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Purpose: Optically stimulated luminescence(OSL)dosimetry has been recently introduced in radiation therapy as a potential alternative to the thermoluminescent dosimeter(TLD) system. The aim of this study was to investigate the feasibility of using OSL point dosimeters in the energy range used in diagnostic imaging. Methods: NanoDotOSLdosimeters (OSLDs) were used in this study, which started with testing the homogeneity of a new packet of nanoDots. Reproducibility and the effect of optical treatment (bleaching) were then examined, followed by an investigation of the effect of accumulated dose on the OSLD indicated doses. OSLD linearity, angular dependence, and energy dependence were also studied. Furthermore, comparison with LiF:Mg,Ti TLD chips using standard CTdose phantoms at 80 and 120 kVp settings was performed. Results: Batch homogeneity showed a coefficient of variation of 0.99. The angular dependence test showed a drop of approximately 70% in the OSLD response at 90° in mammography (25 kVp). With the general radiography unit, the maximum drop was 40% at 80 kVp and 20% at 120 kVp, and it was only 10% with CT at both 80 and 120 kVp. The energy dependence study showed a range of ion chamber-to-OSLDs ratios between 0.81 and 1.56, at the energies investigated (29–62 keV). A paired t-test for comparing the OSLDs and TLDs showed no significant variation (p > 0.1). Conclusions: OSLDs exhibited good batch homogeneity ( 0.1). However, high uncertainty (42%) in the dose estimate was found as a result of relatively high accumulated dose. Furthermore, nanoDots showed high angular dependence (up to 70%) in low kVp techniques. Energy dependence of about 60% was found, and correction factors were suggested for the range of energies investigated. Therefore, if angular and energy dependences are taken into consideration and the uncertainty associated with accumulated dose is avoided, OSLDs (nanoDots) can be suitable for use as point dosimeters in diagnostic settings. |
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