For the study, the researchers analyzed the results of ten patients with cervical cancer who had radiation treatment planned using both a CT taken before PET and a CT taken during the same PET session. The researchers found that the structures identified on the PET images demonstrated better correlation to patient anatomy on the CT taken at the time of PET than to patient anatomy on the traditional separate CT.

"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," said Sasha Wahab, MD, lead author of the study.

The CT taken at the time of PET is not any more accurate than the CT taken at a separate time, say the researchers. It is the fact that the CT is obtained in the same session (with the patient in the same position and with minimal time interval) that makes the CT taken at the time of PET advantageous. "By using a PET and CT taken back to back with the patient in the same position, we reduce the risk of errors due to motion," said Dr. Wahab.

"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," said Dr. W
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Contact: Necoya Lightsey
necoya@arrs.org
604-647-7413
American Roentgen Ray Society
1-May-2006