PET, CT Cancer-Screening Scans Best Done Together

Spacing them apart makes for difficulties in reading the scans, experts say

THURSDAY, May 4, 2006 (HealthDay News) -- Using PET and CT scans in combination could provide more accurate imaging for cancer radiation therapy than using them separately, researchers say.

That's because the combination approach cuts errors caused by the motion of organs and other factors, according to a team at the Washington University School of Medicine in St. Louis, Mo.

The study included 10 cervical cancer patients who had radiation therapy planned using both a CT taken before PET and a CT taken during the same PET session. Structures identified on the PET images had better correlation to patient anatomy on CT images taken at the same time, compared to PET images taken after CT.

The findings were presented this week at the annual meeting of the American Roentgen Ray Society in Vancouver, British Columbia, Canada.

"Until recently, PET/CT simulation involved obtaining a CT scan in one department and a PET in another, often on different days. This process presented challenges for working with patients with cervical cancer because this introduced uncertainties caused by patient position variation, internal organ motion and organ deformation (variable filling volumes of bladder and bowel). We tried to decrease this uncertainty by using a PET and CT acquired during the same session," study lead author Dr. Sasha Wahab said in a prepared statement.

"The better we can see the tumor, the better we can treat it. Using PET and CT to guide treatment planning, we can more effectively target cancer cells so that we can deliver higher radiation doses to the tumor and still spare the dose to normal tissue. This may lead to more effective treatment with lower side effects," Wahab said.

More information

The American Cancer Society has more about radiation therapy.

SOURCE: American Roentgen Ray Society, news release, May 1, 2006
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