Unlike magnetic resonance imaging (MRI) and computed tomography (CT) scans, which reveal structures in the body, the PET (positron emission tomography) scan can reveal not just structures, but their functions.
This is vital information when a physician needs to see if a cancerous tumor has been destroyed by cancer treatment, or if it is still functioning, according to Medical Oncologist and Hematologist Dr. Monte Martin of the Flaget Cancer Center. That’s why the new PET scanner now available at Flaget Memorial Hospital is such an important addition to the hospital’s diagnostic services.
PET and CT scans are being used together to track for abnormalities that could not be seen with CT or MRI alone, Martin said. With PET, a radioactive sugar is injected into a patient’s vein, a substance which travels through the blood and collects in organs and tissues.
“The PET can determine if a cancerous tumor is showing metabolic activity, since the tumor is more likely to use the sugar for energy,” the oncologist said. “It uptakes the sugar, and that’s what lights up on the computer screen.”
With just MRI or CT scan, “you would see a wound or growth, but you wouldn’t know if it was scar tissue or cancer,” Martin said. “With PET/CT, you would see not just anatomy, but the physiology of the growth. You do the PET scan and then do a computer overlay on the CT scan. You get the activity and the size measurements together.”
This advanced technology is excellent for checking for brain problems such as Alzheimer’s Disease, and for scanning for heart function problems and lung function problems as well.
It is invaluable in checking the metabolic activity of cancerous tumors, Martin said.
“It’s essential,” he said. “If you have treated a tumor, you will want to rescan it to see if its metabolic activity has changed. That’s vital information. It tells you whether you need to keep treating that tumor or not.”
The PET/CT scan is an excellent way to tell if a growth is “something that we can wait and watch – or something where we need to go immediately to tissue diagnosis.”
The PET is also extremely valuable in diagnosing new cancers, the physician said. For example, “if a patient has had an abnormal chest CT, a PET/CT scan can help determine if a lung nodule is malignant.”
To prepare for the test, you will need to fast the night before the test, although you can drink plenty of fluids. Four to 6 hours before the test, drink water only.
Tell your health care provider about any prescription or over-the-counter medicines that you are taking, because they may interfere with the test.
Be sure to mention if you have any allergies, or if you have had any recent imaging studies done using injected dye (contrast).
During the test, you may need to wear a hospital gown. Take off any jewelry, dentures, and other metal objects, because they could affect the scan results.
The amount of radiation used in a PET scan is quite low, Martin said. It’s about the same amount of radiation used in most CT scans. It’s excreted from the body within six to eight hours.
Best of all, “we don’t have to send you somewhere where they don’t have your original scans,” the physician said. “This is definitely better for continuity of patient care. You don’t have go to Elizabethtown or Louisville. You have this incredible diagnostic tool right here in your own backyard.”
*Article originally ran in the 2011 Nelson County Medical Guide*