Combination of Imaging Methods Reveals Tumor Motion

Researchers at the Agency for Science, Technology and Research (A*STAR; Singapore), Nanyang Technological University (Singapore), and other institutions have developed a novel hybrid imaging approach that is based on deformable image registration (DIR) and finite element method simulation to fuse a static three dimension (3D)-CT volume, acquired while the patient held his breath, and 3D motion information extracted from a four dimension (4D)-MRI dataset, thus creating a synthetic 4D-CT dataset.

The result is images of the lungs that exhibit high spatial resolution, while at the same time accounting for lung movement due to breathing. When the researchers compared the synthetic 4D-CT dataset with the acquired 4D-CT dataset of six lung cancer patients based on 420 landmarks, the average error was less than two mm. The hybrid approach also achieved a 40% error reduction over using only DIR techniques. The study describing the new hybrid imaging technique was published in the August 2015 issue of Medical Physics.

“The method is expected to greatly assist clinicians when they target tumors in the lungs during radiotherapy,” said study author Soo Kng Teo, PhD, of A*STAR. “Encouragingly, some clinicians are thinking of applying our method to other organs, such as the liver, which also moves significantly with breathing. Also our computational method can combine information from different imaging methods to produce more comprehensive data sets.”

Cancerous tumors in the lungs are often treated by irradiating them with high-energy X-rays, but this therapy is complicated by the fact that tumors are moving targets, due to the expansion and contraction of the lungs as the patient breathes. Currently, 3D-CT provides static high-resolution images, but at the cost of high radiation; in contrast, 4D-MRI does not employ ionizing radiation and allows continuous tracking of lung motion, but its low spatial resolution yields blurred images.

Related Links:
The Agency for Science, Technology and Research
Nanyang Technological University