As it provides the only method for mapping white matter fibers in vivo, diffusion MRI tractography is gaining importance in clinical and neuroscience research. However, despite the increasing availability of different diffusion models and tractography algorithms, it remains unclear how to select the optimal fiber reconstruction method, given certain imaging parameters. Consequently, it is of utmost importance to have a quantitative comparison of these models and algorithms and a deeper understanding of the corresponding strengths and weaknesses. In this work, we use a common dataset with known ground truth and a reproducible methodology to quantitatively evaluate the performance of various diffusion models and tractography algorithms. To examine a wide range of methods, the dataset, but not the ground truth, was released to the public for evaluation in a contest, the "Fiber Cup". 10 fiber reconstruction methods were evaluated. The results provide evidence that: 1. For high SNR datasets, diffusion models such as (fiber) orientation distribution functions correctly model the underlying fiber distribution and can be used in conjunction with streamline tractography, and 2. For medium or low SNR datasets, a prior on the spatial smoothness of either the diffusion model or the fibers is recommended for correct modelling of the fiber distribution and proper tractography results. The phantom dataset, the ground truth fibers, the evaluation methodology and the results obtained so far will remain publicly available on: http://www.lnao.fr/spip.php?rubrique79 to serve as a comparison basis for existing or new tractography methods. New results can be submitted to fibercup09@gmail.com and updates will be published on the webpage.

Background Glioblastoma, a high-grade glial infiltrating tumor, is the most frequent malignant brain tumor in adults and carries a dismal prognosis. External beam radiotherapy (EBRT) increases overall survival but this is still low due to local relapses, mostly occurring in the irradiation field. As the ratio of spectra of choline/N acetyl aspartate> 2 (CNR2) on MR spectroscopic imaging has been described as predictive for the site of local relapse, we hypothesized that dose escalation on these regions would increase local control and hence global survival. Methods/design In this multicenter prospective phase III trial for newly diagnosed glioblastoma, 220 patients having undergone biopsy or surgery are planned for randomization to two arms. Arm A is the Stupp protocol (EBRT 60 Gy on contrast enhancement + 2 cm margin with concomitant temozolomide (TMZ) and 6 months of TMZ maintenance); Arm B is the same treatment with an additional simultaneous integrated boost of intensity-modulated radiotherapy (IMRT) of 72Gy/2.4Gy delivered on the MR spectroscopic imaging metabolic volumes of CHO/NAA > 2 and contrast-enhancing lesions or resection cavity. Stratification is performed on surgical and MGMT status. Discussion This is a dose-painting trial, i.e. delivery of heterogeneous dose guided by metabolic imaging. The principal endpoint is overall survival. An online prospective quality control of volumes and dose is performed in the experimental arm. The study will yield a large amount of longitudinal multimodal MR imaging data including planning CT, radiotherapy dosimetry, MR spectroscopic, diffusion and perfusion imaging. Trial registration NCT01507506 , registration date December 20, 2011.

Purpose: 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. Materials and Methods:Two identical exams, composed of three DTI acquisition schemes (6, 15, and 32 gradient directions), were performed on 12 healthy subjects during two different sessions. For each subject, intra-operator, and inter-exam reproducibility was quantitatively calculated from different fiber tracking algorithms: three deterministic and a probabilistic one. Inter-exam reproducibility was evaluated comparing fiber tracking results from the repetition of the same acquisition one month apart and variation of the fiber density distribution percentile.Results: For each fiber tracking algorithm, the best reproducibility result is obtained in case of 50% of fiber density and for the number of directions equal to 32. The reproducibility is improved using the probabilistic algorithm. Conclusion:This study highlights increased reliability of reproducibility results based on the number of directions used during the acquisition. The method of tractography used and the choice of adequate density fiber tract greatly improve the results. DIFFUSION TENSOR IMAGING (DTI) and tractography have the potential to depict fiber architecture within the white matter. DTI has emerged as a noninvasive imaging modality able to provide in vivo information about the white matter structure (1). The method is based on the sensitivity of measured diffusivity of the water protons to the microstructural environment. The diffusion paths of water molecules are longer along the axis of the myelinated fibers than perpendicular according to the degree of myelination, axonal membrane and subvoxel coherence (2,3). White matter tractography is a promising application of diffusion weighted imaging (DWI) (4-8). It uses the directional information of diffusion tensor maps to estimate connection pathways in white matter. Tractography studies of major white matter tracts in the human brain appear to be in good agreement with the anatomical results obtained with dissection or histological methods (5,6,(8)(9)(10). The knowledge of the architectonical organization and connectivity may contribute to a better understanding of brain anatomy, both in physiological and pathological conditions. It may be useful to assess how brain organization is affected by disorders such as trauma or tumor growth. Therefore, it is very important to determine the relationship between the lesions and the eloquent white matter tracts so that appropriate neurosurgical approaches can be designed to avoid destroying important fiber tracts. However, the question remains whether the DTI fiber tractography results are reproducible and reliable enough to be used as a tool for clinical routine. The reliability and reproducibility of these techniques are known to be limited by the quality of ...

BackgroundWe aimed to identify subventricular zone (SVZ)-related prognostic factors of survival and patterns of recurrence among patients with glioblastoma.MethodsForty-three patients with primary diagnosed glioblastoma treated in our Cancer Center between 2006 and 2010 were identified. All patients received surgical resection, followed by temozolomide-based chemoradiation. Ipsilateral (iSVZ), contralateral (cSVZ) and bilateral (bSVZ) SVZs were retrospectively segmented and radiation dose-volume histograms were generated. Multivariate analysis using the Cox proportional hazards model was assessed to examine the relationship between prognostic factors and time to progression (TTP) or overall survival (OS).ResultsMedian age was 59 years (range: 25–85). Median follow-up, OS and TTP were 22.7 months (range 7.5–69.7 months), 22.7 months (95% CI 14.5–26.2 months) and 6.4 months (95% CI 4.4–9.3 months), respectively. On univariate analysis, initial contact to SVZ was a poor prognostic factor for OS (18.7 vs 41.7 months, p = 0.014) and TTP (4.6 vs 12.9 months, p = 0.002). Patients whose bSVZ volume receiving at least 20 Gy (V20Gy) was greater than 84% had a significantly improved TTP (17.7 months vs 5.2 months, p = 0.017). This radiation dose coverage was compatible with an hippocampal sparing. On multivariate analysis, initial contact to SVZ and V20 Gy to bSVZ lesser than 84% remained poor prognostic factors for TTP (HR = 3.07, p = 0.012 and HR = 2.67, p = 0.047, respectively).ConclusionOur results suggest that contact to SVZ, as well as insufficient bSVZ radiation dose coverage (V20Gy <84%), might be independent poor prognostic factors for TTP. Therefore, targeting SVZ could be of crucial interest for optimizing glioblastoma treatment.

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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 5 0.01). The 75th percentile of ADC within hypointense regions and the 25th percentile of rCBV within nonenhancing lesions were prognostic of disease-free survival (p 5 0.004, p 5 0.05). A significant correlation was found between the 75th percentile of rCBV and the 25th percentile of rADC (p 5 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.

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Background: Glioblastoma is the most frequent malignant primitive brain tumor in adults. The treatment includes surgery, radiotherapy, and chemotherapy. During follow-up, combined chemoradiotherapy can induce treatment-related changes mimicking tumor progression on medical imaging, such as pseudoprogression (PsP). Differentiating PsP from true progression (TP) remains a challenge for radiologists and oncologists, who need to promptly start a second-line treatment in the case of TP. Advanced magnetic resonance imaging (MRI) techniques such as diffusion-weighted imaging, perfusion MRI, and proton magnetic resonance spectroscopic imaging are more efficient than conventional MRI in differentiating PsP from TP. None of these techniques are fully effective, but current advances in computer science and the advent of artificial intelligence are opening up new possibilities in the imaging field with radiomics (i.e., extraction of a large number of quantitative MRI features describing tumor density, texture, and geometry). These features are used to build predictive models for diagnosis, prognosis, and therapeutic response. Method: Out of 7350 records for MR spectroscopy, GBM, glioma, recurrence, diffusion, perfusion, pseudoprogression, radiomics, and advanced imaging, we screened 574 papers. A total of 228 were eligible, and we analyzed 72 of them, in order to establish the role of each imaging modality and the usefulness and limitations of radiomics analysis.