Applications of DTI

 

Contents

   1. Introduction
    2. Neurosurgical Interventions
    3. Clinical Applications of DTI


1. Introduciton

DTI has been used in a wide spectrum of applications. The primary reason is that water diffusion is highly sensitive to differences in the microstructure of cellular membranes in tissues. Increase in the average spacing in tissues will increase the apparent diffusivity, whereas smaller spaces will lead to a lower apparent diffusivity. This sensitivity makes DTI a powerful method in detecting microscopic tissue properties. Nevertheless, the diffusion tensor is a complex construct and should be examined with care.

2. Neurosurgical Interventions

The major application of DTI in neurosurgical intervention is mapping of white matter (WM) prior to surgery [1]. Mapping of WM assists the neurosurgeon with localization of critical white matter pathways, that need to be preserved during surgery. The pathways may be visualized as RGB colormaps or via tractography (see Fig. 3 and Fig. 4 in the part about DTI). 

A recent study published by Powell at al. [2], suggests that tractography could also predict visual field deficits that occur during the resection of the temporal lope.

DTI and tractography have also been successfully implemented in the intraoperative setting to facilitate real-time WM tract mapping, to compensate for shifting tissues during surgery [3].

In addition to visualization of the WM tracts, DTI has also been used to study the effects of surgery on WM pathways. Studies of patients following corpus colosotomy found reduced FA following the surgical intervention, where 2/3 of the anterior corpus callosum was bisected. The decrease in FA was found 2-4 month after surgery which was attributed to increases in the radial diffusivity [4].


Take a look at this video showing BrainLAB's software (BrainLAB iPlan® FiberTracking) for neurosurgical planning based on DTI.

(►Get Windows Media Player)

3. Clinical Applicaitons of DTI

Ischemic stroke 

The clinical diagnosis and characterization of acute ischemic lesions in the CNS is by far the most common clinical application of DTI. In the acute phase of brain ischemia, the MD significantly decreases in the lesion [5]. Resent studies have also shown that the FA appears to increase in acute lesions and decrease below baseline levels in the chronic phase [6].

Neoplasia 

The second most common clinical application of DTI is possibly for the characterization of white matter in patients with brain tumors. This work focuses on using DTI maps and tractography to help localize WM fiber tracts that are important for such critical functions as motion, language, and vision. Based on this information the neurosurgeon can plan surgical procedures that will minimize injury to critical tracts, such as the corticospinal tract [7]. 

                                                                                         

References


 

[1] Witwer BP, Moftakhar , Hasan KM, et al. Diffusion-tensor imaging of white matter tracts in patients with cerebral neoplasm. J. Neurosurg 2002;97:568-575.

[2] Powell HW, Parker GJ, Alexander DC, et al. MR tractography predicts visual field defects following temporal lope resection. Neurology 2005;56:197-204.

[3] Mamata Y, Mamata H, Navavi A, et. al. Intraoperative diffusion imaging on a 0.5 Tesla interventional scanner. J Magn Reson Imaging 2001;13:115-119. 

[4] Cocha L, Gross DW, Wheatley BM, Beaulieu C. Diffusion tensor imaging of  time-dependent axonal and myelin degradation after corpus callosotomy in epilepsy patients. Neuroimage 2006; 32:1090-1099.

[5] Von Gelderen P, De Vleeschouwer MH, DesPres D, et. al. Water diffusion and acute stroke. Magn Reson Med 1994;21:154-163.

[6] Sorensen AG, Wu O, Copen WA, et al. Human acute cerebral ischemia: detection in changes of water diffusion anisotropy by using MR imaging. Radiology 1999;212:785-792.

[7] Laudre BJ, Jellision BJ, Badie B, Alexander AL, Field A. Diffusion tensor imaging of the corticospinal tract before and after mass resection as correlated with clinical motor findings preliminary data. AJNR Am J Neuroradiol 2005; 26:791-796;