measured fields with a mean relative difference of the measured entrance dose from the expected dose of 0.8% and the standard deviation of 2.5%. In conclusion, these results demonstrate that OSL dot dosimeters represent a valid alternative to already established in vivo dosimetry systems

Dosimetric characteristics of high sensitive Mg2SiO4 : Tb solid TL detector

Thermoluminescence dosimetric characteristics of Mg2SiO4:Tb in form of sintered pellets developed at the Institute of Nuclear Sciences, Vinca, Belgrade, are presented. Mg2SiO4:Tb is a TL material with attractive features for dosimetric applications such as ultra high TL sensitivity, simple glow curve with the main TL peak at about 210 degrees C and low fading. The dosimetric properties of this TL detector examined in this study include glow curve shape, TL sensitivity, annealing procedure and reproducibility, photon dose response, minimum detectable dose, energy response, fading characteristics, light induced effect and optically stimulated luminescence (OSC) signal. (C) 2007 Elsevier Ltd. All rights reserved.15th International Conference on Solid State Dosimetry, Jul 08-13, 2007, Delft Univ Technol, Delft, Netherland

Monolithic Integrated Radiation Sensor Using Stimulated Luminescence From Alumina

The project goal was to design and test a monolithic integrated device for radiation sensing, using optically stimulated luminescence (OSL) from Al2O3:C. The device would consist of GaN/InGaN-based components epitaxially grown on each side of a A12O3:C substrate. Radiation energy stored in the substrate would be stimulated by visible emission from a GaN light-emitting diode (LED) grown on one side of the device, and the OSL emission from the substrate (in the blue region of the spectrum) would be detected by the InGaN pi-n diode grown on the other side of the substrate. The primary application of the device would be in space radiation environments. Thus, two major research thrusts were launched during this project. Firstly, research at Oklahoma State University (Dr. Stephen W.S. McKeever and Dr. E.G. Yukihara) concentrated on characterization of the OSL properties of Al2O3:C in radiation fields typical of those experienced in low-Earth orbit. Secondly, research at the University of Washington (Co-Is, Dr. T.G. Stoebe and Dr. T. Chen) focused of device development and GaN/InGaN epitaxial growth. While progress in each line of research has been substantial, the ultimate goal (that of producing a working prototype device) has not yet been reached. We detail the research progress and identify outstanding issues in this paper

COMPARISON OF PADC NEUTRON DETECTORS FROM DIFFERENT SUPPLIERS

The objective of this study was to compare poly-allyl diglycol carbonate (PADC) track detectors from different suppliers for linear energy transfer (LET) spectrometry and neutron dosimetry. PADCs are commonly used for passive personal neutron dosimetry, where a common approach is to couple the PADC with a plastic radiator to generate secondary charged particles. The neutron dose can be estimated using the track density or the average LET of the secondary particles. The characterisation of PADC in terms of LET spectrometric capability and neutron sensitivity was previously performed using PADC from Intercast S.r.l., Parma, Italy, but this company stopped the production. Since it is common experience that material from different suppliers can have different properties, it became necessary to perform a comparison of PADCs from different suppliers with the Intercast material. The study permits to compare the reading procedures used at Politecnico di Milano and at the Paul Scherrer Institute