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| Paper |
Radiation Safety Management Vol.1, No.1 (21-35) |
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| A Method for Determining the Individual Counting Efficiency for Thyroid 125I Monitoring Systems |
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Hiroshi Yamashita and Kunihide Nishizawa
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Radiation Sciences Div., Radioisotope Research Center, Nagoya University
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Received August 28, 2002; accepted September 20, 2002
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| A method for determining an individual subject's counting efficiency of a thyroid 125I monitoring system was developed on condition that health physicists can obtain the subject's parameters, thyroid shape, thyroid weight, and prethyroid tissue thickness, by applying high resolution ultrasonography. The features of counting efficiency and detection limit for anthropomorphic thyroid-neck phantoms were experimentally investigated for various combinations of seven factors; thyroid volume, thyroid shape, prethyroid tissue thickness, neck diameter, rotation angle of the thyroid in the neck, angle between the thyroid and the detector, and the distance between the detector and neck surface. A procedure to determine a unique subject's counting efficiency and detection limit for any detector arrangement was elucidated for a reference man by using a data base on counting efficiency and detection limit. |
| Key words: |
125I, thyroid monitoring, counting efficiency, NaI (Tl) |
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