What is Pet Scan?

Posted By: admin | Posted on: 15 February, 2018 04:54 am

What Is PET Scan And How Does It Work?

A simple answer to what is position emission tomography (pet scan) : PET scan is a type of imaging evaluation which utilizes small amount of radioactive material called trace so as to observe if the organs and tissues in the part of the body are intact or they have been affected by a disease.

This is why it can be used as an important diagnostic tool to assess the occurrence of a disease by detection at a very early stage so the possibility of treating it will be easier.

What is PET scan, pet scan meaning
PET Scanner – Monitor                                                 Image Credits: shutterstock.com)

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PET vs MRI or CT?

The main difference between PET and other imaging tests such as computed tomography (CT) scan or Magnetic Resonance Imaging (MRI) are that the PET reveals metabolic changes that take place within the cells of an organ or tissue eg. PET cancer. Hence, enables the Radiologist to tell the difference between living and dead tissue. Otherwise between benign (non-cancerous) and cancerous abnormalities at very early stage. CT or MRI however, detects abnormal changes only when they begin to occur in the structure of organs or tissues, which are events that manifest or take place a little later.

Which body parts are commonly scanned by PET?

  • Brain
  • Heart
  • Breasts
  • Lungs

 Why is it necessary to perform this scan?

  • Your doctor may suggest you should have this scan to enable them to evaluate your blood flow, oxygen intake. Thus, indicating whether the chemical process that generates energy in the cells are operating properly.
  • This scan result also reveals if metabolism of your organs and tissues is occurring normally or abnormally.
  • This scan can reveal how cancer cells metabolize, and whether cancer has spread (metastasized) from where it originated or began.

Therefore, this scan results provide the doctor with precise knowledge about specific disease conditions such as:

  • Brain tumors
  • Seizures
  • Brain memory disorders
  • Cancer in lungs
  • Congestive heart failures (when the heart is unable to pump enough blood for the body’s needs)
  • Coronary heart disease (CHD), which is blocking of the blood vessel that nourishes the heart

PET scans show if a patient is responding to treatment or not, as follows:

  • Checking responsiveness to treatment of brain, heart, breasts and lungs diseases by routine follow-up scans.
  • Checking the effectiveness of a current treatment. Hence, if it is not working, the doctors will find ways of helping the patients to respond to therapy by changing their medication or treatment method.
  • Checking if a disease had returned (recurrence) by follow-up routines, after it had been completely treated.

PET Procedure:

  • A very small amount of radioactive substance called a trace (an example of commonly used drug is called fluorodeoxyglucose; FDG) is introduced into your blood 1 hour before the scan. This is however done by inserting a needle into the arm vein and administering the tracer with a syringe through the needle.
  • The trace then flows with the blood while slowly accumulating in the tissues and organs. This usually takes about 1 hour.
  • The Radiologist Technologist will then ask you to empty your bladder and lie on a flat scanner bed attached to the scan shown below:


What is pet scan, pet scan meaning



  • The doctor will slide you into the scanner for 20-30 minutes. The scan will detect signal emitted by the trace which had built-up in your organ.
  • The Technologist will ask you to remain still on the bed while performing the test, because of movement it produces blurry images, making reading and interpretation of the image difficult.
  • A 3D computer connecting the scanner records the signals. Use them to create images which therefore, a radiologist specialist reads and interprets.
  • After taking all the images, you will be slid out of the scanner, which means the test is complete.
  • In certain disease conditions, the trace build-up and metabolism is either:
    • Abnormally high, (called hotspot) as in the case of cancer, because the cells in that organ location are overgrowing, or
    • Very low, as in Alzheimer’s disease, because most of the cells have been destroyed in the organs.
  • Cancer cells have a higher metabolic activity rate than normal cells. Because of high level of chemical activity, cancer cells show up as bright spots on PET scans.

These differences, compared to normal trace uptake and metabolism make it possible to detect which part of an organ is affect by a disease.

What are the risks involved with PET?

  • There has been no reports of side effects therefore, it is safe.
  • Nobody has reported pain or discomfort. Although, a prick of needle used to administer tracer might cause a bit of redness swell.
  • The trace introduced into your body is safe since, it has very low radioactivity which is not sufficient to cause any ill health.
  • After PET Scan, how long are you radioactive? The radioactivity of the tracer disappears from the body 2-10 hours after PET procedure. Although, just make sure you drink plenty of fluids for the rest of the day to flush it out with your urine.
  • As a safety precaution, don’t hold or be in close contact with children until the day after your test.

How is the Radiologist able to tell the difference between normal and diseased organ from the PET?

This is something we all wonder about; how the Specialist is able to tell differences in the scanned imaging before our Primary Health Care doctor receives the report. The Radiologists who interpret the imaging are very well trained and have lots of experiences.

Firstly, Image 1 is the scan result of a section of the brain. It shows the difference between normal or healthy (Left) individual. Also, how the neuronal cells (the brain special cell) started getting to destroy (middle) until so much of the cells have died and disappeared from that region of the brain resulting in Alzheimer’s disease (right).

                                                                                                     Image -1

Pet scan meaning,pet scan near me
PET scan of Brain


Secondly, Image-2 is a scan – PET of the lung. It is showing how the Left Lung is nice and clear (healthy) but the Right Lung has a tumor (two red arrow). The Radiologist is able to tell if the tumor is cancerous because of how that part of the lung underwent tracer uptake and abnormally high metabolic changes (hotspot).


pet scan meaning, pet scan in mumbai
PET scan -Lungs

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How to find Pet scan centers near me ?

Click on the links below to get the MRI scan centres at various locations with cost and price comparison option :


Lung Cancer PET  Scan

Whole Body PET  Scan Cost And Procedure Information

PET and The Heart

Metabolic Imaging: How PET Scans are changing Oncology