engleski

Photon dosimetry methods outside the target volume in radiation therapy: Optically stimulated luminescence (OSL), thermoluminescence (TL) and radiophotoluminescence (RPL) dosimetry

The basic principles of dosimetry by thermoluminescence (TL), radiophotoluminescence (RPL) and optically stimulated luminescence (OSL) dosimetry is described in terms of the energy band model of electron-hole production following irradiation. In each case the dosimetry material contains electron and hole traps which can be emptied by suitable stimulation and the emitted radiation detected to form the basic dosimetry data. For TLD, the signal is produced by heating the material and detecting the visible light emission, for RPL, silver activated phosphate glass after being exposed to the ionizing radiation and subsequently to UV light emits orange luminescence for OSL, irradiation with light stimulates further light emission. The glass dosimeter is an accumulation type solid state dosiemeter. The light is emitted every time whenever laser pulses excites the glass therefore the dose can be read multiple times without destroying the signal. Dosemeters used in this work were - TLD: LiF:Mg, Ti, MTS-7 (IFJ PAN, Krakow, Poland) TLD-100, TLD-700 (Harshaw), OSL: Al2O3:C nanoDot (Landauer Inc.) and RPL: rod glass elements GD-352M, Asahi Techno Glass Coorporation) The RPL dosimeters show very good uniformity and reproducibility and there is no need for individual sensitivity corrections. The background reading of RPL dosimeters is negligible. The stability of the RPL centres is high and there is little fading effect of glass dosimeters. The dose response is linear (dose range 0.1 up to 100Gy) and the energy response is flat for medium and low energy X-rays. TLD and OSL dosimeters show high sensitivity, very good batch reproducibility and homogeneity. For the better accuracy individual sensitivity correction factors should be applied. The dose response is linear for a wide range of doses ( up to at least 1Gy) and energy dependence is low across the range of photon energies used (for materials with Zeff close to that of tissue). The main characteristics will be discussed, together with the readout and calibration procedures which lead to a measurement of absorbed dose to water. With suitable calibration, all three dosemeter types are appropriate for dose measurements for the out-of-field dose measurements as well as for the in/out phantom measurements of MV X-rays.

photon dosimetry methods; thermoluminescent dosimeters (TLD); optically stimulated dosimeters (OSLD) radiophotoluminescent dosimeters (RPL); out-of-field dosimetry in radiation therapy

Rad je prezentiran na skupu Workshop: Dosimetry for Second Cancer Risk Estimation EURADOS Annual Meeting Vienna 2012.