Positron emission tomography, or PET scan, is a type of imaging that is classified as nuclear medicine. What differentiates imaging scans in this category from other types of scans is that they use small amounts of radioactive material to diagnose a number of diseases, including many types of cancer.
How Does a PET Scan Work?
These non-invasive exams require the patient to receive radioactive materials called radiopharmaceuticals or radiotracers before undergoing the scan. These radiotracers can be injected into a vein, taken orally, or inhaled as a gas. They collect in the part of the body to be examined and they send out a type of energy called gamma rays. This energy is then read by three devices that work in conjunction with each other, a gamma camera, a PET scanner, and a probe. They measure the level of radiotracer than has been absorbed and that data is programmed into a computer that generates images the show details about the function of organs and tissues.
The difference between nuclear medicine imaging exams like PET scans and other types of medical imaging techniques is that these tests evaluate physiological processes like chemical activity. They do not provide information about actual anatomical structures. Hot spots, which are body regions where a significant amount of radiotracer has collected, are an indication that there is a high level of chemical activity. Cold spots, which are body regions where there is a small amount of radiotracer, are an indication of less chemical activity.
What are the Benefits of Undergoing a PET Scan?
- The unique information provided by this type of imaging scan cannot be gotten by using other diagnostic tools.
- Depending upon the type of disease, the images created by a PET scanner may be the best data a physician has to make an accurate diagnosis and determine course of treatment.
- The data provided by a PET scan is more accurate than what can be discovered from exploratory surgery.
- The identification of modifications of internal processes at the cellular level helps to diagnose medical conditions early on before they would become visible on a CT scan or MRI.
What are the Risks?
The level of radiation to which the patient is exposed is low and on a par with the level of exposure from most CT scans. The radiation doesn’t remain inside the body for very long after the initial exposure.
In addition, there is a slight possibility that the patient will have an allergic reaction to the radiotracer. If the material is injected into a vein, the patient may experience pain, redness, or swelling at the injection site.
Patients with diabetes may not receive accurate test results because blood sugar level and insulin affect test outcomes.
How are PET Scans Combined with MRIs and CT Scans?
Images generated by PET scans can be superimposed on CT scans or MRIs, a procedure called image fusion or co-registration. This allows the data from the different exams to be viewed side-by-side so that it can be interpreted together for a more accurate diagnosis.
Medical imaging device manufacturers are now making machines that combined PET and CT units so that both imaging studies are performed simultaneously.