What is Positron Emission Tomography (PET)?
Positron Emission Tomography (PET) is a non-invasive diagnostic scanning technique that provides visual images of organ function (including blood flow, oxygen consumption, glucose metabolism, and concentrations of molecules in the brain and body tissues). During the scanning process, small amounts of radioactive compounds are injected into the body where they are absorbed by organs and tissues. The PET scanner picks up signals from the radioactive tracers and detects biochemical changes in metabolic processes that aid in disease diagnosis. Other diagnostic techniques such as CT and MRI scans can only detect structural changes after tissue damage has occurred.
Uses of PET
PET scans are utilized to diagnose heart disease, brain tumors, stroke, cancer, epilepsy, head injuries, Parkinson’s disease, and many other disorders. By measuring blood flow to the heart, PET scans can be used to diagnose disorders such as coronary artery disease. PET scans can also help to determine the extent of muscle damage caused by a heart attack. One of the most significant advantages of PET is its ability to detect biochemical changes in body tissues before structural damage occurs from disease. This information allows clinicians to be proactive in their treatments.
Clinicians use PET scans to measure the effectiveness of current disease treatments. Scans taken at various intervals during drug therapy can demonstrate whether the medication is working, or if the treatment should be modified. Post-treatment scans evaluate the effectiveness of the treatment and can also identify early signs of disease recurrence.
Research scientists use PET scans to study brain activity and chemical mechanisms involved in diseases such as schizophrenia, depression, Alzheimer’s disease, alcohol dependence, and substance abuse. By studying tissue concentrations of the absorbed radiotracer, scientists can determine if the tracer is effectively reaching molecular targets. This information can aid scientists in the development of new medications and dosing regimens.
The PET Scanning Process
A radioactive tracer is produced in a cyclotron machine, attached to a naturally occurring body compound (such as glucose), and administered to the patient intravenously. The tracer is absorbed by the body and concentrates in tissues and organs.
The patient lies on a table that slides slowly through a PET scanner. As the patient slides through the circular opening of the scanner, the tracer emits radioactive signals. These signals are recorded by multiple rings of detectors in the scanner and are converted into three-dimensional computer images of tissue concentrations and organ function.
Levels of tissue concentrations and organ function are represented by different colors or degrees of brightness on computer-generated PET images. Some of the radioactive tracer will be seen in normal tissues because healthy tissues use glucose for energy. Cancerous tumors utilize more glucose than normal tissues and will appear much brighter.
Once the scanning session has been completed, a specially trained radiologist will interpret the scan, record their findings, and forward this information to the referring physician to discuss with their patient.
Benefits of PET
- Identifies early biochemical markers of disease before structural changes in body organs take place.
- Provides an opportunity for earlier and more specific diagnosis, intervention, and treatment of disease. (CT and MRI detect structural changes after damage has occurred).
- Enables researchers to detect early biomarkers of disease that can aid in drug development.