What is PET scan?

Positron emission tomography (PET) is a sophisticated radiology technique that has been used to analyze different body tissues to distinguish diseases.PETcan also be used to monitor the progress of such diseases in treating. WhilePETis most widely used in the fields of neurology, oncology and cardiology, applications are currently being studied in other areas.

PET is a type of procedure in nuclear medicine. This indicates that during the treatment, a small amount of a radioactive material, called a radionuclide (radiopharmaceutical or radioactive tracer), is used to aid in the examination of the tissue being studied. In particular,PETstudies examine the metabolism of a specific organ or tissue, so that knowledge on the organ or tissues physiology (functionality) and anatomy (structure) and its biochemical properties are evaluated.PETcan thus detect biochemical changes in an organ or tissue that can define the initiation of a disease process before other imaging methods such as computed tomography (CT) or magnetic resonance imaging (MRI) can show anatomical changes related to the disease.

PET is most widely used by oncologists (doctors specializing in cancer care), neurologists and neurochirurgians (doctors specializing in brain and nervous system care and surgery), and cardiologists (doctors specializing in cardiac treatment). However, this technique is starting to be used more commonly in other areas as developments inPETtechnology continue. Along with otherDiagnostic Testssuch as computed tomography (CT),PETis often used to provide more reliable knowledge about malignant (cancerous) tumours and other lesions. The combination ofPETandCTdemonstrates a particular promise in the diagnosis and treatment of several cancers.

PET procedures are performed in dedicatedPETcentres. The equipment is very expensive. However, a new technology called gamma camera systems (devices used to scan patients that have been treated with small quantities of radionuclides and are currently in use for other procedures in nuclear medicine) is now being modified for use inPETscanning. The gamma camera system can complete a scan faster than a conventionalPETscan, and at less expense.

How doesPETscan work?

PET acts to detect positrons (subatomic particles) released by a radionuclide in the organ or tissue being investigated by using a scanning system (a computer with a large hole at its centre). The radionuclides used inPETscans are created by adding a radioactive atom to chemical substances which the individual organ or tissue use naturally during its metabolic process. For instance, a radioactive atom is added to glucose (blood sugar) to produce a radionuclide called fluorodeoxyglucose (FDG) in brainPETscans, since the brain uses glucose for its metabolism. FDG is used extensively inPETscans. Depending on the intent of the scan, other substances can be used forPETscanning. Where blood flow and perfusion are of concern to an organ or tissue, the radionuclide may be a form of radioactive oxygen, carbon, nitrogen or gallium. The radionuclide is administered via intravenous ( IV ) line into a vein. ThePETscanner then travels slowly across the part of the body that is being investigated. The radionuclide breakdown emits positrons. Gamma rays are produced during positron emission, and the gamma rays are then detected by the scanner. A computer analyzes the gamma rays and makes use of the knowledge to create a picture map of the studied organ or tissue. The amount of radionuclide contained in the tissue determines how brightly the tissue appears on the picture, and shows the degree of function of the organ or tissue. Other potential associated procedures include computed tomography (CT scan) and magnetic resonance imaging ( MRI). For more details, please see these procedures.

Reason for thePETscan procedure?

In general,PETscans can be used to determine the existence of the disease or other diseases in organs and/or tissues.PETcan also be used to measure the function of such organs like the heart or brain. Another use ofPETscans is in evaluating cancer care. More precise explanations forPETscans include the following but are not limited to:

• To diagnose dementias such as Alzheimers disease, as well as other neurological disorders such as Parkinsons disease (a progressive nervous system disorder in which fine tremor, muscle weakness, and an unusual form of gait are observed), Huntingtons disease (an inherited nervous system disease that induces increased dementia, strange involuntary movements, and irregular posture)
• The relevant surgical site to be found before brain surgery
• To examine the brain after trauma to identify the hematoma (blood clot), bleeding, and/or perfusion (blood and oxygen flow)
• To detect cancer spread from the original cancer site into other parts of the body
• Assessing the success of cancer therapy
• To measure myocardial perfusion (heart muscle) as an aid in assessing the effectiveness of a therapeutic procedure to enhance myocardial blood flow
• To classify more lung lesions or masses found onX-Raytorso and/or chest CT
• Helps control and treatLung Cancerby staging lesions and monitoring the development of lesions during treatment
• To detect tumour recurrence earlier than with other methods of diagnosis

Your doctor might come up with other reasons to prescribe aPETscan.

Risks of thePETscan procedure?

For the operation, the amount of radionuclide inserted into your vein is minimal enough to not require precautions against radioactive radiation. The radionuclide injection may cause some mild discomfort. Allergic radionuclide reactions are uncommon, but they can occur. For certain patients, it can cause certain discomfort orPainto have to lie still on the scanning table for the duration of the operation. Patients resistant to or vulnerable to drugs, contrast dyes, iodine, or latex should inform their doctor. If you are pregnant or think you might be pregnant, you should alert your health care provider from aPETscan, because of the possibility of damage to the foetus. If you are lactating, or breastfeeding, your health care provider should be aware of the possibility of radionuclide contamination of breast milk. Depending on your particular medical condition, there may be other dangers. Be sure to speak with your doctor about any questions prior to the operation.

The accuracy of aPETscan can be compromised by certain variables or conditions. These considerations include the following but are not limited to:

• High levels of blood glucose among diabetics
• Ingested caffeine,Alcoholor nicotine within 24 hours of the treatment
• Medicines, such as morphine, sedatives and tranquilizers

If any of the above circumstances can apply to you, inform your doctor.

Before thePETscan procedure?

• Your doctor will describe the procedure and will give you the opportunity to ask any questions you might have about the procedure.
• You will be asked to sign a consent form allowing you to do the procedure. Carefully read the document, and ask questions if there is anything ambiguous.
• If you are allergic to latex and/or sensitive to medicine, contrast colouring, or iodine, notify the radiologist or technologist.
• Fasting is usually needed for a specified period of time before the operation. Your doctor will send you specific instructions in advance as to how many hours you will deprive of food and drink. You will also be told by your doctor about the use of drugs before thePETScan.
• Notify your health care provider of all drugs (prescribed and over-the-counter) and herbal supplements you take.
• You should not drink anyAlcoholor caffeine, or useTobaccofor at least 24 hours before the treatment.
• If you are a diabetic who uses insulin, you might be advised to take the insulin dose several hours before the treatment, with a meal. Your doctor will give you detailed instructions depending on the condition you are in. A fasting blood sugar test can also be obtained before the operation. If the blood sugar is high, insulin may be given to lower the blood sugar.
• Your doctor may order a further detailed preparation based on your medical condition.

Preparation before a PET scan

You need to start preparing for the PET scan a few days before the scan. You will get the list of things to do for the scan. Doctors advise not to avoid any strenuous activity for 24 to 48 hours before the scan. You don't have to worry because your medical team will help you. They will ask you some questions. Like if you have any allergies or any other medical conditions like diabetes. You should tell them if you are pregnant or breastfeeding. If you are claustrophobic then you must inform your doctor.

During the PET scan procedure?

PET scans can be conducted on an outpatient basis or as part of your hospital stay. Procedures can differ according to your condition and the practices of your doctor.

APETscan normally follows the process:

• You will be asked to remove any clothes, jewellery, or other items that could interfere with the scan. If you are asked to remove your pants, you will get to wear a robe.
• Before beginning the procedure, you will be asked to clear your bladder.
• For radionuclide injection one or two intravenous ( IV) lines will be initiated in the hand or arm.
• Some forms of abdominal or pelvic scans can involve the insertion of a urinary catheter into the bladder to drain urine throughout the procedure.
• In certain cases, an initial scan can be done before the radionuclide is injected, depending on the type of research being conducted. Within the scanner, you will be put on a padded table
• They will inject the radionuclide into your vein. The radionuclide would be able to accumulate for about 30 to 60 minutes in the organ or tissue. At that time you can stay in the room. You would not be harmful to anyone because the radionuclide releases less radiation than a normalX-Ray.
• The scan will begin after the radionuclide has been absorbed for the corresponding period of time. The scanner travels slowly across the section of the body being examined.
• Upon completion of the scan, the IV line will be removed. If a catheter is used, it will be removed.

Although thePETscan itself does not cause pain, having to lie still for the duration of the procedure can cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure, such as operation. The technologist will use every possible measure of comfort and complete the operation as soon as possible to reduce any discomfort orPain.

After thePETscan procedure

When you get up from the scanner table, you can step slowly to prevent any dizziness or light headedness from lying flat for the duration of the operation. After the test, you will be advised to drink plenty of water and periodically empty your bladder to help flush the excess radionuclide out of your body for 24 to 48 hours. Any symptoms of redness or swelling will be tested at the IV Site. If you experience any discomfort, redness, and/or swelling at the IV site after returning home after your treatment, you should alert your doctor as this may suggest an infection or some kind of reaction. After the procedure, your doctor can give you additional or alternative instructions, depending on your particular situation.

Advantages of PET scans in the context of cancer:

Early detection: PET scans can detect cancer at an early stage, even before it becomes visible on other imaging modalities such as CT (Computed Tomography) or MRI (Magnetic Resonance Imaging). This early detection allows for prompt intervention and potentially improves treatment outcomes.

Whole-body imaging: PET scans can provide a comprehensive view of the entire body, allowing for the detection of cancer that may have spread (metastasized) to other organs or tissues. This is particularly useful for staging cancer and determining the extent of the disease, which helps guide treatment decisions.

Accurate assessment of tumor activity: PET scans utilize radiotracers, which are substances that emit positrons (positively charged particles) when injected into the body. These radiotracers are often designed to target specific molecules associated with cancer cell activity, such as increased glucose metabolism. By measuring the accumulation of radiotracers in tissues, PET scans can provide information about the metabolic activity of tumors. This information helps differentiate between benign and malignant tumors and can be used to monitor treatment response.

Treatment planning: PET scans are valuable in treatment planning, particularly for radiation therapy. By accurately identifying the location and extent of cancerous tissues, PET scans help in determining the precise areas that need to be targeted with radiation. This improves the effectiveness of treatment while minimizing damage to healthy tissues.

Monitoring treatment response: PET scans can be used to assess the response to cancer treatment, such as chemotherapy or radiation therapy, at an early stage. By comparing pre- and post-treatment PET images, doctors can evaluate the metabolic changes in tumors and make necessary adjustments to the treatment plan. This allows for personalized treatment strategies, optimizing the chances of successful outcomes.

Detection of cancer recurrence: PET scans are highly sensitive in detecting cancer recurrence. By identifying the presence of active cancer cells, even in small amounts, PET scans can help determine if cancer has returned after treatment. Early detection of recurrence enables timely intervention, potentially improving patient outcomes.

It's important to note that while PET scans offer several advantages, they are often used in conjunction with other imaging modalities and diagnostic tests to provide a comprehensive evaluation of cancer. The interpretation of PET scan results requires expertise and should be done by qualified medical professionals.