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Improved nTMS- and DTI-derived CST tractography through anatomical ROI seeding on anterior pontine level compared to internal capsule.

ABSTRACT: Imaging of the course of the corticospinal tract (CST) by diffusion tensor imaging (DTI) is useful for function-preserving tumour surgery. The integration of functional localizer data into tracking algorithms offers to establish a direct structure-function relationship in DTI data. However, alterations of MRI signals in and adjacent to brain tumours often lead to spurious tracking results. We here compared the impact of subcortical seed regions placed at different positions and the influences of the somatotopic location of the cortical seed and clinical co-factors on fibre tracking plausibility in brain tumour patients. The CST of 32 patients with intracranial tumours was investigated by means of deterministic DTI and neuronavigated transcranial magnetic stimulation (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 posterior limb of the internal capsule (PLIC) and/or the anterior inferior pontine region (aiP). The plausibility of the fibre trajectories was assessed by a-priori defined anatomical criteria. The following potential co-factors were analysed: Karnofsky Performance Scale (KPS), resting motor threshold (RMT), T1-CE tumour volume, T2 oedema volume, presence of oedema within the PLIC, the fractional anisotropy threshold (FAT) to elicit a minimum amount of fibres and the minimal fibre length. The results showed a higher proportion of plausible fibre tracts for the aiP-ROI compared to the PLIC-ROI. Low FAT values and the presence of peritumoural oedema within the PLIC led to less plausible fibre tracking results. Most plausible results were obtained when the FAT ranged above a cut-off of 0.105. In addition, there was a strong effect of 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. In summary, we found that the aiP-ROI yielded better tracking results compared to the IC-ROI when using deterministic CST tractography in brain tumour patients, especially when the M1 hand area was tracked. In case of FAT values lower than 0.10, the result of the respective CST tractography should be interpreted with caution with respect to spurious tracking results. Moreover, the presence of oedema within the internal capsule should be considered a negative predictor for plausible CST tracking.

SUBMITTER: Weiss C

PROVIDER: S-EPMC4314616 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Improved nTMS- and DTI-derived CST tractography through anatomical ROI seeding on anterior pontine level compared to internal capsule.

Weiss Carolin C Tursunova Irada I Neuschmelting Volker V Lockau Hannah H Nettekoven Charlotte C Oros-Peusquens Ana-Maria AM Stoffels Gabriele G Rehme Anne K AK Faymonville Andrea Maria AM Shah N Jon NJ Langen Karl Josef KJ Goldbrunner Roland R Grefkes Christian C

NeuroImage. Clinical 20150120

Imaging of the course of the corticospinal tract (CST) by diffusion tensor imaging (DTI) is useful for function-preserving tumour surgery. The integration of functional localizer data into tracking algorithms offers to establish a direct structure-function relationship in DTI data. However, alterations of MRI signals in and adjacent to brain tumours often lead to spurious tracking results. We here compared the impact of subcortical seed regions placed at different positions and the influences of ...[more]

PMID: 25685709

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Project description:ObjectiveTo evaluate brai structural connectivity in children with traumatic injury (TI) following a motor vehicle accident using graph theory analysis of DTI tractography data.MethodsDTI scans were acquired on a 3 T Philips scanner from children aged 8-15 years approximately 2 months post-injury. The TI group consisted of children with traumatic brain injury (TBI; n = 44) or extracranial injury (EI; n = 23). Healthy control children (n = 36) were included as an age-matched comparison group. A graph theory approach was applied to DTI tractography data to investigate injury-related differences in connectivity network characteristics. Group differences in structural connectivity evidenced by graph metrics including efficiency, strength, and modularity were assessed using the multi-threshold permutation correction (MTPC) and network-based statistic (NBS) methods.ResultsAt the global network level, global efficiency and mean network strength were lower, and modularity was higher, in the TBI than in the control group. Similarly, strength was lower and modularity higher when comparing the EI to the control group. At the vertex level, nodal efficiency, vertex strength, and average shortest path length were different between all pairwise comparisons of the three groups. Both nodal efficiency and vertex strength were higher in the control than in the EI group, which in turn were higher than in the TBI group. The opposite between-group relationships were seen with path length. These between-group differences were distributed throughout the brain, in both hemispheres. NBS analysis resulted in a cluster of 22 regions and 21 edges with significantly lower connectivity in the TBI group compared to controls. This cluster predominantly involves the frontal lobe and subcortical gray matter structures in both hemispheres.ConclusionsGraph theory analysis of DTI tractography showed diffuse differences in structural brain network connectivity in children 2 months post-TI. Network differences were consistent with lower network integration and higher segregation in the injured groups compared to healthy controls. Findings suggest that inclusion of trauma-exposed comparison groups in studies of TBI outcome is warranted to better characterize the indirect effect of stress on brain networks.

Project description:Navigated transcranial magnetic stimulation (nTMS) combined with diffusion tensor imaging (DTI) is used preoperatively in patients with eloquent-located brain lesions and allows analyzing non-invasively the spatial relationship between the tumor and functional areas (e.g. the motor cortex and the corticospinal tract [CST]). In this study, we examined the diffusion parameters FA (fractional anisotropy) and ADC (apparent diffusion coefficient) within the CST in different locations and analyzed their interrater reliability and usefulness for predicting the patients' motor outcome with a precise approach of specific region of interest (ROI) seeding based on the color-coded FA-map.Prospectively collected data of 30 patients undergoing bihemispheric nTMS mapping followed by nTMS-based DTI fiber tracking prior to surgery of motor eloquent high-grade gliomas were analyzed by 2 experienced and 1 unexperienced examiner. The following data were scrutinized for both hemispheres after tractography based on nTMS-motor positive cortical seeds and a 2nd region of interest in one layer of the caudal pons defined by the color-coded FA-map: the pre- and postoperative motor status (day of discharge und 3 months), the closest distance between the tracts and the tumor (TTD), the fractional anisotropy (FA) and the apparent diffusion coefficient (ADC). The latter as an average within the CST as well as specific values in different locations (peritumoral, mesencephal, pontine).Lower average FA-values within the affected CST as well as higher average ADC-values are significantly associated with deteriorated postoperative motor function (p = 0.006 and p = 0.026 respectively). Segmental analysis within the CST revealed that the diffusion parameters are especially disturbed on a peritumoral level and that the degree of their impairment correlates with motor deficits (FA p = 0.065, ADC p = 0.007). No significant segmental variation was seen in the healthy hemisphere. The interrater reliability showed perfect agreement for almost all analyzed parameters.Adding diffusion weighted imaging derived information on the structural integrity of the nTMS-based tractography results improves the predictive power for postoperative motor outcome. Utilizing a second subcortical ROI which is specifically seeded based on the color-coded FA map increases the tracking quality of the CST independently of the examiner's experience. Further prospective studies are needed to validate the nTMS-based prediction of the patient's outcome.

Dataset Information

Improved nTMS- and DTI-derived CST tractography through anatomical ROI seeding on anterior pontine level compared to internal capsule.

Publications

Improved nTMS- and DTI-derived CST tractography through anatomical ROI seeding on anterior pontine level compared to internal capsule.

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