4D CT Tracks Lung Tumor Motion During Radiation

A new imaging modality may more accurately track tumor motion in patients being treated for lung cancer than traditional three-dimensional (3D) imaging. The technology, four-dimensional (4D) computed tomography (CT), may allow radiation oncologists to identify and predict tumor movement based on the tumor's location in almost real time.

"One of the major challenges in treating lung tumors with radiation is precisely targeting a moving tumor while simultaneously decreasing the amount of healthy tissue that may be exposed,” remarked Dwight Heron, M.D., assistant professor of radiation oncology, the University of Pittsburgh (UPMC; PA, USA), and study coauthor. "Lung tumors are akin to moving targets. As a patient inhales and exhales, the tumor moves, making it challenging to target the tumor and to avoid exposure of radiation to the area that surrounds the tumor. By being able to predict movement based on its location and attachment to the lung, we have the ability to more precisely target tumors with radiation therapy.”

Lung tumor movement in the study was assessed in 12 patients on multiple images provided by 4D CT. The images were then arranged according to the respiratory cycle phase in which the image was acquired. Results showed that tumor motion correlated considerably with the location of the tumor in the lungs--tumors that moved more than 5 mm were positioned in the lower lobes of the lungs, and those that moved the most were attached to the posterior of the lungs. Results also indicated that tumors that were significantly attached to the chest wall or major airway moved the smallest amount.

"This technology is promising because it may improve our ability to develop more precise treatment plans for the delivery of radiation therapy to lung cancer patients and ensure the tumor receives the full amount of the treatment dose possible,” Dr. Heron said. The 4D CT technology was developed by GE Medical Systems (Waukesha, WI, USA).

"The better we understand lung tumor motion, the better radiation oncologists can plan radiotherapy treatments and track changes in lung tumors that might affect the efficacy of the treatment,” said Edward Brandner, Ph.D., a medical physicist at UPMC, and another coauthor of the study.




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