Hello, everyone. This is my first time to do drug distribution research. Our drugs were sent out for radiolabeling and PET/CT to analyze distribution in organs. We are reading papers to learn how to exactly analyze data. We notice that both %ID and %ID/g are used in papers and %ID/g seems to be more common. Looks like the %ID represents the drug or radiolabel uptake in a specific organ and %ID/g stands for the uptake per gram of this organ. We don't know if our understanding is right. We also have concern about the use of %ID/g. Do we need to use the real organ weight to calculate %ID/g? Many papers reported %ID/g of long monitors in animals without displaying tissue weight. If they did not harvest tissues then how they got the tissue weight to calculate %ID/g at different timepoint? We consulted some technicians and they told us the tissue weight was estimated through 1 gram times tissue volume (ROI). So the tissue weight is actually an estimated value. We wondered if it is accurate to use an estimated tissue weight to calculate %ID/g. We feel like the real weight is better.
Thank you for help.
That is correct, %ID/g relates to the weight of the tissue measured. Percent of injected dose per gram is the unit typically in dynamic PET studies, which are used to generate plots showing how the concentration of tracer changes in the subject's organs over the course of the acquisition. This provides an approximate kinetic model without the need of sacrificing the animal and weighing its organs. Results in %ID/g are not comparable across subjects.
It is the correct unit of measure in actual biodistribution studies, where organs are resected, weighted, and their uptake measured in a gamma counter.
Dear Wang, the difference is %ID/g is normalized to the bodyweight usually used in preclinical studies. It shows a relative uptake from the injected dose (ID) of certain accumulated area. In clinical, it can be translated to the SUVbw. Hope it helps
Syahir
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