F. Tensaouti

Quantitative and reproducibility study of four tractography algorithms used in clinical routine.

To evaluate fiber tracking strategy in terms of acquisition schemes in conjunction with four algorithms used in clinical routine, we studied one of the major tracts, anatomically well known, and which should be preserved as much as possible during neurosurgery: the corticospinal tract.

Prognostic and predictive values of diffusion and perfusion MRI in paediatric intracranial ependymomas in a large national study

OBJECTIVE To assess the relative cerebral blood volume (rCBV) and apparent diffusion coefficient (ADC) derived, respectively, from perfusion and diffusion pre-operative MRI of intracranial ependymomas and their predictive and prognostic values. METHODS Pre-operative MRI and clinical data for intracranial ependymomas diagnosed between January 2000 and December 2013 were retrospectively retrieved from a web-based national database. MRI data included diffusion (62 patients) and perfusion (20 patients) MRI. Patient age, histopathological diagnosis, tumour location, ADC, relative ADC (rADC) and rCBV were considered as potential factors in a survival analysis. Survival rates were estimated using the Kaplan-Meier method. Univariate analyses were performed using the log-rank test to compare groups. We also performed a multivariate analysis, applying the Cox proportional hazards model. RESULTS ADC and rADC values within hypointense regions differed significantly between grades II and III (p = 0.01). The 75th percentile of ADC within hypointense regions and the 25th percentile of rCBV within non-enhancing lesions were prognostic of disease-free survival (p = 0.004, p = 0.05). A significant correlation was found between the 75th percentile of rCBV and the 25th percentile of rADC (p = 0.01) in enhancing regions of grade-III tumours. CONCLUSION Pre-operative rADC and rCBV could be used as prognostic factors for clinical outcome and to predict histological grade in paediatric ependymomas. ADVANCES IN KNOWLEDGE Prognostic value of diffusion and perfusion MRI in paediatric ependymoma was found and may play a role in the prognostic classification of patients in order to design more tailored treatment strategies.

Assessment of Asymmetry in Pyramidal Tract by Using Fiber Tracking

Diffusion Tensor Imaging (DTI) and tractography are able to model fiber architecture within the white matter and become a major component of clinical neuroradiology. The challenge is to answer neuro-anatomic questions by using group studies. In some diseases, the asymmetry between involved tracts is expected to be greater than that in controls. If the quantitative detection of asymmetry is sufficiently sensitive, it will be a good marker of clinically relevant tract-specific abnormalities. In this work, we quantify the range of asymmetry between the right and left pyramidal tract (PT) and explore the side and handedness effects on the microstructure of the PT in healthy subjects by using a probabilistic tractography. The volume and seven DTI parameters (fractional anisotropy (FA), mean, perpendicular and parallel diffusity, geometric diffusion measures) were determined. The statistical analysis revealed substantial PT asymmetries and an average correlation between FA, mean diffusity and the laterality quotient.

Reproducibility and reliability of the DTI fiber tracking algorithm integrated in the Sisyphe software

Diffusion Tensor Imaging (DTI) and tractography are able to model fiber architecture within the white matter. In the laboratory, we developped a software Sisyphe, which is an integrated environment for neuroimaging post-processing and visualization. In this work, we extend this tool to further incorporate white matter DTI fiber tracking. We evaluate the reproducibility and reliability of our algorithm by studying the pyramidal tract.