Positron emission tomography or PET is a non-invasive test that creates a nuclear image of any part of the body, including the lungs and heart. To do this, a radiotracer, also known as a radionuclide, is injected into the blood. When the tracer mixes with blood, it is taken up by muscles and into organs like the heart. The scan determines if the heart is healthy by showing blood flow. For example, arteries narrowed or dead cells from a previous heart attack can be diagnosed using PET scans.
Basic mechanism of PET scanning
To perform a PET CT test, do the following:
- The tracer is injected into the bloodstream. It is an organic compound found in the body that is tagged with a trace amount of radioactive material. Generally, glucose, ammonia or water is used.
- Once inside the body, the tracer produces gamma energy rays.
- The beam is picked up by a detector that goes around the body and sent to the computer. The system converts the signal into a crisp image.
- The complete image is created by combining pictures of thin slices of the heart. Each slice is taken from different directions and angles to produce a holistic and 3D image.
- Healthcare professionals can use images to determine heart function. If the muscles are strong, the tracer will be absorbed well. On the other hand, if the heart cannot survive or if there are dead cells, the tracer is not used. On PET scans, tracer absorption levels are displayed as different color or brightness gradients.
Need for PET testing
Currently, PET scanning is one of the most accurate steps available to detect:
- Coronary artery disease
- Low blood flow
- Damaged tissue
- Dead tissue
Depending on the results of the scan, your doctor can recommend the following heart surgery:
- Percutaneous coronary intervention (PCI)
- Coronary artery bypass surgery
- Surgery can restore proper blood flow to the heart.
PET scan procedure
MRI scans of pets can be done in hospitals or diagnostic labs. It is carried out by nuclear medicine technicians and doctors using PET machines. The first electrode or small metal disc is placed on the patient’s legs, arms, and chest. The electrodes are then attached to the device using wires. These are intended to track and record the patient’s heart rate, called an electrocardiogram. The ECG also indicates when the scan should be performed.
The next step is to create a baseline image of the organ. This is done without adding a tracer and takes about 30 minutes. Once the baseline is scanned, a tracer is injected into the human arm through a venous line taped to it. After the tracer is added, the patient lays flat on the table, which slides into a scanning device that looks like a giant donut.
The scan begins when the detector picks up the signal emitted by the tracer. The data is converted to a digital image using a computer. A single image is actually a collection of many photographs taken sliced from all angles. The whole procedure can take somewhere between 1-3 hours. It is important to be completely stationary throughout the scanning process. Otherwise, the image will be blurry.
Procedures to perform after PET scan
Scanning is a non-invasive process, so you can return to normal activity immediately after the scan is finished. It is recommended to drink plenty of water the next day. Water allows all radioactive substances, the tracer, to be washed away from the body. Also, make an appointment with your doctor to follow up on your test results.
Risks associated with PET
In general, PET scans are very safe for any individual. The amount of radiation that the body is exposed to is very small. Therefore, the kidneys can get rid of it from the body in at most 24 hours. Testing is not recommended in the following cases:
- Breastfeeding mother
- In both cases, the scan can be harmful to the child.