Concurrent PET/CT for radiation therapy planning shows promise over separate PET and CT

Using concurrent PET/CT may improve the accuracy of imaging for radiation therapy treatment planning by decreasing errors caused by organ motion, says a new study by researchers from the Washington University School of Medicine in St. Louis, MO.

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. Wahab.

The full results of the study will be presented on Monday, May 1, 2006 during the American Roentgen Ray Society Annual Meeting in Vancouver, BC.

About ARRS
The American Roentgen Ray Society (ARRS) was founded in 1900 and is the oldest radiology society in the U.S Radiologists from all over the world attend the ARRS Annual Meeting to take part in instructional courses, scientific paper presentations, symposiums, new issues forums and scientific and commercial exhibits related to the field of radiology. The ARRS is named after Wilhelm Röentgen, who discovered the x-ray in 1895.

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