99mTc-Glucoheptonate (99mTc-GHA)

Glucoheptonate is a small carbohydrate that is partly filtered, partly secreted and partly (10-20%) retained in the proximal tubular cells. Its extraction efficiency is the same as that of 99mTc-DTPA. Delayed views at 2-4 hours show good images of the renal cortex, similar to 99mTc-DMSA. It is the preferred tracer for renal trauma assessment because of its ability to image perfusion, excretion and cortical integrity.

Non-Imaging Agents

125I-iothalamate is used as a tracer for GFR assessment. The energy of the photons emitted by iodine-125 is too low for imaging, and the 60 day half-life of this isotope requires a very small injected dose. GFR assessment involves plasma sampling and counting the radioactivity in a well counter.

51Cr-EDTA is a chelate similar to 99mTc-DTPA and is likewise filtered by the glomeruli. The compound is stable and the isotope long-lived. This agent is extensively used in Europe but has limited availability in North America.

Figure 3. Normal 99mTc-DPTA scan. In the early part of the flow phase at 3 seconds per frame (A), the kidneys appear at the same time as the aorta. The left kidney is as intense or more intense than the spleen. In the 1 minute per frame dynamic images (B), activity is seen in the collecting systems and ureters by 2-3 minutes. Note that the bladder is not in the field of view in most of the dynamic images. Better positioning (bottom row on right: pre and post void images) allows visualization of the bladder. Note the image of the injection site (bottom row, third from right) showing no extravasation of tracer.

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