Introduction: Diffusion Tensor Imaging (DTI) is an important adjunct in the surgical planning of gliomas that involve eloquent brain areas. We present an automated and quantitative method for the assessment of white matter (WM) tract integrity in the proximity of tumor between pre- and post-operative images, irrespective of mass effect and edema.
Methods: Three DTI cases (Siemens MRI scanner, 32 diffusion weighted directions, one b0, b= 1000s/mm2) were used to demonstrate this method. In cases 1 and 2, the post-operative DTI sequence was obtained within 24 hours of surgery, while in case 3 the imaging was performed 250 days after initial resection. All patients in this study harbored lesions within or surrounding eloquent brain regions. Deformable registration via attribute matching and mutual-saliency weighting (DRAMMS) was used to register the atlas to the pre-operative image, as well as the pre-to the post-operative image despite edema and mass effect. Ten DTI measures of anisotropy and diffusivity, and their three principal components (PCs), were used to evaluate WM tract integrity in the pre- and post-resection time points. Histograms of these measures were compared using cosine distance.
Results: In test cases 1 and 2, overlap of tract histograms showed no difference between the pre- and post-operative time points, indicating that tract integrity was maintained. In case 3, large differences in all measures except PC3 indicated a compromise of FA with increasing edema. PC 1 and 2 captured Trace and FA, while PC3 elucidated the underlying WM, successfully removing the effect of edema.
Conclusions: This method enables surgeons to accurately and automatically register pre- and post-operative images and evaluate WM tract integrity following resection of intrinsic brain tumors. This technique functions effectively despite the presence of mass effect and edema in the region of the tract. Finally, dynamic resizing of a planned resection ROI will aid pre-operative planning.
Patient Care: This method augments surgical decision making, such as extent of resection, in an effort to limit patient morbidity.
Learning Objectives: 1. White matter tractography is widely used in the pre-operative planning of patients with intrinsic brain lesions surrounding eloquent regions.
2. Automatic registration methods allow quantitative assessment of WM tracts between time points, irrespective of edema and mass effect.