Nuclear imaging can provide images of metabolic activity, if the images are properly calibrated.

Nuclear imaging techniques provide a picture of metabolic activity—what’s actually happening in the body, where other imaging techniques show anatomical features.  Essentially, nuclear imaging cameras record the total amount of radioactive marker compound in a given area, but the images can only be interpreted if you know the total amount of injected active compound.  To do that, the radioactivity of the compound and the amount of compound injected both have to be estimated. There are different methods for doing that, and researchers from the National Cancer Institute Regina Elena in Rome investigated the performance of three different methods by calibrating the syringe volume using an analytical balance.