What is a PET Scan?Preparation and Difference Between PET Scan and CT Scan

What is a PET Scan?Preparation and Difference Between PET Scan and CT Scan

PET or PET Scan stands for Positron Emission Tomography. It refers to a specialized radiology method and is used to examine different body tissues in order to understand their conditions. PET is also used to evaluate the progress of treatment. PET scan is widely done in the niche of neurology, cardiology and oncology while its usefulness in other areas of medical treatment is currently under research.

Know How PET Scan Works

A special device is used for PET scanning. The scanning device having a larger hole at its heart is used to detect positrons which are subatomic particles and emitted by a radionuclide in the tissue or organ under examination.

A radioactive atom is attached to chemical substances to use the radiotracers during PET scanning. The attached substances are naturally used by the tissues or organ during metabolic process. Use of other substance during PET scan, however, depends on the purpose of scanning. If perfusion or blood flow of a tissue or an organ is what needs to be examined, radioactive carbon, oxygen, gallium or nitrogen can be used as radionuclide.

The radionuclide is applied to a vein via an IV (Intravenous) line. Next, the PET scanner is moved over the body part to be examined. Radionuclide breaks down and thereby, causing emission of positrons, which is responsible for creation of gamma rays. The rays are detected by the scanner and the same is analyzed by the computer. The information gathered is used to develop an image map of the tissue or organ currently being studied.

The amount of radionuclide built up in the tissue has a direct effect on the brightness of the tissue on the image, thereby indicating how well the tissue or organ is functioning.

PET scan vs CT scan

  • PET scan is position emission tomography whereas CT scan is computed tomography.
  • PET scan used radioactive tracers that cause emission of positrons. On the other hand, CT scan uses X-ray to create images.
  • It takes less time (maximum 5 minutes) to complete CT scan whereas it takes anything between 2 hours and 4 hours to complete PET scan.
  • The effective radiation ranges between 2-10mSV. In PET scan, radiation varies between moderate to high range.
  • CT scan can accurately outline the bones in the body. PET scanning can generate the processes of biological images in the body.
  • Being non-invasive, CT scan is painless though causes irradiation. PET scanning poses the risk of radiation.

PET scan vs MRI scan

The basic difference between these two is the way the images are conjured up. The scan images are extremely important for the doctors to diagnose the health problems and treat the same.

  • MRI or Magnetic Resonance Imaging scanning uses magnetic technology whereas PET scanning detects an element in the body to develop an image.
  • MRI scan uses different and highly powerful magnetic fields to align particular atoms in the internal body structure. A rotational movement is created at the heart of the atom by the magnetic fields. On the contrary, CT scan is based on positron emission triggered by radioactive tracers.
  • MRI scan can illustrate even the minor differences in the tissues of heart, brain, muscles and other body parts. PET scanning can create images of how a particular tissue or organ is currently functioning.

PET Scan Preparation?

Some precautions must be taken before going for a PET scan test. Here are some tips for PET scan preparation.

  • Pregnant ladies should consult with their doctors before opting for PET scan.
  • The breastfeeding mothers should not breastfeed their children for 24 hours after being administered an injection.
  • Comfortable dresses should be worn. Usually the individuals are required to wear a patient gown for such scan. You must not take any personal belonging to the room where the scanning will be performed. Removal of personal belongings is also required. The attendants in the room will guide you as to what to do and what not.
  • Strenuous activities must be avoided for 24 hours prior to the scheduled timing of scanning.
  • The patients are given liquid called barium. This liquid functions as a contrast agent. More contrast one drinks, the better an image will be generated. Barium could cause discomfort for some individuals.
  • Some patients can develop allergic reaction after having contrast. You should inform the attendants if you ever suffered an allergic reaction to use of any contrast in the past.
  • Never eat anything for four hours ahead of the scheduled time of scanning. No tea or coffee is allowed. However, you can take plain water without any flavor.
  • The physicians may recommend some extra precautions for the diabetic patients or those suffering from cardiovascular problems.

The way you will get  PET scan preparation depends on your personal medical conditions and history. PET scan cost in India ranges from 2000 rupees to 20000 rupees depending on different types and institutions.

Medically Reviewed By
Dr. Kaushal M. Bhavsar (MBBS, MD)Assistant Professor in Pulmonary Medicine, GMERS Medical College, Ahmedabad