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KMID : 1143620170210010070
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Korean Journal of Nuclear Medicine Technology
2017 Volume.21 No. 1 p.70 ~ p.75
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The Effect of Increase in Length and Volume of Source in Radioactive Iodine Thyroid Uptake Rate
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Hwang Dong-Hun
Oh Shin-Hyun
Kim Jung-Yul
Kang Chun-Koo
Kim Jae-Sam
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Abstract
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Purpose : Radioactive iodine thyroid uptake (RAIU) rate is an examination which determines and seeks about general functions of thyroid gland. The size of thyroid gland is normally different between each person, also patients having thyroid diseases have had a variety of size of thyroid gland compared with others. The purpose of this study will investigate about the counting rate which is effected by the geometric factors through the length and volume changes of the source in RAIU rate.
Materials and Methods : I-131 185 kBq (5 μCi) were placed in a cylindrical phantom of 0.5 cm, 1 cm, 1.5 cm, and 3 cm in diameter, respectively, and saline was added to gradually increase the length by 1 cm in the horizontal and vertical directions to give a change in volume. The source was measured 20 times for 20 seconds from a distance of 25 cm to 364.4 keV±20% energy ROI with Captus 3000 thyroid uptake system (Capintec, NJ, USA).
Results : When the source was located in the transverse direction of the detector, the consequence of one-way ANOVA is that even though the length of source is increased each diameter, there is mostly no significant difference. When the source was located in the longitudinal direction and the counting rate of length 1 cm at all diameter is set to 100%, the average is 92.57% for length 2 cm, 86.1% for 3 cm, 80.69% for 4 cm, 74.82% for 5 cm, and 69.68% at 6 cm.
Conclusion : According to this study, it is expected that the gap of RAIU rate has been depended on the thickness of thyroid gland as well as the diameter of the beaker. We know that the change of the volume with the increase of the length of the source had less effect on the change of the counting rate. Thus, in order to reduce the error in the measurement of the counting rate with the thyroid uptake rate equipment, an accurate counting rate can be relatively measured if the counting rate which is measured is corrected by thickness or the distance between the thyroid and the thyroid uptake rate equipment is changed.
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KEYWORD
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131 I, Thyroid uptake, Thickness
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