Common Questions about PET/CT Scans

• What is a PET/CT Scan?

   CT                                    PET                               FUSED IMAGE (overlapping PET/CT)

  

  • A PET/CT scan is an imaging test that helps reveal how your tissues and organs are functioning.  It uses special x-ray equipment and sophisticated computers to produce multiple images/pictures of the inside of the body.
  • This type of scan helps to detect disease.  Cancer cells have a high level of chemical activity (higher than non-cancer cells).  Because of this, cancer cells show up as “bright spots” on PET/CT scans.
  • PET = Positron Emission Tomography.
  • CT or CAT =  Computed (Axial) Tomography (x-rays are projected around the entire body to create images or “slices” of the inside of the body)
• Why is it important to follow a low carb diet for 12 hours and fast before my PET/CT scan?
  • PET/CT scans use a radioactive sugar: Fluorine 18 (radioactive) + FDG (Florodeoxyglucose = sugar)
  • To get the best results your blood sugar needs to be low so your cells will properly absorb the radioactive sugar. 
  • If your body has “too much sugar” (fasting blood sugar over 200) your cells are already “saturated” and your scan will be poor quality. 
• Why must I arrive 30 minutes before my scheduled PET/CT scan time?
  • Extra time is needed to complete your questionnaire, explain the exam, and start an IV in your vein or access your port.
  • The radioactive sugar “decays” or “expires” quickly (one half of the dose we start with is gone within about 2 hours) and it is expensive. 
  • Late arrivals lead to ordering a second dose or rescheduling your appointment. 
• Why shouldn’t I exercise 24 hours before my PET/CT scan?
  • Sugar goes to the parts of the body that are using a lot of energy. 
  • The radioactive sugar used in the PET/CT scan will accumulate in your muscles deteriorating the scan quality.

  Poor quality PET/CT 

  “Bright muscles” possibly due to:

  • Patient ate
  • Patient exercised the day before
  • Blood sugar was too high
  • Patient used long acting insulin
• Why am I not allowed to wear jeans, belts, metal buttons, zippers or jewelry?

  On CT images, dense items like metal appear bright white and create streaks over areas of the body making it difficult to see important structures in the body.

  Example:

  

  Abdominal CT patient was wearing a navel ring resulting in a star like white pattern on the cross section degrading the image.

• Why does my PET/CT appointment take about 2 hours?

  PET/CT exams have a specific series of steps:
  

  Steps	Approximate Time
  1) Exam explanation 2) Patient history questionnaire  3) Finger stick for blood sugar reading 4) IV start (in vein or PORT access)	15 minutes
  5) Injection of radioactive sugar 6) Rest time for the body to absorb the radioactive sugar	45-60 minutes
  7) Empty bladder/Use the restroom: the bladder needs to be empty for the scan	3 minutes
  8) CT portion of Scan, including Contrast given in IV or PORT	2 minutes
  9) PET/CT portion of Scan	15-25 min = scanning “eyes to thighs” for most diagnoses 25-40 min = scanning “top of head to toes” for diagnosis of Melanoma, Multiple Myeloma or  Cutaneous Lymphoma
  TOTAL APPOINTMENT TIME Which includes a SCAN TIME	Approximately 2 hours Actual Scan Portion is about 15-40 min