Consultant Surgical Oncologist & HIPEC Specialist


Some of my patients are concerned more when I ask them to the PET CT scan because they haven’t heard much about this test & also some of them, they’ve heard that these types of tests expose them to more radiation. I’ve put together answers to some commonly asked questions about the PET CT Scan to ease my patients’ minds before going for PET scan.

What is a PET scan?

A positron emission tomography (PET) scan is a type of imaging test that helps doctors see how the organs and tissues inside your body are actually working.

Why PET CT scan is done?

PET scan is an effective way to examine the chemical activity in parts of your body. It may help identify a variety of conditions, including many cancers, heart disease and brain disorders. … A PET scan or a combined CTPET scan enables your doctor to better diagnose illness and assess your condition

How PET CT Scan work?

  • In a PET scan, a very small dose of a radioactive chemical, called a radio tracer, is injected into the vein of your arm. The tracer travels through the body and is absorbed by the organs and tissues that are being studied.
  • Then, 45 minutes after the injection, you will lie down on a flat examination table that is moved into the center of a PET scanner, a doughnut-shaped machine. This machine detects and records the energy given off by the tracer substance.
  • With the aid of a computer, this energy is converted into three-dimensional pictures. A physician can then look at cross-sectional images of the organ from any angle in order to detect any problems

Why PET CT scan used commonly in Cancer now a days?

Cancer cells have a higher metabolic rate than noncancerous cells. Because of this high level of chemical activity, cancer cells show up as bright spots on PET scans. For this reason, PET scans are useful both for detecting cancer and for:

  • seeing if the cancer has spread
  • seeing if a cancer treatment is working
  • checking for a cancer recurrence

However, these scans should be read carefully by your Oncologist doctor, as it’s possible for noncancerous conditions to look like cancer on a scan. It’s also common for solid tumors to fail to appear on PET scans.

How does the PET scan compare to other tests?

PET scans show metabolic changes occurring at the cellular level in an organ or tissue. This is important because disease often begins at the cellular level. CT scans and MRIs can’t reveal problems at the cellular level. This change in the metabolism may be seen before a physical change can be seen on a CT or MRI.

How long does a PET scan take?

After the radiotracer is injected into a vein, it usually takes up to one hour to travel throughout the body and be absorbed into the organs or tissues that are being examined. The PET scan itself may take another 30 to 60 minutes.

Depending on which organ is being examined, there may be other tests and dyes or chemicals used that may increase the appointment time to two to three hours.

How should I prepare for a PET scan?

A PET scan is usually done on an outpatient basis (you will go home after the procedure). Your doctor will give you detailed instructions on how to prepare for your scan, including what you may or may not eat or drink before your exam.

Here are some important points to note before you undergo the scan:

  • Tell your doctor of any medications—prescription and over-the-counter—that you are taking, as well as any herbal medications and vitamins. If you are taking certain medications or have certain diseases, such as diabetes, you will receive specific instructions about preparing for your scan.
  • Most patients are told not to eat anything for at least six hours before the scan. Heart patients are also told to not take any product with caffeine for at least 24 hours.
  • You should wear comfortable clothes to your appointment. You may be asked to change into a hospital gown during the test

Is PET CT scan safe?

The PET scan involves radioactive tracers, but the exposure to harmful radiation is minimal. As Experts says, the amount of radiation in the tracer is small, so the risks to your body are low. Still, it’s a good idea to discuss possible risks with your doctor. The risks of the test are also minimal in comparison to how beneficial the results can be in diagnosing serious medical conditions.

How soon will the PET scan results be available?

A radiologist who has specialized training in PET scans will interpret the images, write a report, and deliver the results to your doctor. This process usually takes 24 hours

Is it safe to be around someone after a PET scan?

During a positron emission tomography (PET) scan, your body’s tissue will be exposed to radiation. … Close contact with pregnant women, babies or young children should be avoided for a few hours after having a PET scan

People with allergies and other health conditions

It’s possible to have an allergic reaction to the tracer. People who are allergic to iodine, aspartame, or saccharin should alert their doctor..

People who are pregnant

Radiation is not considered safe for developing fetuses. If you’re pregnant or think you may be pregnant, you should not get a PET scan.

After the procedure

After the test you can carry on with your day as usual, unless your doctor tells you otherwise. You’ll need to drink plenty of fluids to help flush the tracer from your body.

Dr Vimalathithan , senior Oncologist in Chennai says about the PET CT scan , It is an advanced, non invasive, painless “state-of-the-art” molecular Imaging technology used now a days in field of Oncology .

For any test, it’s always important to look at the risks and the benefits. In most cases especially in PET scan , the benefit of finding cancer or confirming the need for surgery outweighs the risk from radiation exposure from a PET /CT scan.so people no need much concern about the minimal risk  when planning for PET Scan .Hope I have discussed the common facts about the PET scan procedure in view of patient concern, to ease my patients’ minds before going for PET scan.