Thermal dosimetry for bladder hyperthermia treatment. An overview.

The urinary bladder is a fluid-filled organ. This makes, on the one hand, the internal surface of the bladder wall relatively easy to heat and ensures in most cases a relatively homogeneous temperature distribution; on the other hand the variable volume, organ motion, and moving fluid cause artefacts for most non-invasive thermometry methods, and require additional efforts in planning accurate thermal treatment of bladder cancer. We give an overview of the thermometry methods currently used and investigated for hyperthermia treatments of bladder cancer, and discuss their advantages and disadvantages within the context of the specific disease (muscle-invasive or non-muscle-invasive bladder cancer) and the heating technique used. The role of treatment simulation to determine the thermal dose delivered is also discussed. Generally speaking, invasive measurement methods are more accurate than non-invasive methods, but provide more limited spatial information; therefore, a combination of both is desirable, preferably supplemented by simulations. Current efforts at research and clinical centres continue to improve non-invasive thermometry methods and the reliability of treatment planning and control software. Due to the challenges in measuring temperature across the non-stationary bladder wall and surrounding tissues, more research is needed to increase our knowledge about the penetration depth and typical heating pattern of the various hyperthermia devices, in order to further improve treatments. The ability to better determine the delivered thermal dose will enable clinicians to investigate the optimal treatment parameters, and consequentially, to give better controlled, thus even more reliable and effective, thermal treatments

The relevance of point defects in studying silica-based materials from bulk to nanosystems

The macroscopic properties of silica can be modified by the presence of local microscopic modifications at the scale of the basic molecular units (point defects). Such defects can be generated during the production of glass, devices, or by the environments where the latter have to operate, impacting on the devices’ performance. For these reasons, the identification of defects, their generation processes, and the knowledge of their electrical and optical features are relevant for microelectronics and optoelectronics. The aim of this manuscript is to report some examples of how defects can be generated, how they can impact device performance, and how a defect species or a physical phenomenon that is a disadvantage in some fields can be used as an advantage in others

Using microelectrode models for real time cell-culture monitoring

This paper proposes a cell-microelectrode model for cell biometry applications, based on the area overlap as main parameter. The model can be applied to cell size identification, cell count, and their extension to cell growth and dosimetry protocols. Experiments performed with comercial electrodes are presented, illustrating a procedure to obtain cell number in both growth and dosimetry processes. Results obtained for the AA8 cell line are promising.Junta de Andalucía P0-TIC-538

Advanced dosimetry systems for the space transport and space station

Advanced dosimetry system concepts are described that will provide automated and instantaneous measurement of dose and particle spectra. Systems are proposed for measuring dose rate from cosmic radiation background to greater than 3600 rads/hr. Charged particle spectrometers, both internal and external to the spacecraft, are described for determining mixed field energy spectra and particle fluxes for both real time onboard and ground-based computer evaluation of the radiation hazard. Automated passive dosimetry systems consisting of thermoluminescent dosimeters and activation techniques are proposed for recording the dose levels for twelve or more crew members. This system will allow automatic onboard readout and data storage of the accumulated dose and can be transmitted to ground after readout or data records recovered with each crew rotation

3D silicon pixel detectors for the ATLAS Forward Physics experiment

The ATLAS Forward Physics (AFP) project plans to install 3D silicon pixel detectors about 210 m away from the interaction point and very close to the beamline (2-3 mm). This implies the need of slim edges of about 100-200 $\mu$m width for the sensor side facing the beam to minimise the dead area. Another challenge is an expected non-uniform irradiation of the pixel sensors. It is studied if these requirements can be met using slightly-modified FE-I4 3D pixel sensors from the ATLAS Insertable B-Layer production. AFP-compatible slim edges are obtained with a simple diamond-saw cut. Electrical characterisations and beam tests are carried out and no detrimental impact on the leakage current and hit efficiency is observed. For devices without a 3D guard ring a remaining insensitive edge of less than 15 $\mu$m width is found. Moreover, 3D detectors are non-uniformly irradiated up to fluences of several 10$^{15}$ n$_{eq}$/cm$^2$ with either a focussed 23 GeV proton beam or a 23 MeV proton beam through holes in Al masks. The efficiency in the irradiated region is found to be similar to the one in the non-irradiated region and exceeds 97% in case of favourable chip-parameter settings. Only in a narrow transition area at the edge of the hole in the Al mask, a significantly lower efficiency is seen. A follow-up study of this effect using arrays of small pad diodes for position-resolved dosimetry via the leakage current is carried out.Comment: 10 pages, submitted to JINS

A Superheated Droplet Detector for Dark Matter Search

We discuss the operation principle of a detector based on superheated droplets of Freon-12 and its feasibility for the search of weakly interacting cold dark matter particles. In particular we are interested in a neutralino search experiment in the mass range from 10 to 10^4 GeV/c^2 and with a sensitivity of better than 10^-2 events/kg/d. We show that our new proposed detector can be operated at ambient pressure and room temperature in a mode where it is exclusively sensitive to nuclear recoils like those following neutralino interactions, which allows a powerful background discrimination. An additional advantage of this technique is due to the fact that the detection material, Freon-12, is cheap and readily available in large quantities. Moreover we were able to show that piezoelectric transducers allow efficient event localization in large volumes.Comment: 15 pages LATEX; 11 figures on request from [email protected] submitted to Nuclear Instruments and Methods

Gamma irradiation response of photonic crystal and standard optical fibre Bragg grating sensors for radiation dosimetry

This study investigates the use of Optical Fibre Bragg Grating Sensors (FBGs) for Gamma Radiation Dosimetry. A comparative analysis of responses to gamma irradiation between standard commercial FBGs and new generation FBGs written in Photonic Crystal fibre (PCF) were examined under similar regimes and conditions. Current research suggests that the FBGs performance, when exposed to Cobalt-60 gamma irradiation, can suffer cross sensitivity problems resulting from different external effects such as temperature. However, FBGs written in PCFs may be able to overcome these problems due to their design, flexibility of the shape, and size of the micro-holes in a PCF. Previous research has indicated the Bragg wavelength shift (BWS) of standard FBGs increases with accumulated Gamma dose. This shift appears to be permanent, indicating that gamma irradiation permanently affects the Bragg wavelength of the FBG. To better understand these effects, and determine the suitability of particular FBGs for use in radiation dosimetry, measurements in relation to the effects of pre-irradiation, dose rates and accumulated dose, and relaxation effects were performed on both sets of FBGs. To simulate real time conditions of a radiation dosimeter, the FBGs are examined through three consecutive radiation stages followed by limited recovery times. There is a lack of research in the areas of small recovery times and multiple periods of irradiation. The experimental regime and setup consisting of the three stages with very limited recovery comparing PCF-FBGs and standard FBGs (STD-FBGs) is unique. The experiments and gamma irradiation were conducted at ANSTO (Australian Nuclear Science and Technology Organisation) using the GATRI (Gamma Technology Research Irradiator) irradiation facility. The responses after exposure to gamma irradiation, including relaxation periods between commercially manufactured FBGs written in Germanium (Ge) doped optical fibres, with and without hydrogen loading, along with the standard SMF-28 fibre with Hydrogen are shown. The FBG inscription in PCF was completed at Interdisciplinary Photonics Laboratories (iPL), University of Sydney. The FBGs in each fibre are written by Ultraviolet (UV) low energy irradiation. In nuclear environments, when FBGs have been exposed to gamma irradiation, changes in the Bragg wavelength occur, although the exact cause or trigger is still unclear. The main outcome of this research has indicated that PCF-FBGs, compared to standard FBGs, are a strong candidate for use in the field of radiation dosimetry. This is due to their very consistent behaviour and recovery aspects after irradiation exposure. This work will compliment established research and help in the absolute quantitative comparison between the individual standard FBGs and PCF-FBGs. It will help in establishing FBGs as a possible replacement to present physical and chemical sensors currently being used as radiation dosimeters

Development and Characterisation of Radiation Monitoring Sensors for the High Energy Physics Experiments of the CERN LHC Accelerator

The Radiation monitoring at the High Energy Physic experiments of the LHC, the next CERN particle accelerator, will be a challenge for the existing dosimetry technologies. The radiation environment generated by the high-energy proton collisions will be complex reaching locally very high levels. The measurement of the energy deposition, in the IEL and NIEL channels, for semiconductor materials will therefore help to insure the reliability of the electronic systems during the LHC operation. In this work, the qualification of RadFET and p-i-n diode dosimeters, suitable for the measurements in the LHC radiation field, is presented. A series of two RadFETs and two p-i-n diodes have been then selected and characterized in detail in view of their installation at the LHC. Sensors integration issues, supported by Monte Carlo simulations studies, are also presented. Finally, the applicability of OSL materials for the dosimetry of the mixed fields at the LHC has been also discussed here

Optical fibers and optical fiber sensors used in radiation monitoring

peer-reviewedBy their very nature, optical fibers and, by extension, intrinsic and extrinsic optical fiberbased sensors are promising devices to be used in very different and complex environments considering their characteristics such as: capabilities to work under strong electromagnetic fields; possibility to carry multiplexed signals (time, wavelength multiplexing); small size and low mass; ability to handle multi-parameter measurements in distributed configuration; possibility to monitor sites far away from the controller; their availability to be incorporated into the monitored structure; wide bandwidth for communication applications. In the case of the optical fibers, the possibility to be incorporated into various types of sensors and actuators, free of additional hazards (i.e. fire, explosion), made them promising candidates to operate in special or adverse conditions as those required by space or terrestrial applications (spacecraft on board instrumentation, nuclear facilities, future fusion installations, medical treatment and diagnostics premises, medical equipment sterilization). Major advantages to be considered in using optical fibers/optical fiber sensors for radiation detection and monitoring refer to: real-time interrogation capabilities, possibility to design spatially resolved solutions (the capability to build array detectors), in-vivo investigations (i.e. inside the body measurements).PUBLISHEDpeer-reviewe