Study of dosimetric properties of Al2O3:C,Mg radiophotoluminescent (RPL) detectors

Muthu saravanan Ramakrishnan, Marijke De Saint-Hubert

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The aim of thesis is to develop an in vivo dosimetric technique to monitor and adapt the radiotherapy treatment for daily dose delivery by developing a 2D reading system to improve the sensitivity by finding the optimum dosimetric concentration for entire dose range of interest in medical dosimetry. In vivo dosimetry technique was developed by the application of the dosimetric material Al2O3:C,Mg coating on a thermoplastic efficast material provided by ORFIT industries, this efficast material is used currently in the radiotherapy treatments as a immobilization devices such as body masks, head masks etc. in order to achieve accuracy in patient positioning. Al2O3:C,Mg is a Radiophotoluminescence (RPL) detector and it offers great advantage such as non-destructive readout and its insensitivity to room light could be utilized for the dosimetry application in radiotherapy treatment by accumulating the doses during the treatment sessions. The 2D reading system requires firstly a stimulation source, red laser and blue laser are used for this purpose. The red laser of wavelength (635nm) is used to read the RPL center (2 Mg) which is created when the colour centers (2 Mg) capture an electron and undergo radiochromic transformations. When these RPL centers were excited with red laser it emits fluorescence in near infrared emission band centred at 750 nm. The blue laser of wavelength 435nm is also used as a stimulation source in order to read colour center which results in emission in the green region of wavelength 520 nm. Secondly, these emitted photons were detected using the Multi Pixel Photon Counter (MPPC). Thirdly, the dosemask software which is created in SCK-CEN was used to steer the 2D reading system from a remote desktop. Test have been performed to find optimum protocols for both the setup using red laser and blue laser by finding proper filter combinations in order to improve sensitivity and achieve linear response. The results of this work showed excellent dose linearity from 250mGy to 50Gy with minimal fading. The optimum protocols for both the lasers have been found. The spatial resolution of the setup has been improved to 2mm. The dosemask software has been greatly improved and a sweep mode protocol of step size 0.2mm and sweep time 20ms has been found; with this protocol a patient mask of size 1100cm2 would take approx. 2.5hrs to read the complete mask with this protocol. In the future, this time can be improved further and tests can be performed for doses <250mGy and >50Gy for linear dose response.
Original languageEnglish
Awarding Institution
  • Ruprecht-Karls Heidelberg Universität
  • De Saint-Hubert, Marijke, SCK CEN Mentor
Date of Award10 Aug 2016
StatePublished - 10 Aug 2016

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