Department of Nuclear Medicine Samsung Medical Center Joon Ho YEON Evaluation of Pre-Dose Count in the GFR Test Using 99mTc-DTPA Department of Nuclear Medicine Samsung Medical Center Joon Ho YEON 1

Introduction GFR is the total amount of filtrate formed per minute by the kidneys Simple measurement method Usually, Kidney scintigraphy using technesium DTPA is performed to check the function of kidney. And, glomerular Filtration rate is a one of the kidney function. Although the GFR test using a technesium DTPA shows underestimated result, it is not only simple, but also relatively accurate and quantitative method. But this test is influenced by several parameters, such as net syringe count, kidney depth and corrected kidney counts etc. Critical parameters

Purpose Evaluation of the predose count according to matrix size and concentration of radioactivity Influence on the GFR results by predose count Optimization of the adequate administration dose and the acquisition time

Materials Collimator LEGP Matrix size Zoom factor 1.0 64 × 64 GE. Infinia Collimator LEGP Matrix size 64 × 64 128 × 128 256 × 256 Zoom factor 1.0

Methods Phase 1 Phase 2 Phase 3 Calculation Processing Acquisition

Result (count rate) Result (total counts) 64 × Acquisition Time 134 172 208 245 276 268 345 415 491 553 533 688 831 980 1104 800 1031 1246 1445 1550 1064 1365 1594 1777 1892 1300 1630 1868 2038 2113 1503 1866 2093 2280 2321 Predose Activity 5 10 20 30 40 50 60 222 296 370 444 518 Predose Activity 26.8 34.5 41.5 49.1 55.3 26.7 34.4 41.6 49.0 55.2 48.2 51.7 26.6 34.1 39.9 44.4 47.3 26.0 32.6 37.4 40.8 42.3 25.1 31.1 34.9 38.0 38.1

Result (count rate) Result (total counts) 128 × Acquisition Time 127 172 205 242 271 253 334 410 484 543 505 667 822 966 1087 758 1001 1232 1452 1626 1008 1333 1642 1931 2169 1263 1665 2050 2414 2707 1511 1994 2453 2890 3244 Predose Activity 5 10 20 30 40 50 60 222 296 370 444 518 Predose Activity 25.3 33.4 41.0 48.4 54.3 41.1 48.3 54.4 54.2 25.2 33.3 54.1 33.2 40.9 48.2 7

Result (count rate) Result (total counts) 256 × Acquisition Time 137 168 204 240 273 255 337 408 481 547 510 623 816 960 1092 766 1007 1223 1439 1637 1018 1342 1632 1918 2183 1271 1677 2034 2394 2727 1524 2011 2439 2869 3268 Predose Activity 5 10 20 30 40 50 60 222 296 370 444 518 Predose Activity 25.5 33.7 40.8 48.1 54.7 48.0 33.2 54.6 33.6 25.4 33.5 40.7 47.9 54.5 47.8

Result (total count) 64×64 128×128 256×256 (kcout) (sec) (kcout) (sec)

Result (count rate) 518 MBq 64×64 128×128 256×256 (kcps) (sec) (kcps)

Result (% difference) 256 × 64 × 128 64 × Acquisition Time 0.00 0.34 0.21 0.18 0.30 0.39 0.59 0.25 0.42 0.37 0.69 Acquisition Time Predose Activity 222 296 370 444 518 5 10 20 30 40 50 60 Acquisition Time Predose Activity 64 × 222 296 370 444 518 5 10 20 30 40 50 60 0.00 0.37 0.29 0.24 0.20 0.18 1.83 6.51 0.75 1.16 3.86 9.57 14.47 2.99 5.51 9.88 16.90 23.51 6.34 9.86 15.90 22.61 30.02 128 0.21 0.40 0.30 0.60 0.41 Acquisition Time Predose Activity 64 × 222 296 370 444 518 5 10 20 30 40 50 60 0.00 0.37 0.29 0.24 0.20 0.18 1.83 6.51 0.75 1.16 3.86 9.57 14.47 2.99 5.51 9.88 16.90 23.51 6.34 9.86 15.90 22.61 30.02

Result (% difference) 64×64 128×128 256×256 (%) (sec) (%) (sec) (%)

GFR Analysis { } % Renal uptake e GFR (㎖/min) = × 9.8127 – 6.82519 U : 99mTc- attenuation coefficient X : kidney depth (Rt. & Lt.) { } (Lt. Kidney count – Lt. BKG count) + (Rt. Kidney count – Rt. BKG count) e -μXRt. Predose count – Postdose count -μXLt. % Renal uptake GFR (㎖/min) = × 9.8127 – 6.82519

Result (% Difference of GFR) Acquisition Time Predose Activity 64 × 222 296 370 444 518 5 10 20 30 40 50 60 0.00 0.37 0.29 0.24 0.20 0.18 1.84 6.96 0.75 1.17 4.01 10.59 16.91 3.08 5.83 10.96 20.34 30.73 6.77 10.93 18.91 29.21 42.89

Result (% Difference of GFR) Predose Activity 256 × 0.00 0.36 0.21 0.18 0.30 0.39 0.59 0.25 0.42 0.37 0.60 0.63 Acquisition Time 222 296 370 444 518 5 10 20 30 40 50 60 Acquisition Time Predose Activity 128 × 222 296 370 444 518 5 10 20 30 40 50 60 0.00 0.24 0.21 0.18 0.39 0.30 0.37 0.40 0.60 0.41

Image of Overflow Dose Activity Acquisition Time 333 MBq 60 second 64×64 128×128 256×256 Dose Activity 333 MBq Acquisition Time 60 second

Conclusion Exceed 1,500 kcounts, count rate is decreased due to the overflow phenomenon in 64×64 of matrix size. Percentage difference of total counts is 30.02 % , GFR values are overestimated up to 42.89 %. There is no big difference in the 128×128, and 256×256 of matrix size. Compromization suitable for condition of gamma camera.

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