PET Scan

What are PET scans?

Positron emission tomography (PET) scan, or PET imaging, is a type of imaging test that provides valuable information about the functioning of organs and tissues within the body. It is commonly used in diagnosing, staging, and monitoring various medical conditions, including cancer, heart disease, and neurological disorders.

A PET scan involves the use of a safe and injectable radioactive chemical known as a radiotracer, along with a device called a PET scanner. The radiotracer substance gets absorbed by diseased cells or tissues within the body. By detecting areas that accumulate a significant amount of the radiotracer, the PET scanner can help identify abnormalities.

Who performs PET scan?

PET scans are typically performed by doctors who specialize in nuclear medicine or radiology. Nuclear medicine technologists are trained doctors who operate the PET scanner and administer radiotracers to patients.

What are the uses of PET scans?

PET scans are used to:

  • Detect and stage cancer: PET scans can help identify the presence and location of cancerous cells within the body. They can also determine the extent of cancer spread and aid in treatment planning.
  • Assess cardiac health: PET scans can evaluate the blood flow to the heart, assess the function of the heart muscle, and identify areas of damaged or scarred tissue.
  • Evaluate neurological conditions: PET scans can provide information about brain activity, helping diagnose and monitor conditions like Alzheimer’s disease, epilepsy, and brain tumours.
  • Monitor treatment response: PET scans can track the effectiveness of ongoing treatments, such as chemotherapy or radiation therapy.

How does a PET scan work?

PET scans are a form of nuclear medicine imaging that involves using small and safe amounts of radioactive material, known as radiotracers, administered through an intravenous (IV) injection.

During a PET scan, the radiotracer is taken up by diseased cells in the body, resulting in higher radiation accumulation levels than healthy cells. These areas with increased radioactivity, referred to as “hot spots,” are detected by the PET scanner and it generates images of the affected tissues.

Preparing for a PET scan

PET scans are typically performed as an outpatient procedure, allowing the patient to return home on the same day. Here are some general guidelines:

  • Inform the doctors with an updated list of medications, vitamins, supplements, and allergies.
  • Inform the doctors about the pregnancy and breastfeeding.
  • The patient is advised to undergo a creatinine test (blood test) before the scan.
  • Refrain from eating anything for six hours before the test (unless advised differently for diabetes).
  • Drink only water before the scan.
  • Avoid consuming caffeine for 24 hours prior to the scan, If the patient is undergoing heart-related tests.
  • Dress comfortably and avoid wearing metal accessories such as jewellery, eyeglasses, dentures, and hairpins.

During the PET Scan Procedure

  • A safe amount of a radioactive drug will be administered through an intravenous (IV) injection.
  • An IV injection of contrast dye may be administered to enhance CT image quality.
  • The patient will be positioned on an exam table that moves in and out of the doughnut-shaped PET/CT scanner, with a tunnel opening measuring about 30 inches in diameter.
  • Maintaining stillness throughout an approximately 30-minute scan is crucial, as movement can distort images, impacting result accuracy.
  • The scanner will emit buzzing and clicking sounds while capturing necessary images, which are normal aspects of the scanning process.
  • Following the scan, a technologist will assess the obtained images to ensure they exhibit clarity and focus.

In most cases, the patient can resume regular activities immediately after the scan.  After a PET scan, it is recommended to drink plenty of water to help flush out the radioactive substance from the body. 

A specialized radiologist will review the images and prepare a detailed report following the PET scan. This process typically takes around 24 hours. The report will then be sent to the referring doctor, who will discuss the findings with the patient during a follow-up appointment.

In which situations are PET scans avoided?

A few contraindications or factors may make a PET scan unsuitable. These include:

  • PET scans should be avoided by women who are pregnant or breastfeeding. The radiation used in PET scans can potentially harm the developing foetus and can be passed to an infant through breast milk.
  • Some individuals may have allergies or adverse reactions to the radiotracer used in PET scans, necessitating prior notification to the doctor who is going to perform the PET scan.
  • For individuals with diabetes, the absorption of sugar in the radiotracer used during PET scans may be impacted, potentially affecting the accuracy of the scan results. To address this, the doctor may recommend modifying diet and medications before the test.

In general, PET scans are safe and rarely cause problems. The amount of radiation in the radioactive tracer is very low. It does not stay in the body for long. Drinking lots of water after a PET scan would be best to help flush the radioactive drug from the body.


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