Article
Usefulness of FAT and MFL values for plausiblity prediction in deterministic, nTMS-based tractography
Search Medline for
Authors
-
Carolin Weiss
- Klinik für Allgemeine Neurochirurgie, Universitätsklinikum Köln
-
Irada Tursunova
- Klinik für Allgemeine Neurochirurgie, Universitätsklinikum Köln
-
Hannah Lockau
- Institut für Diagnostische und Interventionelle Radiologie, Universitätsklinikum Köln
-
Volker Neuschmelting
- Klinik für Allgemeine Neurochirurgie, Universitätsklinikum Köln
-
Christian Grefkes
- Institut für Neurowissenschaften und Medizin, Forschungszentrum Jülich; Klinik und Poliklinik für Neurologie, Universitätsklinikum Köln
-
Roland Goldbrunner
- Klinik für Allgemeine Neurochirurgie, Universitätsklinikum Köln
| Published: | June 2, 2015 |
|---|---|
| Published with erratum: | June 17, 2015 |
Outline
Text
Objective: Imaging of the course of the corticospinal tract (CST) by diffusion tensor imaging (DTI) is useful for function-preserving tumour surgery and can be facilitated by the use of navigated transcranial magnetic stimulation (nTMS) for the delineation of starting ROIs for tractography. However, alterations of MRI signals in the neighbourhood of the tumour often lead to spurious tracking results. Parameters such as the minimal fibre track length (MFL) and the fractional anisotropy threshold (FAT) may reflect an unfavourable signal-to-noise ratio and, thus, the risk for non-plausible tractography results. We, therefore, investigated the predictive value of FAT and MFL for tractography of the pyramidal tract.
Method: The CST of 32 patients with intracranial tumours was investigated by deterministic DTI (iPlanNet) and nTMS. The cortical seeds were defined by the nTMS hot spots of the primary motor area (M1) of the hand, the foot and the tongue representation. The CST originating from the contralesional M1 hand area was mapped as intra-individual reference. As subcortical region of interests (ROI), we used the anterior inferior pontine region (aiP). The plausibility of the fibre trajectories was assessed by a-priori defined anatomical criteria by two independent raters. As potential co-factors i.a. the FAT and the MFL were analysed.
Results: Low FAT values (cut-off of 0.105) and long MFL (cut-off 121.5 mm) led to less plausible fibre tracking results. In addition, there was a strong effect of the somatotopic location of the seed ROI; best plausibility was obtained for the contralateral hand CST (100%), followed by the ipsilesional hand CST (>95%), the ipsilesional foot (>85%) and tongue (>75%) CST.
Conclusions: In summary, we found excellent plausibility rates using a deterministic multiple-ROI approach with a cortical, nTMS-derived ROI and an additional ROI in the anterior pontine region. However, due to the technical limitations of the method, the results should always be interpreted with caution, especially when dealing with FAT values lower than 0.105 or MFL exceeding 121.5 mm.
