Prog Med Phys.  2014 Mar;25(1):31-36. 10.14316/pmp.2014.25.1.31.

Evaluation of Dosimetric Characteristics of Reproducibility, Linearity and Dose Dependence of Optically Stimulated Luminescence Dosimeters in Co-60 Gamma-rays

• Han SC
• Choi SH
• Park S
• Kim CH
• Jung H
• Kim MS
• Yoo HJ
• Kim CH
• Ji YH
• Yi CY
• Kim KB

• KMID: 1910556
• DOI: http://doi.org/10.14316/pmp.2014.25.1.31

Abstract

We aimed to evaluate the dosimetric characteristics of reproducibility, linearity and dose dependence of optical stimulated luminance dosimeter (OSLD) in the Co-60 Gamma-rays and to analyze with a precedent study in field of the diagnostic radiography and radiotherapy. The reproducibility was 0.76% of the coefficient of variation, the homogeneity was within 1.5% of the coefficient of variation and OSLD had supra-linear response more than 3 Gy. So the correlation between dose and count was fitted by quadratic function. The count depletion by repeated reading was 0.04% per reading regardless of the irradiated dose. And the half time of decay curve according to the irradiated dose was 0.68 min. with 1 Gy, 1.04 min. with 5 Gy, and 1.10 min. with 10 Gy, respectively. In case of annealing for 30 min, the removal rate was 88% with 1 Gy, 90% with 5 Gy, and 92% with 10 Gy, respectively and 99% in case of annealing time for 4 hour. It is feasible to use OSLDs for dose evaluation in Co-60 Gamma-rays when considering the uncertainty on the procedure according to the irradiated dose.

Keyword

Optical stimulated luminance dosimeters; Dosimetric characteristics; Co-60

MeSH Terms

Luminescence*
Radiography
Radiotherapy
Uncertainty

Figure

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  Fig. 1. Decay time of the OSLD count rate (S(t)/S(t)f) as a function of reading time after irradiating dose (1, 5, and 10 Gy). S(t) is the OSLD count at time t. S(t)f is the OSLDs count at 1 min., after the irradiation. Each data point is the average response of three individual dosimeters.

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  Fig. 2. The depletion of OSLD count when given sequential readings after irradiating dose (1, 5, and 10 Gy) OSLDs were irradiated to 1, 5, and 10 Gy of 60-Co Gamma- ray and Kept in the dark for 11 min, After the dark period, the OSLDs was read 50 times. The OSLD counts were normalized to value of the first reading (Cf).

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  Fig. 3. OSLD response (count) Vs dose. The dose response of the OSLD with the absorbed dose was measured using three dosimeters that was same group. The nanodot was not optically annealed between irradiation.

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