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PET Scan: Procedure, Benefits, Uses and How Does Machine Work?


Positron Emission Tomography (PET) imaging or PET scan is a nuclear medicine imaging. Nuclear medicine images use a small quantity of a radioactive substance to detect, evaluate, or treat various diseases. These diseases include cancers, heart disease, endocrine, gastrointestinal or neurological diseases, and many other abnormalities. As nuclear exams can point out the molecular activity, they can identify diseases at their early stages. They are also helpful in monitoring whether a patient is responding to treatment.

The nuclear medicine imaging is a non-invasive procedure, with the only exception of intravenous injection, and they are usually painless. These scans utilize radioactive materials called radiopharmaceuticals or radiotracers to help the doctors to evaluate medical conditions.

Radiotracers are the molecules labelled with a small amount of radioactive compounds that can be detected in the PET CT scan. Radiotracers get accumulate in the tumour or the region of inflammation. They can also bind with specific proteins in the body. F-18 fluorodeoxyglucose (FDG), a molecule similar to glucose, is the most commonly used radiotracer. Cancerous cells are metabolically more active than normal cells and can absorb glucose at a higher rate. These higher rates can be seen in a PET CT scan. This allows the doctors to identify diseases before it may be detected on other imaging tests.

Depending upon the type of scan/exam, the radiotracer is injected, inhaled as a gas, or swallowed. It eventually accumulates in the region of the body under examination. A camera or imaging device detects radioactive emissions from the radiotracers. The machine produces precise images and provides molecular information. A PET scan analyses essential body functions such as metabolism and helps the doctors to ensure how well the organs and tissues are functioning.

Common Uses of PET Scan

Doctors recommend PET CT scans to:

  • Detect cancers
  • Evaluate prognosis
  • Determine whether cancer has been spread in the body
  • Estimate the response of treatment
  • Determining the re-occurrence of cancer
  • Assess tissue metabolism
  • Assess brain abnormalities, such as seizures, memory disorders, tumours, etc.
  • Analyses the effect of a heart attack on the various regions of the heart.
  • Parkinson Disease

What Does The Equipment Look Like?

A PET scanner is a large device with a round donut-shaped hole in the middle. It is very much similar to CT or MRI machine. There are multiple rings of the detectors inside the machine which record the emission of energy from the radiotracer in the body.

The CT scanner is a large donut-shaped machine with a short tunnel in the centre. The patient will be asked to lie on the examination table that slides in and out of the tunnel. The X-ray tubes and X-ray detectors are located opposite to each other in a ring known as a gantry and are rotated around the patient.

Combined PET/CT scanners look familiar to both the PET and CT scanners. A computer helps in creating images from the data obtained by the camera.

How Does The PET Scan Machine Work?

Nuclear medicine examination use a radioactive called radiotracer. This radiotracer is a chemical compound injected into the blood, swallowed, or inhaled as a gas. The compound assembles in the area of the body under the examination, where it gives off gamma-rays in the form of energy. Specialized cameras detect this energy and produce pictures with the help of computers.

PET Scan Procedure

Nuclear medicine imaging is normally for outpatients and hospitalized patients. The patients are advised not to eat for at least 4-6 hours before the scan. But they should drink plenty of water. Also, they may have to avoid caffeine for at least 24 hours before the scan.

The doctor or technician will inject a small amount of radiotracer into a vein. The tracer can also be taken orally or in other ways. It may take 30-90 minutes for the radiotracer to reach the targeted part of the body. Meanwhile, the patient will be asked to stay still and avoid talking.

The patient will need to wear a gown and remove their jewellery and other objects. When the patient is ready, they will be taken for the scan. They will be asked to lie down on the examination table. The table slides into a large tunnel-shaped hole of the scanner. The machine takes images during the scan. The whole process may take approximately two hours or more.

After the scan, the patients are asked to drink plenty of water to flush out the radioactive chemical out of the bodies.

PET Scan Benefits Vs Risks


  • Nuclear medicine imaging provides distinctive information including details on the anatomy and functions of the body. This is usually unattainable using other imaging procedures.

  • Nuclear medicine scans give the most useful diagnostic or treatment information for many specified diseases.

  • By identifying changes in the body at the cellular level, PET imaging detects the early onset of diseases before it is noticeable on any other scans.

Benefits of Combined PET/CT Scan:

  • Higher detail with greater accuracy; because both the tests are performed in one go without the change in positions.

  • Greater convenience for an individual as they undergo both PET and CT at one time.


  • It is not suitable for pregnant women, as the radioactive compound can harm the foetus.

  • An individual may suffer a very mild allergic reaction from a radioactive compound.

Diagnostic and Pathology Tests Available At House of Diagnostics (HOD).





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PET Scan: Procedure, Benefits, Uses and How Does Machine Work?
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PET Scan: Procedure, Benefits, Uses and How Does Machine Work?
Read about PET MRI and PET CT benefits, uses, how machine work and procedure. A positron emission tomography, also known as a PET scan, uses radiation to show activity within the body on a cellular level.
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