How does a positron emission tomography (PET) scan of the lung, heart or any other part of the body work? Understanding the basics

Positron emission tomography, or PET, is a non-invasive test that creates a nuclear image of any part of the body, such as the lung or heart. To do this, a radioactive tracer, also known as radionuclides, is injected into the blood. Once the tracer mixes with the blood, it is absorbed by the muscles and into an organ such as the heart. The scan determines whether or not the heart is healthy by showing the flow of blood. For example, narrowed arteries or dead cells from a previous heart attack can be diagnosed using a positron emission tomography (PET) scan.

The basic operation of a PET scan

To perform a PET CT test, the following steps are performed:

1. A tracer is injected into the bloodstream. It is an organic compound found in bodies marked with a minute amount of radioactive material. Glucose, ammonia or water is generally used.
2. Once inside the body, the tracer generates gamma energy beams.
3. The rays are picked up by a detector that surrounds the body and then sent to a computer. The system converts the signals into clear images.
4. The full image is made by putting together images of thin slices of the heart. Each slice is photographed from different directions and angles to produce a holistic, three-dimensional image.

A healthcare professional can determine heart function using the image. If the muscles are strong, the tracer is excellently absorbed. On the other hand, if the heart is no longer viable or has dead cells, the tracer is not taken. On positron emission tomography, the level of tracer absorption is seen as different colors or gradations of brightness.

The need for PET tests

Today, PET scans are one of the most accurate procedures that can be used to detect:

1. coronary artery disease
2. low blood flow
3. injured tissue
4. dead tissue

Depending on what the scan shows, a doctor may recommend a heart procedure such as:

1. percutaneous coronary intervention (PCI)
2. coronary artery bypass surgery
3. The operations will be able to restore adequate blood flow to the heart.

The procedure of a PET scan

A pet MRI can be done in a hospital or diagnostic lab. It is performed by a nuclear medicine technician and a physician using a PET machine. Electrodes or small metal discs are first attached to the patient’s legs, arms, and chest. The electrodes are then connected to a device using wires. These are meant 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 reference image of the organ. This is done without the addition of the marker and takes about half an hour. Once the baseline is scanned, injection of the tracer takes place through an IV line that is placed into the person’s arm. After the marker is added, the patient lies on a table that slides into the scanning device that looks like a huge doughnut.

Scanning begins when the detectors pick up the signals emitted by the tracer. The data is converted into a digital image using a computer. A single image is actually an accumulation of many photographs taken from all angles and in sections. The entire procedure can take between one and three hours. It is vital to be completely still during the entire scanning process, or the images will be blurry.

Steps to follow after the PET scan

Because the CT scan is a non-invasive process, the person can return to their usual activity immediately after it is finished. It is recommended to drink a lot of liquid for the next day. The water allows all the radioactive material, that is, the tracer, to be removed from the body. Also, make an appointment with the appropriate doctor to follow up on the test results.

The risks related to PET

Generally, PET scanning is exceptionally safe for any individual. The amount of radiation to which the body is exposed is very small. Therefore, the kidneys can remove it from the body in a maximum of 24 hours. The test is not recommended if the person is:

1. pregnant
2. mother nurse

In both cases, the scan may harm the child.

The last word

Anyone who wants to know more about PET scanning before the procedure should consult a doctor. Some questions that can help clarify all doubts are:

• How is this test better than any other?
• What are the steps that need to be taken in preparation for the scan?
• Will there be a need for additional tests after the scan?
• When can you expect the results?