Having a PET/CT

McLaren Health Care and Karmanos Cancer Institute offer positron emission tomography-computed tomography (PET-CT) scanning technology that combines a diagnostic PET scan and a low dose non diagnostic CT into one unit to provide faster scan times and higher-quality images. PET-CT scans are commonly used to find changes in the body during the early stages of disease and for staging and restaging of cancers.

What is a PET-CT Exam?

PET-CT exam combines two types of scans to help pinpoint abnormal activity in the body.

A PET (positron emission tomography) scan creates an image of your body's metabolic activity and shows the rate at which your body's cells break down and use sugar (glucose). This is done by injecting a small amount of radioactive material into your blood stream and waiting for it to disperse to the area of focus. The PET scan is then performed to detect the radioisotope and creates an image on the computer screen.

A CT (computed tomography) scan is a non-invasive medical test that uses special x-ray equipment to produce multiple images or pictures of the inside of the body and a computer to join them together in cross-sectional views of the area being studied.

A PET-CT combines the functional information from a PET scan with the anatomical information from a CT scan. When a CT scan is superimposed over a PET scan, doctors can pinpoint the exact location of abnormal activity. They can also see the level and extent of that activity. Even when an abnormal growth is not yet visible on a CT scan, the PET scan may show the abnormal activity.

  • PET (positron emission tomography) looks at how the cells in your body process a radioactive tracer material that you have injected.
  • CT (computed tomography) uses x-ray technology to produce detailed images.
  • By combining two scans, a PET-CT shows both your anatomy and how your cells are behaving.
  • The exam may take two hours or more. Actual scanning time is 25 to 35 minutes.
  • Every exam is interpreted by a radiologist.
  • We use the latest technology and the capabilities of our state-of-the-art scanners play a key role in tailoring each exam to your specific needs and reduce radiation exposure.
Pet-CT machine


  • CT: CT examinations improve healthcare and are an essential part of diagnosis and treatment planning. However, because there are risks associated with the level of radiation exposure during a CT, the medical benefit of conducting the exam should always outweigh any risks involved. No direct data has shown that CT examinations are associated with an increased risk of cancer. Extrapolations from studies of radiation exposure suggest there is a very small incremental risk.

    We pay special attention to minimizing radiation exposure without giving up image quality. We use many strategies to reduce radiation exposure, from employing the latest technology to customizing exams for each patient.

  • PET: The dose of radiotracer administered is small, resulting in minimal radiation exposure. Nuclear medicine has been used for more than five decades and there are no known long-term adverse effects from such low-dose exposure. Allergic reactions to radiopharmaceuticals may occur but are extremely rare.

    Women should always inform their physician or technologist if there is any possibility that they are pregnant or if they are breastfeeding. Some of the pharmaceuticals that are used for the study can pass into the mother's milk and subsequently be consumed by the child. To avoid this possibility, it is important that a nursing mother inform her physician and the nuclear medicine technologist about this before the examination begins. Usually, you will be asked to discontinue breast-feeding for a short while, pump your breasts in the interim and discard the milk.

What to Expect


  • Medications: Most claustrophobic patients are able to tolerate a PET-CT or PET scan. Talk to your physician if you think you need some additional anti-anxiety medication for the scan. We cannot prescribe or supply medication.

  • Food and drink: Do not eat or drink anything for at least six hours before the exam. If your physician has told you to take your regular medicine, take it with water. If you are diabetic, do not drink or eat anything for at least four hours prior to your scan. Take your diabetic medication as usual. If your physician has told you to take your regular medicine, take it with water. Avoid candies, gum, or beverages other than water.

  • Exercise: Do not exercise for at least 24 hours before the exam.

  • When to arrive: Check in 10 minutes before your appointment time.

  • What to wear: Wear loose-fitting, comfortable clothes with no metal (zippers, under wire bras, etc.). Leave your watch, jewelry, and other valuables at home.

  • Intravenous preparation: The technologist will place an IV in your arm or hand prior to the test.


  • Scanning: You will be required to lie flat with your arms raised above your head. If you think you will be unable to keep your arms above your head for approximately 35 minutes, please notify the technologist.

  • Length of exam: You should plan to be here for approximately 2-3 hours. The actual scanning and preparation time varies with the type of scan you are having.


  • Instructions: You can drive and resume normal activities immediately after leaving, unless you have taken medication to relax you. It is important that you drink as much water or fluids as possible for the rest of the day and empty your bladder as often as possible. This will result in a more rapid clearance of radioactivity from your body.

  • Exam results: All PET-CT exams are interpreted by a radiologist. Your referring physician will communicate these results to you.

PET/CT Locations Near You