| SPENDO EXPERIMENT, RESPONSIBLE: GRAZIA GAMBARINI
The main objective of the experiment is that of studying and setting up the proper dosimetry and spectrometry methods useful for the advanced modalities of radiotherapy that are presently used or proposed.
The experiment is carried out by the two Italian INFN groups, but the research involves other institutions and research groups, both national and international.
The aim of the project is the improvement of dosimetry and spectrometry methods developed in the laboratories of this projects and the study of new instrumental approaches for radiation fields of specific interest. The interest is turned to photon fields, principally for conformal radiotherapies as intensity modulated radiotherapy (IMRT) or high-dose-rate (HDR) brachytherapy, and thermal/epithermal neutron fields designed for boron neutron capture therapy (BNCT).
Concerning conformal radiotherapies, the goal of this project is the development of dosimeters and methods for achieving images of the spatial distribution of the absorbed dose, also in absolute dosimetry for complex fields like those of IMRT or HDR brachytherapy. The studied dosimeters are Gafchromic films and Fricke-gel-layer dosimeters (FGLD) suitably developed in laboratory. The possibility of a clinical use of FGLDs for quality controls will be also evaluated.
It was recently undertaken a study on in-vivo dosimetry, in particular for HDR brachytherapy. The scientific interest aroused by these results has given rise to some cooperation with regard to in-vivo dosimetry, which will also involve other methods, such as optical fibres and mosfet detectors. Moreover, a collaboration is now started with the Centre for Medical Radiation Physics of the University of Wollongong (Australia) concerning studies for achieving in vivo dosimetry in real time during patient treatment. The studied methodology is based on a miniaturized detector named MOSkin that is designed with MOSFET technology and developed at Wollongong University..
Concerning BNCT, proper dosimetry and spectrometry methods are studied and set up in the experiment SPENDO.
A dosimetry method based on FGLDs is developed and continuously improved. This method gives the capability of attaining reliable information about the spatial distribution of absorbed dose for each dose component in tissue exposed to thermal/epithermal neutrons. With the recent improvements, circular images with a diameter of 16 cm were achieved. No other experimental method gives the possibility of obtaining dose images of all dose contributions in epithermal neutron fields. The method is applied at the LVR-15 reactor at the Department of Reactor Physics at Rez (Prague, Czech Rep.) for in-phantom dose measurements and for the characterization of the epithermal neutron beam designed and used for BNCT treatments of patients.
Also the improvement of dosimetry methods based on thermoluminescence detectors (TLDs) is a goal, to carry measurements, in reference positions, in order to perform inter-comparison of results.
Spectrometry methods for neutron beams are developed and improved too.
One method is based on the LES spectrometer that was recently optimized by means of MonteCarlo simulations with the aim of determining with better precision the response curves at low energies, in particular behind 10 keV, in order the expand the measured energy spectrum to low energies.
Moreover, a study of the feasibility of a system for neutron spectrometry, based on a THGEM (Thick Gaseous Electron Multiplier) detector was undertaken. This work was carried out in collaboration with the Weizmann Institute of Science (Department of Particle Physics, Radiation Detector Physics Laboratory) in Israel and the PTB (Physikalisch-Technische Bundesanstalt, Braunschweig) in Germany.
| GOALS OF SPENDO EXPERIMENT
|* Improvement of dosimetry methods designed to perform measurements (images, profiles or maps) of the absorbed dose in photon or neutron fields for radiotherapy.
- Concerning photons, the interest is turned to the intensity modulated radiotherapy (IMRT) and to high dose rate (HDR) brachytherapy. One dosimetry method is based on gel dosimeters in form of layers whose protocols for preparation, utilization and analysis are continuously improved in laboratory. The last enhancements have brought to the possibility of performing absolute measurements of spatial dose distributions with a precision within 3%. Other dose-imaging methods for 2D dose measurements are exploited and studied, using GAFCHROMIC® films, optical fibres and MOSFET detectors.
- Concerning neutrons, the interest is turned to boron neutron capture therapy (BNCT). The proposed method based on Fricke-gel dosimeters in form of layers allows obtaining dose images of each contribution to the absorbed dose; this goal is particularly important in epithermal neutron fields designed for BNCT treatments of internal tumours, where behind thermal neutron and gamma dose, also the fast neutron dose must be measured. The purpose is that of developing and applying a methods suitable for the characterization of the epithermal neutron beam of a reactor, for measuring dose distribution in the standard water phantom and in tissue-equivalent phantoms, also of very small dimensions.
Also the improvement of dosimetry methods based on thermoluminescence detectors (TLDs) is a goal, in order to perform measurements, in reference positions, in order to carry out inter-comparison.
** Improvement of neutron spectroscopy methods.
- A purpose is the LES spectrometer optimization by means of MonteCarlo (MCNPGN) simulations with the aim of determining with better precision the response curves at low energies, in particular behind 10 keV, in order the expand the measured energy spectrum to low energies.
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