What is PET (Positron Emission Tomography) scan?
An imaging test that can reveal the proper functioning of the organs and tissues is known as positron emission tomography (PET). This test makes use of a small quantity of radioactive material that is required for showing the functioning of the organs and tissues.
The delivery method and the type of radioactive material to be used depend on tissue or organ that is being considered by the PET scan. The injection of this radioactive material can be done into a vein or it can also be swallowed or inhaled.
The accumulation of radioactive material can be majorly seen in those areas where there are high levels of chemical activity. Brighter spots on a PET scan can be seen when these areas correspond to the areas of disease. This scan helps in evaluating a number of conditions such as cancer, neurological problem and heart disease.
What does a PET scan show?
- It can show the difference between active cancer tissue and scar tissue
- The presence of a cancer can also be seen
- It can also decide an appropriate treatment for cancer
- It can also determine the stage of cancer
- It can show the spread of the cancer to different parts of the body
- It can show how the treatment for cancer is working
- The presence of a lump in cancer can also be seen
The use of PET scan for Doctors
A PET scan is useful in staging and diagnosing a number of cancers. It can be sued for –
- Evaluating and staging of recurrent bowel cancer
- Staging of Hodgkin’s lymphoma and Non-Hodgkin lymphoma
- Staging of non-small cell lung cancer
Following conditions can be examined with the help of PET scans that include –
- Heart Disease : The specific scarred or damaged parts of the body can be easily detected by a PET scan. Improper functioning of the heart can also revealed by this scan.
- Epilepsy : The affected part of the brain caused by epilepsy can also be revealed through a PET scan. The doctors through this scan can determine an appropriate treatment for epilepsy. People who have first seizure are advised for CT or MRI scans.
- Medical Research : A crucial data can be collected by using PET scan especially for those researchers who studies the functioning of the brain.
- Cancer : The specific cancer, its stage and its spread to different areas of the body can be revealed by performing PET scans. This helps in determining the best treatment and it can also indicate the effectiveness of ongoing chemotherapy. The responsiveness of tumor to the treatment in case of lung cancer can also be revealed by this scan.
- Alzheimer ’s disease : Alzheimer disease can be easily diagnosed with the help of a PET scan. The accuracy of the diagnosis is improved by this scan especially in the case of dementia that has often been assumed as Alzheimer disease. The diagnosis helps in measuring the uptake of sugar in the brain.
How does a PET scan work?
Radiotracer : The first step before beginning a PET scan is to use a machine named cyclotron that helps in producing a radioactive medicine. A natural chemical that can be ammonia, glucose or water is tagged with the radioactive medicine. The name given to this tagged natural chemical is radiotracer. The insertion of this tracer is then done into the human body. The radiotracer will then travel to different areas within the body that makes use of the natural chemical. Fluorodeoxyglucose or FDG is a type of radioactive drug that shows the presence of cancers as cancers use glucose differently from normal tissue.
Detecting Positrons : The energy emitted by a positron (a positively charged particle) can be detected by a PET scan. Positrons are made when the radiotracer is broken down within the body of patient. This looks like a 3-dimensional image on a computer screen.
PET scan Images : The image will reveal the functioning of the different parts of the body when they are breaking down the radiotracer. The various levels of positrons will be displayed according to color and brightness by a PET image. The examination of the complete image is the done by a radiologist.
Importance of a PET scan
A PET scan helps in detecting the abnormalities of those areas of the body where chemical activity is happening. This scan is most effectively used for those people who have brain disorders, cancer or heart disease.
Brain disorders : The different areas of the brain having majority of activities while performing various tasks can be revealed by a PET scan. Specific brain abnormalities can also be evaluated by this scan that include –
- Seizures
- Memory disorders
- Tumors
Cancer : Bright spot of cancer cells can be seen in a PET scan due to their high metabolism rate as compared to normal cells. The scan helps in determining –
- Whether the cancer has recurred
- The response of the cancer to the treatment
- The spread and extent of some cancers
A proper interpretation of the PET scans is required as some non-cancerous conditions may look like cancer. It is also possible that certain cancer types may also not appear on PET scans. Following are the different cancer types that will appear on PET scans such as –
- Thyroid
- Brain
- Pancreatic
- Lymphoma
- Breast
- Melanoma
- Lung
- Cervical
- Esophageal
- Colon
Procedure of PET scans
A little quantity of radioactive material is used in a PET scan. The tracer is then given by the means of a vein that is located within the elbow. The tissues and organs are then collected as the tracer is traveling through the blood. A patient is required to wait for about 1 hour as the body is absorbing the tracer. A patient then lies down on the table that slides into a big scanner. The signals from the tracer are then detected by a PET scan. These signals are then changed into 3-D images by the computer. A doctor then can read these images that are displayed on a monitor. Any physical movement of patient during the teat can cause errors and blur images. After the procedure, no problems can be seen in the position, size, or shape of an organ.
Cost of a PET scan
A PET scans has proved itself as an efficient tool for diagnosing the cancer. The cost of a PET scan in India varies from Rs 7000 in case of government set-up and Rs 13,000 in case of private set-up. The radioactive material FDG determines the cost of PET scan.