Positron Emission Tomography ( PET ) is an advanced nuclear imaging technique which is used to study the blood flow, use of oxygen by the human body tissues and to study the metabolism of organs of the body with the help of a radioactive substance or a radionucleotide . Positron emission tomography commonly referred to as PET or PET scan is a fairly new imaging technique in the field of nuclear medicine, but has proved to be very useful in diagnosing abnormalities in the brain, heart, stomach and other organs of the body and also in following up the progress after a treatment is started.
What is the principle of a PET scan ?
PET scan is nuclear imaging procedure which utilizes the gamma rays to image the human organs and study them. These gamma rays are produced by the interaction of a positron and electron which collide and two gamma rays are produced which travel in the opposite direction and are picked up by a dome shaped machine which absorbs these gamma rays and they are later converted into images. The interaction of the positron and electron occur because of a radionucleotide or a tracer which is injected into the patient’s body or into the specific organ which needs to be imaged. Most common tracer which is used for a PET scan is Flouride (F-18), as it uses glucose for its metabolism and glucose converting it into fluorodeoxyglucose which produces very clear images of the organ being imaged. Other tracers which can be used are carbon, oxygen, nitrogen and gallium.
How does a PET scan machine look like ?
A PET scan machine resembles a round, dome or doughnut shaped machine, which has an examination table on which the patient is made to lie down during the examination. The part of the body which needs to be imaged is brought in focus and images are obtained when the gamma rays are emitted because of the interaction caused by the tracer used in the human body.
When is a PET scan advised ?
A PET scan is one of the most advanced techniques for imaging of the human body and its organs. When PET scan was newly introduced it was primarily used for the imaging of the brain, heart, lungs and breast to diagnose cancer and its spread. The most common uses of a PET scan are mentioned as under:
- To diagnose brain disorders like Alzheimer’s disease, Parkinson’s, type of epilepsy, Huntington’s disease and diagnose conditions affecting the brain such as memory loss, forgetfulness, loss of control over body movements
- To aid in the surgical procedure of involving the brain to locate the surgical site
- To help in diagnosing cancer, and also recurrent cancer or its spread to other parts of the body.
- To monitor the treatment of cancer and recovery after the treatment is started
- To identify abnormalities in the lungs which cannot be easily detected on an X-ray or by a CT scan
- To study deep seated lesions in lungs, stomach, gastrointestinal system and the brain
- To guide the surgical treatment in case of traumatic injuries
When a PET scan is not advised ?
There’s absolute no contraindication of a PET Scan as the amount of radiation used is much lesser than when compared to conventional radiology techniques. It is still not advised to undergo a PET scan during pregnancy or breast feeding unless it is mandatorily required. Since the PET scan uses glucose to study the metabolism, uncontrolled diabetes is a condition where it is not advised. Also, consumption of caffeine, alcohol or tobacco should be avoided at least 24 hours before the procedure as they might interfere with the test. It is also advised to tell your doctor if you are taking any medication and if that needs to reviewed before the test. It is also advised to tell your doctor if you are allergic to any medication or dyes which will be used during the scan. Also if you are claustrophobic it is important to inform your doctor about the same.
How do you prepare for a PET scan ?
Once your treating doctor has advised you to undergo a PET scan you will be asked to abstain from any caffeine, alcohol and tobacco consumption at least 24hours before the procedure and any food and liquids 4-6 hours before the scan is supposed to start. You will be asked to wear comfortable clothing and remove any jewelry during the test. The radiologist or nuclear medicine specialist with a technician will inject the radioactive tracer about an hour before the scan is supposed to start. You will be asked to empty your bladder before the test as you will not be allowed to leave the test in between.
How is a PET scan performed ?
As you are prepared for the scan you will be taken to the PET scan room where you will be made to lie on the table of the scanning machine. Occasionally some images are taken before the radiotracer is through your blood. After the radiotracer is introduced into the body through an IV (intravenous) line, you will be made to lie down for about an hour till the tracer is absorbed by the cells of the body. Once you are ready for the scan the technician or your radiologist will start the scanning procedure. During the scan procedure the gamma rays which are produced are picked by the detectors in the PET machine and are then transferred to the computer/monitor in the form of image signals. Once the scan is completed your IV line will be removed and also urinary catheter is any was used. You will be asked to drink lots of water during the next one day to flush out any traces of the radioactive material used.
Who reports a PET scan ?
A PET scan is reported by a nuclear medicine specialist or a radiologist who is trained in nuclear medicine.
When is the PET scan report made available ?
The PET scan reporting is done by the specialist in nuclear medicine and depending upon the scan a brief reporting is done to your doctor after your scan is completed and the same scans are made available for your doctor also to check. Hard copies or CD of the PET scan with a detailed report are given as per the hospital or laboratory policy.
Can you go home after the PET scan ?
PET scan is performed on outpatient basis and you will be allowed to go home after the test is completed.
What are the benefits of the PET scan ?
PET scan is of great used when a disease or cancer needs to be diagnosed at a very early stage as a PET scan studies and images the metabolism of individual cells of the human body and any initial abnormality/changes in any cell, tissue or organ can be detected. So PET scan is effective in diagnosing spread of cancer, recurrence of cancer and diagnosing diseases which are not easily diagnosed with other imaging techniques.
Are any risk and complications associated with PET scan ?
PET scan is a rather safe procedure and the amount of radiation used is also much lesser. The complications can only be related to the dye or tracer which is used, if any allergic reaction occurs in reaction to it. It is also advised to ask your treating doctor about the risks, benefits and suitability of the scan for you.
Disclaimer: The content provided here is meant for general informational purposes only and hence SHOULD NOT be relied upon as a substitute for sound professional medical advice, care or evaluation by a qualified doctor/physician or other relevantly qualified healthcare provider.
