Diffusion tensor eigenvector directional color imaging patterns in the evaluation of cerebral white matter tracts altered by tumor

Abstract

Purpose: To categorize the varied appearances of tumoraltered white matter (WM) tracts on diffusion tensor eigenvector directional color maps. Materials and Methods:Diffusion tensor imaging (DTI) was obtained preoperatively in 13 patients with brain tumors ranging from benign to high-grade malignant, including primary and metastatic lesions, and maps of apparent diffusion coefficient (ADC), fractional anisotropy (FA), and major eigenvector direction were generated. Regions of interest (ROIs) were drawn within identifiable WM tracts affected by tumor, avoiding grossly cystic and necrotic regions, known fiber crossings, and gray matter. Patterns of WM tract alteration were categorized on the basis of qualitative analysis of directional color maps and correlation analysis of ADC and FA.Results: Four basic patterns of WM alteration were identified: 1) normal or nearly normal FA and ADC, with abnormal tract location or tensor directions attributable to bulk mass displacement, 2) moderately decreased FA and increased ADC with normal tract locations and tensor directions, 3) moderately decreased FA and increased ADC with abnormal tensor directions, and 4) near isotropy. FA and ADC were inversely correlated for Patterns 1-3 but did not discriminate edema from infiltrating tumor. However, in the absence of mass displacement, infiltrating tumor was found to produce tensor directional changes that were not observed with vasogenic edema, suggesting the possibility of discrimination on the basis of directional statistics. Conclusion:Tumor alteration of WM tracts tends to produce one of four patterns on FA and directional color maps. Clinical application of these patterns must await further study.

Quantitative apparent diffusion coefficients in the characterization of brain tumors and associated peritumoral edema

“…One must keep in mind the high degree of normal variation in FA depending on location in the brain which must be considered and may help explain disparity across studies (118,133). Directionally encoded color maps of FA can be categorized into four major patterns of tumor-altered white matter tracts: 1) deviated, 2) edematous, 3) infiltrated, and 4) destroyed (134). Classification by these patterns may aid presurgical planning and thereby potentially avoid damaging an intact tract during surgery (118).…”

Incorporating Functional MR Imaging into Diffusion Tensor Tractography in the Preoperative Assessment of the Corticospinal Tract in Patients with Brain Tumors

“…Edema and tumor infiltration typically cause reduction of the FA measured in these voxels. 23,34 This can cause significant problems in fiber tracking, with fibers terminating prematurely due to crossing the chosen minimal FA threshold. 20 The optimal tractability threshold of FA for DT tractography of the CST is commonly considered to be around 0.20.…”

“…20,22 Therefore, anatomic landmarks may be insufficient to position the seed region of interest to visualize the CST and its most important subcomponents (ie, the hand and foot fibers). Besides that, edema and tumor infiltration can cause the diffusivity and anisotropy of the white matter tract to change, 23 compromising fiber tracking in these areas when one uses conventional parameter thresholds for termination of the tracking. The tracking of fibers in the vicinity of brain tumors, therefore, requires a custom-based approach, with more specific region-of-interest selection and optimization of parameter settings for DT tractography.…”

Non-rigid alignment of pre-operative MRI, fMRI, and DT-MRI with intra-operative MRI for enhanced visualization and navigation in image-guided neurosurgery

“…Therefore, because fMRI of motor and language tasks is feasible in patients with cerebral tumors (Mueller et al 1996), several groups have proposed the integration of functional data into the neuronavigation system in recent years (Krishnan et al 2004, Gralla et al 2003, Jannin et al 2002, Roessler et al 2005, Reithmeier et al 2003, Talos et al 2003, O'Shea et al 2006. And strong evidence that a more radical tumor resection may be achieved by using fMRI information during neurosurgery has been demonstrated by Krishnan et al 2004, Haberg et al 2004 Diffusion tensor imaging (DTI) has recently emerged as a potentially valuable tool for preoperative planning (Tummala et al 2004, Field et al 2004, Clark et al 2003, Wieshmann et al 2000, Moller-Hartmann et al 2002, Coenen et al 2003 and postoperative follow-up (Alexander et al 2003) of surgically treated brain tumors and vascular malformations. DTI provides information about the normal course, displacement, or interruption of white matter tracts in and around a tumor, as well as detecting the widening of fiber bundles due to edema or tumor infiltration (Beppu et al, 2003;Clark et al, 2003;Hendler et al, 2003;Lu et al, 2003;Price et al, 2003;Tummala et al, 2003;Wieshmann et al, 1999;Yamada et al, 2003).…”