Artikel
Diffusion tensor imaging-based fiber tracking for preoperative planning. Which distance to the pyramidal tract influences outcome?
Diffusions-Tensor Bildgebung als Grundlage der Faserdarstellung für die Operationsplannung. Welche Distanz zur Pyramidenbahn hat Einfluss auf das neurologische Ergebnis?
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Veröffentlicht: | 11. April 2007 |
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Objective: Imaging of eloquent cortical areas has been established for preoperative planning since implementation of functional MRI. Still, the analysis of the topographical relationship between the pyramidal tract (PT) and lesions of the deep white matter remains challenging. Since introduction of Diffusion Tensor Imaging (DTI) and processing software, based on fiber tracking algorithms, an indirect visualisation of white matter tracts seems possible. In a prospective study we evaluated the feasibility of indirect white matter tractography by DTI-based fiber tracking. For that purpose, the distance between the PT and adjacent lesions was correlated with functional outcome.
Methods: In 20 consecutive patients (14 gliomas, 4 cavernomas, 2 metastasis) with deep white matter lesions adjacent to the PT, pre- and postoperative DTI (12 diffusion directions) was acquired employing a 3 Tesla MR-scanner. The PT, the lesion (preoperativ) and the tumor-cavity (postoperativ) were visualized and segmented three-dimensionally. For fiber tracking and neuronavigation the planning-software iPlan 2.5Cranial (BrainLab®, Heimstetten) was used. The distance between the PT and the tumour-cavity was defined by the postoperative DTI and related to the postoperative clinical outcome (NIH stroke score).
Results: Visualization of the PT succeeded in all patients. According to the anatomical and functional data sets a separate segmentation of the PT relating to the foot-, hand- and tongue-area was possible in 13 patients. 9 patients presented postoperatively a deterioration or a new neurological deficit, with complete recovery in eight or partial improvement in one patient. In 6 of these patients the deficit was possibly associated with an impairment of the PT, with a minimum distance between PT and tumor-cavity of less then 3.5mm.
Conclusions: Indirect visualization of the PT by DTI-based fiber tracking is feasible in the preoperativ planning. Although our study population is small, the data suggest that in order to preserve motor function a minimum distance of 3.5mm to the PT should be safeguarded, additionally to the safety margins of dependent devices such as neuronavigation.