EPR/alanine dosimetry for ion beamradiotherapy

Project coordinator: Barbara Michalec, Ph.D., Eng.

Lead time: 10.2011-09.2013

The project was realized under the POMOST programme, implemented by the Foundation for Polish Science, co-financed by structural funds as part of Measure 1.2, "Strengthening the human resources potential of science" Innovative Economy Operational Programme 2007-2013.

EPR/alanine dosimetry is based on frequently observed radiation effect in solids – generation of paramagnetic centres in irradiated substances. Under the influence of irradiation the paramagnetic centres in form of free radicals, which concentration is a linear function of dose absorbed, are generated in alanine. Selective and very sensitive method of examining paragnetic centres is an electron paramagnetic resonance, EPR. The dosimetric value equals to an amplitude of EPR central line signal of an irradiated alalnine. For the particular spectrometer and for the required measuring parameters, the value is proportional to the ion irradiation dose absorbed in a dosimeter. For dose estimation it is necessary to use a calibration curve, that is a relation between an amplitude of EPR signal and a dose absorbed, measured with an absolute dosimeter or reference dosimeter.

Main advantages of the alanine dosimeters are:

  • similar chemical composition of the alanine to the human tissues;
  • linearity of the response in dose function in the range 2 Gy- 5 kGy;
  • non-destructive read-out;
  • very stable singnal;
  • non-dependence of the signal on a dose rate and irradiation type;
  • little sensitivity to environmental conditions;
  • possibility of forming various shapes of disimeters.
EPR spectrometer Alanine detectors

The EPR spectrometry of α-L-alanine has been applied as a dosimetry method for high doses measurements for over 40 years. The improving quality of commercially available dosimeters causes that they are applied in radiotherapy, both conventional and the one using hadron beams, especially protons, more eagerly.

The main goal of this project is to develop a protonbeam dosimetry method using the EPR alanine spectrometry. The basic aim of the project was devided into several R&D tasks:

  • activation of a Bruker ESP300 spectrometer in order to measure the alanine samples;
  • developing an alanine dosimetry method for 60 MeV proton beam in the eyeball cancer proton therapy facility at IFJ PAN;
  • implementation of the EPR/alanine dosimetry as a standard proton beam dosimetry control method in the above-mentioned facility;
  • application of the method for the purposes of 230 MeV proton beam dosimetry, which will be delivered by the newly installed at IFJ PAN, Proteus C-235 cyclotron.