Purpose
To obtain static images of the functioning renal cortical mass.

Patient preparation
No preparation required.

Tracer used
Tc99m DMSA is ideal. Dose 10 – 100 MBq (0.3 – 3.0 mCi)
Tc99m GHA can also be used. Dose 20- 300 MBq (0.5 – 8.0 mCi)

Administration
IV injection outside the camera room is enough.
If dynamic study is desired with Tc99m GHA may be injected over the camera as for Renogram.

Image Acquisition
Scan Timing: To be acquired 2-4 hours after the injection. In patients with poor renal function, background activity will continue to be high and further delay until 24 hours may be required.
Voiding of bladder before scan recommended. Diuretic and or catheterization may be needed if activity is retained in dilated collecting system.
When GHA is used biliary activity in gall bladder and intestines may interfere with the interpretation.
Views: Planar with High resolution collimator
Posterior and posterior oblique images are required.
256 X 256 Matrix, 300 K – 500 K per view.
Isotime Ant & Post Images are needed to calculate geometric mean counts from the kidneys.
Optional: Pin hole images or SPECT
Sedation Not needed for planar imaging.
Needed for children if Pin hole or SPECT imaging is performed.

Image Processing
Split Function: This can be calculated from either a single posterior view or
by the Geometric Mean Ratio method from both anterior & posterior views.
Geometric Mean counts of an organ is calculated by the formula:
= Sq Root of {Ant cts X Post cts.}
This is more accurate than the result from a single view since this takes care of the differential attenuation. More important in ectopic kidneys.
Background subtraction is not critical when there is little background activity but becomes critical if the background is significant.