The reason we ask that you fast for a PET/CT scan is because the injection given for this procedure (called “FDG”) is based on glucose (sugar). If a patient eats before the procedure, the glucose (sugar) level in the blood may be elevated and will interfere with the uptake of the radiotracer. To make sure that the cells of the body receives the correct amount of FDG, and to improve image quality, we ask you to fast so that there is no competition with glucose (sugar) in the blood. Yes, please inform the technologist if you ate within the last 4 hours so it can be noted on the chart. ** If you are having a PET/CT Bone scan or Cardiac PET/CT scan, you do not have to be fasting. **
PET/CT scans use a sugar-based agent to provide very high quality and detailed images. In order to work correctly, our agent must distribute on its own. If you have any calories, such as sugar, within that four hour timeframe, that will compete with our agent and significantly change the results of your test. Ultimately, this could affect your diagnosis and treatment.
However, we understand that accidents happen! If for any reason you do eat or drink anything other than water within this timeframe, please let us know. We would be happy to reschedule you in order to obtain the best possible images, which will lead to better care. Call us if you have any more questions.