Diffusion Tensor Imaging Assists Removal of Brain Tumors

A new study has found that the planning of the operative trajectory for removing benign Juvenile Pilocytic Astrocytoma (JPA) tumors in the thalamus could be augmented with Diffusion Tensor Imaging (DTI).

Researchers at New York University (NYU, USA) used DTI to localize the posterior limb of the internal capsule (PLIC) on preoperative magnetic resonance imaging (MRI) in six children undergoing resection of thalamic JPAs. After review of the standard MRI sequences, the anticipated position of the PLIC was determined; this result was compared with the location of the PLIC determined by a blinded radiologist with the use of DTI. Subsequently, the utility of DTI in determining the surgical approach to a thalamic JPA, degree of resection, and neurological outcomes were all evaluated.

The results showed that DTI confirmed the expected location of the PLIC as approximated on conventional T2-weighted MRI images in all six cases. In one patient in particular, unexpected medial deviation of the PLIC was identified, and this proved useful in tailoring the approach to a more lateral trajectory. Gross-total resection of all cystic and solid tumor components was confirmed on postoperative imaging in all cases. All of the patients experienced mild to moderate worsening of neurological status immediately following resection, but four of the six patients were back to their preoperative baseline at 6-month follow-up. The study was published in the December 2009 issue of the Journal of Neurosurgery: Pediatrics.

"Using advanced MRI technology can help identify distorted nerve fiber bundles around brain tumors,” said lead author Jeffrey Wisoff, M.D., director of the division of pediatric neurosurgery at the NYU Langone Medical Center. "This allows an otherwise inoperable tumor to be completely removed, which can hopefully lead to a cure."

Diffusion Tensor Imaging, a variation of MRI, can help identify white matter, or nerve fiber bundles, using specific radio frequency (RF) and magnetic field pulses to track the movement of water molecules of the brain. In most brain tissue, water molecules diffuse in all different directions. But they tend to diffuse along the length of axons, whose coating of white, fatty myelin holds them in. By analyzing the direction of water diffusion, images of the axon fibers can be determined.

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