Diffusion tensor tractography in patients with cerebral tumors: A helpful technique for neurosurgical planning and postoperative assessment

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Abstract

Objective:

To demonstrate the role of diffusion tensor tractography (DTT) in preoperative mapping of eloquent tracts in relation to cerebral tumors and to determine whether it is helpful for neurosurgical planning and postoperative assessment.

Methods and materials:

Sixteen patients with brain tumors underwent diffusion tensor imaging (DTI). The pyramidal tract, corpus callosum and optic radiation were reconstructed and the exact location of a lesion with respect to these tracts was observed to design a reasonable surgical plan for preserving vital tracts while maximizing tumor resection. After surgery, DTI was performed again and these tracts were evaluated to investigate the surgical outcomes. Twenty-four patients with suspicion of pyramidal tract involvement were also evaluated as a control group.

Results:

The relationship between tracts and tumors was classified as three types: type I is simple displacement, type II is displacement with disruption and type III is simple disruption. Twelve cases involved in pyramidal tract (DTT group), one was type I with reduction of displacement after surgery, nine were type II with reduction of displacement and other two were type III without any improvement. The extent of tumor resection (p = 0.045) and postoperative improvement of locomotive function (p = 0.015) of DTT group were significantly higher than those of control group. Corpus callosum was involved in seven cases, three were type II with reduction of displacement and four were type III without any improvement. Optic radiation was involved in three cases, all were type I with reduction of displacement.

Conclusion:

DTT allowed for visualization of the exact location of tumors relevant to eloquent tracts and was found to be beneficial in the neurosurgical planning and postoperative assessment.

Introduction

Preservation of vital white matter tracts while maximizing tumor resection is a principal goal in neurosurgery. Many brain tumors originate within and involve in the white matter of the brain. In most situations, the eloquent white matter tracts are intact or only displaced. So it is essential to distinguish intact from disrupted white matter tracts during excision of brain tumors.

Conventional MR techniques (include T2-weighted, T1-weighted and FLAIR imaging) have widely used for radiological assessment and localization of brain tumors. But these MR methods could not give any precise information about the integrity and location of white matter tracts in the immediate region surrounding tumors. Functional MRI can be used to localize important cortical areas near brain tumors [1], [2]. However, this imaging modality can not show the exact location of a possibly displaced tract.

Recently, diffusion tensor imaging (DTI) has been used to assess white matter tracts in the brain [3], [4], [5]. It is sensitive to the diffusion of water molecules and can measure the displacement of diffusion which revealing the orientation of white matter tracts in brain. This orientation information can then be used to delineate white matter tracts of the brain by employing tractography (also called fiber tracking) algorithms [6], [7], [8].

Currently, diffusion tensor tractography (DTT) is the only imaging modality with the potential to generate realistic fiber-tract trajectories in white matter of the brain in vivo. This technique has hitherto been largely restricted to studies of the healthy human brain and has provided demonstrations of white matter tracts that have coherence with known anatomy [9], [10]. Previous investigations in patients with brain tumors have employed DTI to demonstrate local abnormalities in tract orientation and surrounding edema [11], [12], [13], and used DTT to illustrate displacement of some vital white matter tracts [14], [15], but they were all restricted to preoperative assessment. In this study, we have applied DTT to investigate clinically eloquent white matter tracts in 16 patients with cerebral tumors, and to investigate the potential of DTT for neurosurgical planning and postoperative assessment. Current limitations of this technique are also discussed.

Section snippets

Patient selection

From August 2003 to June 2004, diffusion-tensor MR images were obtained in 16 consecutive patients (12 men, 4 women; age range: 20–72 years; mean age: 51.7 years) who were undergone preoperative and postoperative evaluation of brain tumors. Patients whose pyramidal tract was affected by tumors on the DTT images were regarded as DTT group (12 patients). A control group of 24 patients (17 men, 7 women; age range: 25–68 years; mean age: 52.5 years) with suspicion of pyramidal tract being involved

Results

The exact location of tumor relevant to eloquent white matter tracts could be displayed with the aid of DTT in each case. The relationships between tumor and tracts could be divided into three types: simple displacement (type I), displacement with disruption (type II) and simple disruption (type III). The location of brain tumors relevant to the eloquent tracts and the surgical outcomes were also shown in Table 1.

In sixteen patients, pyramidal tract was involved in 12 cases (DTT group), only 1

Discussion

In the surgery of patients with brain tumors, preservation of vital cerebral function is as important as maximizing tumor resection. The associated morbidity of aggressive resections can be significantly reduced by carefully preservation of vital cerebral function, and the quality of life of these patients will be largely improved. Simultaneously maximizing tumor resection can reduce the chance of recurrence of tumors and improve longer patient survival and long-term functional status [19], [20]

Conclusion

Our study showed diffusion tensor tractography allowed for assessment of the exact location of tumors relevant to eloquent white matter tracts and it was a beneficial technique not only in neurosurgical planning but also in postoperative assessment.

Acknowledgement

Supported by the Natural Science Foundation of China (30470519).

References (30)

  • D.K. Jones et al.

    Non-invasive assessment of axonal fiber connectivity in the human brain via diffusion tensor MRI

    Magn Reson Med

    (1999)
  • H. Mamata et al.

    High-resolution line scan diffusion tensor MR imaging of white matter fiber tract anatomy

    AJNR Am J Neuroradiol

    (2002)
  • S. Lu et al.

    Diffusion-tensor MR imaging of intracranial neoplasia and associated peritumoral edema: introduction of the tumor infiltration index

    Radiology

    (2004)
  • J.M. Provenzale et al.

    Peritumoral brain regions in gliomas and meningiomas: investigation with isotropic diffusion-weighted MR imaging and diffusion-tensor MR imaging

    Radiology

    (2004)
  • S. Lu et al.

    Peritumoral diffusion tensor imaging of high-grade gliomas and metastatic brain tumors

    AJNR Am J Neuroradiol

    (2003)
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