Diffusion tensor tractography in patients with cerebral tumors: A helpful technique for 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).
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