Positron Emission Tomography, also called PET, is a diagnostic tool that produces images that demonstrate organ function. PET images are based on the detection of subatomic particles, specifically positrons.

Positrons are emitted from a radioactive substance administered to the patient and are ultimately detected by special crystals within the PET scanner. This information is then digitized to produce a 3-Dimensional image of the whole body or of a specific organ. With PET/CT, Computerized Tomography images are also obtained, which show detailed views of the structure of the body part being examined. The two types of images are “fused” by a computer into a set of pictures that shows both anatomical detail and function of the area being examined.

PET/CT scans are most often used to determine whether a growth is malignant (cancerous) or benign (non-cancerous), to evaluate the progression of disease and to assess the effects of clinical therapies. In addition, PET/CT is used to evaluate patients who have memory disorders such as Alzheimer’s Disease, seizure disorders that are not responsive to medical therapy and for the assessment of cardiovascular disease.

What to Expect​

Resting Phase

The PET/CT procedure typically lasts 2-3 hours. It begins with an injection of a tiny amount of radioactive glucose (sugar) “tracer” solution that enables evaluation of glucose metabolism (function) in the body. There are no known side effects to this injection. Once injected, you will be asked to rest in a quiet room and avoid significant movement or talking, which may alter the localization of the tracer. The resting period lasts approximately 60 min.

Imaging Phase

The PET/CT scanner is very similar in size to a CT scanner and looks like a large doughnut. You will be asked to lie on an imaging table with a pillow positioned under your knees for additional comfort. It will take approximately 30-45 minutes for your scan and possibly longer depending on the type of scan your physician has requested. It is very important that you not move during the scan.

Scans generally take approximately 30 minutes. In some cases, more than one scan is required; you will be notified of the number of scans at the time of injection.

Your total time commitment will be approximately 2 hours and reports should be in your doctor's office within 48 hours.

How to Prepare

When you schedule your appointment, we will inform you about any specific preparations depending upon the specific procedure your doctor has ordered. Please contact the Scheduling Department at 949-764-5573 if you have any questions.

If your physician has ordered your procedure with radiographic contrast:

  • You should inform your physician if you have any allergies. If you have been told you are allergic to contrast or have ever had a reaction to Iodine or any form of contrast media, your doctor may prescribe medications to reduce the risk of an allergic reaction. A Radiology nurse should contact you. If you have not been contacted by a Radiology nurse at least 24 hours prior to your appointment, please contact the Imaging Scheduler immediately.
  • If you have diabetes, kidney problems, lupus, surgery on your kidneys or multiple myeloma, you must have lab work that includes a BUN and Creatinine performed within 30 days of your exam. If you are over the age of 65 you must have lab work within 90 days of your exam. This provides us with information regarding your current kidney function. Please call your physician if you have not had this blood work.
  • If you have been diagnosed with diabetes and/or you are currently taking any of the following medications: Metformin, Gluicophage, Glucophage XR, Fortamet, Riomet, Metaglip, Glucovance, Actoplus Met, Avandament or Junamet, stop taking your medication for a total of 48 hours after your exam. You must contact your physician for alternative medications and instructions prior to your exam.
  • If you are currently receiving Dialysis; please schedule your dialysis to follow your procedure with Contrast or the following day. It is imperative you have dialysis no later than the following day after you have received contrast for your procedure.
  • We encourage you to hydrate with oral fluids at least 24 hours prior to your study. You may have only clear liquids as well as your necessary medications 2 hours before your exam.

Instructions for the 12 hours prior to your exam time

Stay on a low carbohydrate diet.

Do NOT engage in any strenuous exercise.

Do NOT chew gum and avoid mints.

Refrain from consuming any caffeine, including any decaf products for 24 hours prior to your exam.

Day of the Exam

Do NOT eat anything six (6) hours prior to your appointment time. Please drink several glasses of water (2-6) and take medications. If you need to eat, please limit yourself to a small protein-only meal. If you are diabetic, please consult your doctor for questions regarding medication.

Wear warm and comfortable clothes.

You will receive an injection.

If you're having a CT, you may be asked to drink oral contrast.

You will be asked to sit quietly in the waiting room for 60-90 minutes after the injection.

Wear comfortable, warm clothing. Do not wear jewelry or clothing with metal zippers or buttons. (Sweats are recommended)

Please complete, print out and bring with you the following forms to your appointment:

Outpatient Medication Reconciliation - Download PDF

Side Effects/Follow-Up Care

Side Effects and Complications

As with many diagnostic procedures, there are some risks associated with radiation exposure. Most clinicians believe the beneficial information gained from PET/CT exams outweigh the exposure risks. There are no residual side effects from a PET scan. On rare occasions, CT contrast may cause reaction. You will be able to drive yourself home. Consult your physician before the exam if you may possibly be pregnant or are breast-feeding.

Follow-Up Care

There are no restrictions after the test, although you should drink plenty of fluids to flush the radioactive substance from your body.


Locations where NHRA provides PET/CT services