AbstractBackgroundOptically stimulated luminescence dosimeters (OSLDs) have a number of advantages in radiation dosimetry making them an excellent dosimeter for in vivo dosimetry. The study aimed to study the dosimetric characteristics of a commercial optically stimulated luminescence (OSL) system by Landauer Inc., before using it for routine clinical practice for in vivo dosimetry in radiotherapy. Further, this study also aimed to investigate the cause of variability found in the literature in a few dosimetric parameters of carbon-doped aluminium oxide (Al2O3:C).Materials and methodsThe commercial OSLD system uses Al2O3:C nanoDotTM as an active radiation detector and InLightTM microStar® as a readout assembly. Inter-detector response, energy, dose rate, field size and depth dependency of the detector response were evaluated for all available clinical range of photon beam energies in radiotherapy.ResultsInter-detector variation in OSLD response was found within 3·44%. After single light exposure for the OSL readout, detector reading decreased by 0·29% per reading. The dose linearity was investigated between dose range 50–400 cGy. The dose response curve was found to be linear until 250 cGy, after this dose, the dose response curve was found to be supra-linear in nature. OSLD response was found to be energy independent for Co60 to 10 MV photon energies.ConclusionsThe cause of variability found in the literature for some dosimetric characteristics of Al2O3:C is due to the difference in general geometry, construction of dosimeter, geometric condition of irradiation, phantom material and geometry, beam energy. In addition, the irradiation history of detector used and difference in readout methodologies had varying degree of uncertainties in measurements. However, the large surface area of the detector placed in the phantom with sufficient build-up and backscatter irradiated perpendicularly to incident radiation in Co60 beam is a good method of choice for the calibration of a dosimeter. Understanding the OSLD response with all dosimetric parameters may help us in estimation of accurate dose delivered to patient during radiotherapy treatment.
EP-1537: Developing an in vivo dosimetry system for TomoTherapy® using the CT detector array
