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PET Scan (Positron Emission Tomography)

Nuclear medicine imaging procedures are noninvasive medical tests that help physicians diagnose medical conditions. These imaging scans use radioactive materials to help determine if cancer may be present before or after a biopsy (or surgery.) It may be done along with an MRI or CT scan, depending on the situation. A PET scanner is a large machine with a round, doughnut shaped hole in the middle, similar to a CT unit. Within this machine are multiple rings of detectors that record the emission of energy from the radio tracer in your body. A nearby computer aids in creating the linages from the data obtained by the scanner.

Unlike other imaging techniques, PET does not produce structural linages but rather a rendering that reflects the level of chemical activity in your body. Areas of greater intensity, called “hot spots”, indicate where there is a high level of chemical activity. Less intense areas, or cold spots, indicate less chemical activity.

Nuclear medicine imaging is usually performed on an outpatient basis, usually at a center as recommended by your physician. Your physician will order the test and you will be contacted by the PET center to schedule the test and for instructions.

On the day of testing, a very small dose of a radioactive chemical, called a radiotracer, is injected into the vein of your ann. The tracer travels through the body and is absorbed by the organs and tissues being studied. Next, you will be asked to lie down on a flat exarrrination table that is moved into the center of a PET scanner. This machine detects and records the energy given off by the tracer substance and, with the aid of a computer, this energy is converted into threedimensional pictures. A physician can then look at cross-sectional itnages of the body organ from any angle in order to detect any problems.

A radiologist will interpret the images and forward a report to your referring physician. You will be called about the results in about 7 days, or you may be given other instructions regarding review of test results. Drs. Theilen & Williams will review the results in the context of your specific situation. Please call 972-402-8404, extension 130 for questions about the results, IF you have not been called as instructed.

The following are instructions for patients getting a PET scan. You may receive detailed, slightly different instructions from the PET center. Please call the PET center if you have questions/concerns, about the test itself.

Don’t have any food for 6 hours prior to appointment (including gum, breath mints, hard candy, etc). If you have an appointment after 1:00 PM, start fasting at 7:30 AM.

  • Follow the high protein, low carbohydrate diet below for 24 hours prior to your test.
  • You may drink ONLY water up to the time of your test. No other type of liquid is allowed.
  • Take medications as scheduled prior to your appointment as long as they are tolerated on an empty stomach.
  • NO strenuous exercising 24 hours prior to appointment.
  • Wear warm, loose-fitting clothing. The scanners tend to get cool. You will NOT be required to remove the clothing prior to the scan.
  • Allow 2-3 hours for the exam.
  • You must be able to lay still and mostly flat for about 30 minutes.
  • If you need pain or anxiety medication, take medication prescribed by your physician 1 hour before the scan (notify Drs. Theilen or Williams if you feel you need this)

Follow this high protein / low carbohydrate diet, beginning 24 hours before the PET scan.

2 eggs, any style
Bacon or sausage
No juice
No toast or potatoes

Lunch and Dinner:
Entrees (choose one):
8 oz. grilled steak,
half a baked or broiled chicken
or 8 oz. grilled salmon fillet.

Side items (choose one):
Grilled or steamed broccoli or asparagus
Sauteed mushrooms or any type of green vegetable salad.
Desert – cheese and salami slices

FOODS TO AVOID: Refined sugar, all fruits, raisins, beets, carrots, com, kidney beans, peas, yarns, cereal, rice cakes, all bread, muffins, tortillas, potatoes, pretzels, chips, rice, granola, oatmeal, pasta, all sodas, all fruit juices.


  • You may drink ONLY water up to the time of your test. No other type of liquid is allowed.
  • Diabetics who take ORAL medications should wait until the exam is complete to take them.
  • Insulin- dependent patients should have their last injection about 4 hours prior to the appointment.
  • Take other regularly scheduled medications prior to appointment as long as they are tolerated on an empty stomach.

This is meant to be general information about PET scans. Please call the office at 972-402- 8404, extension 130 if you questions. For instructions related to the preparation and details of the PET scan itself, please call the PET scan center. This will most likely be Baylor Medical Center Irving or PET Dallas (or other places depending on insurance or medical matters.)

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