Free radical dosimetry employing ESR spectroscopy for clinical use
1998 (English)Licentiate thesis, comprehensive summary (Other academic)
In all radiation therapy treatment it is important to thoroughly determine the absorbed dose in the tumour, in surrounding normal tissue and in risk organs. The dose distributions are usually calculated by means of computerised dose-planning systems. It is however necessary to compare the calculated dose distributions with experimental measurements.
For measurements around brachytherapy sources, a tissue equivalent dosimeter material with a wide linear dose range and allowing a high spatial resolution, would be ideal because of the steep dose gradients around brachytherapy sources.
These requirements can be met by free radical dosimetry (FRD), where the stable radiation induced radicals found in some crystalline substances can serve as a measure of the absorbed dose in the substance. The analysis is made by means of electron spin resonance (ESR) spectroscopy. The most common dosimeter material in FRD is the amino acid L-α-alanine.
Various types of gel dosimeters are now being developed to obtain a three dimensional dosimeter where the gel is both dosimeter material and phantom material. The gel developed in this work is an alanine/agarose gel, where small alanine crystals are homogeneously distributed in the stiff agarose gel. The linear dose response of the alanine is not affected by the agarose gel, but the signal intensity and the stability of the radicals are somewhat lower because of the wet surroundings. In order to make measurements of the absorbed dose in absolute terms, the gel has been calibrated.
Since a fine spatial resolution is crucial in brachytherapy measurements, a high sensitivity is needed. New dosimeter materials are tested to find a substance with the advantages of alanine but with higher sensitivity. Here the crystalline substance ammonium tartrate is presented. It is twice as sensitive as alanine, and by deuterating the crystals the sensitivity can be further increased by a factor of 1.6. The dose response is linear at least from 0.5 Gy to 4 kGy, and the energy dependence is even less than for alanine. We thus find ammonium tartrate promising for clinical use.
Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 1998. , 28 p.
Linköping Studies in Health Sciences. Thesis, ISSN 1100-6013 ; 38
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-27570Local ID: 12233ISBN: 91-7219-054-XOAI: oai:DiVA.org:liu-27570DiVA: diva2:248122
Papers, included in licentiate theses, are not registered and included in the posts from 1999 and earlier.2009-10-082009-10-082013-07-08