Diffusion Tensor Tractography

Abstract

BACKGROUND AND PURPOSE:The limbic system, relevant to memory and emotion, is an interesting subject of study in healthy and diseased individuals. It consists of a network of gray matter structures interconnected by white matter fibers. Although gray matter components of this system have been studied by using MR imaging, the connecting fibers have not been analyzed to the same degree. Cerebrospinal fluid (CSF) signal intensity contamination of the fornix and cingulum, the 2 major white matter tracts of the limbic system, can alter diffusiontensor imaging (DTI) measurements and affect tractography. We investigated the effect of CSF signal intensity suppression on fiber tracking of the limbic connections and characterized the diffusion properties of these structures in healthy volunteers.METHODS: Nine healthy individuals were scanned with standard and CSF-suppressed DTI. Tractography of the fornix and cingulum was performed for both acquisition methods. We report mean diffusivity and fractional anisotropy measurements of the crus, body, and columns of the fornix, and descending, superior, and anterior portions of the cingulum.RESULTS: Diffusion measurements were improved and tractography was facilitated by using CSF-suppressed DTI. In particular, tract volume increased, whereas decreases of the mean diffusivity and increases of diffusion anisotropy more accurately represented the underlying tissue by minimizing deleterious partial volume averaging from CSF. This was particularly true for the fornix because it is in closest contact to CSF. Diffusion measurements throughout the limbic connections were consistent in healthy volunteers. CONCLUSION:We recommend the use of CSF suppression when performing diffusiontensor tractography of the limbic system.

Optimal Factors of Diffusion Tensor Imaging Predicting Corticospinal Tract Injury in Patients with Brain Tumors

“…Studies have shown that in cases of simple compression, the structure of neural fibers can still retain their integrity ( 22 23 ). Long-term continuous compression may lead to a decrease in the number of neural fibers or demyelination, causing a change in the FA ( 13 24 ). In a study of meningioma patients, motor weakness was found to be related to lower FA resulting from increased radial diffusivity (RD) of the CST ( 13 ).…”

Recovery of White Matter Tracts in Regions of Peritumoral FLAIR Hyperintensity with Use of Restriction Spectrum Imaging

“…However, the ability to estimate white matter structure in regions of peritumoral FLAIR-HI associated with edema in patients with high grade glioma has remained a challenge 11, 19 . Ng et al 16 reported on motor outcome in 12 patients who underwent resection of tumors adjacent to the CST. Despite lower FA in patients whose CST was affected by the presence of peritumoral edema versus those patients without edema, there were no differences between the groups in motor outcome.…”

“…Taken together, these results suggest that the underlying structure of white matter was largely intact in peritumoral tissue, but artifactually masked by edema. This information is critical in surgical planning of patients with high-grade gliomas who are likely to have large regions of peritumoral FLAIR-HI associated with edema causing mass effect, midline shift, and temporary clinical morbidity 16 . Deciphering intact from destroyed white matter tracts in regions of FLAIR-HI would not only assist neurosurgeons in planning the optimal surgical route, but it would also provide clinicians with information as to whether a patient’s neurological deficits are likely chronic, resulting from destroyed fiber tracts, or temporary and likely to subside once the edema and associated pathology resolve.…”

“…Therefore, reduced FA in regions of FLAIR-HI associated with edema can prevent the accurate visualization of fiber tracts, resulting in an underestimation of the extent of intact white matter surrounding a tumor. This observation may explain why previous studies have reported dissociations between the actual degree of neurological deficits following surgery and the expected degree of neurological deficits based on the preoperative FA of fiber tracts in regions of FLAIR-HI 16 .…”

A pilot study of pre-operative motor dysfunction from gliomas in the region of corticospinal tract: Evaluation with diffusion tensor imaging

“…This may result in smaller axonal diameter and thinner myelin which may cause decreased transmission of nerve impulses[ 29 ]. Although prior studies have shown that the size of benign brain tumors was not significantly different between hemiplegia versus non-hemiplegic groups[ 30 ], these results may be due to tumor location, duration of diseases, pathological type and sample size among other factors.…”