Program Information
Investigation of NanoDot OSLD Correction Factors in Different Clinical Settings
T Lin*, B Peng , S Zhang , M Liu , R Al-Senan , Columbia University New York Presbyterian Hospital, New York, NY
Presentations
SU-H1-GePD-I-5 (Sunday, July 30, 2017) 3:00 PM - 3:30 PM Room: Imaging ePoster Lounge
Purpose: To investigate the energy dependent correction factors for nanoDot OSLDs throughout the diagnostic energy range under various exposure conditions (e.g. beam filtration, angle, and scatter).
Methods: Landauer nanoDots and an ionization chamber were exposed with a general radiography unit (GE Definium 8000) at tube voltages ranging from 50 to 130 kVp under the following conditions: (1) in air, at 0⁰, without filtration, (2) in air, at 0⁰, with copper filtration, (3) in air, at 90⁰, without filtration, and (4) on the surface of a body CTDI phantom, at 0⁰, without filtration. 0⁰ and 90⁰ refer to nanoDots positioned with their serial numbers parallel to and perpendicular to the x-ray field respectively. Prior to irradiation, nanoDots were screened to exclude those greater than 3% variation. Three nanoDots were used per exposure and read with a MicroStar reader (Landauer, Inc.) calibrated using the calibration set provided by the manufacturer. Correction factors were calculated by taking the ratio of the chamber reading to the nanoDot reading.
Results: As expected, correction factors decreased with decreasing energy due to the over-response of nanoDots at lower energies. Correction factors also decreased with the addition of copper filtration; this effect was more pronounced for higher beam filtration. The opposite trend was observed with nanoDots positioned at 90⁰: correction factors increased by as much as 36%, with greater increases at lower energies. Introduction of scatter also affected correction factors, although its effect was less pronounced compared to the effect of nanoDot angle.
Conclusion: This study illustrates significant variation in nanoDot correction factors among different exposure conditions. Due to these variations, calibration of nanoDots based on exposure conditions is recommended for accurate patient dose estimation. Future work will be aimed at assessing correction factors for different vendors, diagnostic modalities (e.g. CT and mammography), and extended energy spectrum.
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