Patient name____________________________ ID______________ Date___________
Referring physician_______________ht______(kg) Height______(cm) Age_____(yr)
NOTE: Many nuclear medicine computers have software that performs one or more of the steps below automatically.
STEP 1 Counting the external syringe dose calculate the net injected dose from the syringe images:
Pre injection (cts) - Post injection (cts) = Net injected dose (cts)
__________(cts) - __________(cts) = __________(cts)
STEP 2 Calculate the renal depth of both kidneys using the method of Taylor:
[151.3 x weight (kg) ) height (cm)] + 0.22 age (yr) - 0.77 = Right kidney depth (mm)
[151.3 x _____(kg) ) _____(cm)] + 0.22 x _____(yr) - 0.77 = _____(mm)
[161.7 x weight (kg) ) height (cm)] + 0.27 age (yr) + 0.70 = Left kidney depth (mm)
[161.72 x _____(kg) ) _____(cm)] + 0.27 x _____ (yr) + 0.70 = _____(mm)
STEP 3 Calculate the percent uptake of the injected dose in each kidney at 2 to 3 minutes using the equation:
Where: U = percent uptake (%)
A = counts per pixel right or left kidney
(cts/px)
B = counts per pixel corresponding background (cts/px)
P = pixels
in kidney region of interest (px)
e = natural log = 2.718 (no units)
u =
attenuation coefficient for Tc-99m = 0.0153 (1/mm)
Y = kidney depth (mm)
D
= net counts for syringe containing dose (cts)
exp =
exponent
Right kidney:
Left kidney:
[2.718 exp -0.153 (1/mm) x _____(mm)] x ____(cts)
STEP 4 Calculate the glomerular filtration (GFR) rate for each kidney using the equation:
Right kidney: U (%) x 9.75621 - 6.19843 = GFR (mL/min)
_____(%) x 9.75621 - 6.19843 = ______(mL/min)
Left kidney: U (%) x 9.75621 - 6.19843 = GFR (mL/min)
_____(%) x 9.75621 - 6.19843 = ______(mL/min)
STEP 5 Add the glomerular filtration rates for the two kidneys together to obtain the global GFR:
Right GFR (mL/min) + Left GFR (mL/min) = global GFR (mL/min)
_______(mL/min) + _______(mL/min) = _______(mL/min)