What is the purpose of glucose loading before FDG injection?

The purpose of glucose loading before the injection of fluorodeoxyglucose (FDG) is primarily to prime the myocardium for glucose uptake. When a patient is administered glucose prior to an FDG scan, it stimulates the heart muscle and other tissues to increase their utilization of glucose, which enhances the effectiveness of the FDG as a tracer in imaging.

FDG is a radiopharmaceutical that mimics glucose and is taken up by cells in a manner that is dependent on the metabolic activity of those cells. In the context of myocardial perfusion imaging, for example, priming the myocardium with glucose ensures that the heart is ready to absorb FDG during the imaging process, allowing for more accurate evaluation of its metabolic state and any potential ischemia or viability issues.

This process facilitates the assessment of areas of different metabolic activity, providing valuable information in conditions such as coronary artery disease or heart failure, thereby improving the diagnostic yield of the PET scan.