RENAL TUBULAR FUNCTION (% UPTAKE) WORKSHEET

Patient name_______________________________ ID____________ Date___________

Referring physician____________ Weight______(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) + 0.7 = Left kidney depth (mm)

[161.72 x _____(kg) ) _____(cm)] + 0.27 x _____ (yr) + 0.7 = _____(mm)

STEP 3 Calculate the percent uptake of the injected dose in each kidney at 2 to 3 minutes using the equation:

[A-B] x P
_____________________ x 100% = U (%)
[e exp -uY] x D

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:

[_________(cts/px) - ________(cts/px)] x ______(px) x 100%
___________________________________________________________ = ______% uptake
[2.718 exp -0.153 (1/mm) x _____(mm)] x ____(cts)

Left kidney:

[_________(cts/px) - ________(cts/px)] x ______(px) x 100%
___________________________________________________________ = ______% uptake

[2.718 exp -0.153 (1/mm) x _____(mm)] x ____(cts)

STEP 4 Add the percent uptakes of the two kidneys together to obtain the global percent uptake (a measure of renal clearance):

Right (% uptake) + Left (% uptake) = global (% uptake)

_______(% uptake) + _______(% uptake) = _______(% uptake)

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