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KMID : 0861420100140010094
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Korean Journal of Nuclear Medicine Technology
2010 Volume.14 No. 1 p.94 ~ p.100
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The Evaluation of Predose Counts in the GFR Test Using 99mTc-DTPA
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Yeon Joon-Ho
Lee Hyuk
Ji Yong-Gi
Kim Soo-Young
Lee Kyoo-Bok
Seok Jae-Dong
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Abstract
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Purpose:We can evaluate function of kidney by Glomerular Filtration Rate (GFR) test using 99mTc-DTPA which is simple. This test is influenced by several parameter such as net syringe count, kidney depth, corrected kidney count, acquisition time and characters of gamma camera. In this study, we evaluated predose count according to matrix size in the GFR test using 99mTc-DTPA.
Materials and Methods: Gamma camera of Infinia in GE was used, and LEGP collimator, three types of matrix size (64×64, 128×128, 256×256) and 1.0 of zoom factor were applied. We increased radioactivity concentration from 222 (6), 296 (8), 370 (10), 444 (12) up to 518 MBq (14 mCi) respectively and acquired images according to matrix size at 30 cm distance from detector. Lastly, we evaluated these values and then substituted them for GFR formula.
Results:In 64×64, 128×128 and 256×256 of matrix size, counts per second was 26.8, 34.5, 41.5, 49.1 and 55.3 kcps, 25.3, 33.4, 41.0, 48.4 and 54.3 kcps and 25.5, 33.7, 40.8, 48.1 and 54.7 kcps respectively. Total counts for 5 second were 134, 172, 208, 245 and 276 kcounts from 64×64, 127, 172, 205, 242, 271 kcounts from 128×128, and 137, 168, 204, 240 and 273 kcounts from 256×256, and total counts for 60 seconds were 1,503, 1,866, 2,093, 2,280, 2,321 kcounts, 1,511, 1,994,
2,453, 2,890 and 3,244 kcounts, and 1,524, 2,011, 2,439, 2,869 and 3,268 kcounts respectively. It is different from 0 to 30.02 % of percentage difference in 64×64 of matrix size. But in 128×128 and128×128, it is showed 0.60 and 0.69 % of maximum value each. GFR of percentage difference in 64×64 represented 6.77% of 222 MBq (6 mCi), 42.89 % of 518 MBq (14 mCi) at 60 seconds respectively. However it is represented 0.60 and 0.63 % each in 128×128 and 256×256.
Conclusion:There was no big difference in total counts of percentage difference and GFR values acquiring from 128×128 and 256×256 of matrix size. But in 64×64 of matrix size when the total count exceeded 1,500 kcounts, the overflow phenomenon was appeared differently according to predose radioactivity of concentration and acquisition time. Therefore, we must optimize matrix size and net syringe count considering the total count of predose to get accurate GFR results.
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KEYWORD
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Matrix size , Glomerular Filtration Rate (GFR) test , Overflow phenomenon
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