The imaging technique of diffusion tensor imaging (DTI) allows neurosurgeons to visualize important pathways in the brain. This allows them to better adapt brain tumor surgeries and preserve language, visual function, and motor function while removing cancerous tissue. This ability to visualize relevant white matter tracts during glioma resection surgeries can improve accuracy and, in some groups, significantly extend survival (median survival 21.2 months) compared to cases where DTI was not used (median survival 14 months).
“We can view the brain from the inside out now, with 3D images detailing connectivity within the brain, making a virtual intraoperative map,” said senior author Steven Brem, MD, professor of Neurosurgery, chief of the Division of Neurosurgical Oncology and co-director of the Penn Brain Tumor Center in Philadelphia, Pennsylvania. The study was published in Neurosurgical Focus (2013; doi:10.3171/2013.1.FOCUS12412).
Brem said, “Penn is at the forefront of a major shift in the field— we now have such detail about each individual’s brain tumor—combining diffusion tensor imaging and advanced imaging with the entire personalized diagnostics analysis available for all brain tumor patients at Penn Medicine.”
Diffusion tensor imaging (DTI) provides a rendering of axon pathways, by tracking water molecules in the brain as they travel in a direction parallel to axonal fibers, in a 3D model known as “the diffusion tensor.” The diffusion tensor directly represents the direction of water and indirectly represents the orientation of white matter fibers. The colorful images, captured as part of an 8-minute sequence during an MRI, show representations of clusters of axon fibers, where each color indicates a direction of travel, and offer a glimpse of the interwoven communication superhighways of the brain.
“The DTI images can be overlaid with structural and functional MRI images, providing a hybrid map showing topography layered with a road map,” said lead author and neurosurgery resident Kalil Abdullah, MD. “This rendering gives us increased clarity to visualize important white matter tracts in the brain and adapt our surgical approaches to each person’s case. Rather than focusing on solely taking the tumor out, we can avoid damage to healthy tissue and preserve important pathways responsible for speech, vision, and motor function. “
Relying heavily on the expertise of radiologists who process and analyze the DTI images, including Ronald L. Wolf, MD, PhD, associate professor of Radiology at Penn, the research on DTI is being translated into clinical practice to guide surgical procedures. Further research efforts are targeted at defining language deficits before surgery and following up postoperatively to determine any changes or improvements following treatment based on the use of DTI.