Xiangyu Yang PhD, Presenter: Nothing to Disclose

Leo Ditzel MD, Abstract Co-Author: Nothing to Disclose

Lori Lynn Mattox, Abstract Co-Author: Nothing to Disclose

Daniel Prevedello MD, Abstract Co-Author: Nothing to Disclose

Michael Vinzenz Knopp MD, PhD, Abstract Co-Author: Nothing to Disclose

To validate that postsurgical white matter (WM) fiber damage can be assessed with Diffusion Tensor Imaging (DTI) and probabilistic tractography in a porcine model.

Two experienced neurosurgeons performed stereotactic brain surgical procedures simulating skull base surgery in human patient in nine adolescent female pigs. Pre- and postsurgical DTI data were acquired on a 3T MRI (Achieva, Philips Healthcare, Cleveland, OH) with a 32-channel cardiac coil using a high-angular resolution protocol with 240x240 mm FOV, 1.9x1.9x2 mm3 voxel, TR/TE/Flip Angle = 8100 ms/67 ms/90⁰, b = 0/1000 s/mm2, and 60 gradient directions. The DTI data were analyzed with the probabilistic tractography approach using FSL (FMRIB, Oxford, UK). Pre- and postsurgical data were registered with affine linear registration. Fractional anisotropy (FA), mean diffusivity (MD), radial (Dr) and axial diffusivity (Da) were measured on 3x3x3 mm3 seed Region-Of-Interests (ROIs) placed in WM on surgical trajectory (4/animal) and on a reference fiber tract (2/animal) that connects primary and secondary visual cortex. Damage of WM fiber tracts from the surgical seed ROIs was quantified by the fraction of overlap between the pre- and postsurgical fiber volumes (OF = Vpre∩post/Vpre). Linear mixed effect model was used for the statistical analysis.

The reference seeds have a mean OF value of 0.38 that reflects the inherent variability of the tractography technique and the registration error due to brain tissue loss, hemorrhage, and ventricular dilation. The surgical seeds have significantly lower OF (0.27, p=3e-8) than the reference seeds. No significant difference was found between pre- and postsurgical FA, MD, Dr, or Da values at the site of surgery, suggesting the difference in OF is related to direct mechanical damage to fibers in surgery, not secondary axonal damage or edema.

Surgical damage to WM fiber tracts can be effectively detected by DTI and probabilistic tractography within a few hours after brain surgery. Surgical damage to fiber is associated with low OF between pre- and postsurgical fiber volumes but not with any other diffusion parameter.

DTI can be used as an objective quantitative tool for prospective evaluation of brain surgical techniques in animal model, and retrospective assessment of surgical outcome in human patient.

Yang, X, Ditzel, L, Mattox, L, Prevedello, D, Knopp, M, Assessment of Surgical Damage to White Matter Fiber Tracts with Probabilistic Tractography in a Preclinical Porcine Model.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014647.html