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CCD-Based Dosimetry System for Use in Diagnostic Radiology

E Gopan

E Gopan1*, D Hintenlang1, (1) Department of Biomedical Engineering, University of Florida, Gainesville, FL

TU-A-116-3 Tuesday 8:00AM - 9:55AM Room: 116

Purpose: To develop a new dosimetry system, for use in the diagnostic radiology energy range, which will be able to quantify dose more rapidly, effectively and consistently. The system is based on an array of cylindrical silica scintillators coupled to optical fibers and a CCD camera.

Methods: An Andor Luca electron-multiplying camera was used for readout, resulting in a strong output even from a small number of impinging photons. The camera has a cooling system to maintain a low detector temperature (-20 degrees Celsius). It was sealed in a light-tight enclosure to shield it from background light which could contaminate the readings. A 10 mm diameter, 8 mm effective focal length aspheric lens was mounted to focus the light from the fibers onto the CCD detector. The system was evaluated for reproducibility, energy dependence and linearity, across a range of energy (40-100 keV), current (6 to 19.5 mAs) and dose (1 to 30 mGy), validating its feasibility for future use.

Results: A signal was acquired at the diagnostic radiology energy range, a result which has not been attained by other investigators. The system showed high reproducibility, with a coefficient of variation of 1.08 % at 10 mGy. The energy dependence was fairly linear at lower energies, with a correlation coefficient of 0.995 from 40 to 80 keV, but showed greater increases between counts at higher energies. Dose (mean counts) as a function of current-time (mAs) was also linear, with a correlation coefficient of 0.998.

Conclusion: The system shows high reproducibility, linearity and immediate readout. Because the camera acts as a single readout channel, dose from multiple organs can be quantified more rapidly and consistently. The system is expected to be very useful in organ dose quantification from any imaging modality with dose to multiple organs, such as CT or CBCT.

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