Positron Emission Tomography

PET is an imaging technology that studies the body’s biological functions by measuring energy emitted by a radioactive substance injected prior to the procedure. PET is unique because it produces images of the body’s basic biochemistry or function. Traditional diagnostic techniques, such as x-rays, CT scans or MRI, produce images of the body’s anatomy or structure. PET is an imaging technique that is used to visualize some of these metabolic alterations. Even in early disease where there is no gross structural abnormality visible on CT or MRI, the PET scan may be able to show a biochemical change.

A PET scan is a simple procedure. It involves the use of a small amount of a radioactive material, similar to what is used in other nuclear medicine procedures.

PET-CT technology is the combined use of PET scans and CT scans to evaluate and diagnose conditions within the body. The combined PET and CT scans provide images that can specifically locate abnormal metabolic activity within the body. The combined scans provide more accurate diagnoses than the two scans performed separately. PET-CT technology can be used to diagnose and evaluate a number of conditions within several medical specialties. In addition to diagnosis, it can be used to evaluate the effectiveness of certain medical treatments. It can also be used to determine the best place for a biopsy, if needed.

  1. Accurate staging of malignancy due to its ability to detect metastases in the whole body
  2. Detecting the primary tutor in metastasis of unknown origin
  3. Accurate post therapeutic assessment leads to saving patient’s time, money and side effects from ineffective drugs
  4. Localizing occult malignancy in the presence of clinical indicators such as elevated tumor markers
  5. Localization for biopsy

The first step is the injection of a radioactive material, called a tracer, into the body. After enough time has passed for the tracer to spread throughout the body (60-90 minutes), the patient lies down on the PET scan table and is moved into the machine, where an array of ring-shaped detectors measure the emission and create an image. Scanning itself then lasts 20 minutes.

These images appear on a computer screen beside the machine, with different colors depicting various concentrations of the tracer. This information helps radiologists determine, for example, that cancer is present in an area with high glucose absorption (indicating rapid cell metabolism).

The only discomfort that might be associated with PET scans may come from the injection of the tracer or from having to remain still within the scanning apparatus. Neither the injected material itself nor the scanner cause pain.

  1. Cases Without Anesthesia: Patient should abstain from eating anything for five hours. However, drinking water is advisable for better test results. Cases With Anesthesia: Patient should abstain from eating or drinking anything for five hours. Water is NOT allowed. In both cases, patients cannot be injected with Intravenous glucose.
  2. Blood glucose level should be below 150mg. The exam will be cancelled if glucose level is higher.
  3. Recent kidney functions (creatinine level) is needed to check the kidneys condition before contrast injection.
  4. Preferably last chemotherapy should be two weeks ago, and radiotherapy 2 months ago.
  5. Patient should come prepared with the all the previous scans/biopsies results. In case of a patient coming to follow-up on his/her PET-CT scan, he/she should come with all the last PET-CT results (Films, Report and CD).
  6. Patient should dedicate at least 3 hours of his/her time for the scan.
  7. It is allowed to take any medications on the same morning, except insulin. Insulin should be taken 5 hours before the scan appointment time.
  8. It is advisable to physically rest for 24 hours before the exam time.
  9. All metal objects, including hearing aids, must be removed prior to the exam.

After the exam:

  • Patient can eat or drink anything
  • It is advisable to stay away from children and pregnant women for 6 hours after the exam
  • It is advisable to drink large amount of fluids to get the radioactive material outside the body faster


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