Dual-imaging technique helps surgeons navigate the brain

Caren B. Les

Patients faced with brain surgery may someday be helped with a dual-imaging technique developed by brain specialists associated with the Neuroscience Institute at the University of Cincinnati and at University Hospital of Cincinnati.

The technique shows promise in optimizing surgery to treat brain tumors, with the overall effect of improving the post-surgical abilities of the patients, including their speech, movement, memory and vision. Combining functional MRI and diffusion tensor tractography data, the method enables surgeons to discern key areas of brain function and their connections before surgery and to transfer the information to the operating room, where the areas are tracked, in real time, during the surgical procedure.

The approach, which has been used in 20 cases at the hospital, enables neurosurgeons to determine more precisely the amount of tumor that can be removed safely without damaging critical areas of the brain or disrupting important electrical connections. Traditionally, surgeons have used electrical stimulation during surgery to identify brain areas that should be circumvented, which can cause seizures; in some cases, it can require patients to be awake so that areas of the brain controlling language can be identified. It also necessitates a larger opening of the skull and more exposure of the brain.

As part of the new method, physicians perform the MRI and diffusion tensor tractography scans on patients about a week prior to surgery. Standard visual-, sound- and voice-based test results are measured by MRI, performed on a high-field-strength (3 T) scanner.

Neuroradiologists use functional MRI to help identify critical areas of brain function before the surgical removal of a tumor. The color-coded image shows the vision area (yellow), hand movements (pink), movement tracts (purple) and the tumor ( green). Photos are courtesy of the University of Cincinnati.

To combine the imaging techniques in the operating room, the surgeons use the surgical navigation system known as BrainLab, which incorporates the functional MRI data identifying brain areas linked to speech, movement and vision and the diffusion tensor imaging data that maps “white-matter tracts,” critical electrical connections between parts of the brain that should be avoided during surgery.

Patients can see a color-coded picture of their brain prior to surgery showing the location of the tumor in relation to brain areas that control critical functions. The image could help them to understand what is happening in their head and how the surgery will be conducted, perhaps alleviating some of their apprehension.

This functional MRI image of the brain shows a tumor (green) and other areas of brain function, including “expressive” speech (orange), visual stimulation (yellow) and hand movement (pink). The growth of a tumor can cause functional areas of the brain to shift from their original locations. A dual-imaging technique may help neurosurgeons remove a tumor without harming critical areas and connections in the brain.

There are some limitations to the dual-imaging technique. For example, patients with limited vision may not demonstrate as much activity in the brain areas linked to vision during the functional MRI testing. The activity may be there, but the MRI may not be sensitive enough to detect it.

The team, led by Dr. James L. Leach, presented its preliminary research on the technique in a scientific exhibit at the American Society of Neuroradiology’s annual meeting in June.