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observer were behind the patient). Transplanted kidneys are more anterior than native kidneys, so the study is acquired with the camera anterior to the abdomen and pelvis.

As with any nuclear medicine procedure, renal scanning involves injecting a radioactive tracer and watching where it goes. Renal perfusion can be assessed with the various 99mTc-labeled tracers with the camera set to take rapid sequence images at a rate of 1-3 seconds per frame during the first minute of the acquisition. The remaining 20-30 minutes of the study is usually performed at a framing rate of 2060 seconds to evaluate the uptake and excretion phases (Figs. 3 and 4). A 30-second image of the injection site is highly recommended at the end of the study. If a substantial portion of the injection is interstitial instead of intravenous, this can have a great effect on the renogram, with delayed excretion and a stretched-out curve. Interstitial injections invalidate efforts to quantify renal function.

Quantification of Renal Function

Computer Analysis of Renal Scans

By placing appropriate regions of interest (ROIs) over the kidneys, various parameters of renal function can be derived. These include differential renal function measurements, renogram curves generated from ROIs placed around the entire kidney (Fig. 5), renogram curves generated from ROIs placed over the cortex of the kidney (Fig. 6), and pelvic emptying curves (Fig. 7).

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