What to expect?

  1. The individual scheduling the PET-CT scan or the technologist performing your PET-CT scan will instruct you regarding preparation for your scan. If you are diabetic, please inform the individual scheduling your scan.
  2. Upon arrival for your PET-CT scan, you will receive an injection of radioactive sugar (FDG) into your vein, which is similar to having a tube of blood drawn. The amount of radioactivity is low.
  3. You will then be asked to lie still on a reclining chair without talking for about one hour in order for the sugar to distribute in your body. Afterward, you will be taken into the PET-CT scanner room for imaging. The PET-CT scanner is a doughnut-shaped device with a padded examination table in its center.
  4. You will be asked to lie flat on the scanner table, which is designed to move you slowly through the center of the scanner ring. The scanning procedure will last approximately 20-30 minutes. The entire procedure, including registration, will take approximately two hours.
  5. An additional CT portion is sometimes performed with an injection of a material called "contrast." Before receiving the contrast injection, check with your referring physician to assure that you are permitted to receive the contrast
  6. After completion of the images, the PET-CT technician will release you. As a rule, the radiologist does not review the results with you, but will send a report to your physician in one or two business days.

How to prepare for the images?

  1. PET-CT is done on an outpatient basis. You will receive detailed instructions on how to prepare for your examination. On the day before your PET-CT scan, drink plenty of fluids (any beverage), and on the morning of your scan, drink several extra glasses of plain water.
  2. You should wear comfortable, WARM, loose-fitting clothing. It is best not to wear clothes with metal, like zippers and snaps, as this can affect the images.
  3. You may also be asked to remove hairpins, jewelry, eyeglasses, hearing aids and any removable dental work, depending on the part of the body that is being scanned. Your doctor will instruct you regarding the use of medications before the test.

Will it hurt?

The part of the procedure that will hurt the most is the injection, which feels like a small pinch or pinprick. After that, the only discomfort you may feel is from lying still for up to 45 minutes (usually 20-30 minutes).

How are images obtained?

Although our highly specialized PET-CT hybrid camera can perform the CT and PET portions of the examination almost simultaneously, these are still two separate examinations that consist of the following:


Sugar (glucose) is an important source of energy for most cells including tumor cells, and because many tumor cells are very active, these cells require even more energy and therefore more glucose. By attaching a small amount of radioactivity (Fluorine-18) onto the glucose. This process is called radioactive labeling, or radio-labeling for short. The radiolabeled glucose is later injected into your blood and after waiting for approximately one hour for it to travel through your blood to different parts of your body; the physician can then obtain images. These images demonstrate where the glucose has localized. By knowing the normal distribution of glucose and by looking for intense areas of radiolabeled glucose accumulation, one can identify areas of possible cancer spread.

In some instances additional CT images will be performed utilizing a substance typically referred to as "Contrast". This will be injected into your vein using the same injection line used initially in order to avoid injecting you twice.


The CT consists of a small amount of radiation passing through you, and a small X-ray image is obtained and stored on a computer. By performing this same process many times around the outside of the body in a circular motion, the computer obtains an "image-in-the-round" of the body.
Through computer processing, these images allow the construction of highly detailed cross-sectional images of many of the organs and structures in your body. This would essentially be the same as if one took multiple little X-rays around a loaf of bread, and then with computer processing, an image is displayed showing you the details of each of the slices of bread in the loaf. The image of that one slice of bread from the middle of the loaf is a cross-sectional image. As noted, CT scans use X-ray; however, the amount of radiation is low.

Our computers will later join the PET and the CT images in a process called Coregistration. This is different from Fusion which can happen when images are joined, but were performed in two different cameras. In our center, most of the images are obtained with the same hybrid camera.

Patient Information

To make an appointment for a PET/CT scan, please call the Division of Nuclear Medicine Scheduling Dept. at (202) 877-9240 (press option 2 then option 3), between the hours of 8:00 AM to 5:00 PM, Monday - Friday