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TOPIC OF THE ISSUE-EDITORIAL
Year : 2010  |  Volume : 58  |  Issue : 6  |  Page : 877-878

Diffusion tensor imaging: A colorful collage or a clinical tool?


Department of Imaging Sciences and Interventional Radiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India

Date of Web Publication10-Dec-2010

Correspondence Address:
Bejoy Thomas
Department of Imaging Sciences and Interventional Radiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala - 695 011
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.73733

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How to cite this article:
Thomas B. Diffusion tensor imaging: A colorful collage or a clinical tool?. Neurol India 2010;58:877-8

How to cite this URL:
Thomas B. Diffusion tensor imaging: A colorful collage or a clinical tool?. Neurol India [serial online] 2010 [cited 2019 Sep 22];58:877-8. Available from: http://www.neurologyindia.com/text.asp?2010/58/6/877/73733


Detection of anisotropic  Brownian motion More Details of water molecules along structurally oriented tissue forms the basis of diffusion tensor imaging (DTI). [1],[2] Over the past two decades, it has evolved as one of the most powerful magnetic resonance imaging (MRI) tools to study microstructural alterations occurring in the brain. These techniques have been perfected by Pierpaoli and Baser [2] and several other investigators since then. [3],[4]

In the initial years of its development, DTI remained mainly as a research tool and its clinical utility was very much limited. Availability of this sequence and post-processing software on clinical scanners and increased awareness among clinical colleagues have led to development of many novel applications for DTI. The greatest clinical impact was thought to be in demonstrating eloquent white matter fiber tracts preoperatively, in epilepsy and brain tumor surgeries. White matter pathways of the human brain can be demonstrated either as a DTI-based color orientation map or as 3D fiber tracts superimposed on anatomical images for orientation. Various projection, association and commissural pathways can be demonstrated by DTI [4] [Figure 1]. In a review of nine cases, Cao et al. [5] demonstrated the usefulness of DTI in providing extremely valuable information regarding the relationship between the principal fiber tracts and brainstem lesions, which was useful in neurosurgical planning of resection of these tumors. Similar results have been reported earlier by other investigators also. [6] However, one should be careful in inferring the relative positions of the thickly packed fibers in the brainstem, especially adjacent to lesions like cavernous angiomas which can induce significant susceptibility artifacts and hence spuriously distort the DT images. Carvi et al.[7] have shown utility of DTI in demonstrating the alterations of posterior fossa white matter tracts caused by the tumors in the region. Integration of the tract information to the neuronavigational systems and the availability of per-operative fiber tracking may further help the surgeons to reduce morbidity in resection of complex brain lesions.
Figure 1: DTI fiber tractography showing callosal and cortico-spinal fibers

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In addition to demonstrating the fiber orientation adjacent to the tumors, directional averaged mean diffusivity (Dav) is considered to be useful in predicting tumor consistency. Fractional anisotropy (FA), a measure of the degree of anisotropic diffusion, was generally considered to be less useful in differentiating tumor subtypes. [8] However, recent reports have shown that in addition to looking at FA, a more elaborate evaluation of the diffusion metrics can characterize and grade various brain tumors. [9],[10],[11]

Detection of microstructural changes early in the course of a disease process is considered to be an important application of DTI. Multiple sclerosis, motor neuron disease, normal and abnormal aging processes and detecting hitherto unknown substrates of focal epilepsy are examples of such applications. However, most of these applications still remain to be confined to the neuroscience research domain. Wang et al., in this issue, have shown the utility of DTI in demonstrating possible pathophysiological mechanisms underlying cognitive impairment in temporal lobe epilepsy attributable to microstructural changes in the frontal lobe. [12]

The horizon of applications of DTI is unlimited and potentially it could be extended to study any disease process involving brain or even other organs. However, DTI has several limitations too. The most important among them is the lack of specificity, with most disease processes showing an increase in Dav and a reduction in FA. The inferences from DTI based studies should not overstate its utility. A DTI fiber tract has, if at all, only indirect relationship to the real number of axons, and is highly dependent on the resolution of the DTI scan and the chosen FA and angular deflection thresholds. Neurosurgeons should be aware of such limitations as spurious visualization or non-visualization of tracts could be a practical limitation of the technique. Another important difficulty is mapping of crossing and/or branching fibers like in the case of optic chiasm. High angular diffusion imaging and diffusion spectrum imaging aim to overcome some of these limitations by reconstructing the diffusion displacement profile by sampling diffusion over a wide range of angles. [13] With advancements in MR imaging and post-processing capabilities, these limitations could be potentially reduced or eliminated in the future. [14]

 
  References Top

1.Hajnal JV, Doran M, Hall AS, Collins AG, Oatridge A, Pennock JM, et al. MR imaging of anisotropically restricted diffusion of water in the nervous-system: Technical, anatomic, and pathological considerations. J Comput Assist Tomogr 1991;15:1-18.  Back to cited text no. 1
[PUBMED]    
2.Pierpaoli C, Basser PJ. Toward a quantitative assessment of diffusion anisotropy. Magn Reson Med 1996;36:893-906.  Back to cited text no. 2
[PUBMED]    
3.Pierpaoli C, Jezzard P, Basser PJ, Barnett A, Di Chiro G. Diffusion tensor MR imaging of the human brain. Radiology 1996;201:637-48.  Back to cited text no. 3
[PUBMED]  [FULLTEXT]  
4.Wakana S, Jiang H, Nagae-Poetscher LM, van Zijl PC, Mori S. Fiber tract-based atlas of human white matter anatomy. Radiology 2004;230:77-87.  Back to cited text no. 4
[PUBMED]  [FULLTEXT]  
5.Cao Z, Lv JP, Wei X, Quan W. Appliance of preoperative diffusion tensor imaging and fiber tractography in patients with brainstem lesions. Neurol India 2010;58:886-90.  Back to cited text no. 5
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6.Chen X, Weigel D, Ganslandt O, Buchfelder M, Nimsky C. Diffusion tensor imaging and white matter tractography in patients with brainstem lesions. Acta Neurochir (Wien) 2007;149:1117-31.  Back to cited text no. 6
[PUBMED]  [FULLTEXT]  
7.Carvi y Nievas MN, Hoellerhage HG, Drahten C. White matter tract alterations assessed with diffusion tensor imaging and tractography in patients with solid posterior fossa tumors. Neurol India 2010;58:914-21.  Back to cited text no. 7
    
8.Sinha S, Bastin ME, Whittle IR, Wardlaw JM. Diffusion tensor MR imaging of high-grade cerebral gliomas. AJNR Am J Neuroradiol 2002;23:520-7.  Back to cited text no. 8
[PUBMED]  [FULLTEXT]  
9.Jolapara M, Patro SN, Kesavadas C, Saini J, Thomas B, Gupta AK, et al. Can diffusion tensor metrics help in preoperative grading of diffusely infiltrating astrocytomas? A retrospective study of 36 cases. Neuroradiology 2010 [In Press].  Back to cited text no. 9
    
10.Jolapara M, Kesavadas C, Radhakrishnan VV, Thomas B, Gupta AK, Bodhey N, et al. Role of diffusion tensor imaging in differentiating subtypes of meningiomas. J Neuroradiol 2010 [In Press].  Back to cited text no. 10
    
11.Santhosh K, Thomas B, Radhakrishnan VV, Saini J, Kesavadas C, Gupta AK, et al. Diffusion tensor and tensor metrics imaging in intracranial epidermoid cysts. J Magn Reson Imaging 2009;29:967-70.  Back to cited text no. 11
[PUBMED]  [FULLTEXT]  
12.Wang XQ, Lang SY, Hong LU, Lin MA, Yan-ling MAO, Yang F. Changes in extratemporal integrity and cognition in temporal lobe epilepsy: A diffusion tensor imaging study. Neurol India 2010;58:891-9.  Back to cited text no. 12
  Medknow Journal  
13.Frank LR. Anisotropy in high angular resolution diffusion weighted MRI. Magn Reson Med 2001;45:935-9.   Back to cited text no. 13
[PUBMED]  [FULLTEXT]  
14.Thomas B, Sunaert S. Diffusion tensor imaging: Technique, clinical and research applications. Rivista di Neuroradiologia 2005;18:419-35.  Back to cited text no. 14
    


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[Pubmed] | [DOI]



 

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