Various types of radiologic scans are important components for diagnosing primary and recurrent malignant disease. These include computed tomography (CT) scans, computed axial tomography (CAT) scans, positron emission tomography (PET) scans and magnetic resonance imaging (MRI).
Another type of beneficial radiologic technology is the ultrasound. “For gynecological cancer of the ovaries, cervix and uterus, the first line is ultrasound,” said Dr. Marc Ford, a radiologist at Central Baptist Hospital. “Ultrasound has much better details of those organs than a CT scan does.” But if a clearer picture is needed, an MRI is the next phase. “MRI offers really good detail of the female pelvic organs,” Ford said.
A whole-body CAT scan is helpful when staging a disease to see if it has spread to other organs. PET scans are also used primarily for staging. A follow-up scan is compared to a baseline scan to note any changes. “It’s a way to find recurrence and progression,” Ford said.
PET scans can help physicians pinpoint areas for biopsy.
“There’s a lot of overlap in the appearance of benign lung nodules and cancerous lung nodules,” Ford said. “The same thing goes for the liver and the pancreas and other solid organs. If you have a confusing picture where you have one or more abnormalities, if you’re not sure it’s something you need to go ahead and biopsy or if you have multiple possible targets for biopsy, the PET scan helps you choose whether to proceed and which target to choose.”
A PET scan is particularly helpful for Kentucky physicians who see a great deal of lung cancer. “Many cancers have only dead tissue and necrosis in the center and only one part of it or one edge will actually have an active tumor,” Ford said. “The PET scan helps you know where to biopsy. Also, if the tumor can’t be surgically removed, the PET scan shows where to do radiation.”
Solid organs such as the pancreas and liver are best viewed with a PET scan. “The liver and pancreas often have benign nodules or cysts that are hard to figure out what they are,” Ford said. “The PET scan is helpful in determining if it’s cancerous or non cancerous.”
For primary cancers of the brain, a brain MRI, preferably with contrast, is the starting point. “If you think there’s likely a tumor, you start with an MRI,” Ford said. “If you feel the patient may have an injury or a lesion or might have had a stroke, you do a CAT scan. If they’ve had some lingering symptoms that are slowly increasing or slowly progressive symptoms, MRI will offer you a better evaluation.”
Computer-assisted diagnosis is widely used with mammograms. “A computer looks at the breast pattern and signals areas it thinks may be of interest,” Ford said. “It shows up many that you can just automatically dismiss as obviously not a problem, but others that are subtle. Hopefully we will catch more smaller things early.”
Ford says fusion of modalities helps create a better picture of malignant disease and define treatment options. “You can use the information off the different scans and correlate them better,” he said. “When I first started, you got a PET scan and a separate CAT and you compared them. Now our PET scanners have a CAT scan married to them. Now the patient goes through the scanner the first time and it does a CAT scan. The patient goes through a second time and it will do a PET scan completely perfectly registered to a CAT scan. It gives a more accurate picture and it’s registered down to the millimeter level.”
Another important benefit of these technologies is the way they have prompted collaborative medicine.
“This is where the physician develops a relationship with one or more radiologists and discusses cases either beforehand or after the fact with them,” Ford said. “This helps the physician to determine the best way to work up a patient or proceed with a patient and eliminate duplication or repeat testing.”
By Tanya J. Tyler, Associate Editor