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CONFERENCISTAS

Dr. David Bradley
Title: Novel media and mechanisms applied to radiation dosimetry
Department of Physics, University of Surrey, Guildford, GU2 7XH, UK Institute for Healthcare Development, Sunway University, 46150 PJ, Malaysia
 
Abstract: We discuss development of novel dosimetric media, specifically Ge-doped silica and carbon nanontubes (CNTs). The defects giving rise to electron trapping are of particular interest, readout of the radiation sensitive signal being obtained through use of one or other of the related stimulated luminescence phenomenon, thermoluminescnce (TL) and radioluminescence (RL). Working with CNTs, use has also been made of photoelectron spectroscopy (XPS), a surface-sensitive technique which provides interrogation of bonding rearrangements in the irradiated material.

During the course of studies, various manipulations of the media have been made in an attempt to improve their radiation sensitivity, as an example in TL studies starting from simple use of standard Ge-doped silica telecommunication fibres (SMF), through to tailor-made Ge-doped flat fibres (FFs) as well as Ge-doped photonic crystal fibres (PCF) co-doped with boron.

The FFs and PCFs are formed of capillaries that at high temperatures and under vacuum are made to collapse inwards, the internal walls fusing and generating strain-related defects. Currently in use of such glassy media, we have made successful measurements of terrestrial natural radiation dose (eg 1 or 2 mGy per year), the very low doses of dental radiography (~ 10s µGy delivered in a few ms), the tens of Gy doses of radiotherapy, through to 10s of kGy used in radiation processing.

For the CNTs, developments point to their use in skin dosimetry. In use of RL, we have compared the signal originating from Ge-doped silica optical fibres and commercial nanoDot Al2O3:C dosimeters, the RL signal being guided through PMMA optical fibre cables to obtain real-time measurements. For the Ge-doped fibre the manifest absence of an appreciable memory effect or afterglow, favours its preferential use in real-time evaluations.


 Dr. Oswaldo Baffa

Title: Exotic Dosimetric Techniques
Department of Physics-FFCLRP-USP Ribeirao Preto, SP, Brazil
 
Abstract: Dosimetric techniques somehow measure the energy deposited in a given medium through the effects of ionizing radiation on it. Ionizing radiations can be electromagnetic, charged and neutral particles. The media can be gases, liquids, solids and soft matter. Depending on the combination of radiation and material different dosimetry techniques may be proposed based on different physical interactions.
 
Some of them are already well established in the clinical environment such as ionometry, optical densitometry with radiological films, thermoluminescence, semiconductor devices and others are beginning to gain increasing importance as optically stimulated luminescence, radiochromic films, radiophotoluminescence, with commercial products available. However, there is a plethora of other techniques available that may have specific applications and significant developments in recent years that may make them accessible at the clinical settings. A review of the state of the art of some of these still exotic techniques will be carried out showing its potentialities and applications.

 Dr. Richard Hugtenburg
Title: Pulse-by-pulse dosimetry of IMRT with a diamond-based CVD detector
Authors: RP Hugtenburg1, MAM Hanifa1, RF Page2 and JJ Velthuis2
1. Swansea University, UK.
2. University of Bristol, UK.
 
Abstract: Intensity modulated radiotherapy brings new challenges to dosimetry, including correcting for the effects of small radiation fields and varying dose-rates on dosimeters. Recently artificial diamonds from chemical vapour deposition (CVD) process have been shown to achieve high orders of dosimetric precision, however non-linearities in dose-rate response create complexities for emergent modalities with large variations in dose-rate, such as volumetric modulated arc therapy (VMAT) and flattening-filter free systems.
 
An electrometer has been designed to operate at MHz resolution, in order to resolve individual LINAC pulses, whilst recording dose. In this configuration we observe high orders of linearity, suggesting that non-linear effects observed in other studies may not simply be due to recombination processes, e.g. the Fowler effect, and may be due to signal processing. We show that the ability to resolve individual pulses provides an independent measurement of the LINAC monitor unit and to distinguish between average and instantaneous dose-rate effects.

 Dr. Luis Berges
Title: Experiencia cubana sobre el uso de la Terapia electroquímica en cáncer.
 
Resumen:La terapia electroquímica se usa para el tratamiento de tumores malignos y benignos. La misma es segura, simple, induce efectos adversos mínimos en el organismo, efectiva, de bajo costo y se puede aplicar cuando la terapias convencionales (cirugía, radioterapia, quimioterapia e inmunoterapia) fracasan o no pueden aplicarse. El objetivo es mostrar las experiencias cubana e internacional sobre los efectos que induce esta terapia en el tumor y en el organismo.
 
Se muestran los principales resultados de los estudios in vitro, preclínicos y clínicos. Además, se exponen los mecanismos de acción antitumoral de la terapia electroquímica y las problemáticas existentes que conllevan al uso de las modelaciones matemáticas. Por otra parte, se exponen los principales resultados que se obtienen de la aplicación e interpretación de esta terapia en la cinética de crecimiento de tumores.