Applicability of a practical calibration for the small-type OSL dosimeter for measuring doses from direct X-rays and penetrating X-rays affected by scattered radiation

A small type optically stimulated luminescence dosimeter, nanoDot, is expected to be applied to radiation dose evaluation on medical field. Dose calibration of a nanoDot is carried out by the air Kerma from incident X-ray generated by a diagnostic X-ray equipment. However the main component of exposure is not only direct X-ray beam but also scattered X-rays and penetrating X-rays. Therefore we evaluated the reliability of the dose calibration of nanoDot dosimeters on the exposure of different quality X-rays. The main calibration curve was determined by the air Kerma of 83 kV X-rays in the dose range of 3 μGy to 2 mGy. To validate the reliability of the calibration curve, the air kerma exposed to nanoDots and the response of nanoDots to scattered X-rays, penetrating X-rays and/or the entrance surface dose due to the 83 kV X-rays were evaluated. In the same manner, 55 and 108 kV X-rays were irradiated. The responses of nanoDots exposed by each condition were in good agreement with the main calibration curve and the reliability of it is ±15% even in 3 μGy. We concluded that the dose of diagnostic X-rays can be evaluated by the response of nanoDot calibrated by the air Kerma of 83 kV X-rays. (author)