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Thomas TOURDIAS




Enseignant-Chercheur

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Cursus:
MD: Radiology, Bordeaux (2008)
PhD: Neurosciences, Bordeaux (2011)
Post doc: Stanford University, CA, USA (2013)
Professeur des Universités - Praticien Hospitalier; PU PH (2016)






75 publication(s) depuis Décembre 2006:


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Les IF indiqués ont été collectés par le Web of Sciences en


08/2011 | Exp Neurol   IF 4.6
Adapted focal experimental autoimmune encephalomyelitis to allow MRI exploration of multiple sclerosis features.
Tourdias T , Hiba B , Raffard G , Biran M , Nishiguchi T , Aussudre J , Franconi JM , Brochet B , Petry KG , Dousset V

Abstract:
We aimed to determine an optimal protocol for inducing a focal inflammatory lesion within the rat brain that could be large enough for an easier MRI monitoring while still relevant as a multiple sclerosis (MS) like lesion. We adapted a two-hit model based on pre-sensitization of the Lewis rat with myelin oligodendrocyte protein (MOG) followed by stereotaxic injection of pro-inflammatory cytokines (TNFalpha+IFNgamma) within the internal capsule. We compared the following two strategies to increase focal lesion development for an easier MR translation: (1) a higher sensitization step (MOG50) or (2) a higher cytokine step with lower sensitization (MOG25). Control animals were administered only cytokines without MOG pre-sensitization. Animals were followed with T2, diffusion and T1 post gadolinium weighted images at 1, 3 and 7days following cytokine injection. Immunostaining was performed at the same time points for macrophages (ED1), myelin (MBP and Luxol Fast Blue) and blood brain barrier integrity (IgG). At day 1, the focal lesions depicted with T2-weighted images were very similar among groups and related to vasogenic edema (high apparent diffusion coefficient (ADC), gadolinium enhancement and IgG extravasation) induced by cytokines irrespective of the pre-sensitization step. Then, at day 3, MOG50 rats developed statistically larger T2 lesions than MOG25 and control rats that were correlated with inflammatory cell accumulation. At day 7, MOG50 rats also showed larger T2 lesions than MOG25 and control rats, together with loss of anisotropy that were correlated with demyelination. In contrast, MOG25 and control rats developed similar MR lesions decreasing over time and almost undetectable at day 7. We conclude that with a high pre-sensitization step, the focal lesion can be monitored by MRI whose signal reflects some features of a MS-like lesion, i.e. edema, inflammatory cell accumulation and later demyelination.




24/05/2011 | Neurology   IF 8.7
Fenestration of the internal carotid artery mimicking floating thrombus on CT and MR angiography.
Tourdias T , Berge J , Menegon P , Sibon I

Abstract:





02/2011 | AJNR Am J Neuroradiol   IF 3.3
Final cerebral infarct volume is predictable by MR imaging at 1 week.
Tourdias T , Renou P , Sibon I , Asselineau J , Bracoud L , Dumoulin M , Rouanet F , Orgogozo JM , Dousset V

Abstract:
BACKGROUND AND PURPOSE: Stroke volume, an increasingly used end point in phase II trials, is considered stationary at least 30 days after the ictus. We investigated whether information conveyed by MR imaging measurements of the 'final' infarct volume could be assessed as early as the subacute stage (days 3-6), rather than waiting for the chronic stage (days 30-45). MATERIALS AND METHODS: Ninety-five patients with middle cerebral artery stroke prospectively included in a multicenter study underwent MR imaging during the first 12 hours (MR imaging-1), between days 3 and 6 (MR imaging-2), and between days 30 and 45 (MR imaging-3). We first investigated the relationship between subacute (FLAIR-2) and chronic volumes (FLAIR-3), by using a linear regression model. We then tested the relationship between FLAIR volumes (either FLAIR-2 or FLAIR-3) and functional disability, measured by the mRS at the time of MR imaging-3, by using logistic regression. The performances of the models were assessed by using the AUC in ROC. RESULTS: A linear association between log FLAIR-2 and log FLAIR-3 volumes was observed. The proportion of FLAIR-3 variation, explained by FLAIR-2, was high (R(2) = 81%), without a covariate that improved this percentage. Both FLAIR-2 and FLAIR-3 were independent predictors of mRS (OR, 0.79 and 0.73; 95% CI, 0.64-0.97 and 0.56-0.96; P = .026 and .023). The performances of the models for the association between either FLAIR volume and mRS did not differ (AUC = 0.897 for FLAIR-2 and 0.888 for FLAIR-3). CONCLUSIONS: Stroke damage may be assessed by a subacute volume because subacute volume predicts the 'true' final volume and provides the same clinical prognosis.




2011 | J Neuroinflamm   IF 5.7
Differential aquaporin 4 expression during edema build-up and resolution phases of brain inflammation.
Tourdias T , Mori N , Dragonu I , Cassagno N , Boiziau C , Aussudre J , Brochet B , Moonen C , Petry KG , Dousset V

Abstract:
BACKGROUND: Vasogenic edema dynamically accumulates in many brain disorders associated with brain inflammation, with the critical step of edema exacerbation feared in patient care. Water entrance through blood-brain barrier (BBB) opening is thought to have a role in edema formation. Nevertheless, the mechanisms of edema resolution remain poorly understood. Because the water channel aquaporin 4 (AQP4) provides an important route for vasogenic edema resolution, we studied the time course of AQP4 expression to better understand its potential effect in countering the exacerbation of vasogenic edema. METHODS: Focal inflammation was induced in the rat brain by a lysolecithin injection and was evaluated at 1, 3, 7, 14 and 20 days using a combination of in vivo MRI with apparent diffusion coefficient (ADC) measurements used as a marker of water content, and molecular and histological approaches for the quantification of AQP4 expression. Markers of active inflammation (macrophages, BBB permeability, and interleukin-1beta) and markers of scarring (gliosis) were also quantified. RESULTS: This animal model of brain inflammation demonstrated two phases of edema development: an initial edema build-up phase during active inflammation that peaked after 3 days (ADC increase) was followed by an edema resolution phase that lasted from 7 to 20 days post injection (ADC decrease) and was accompanied by glial scar formation. A moderate upregulation in AQP4 was observed during the build-up phase, but a much stronger transcriptional and translational level of AQP4 expression was observed during the secondary edema resolution phase. CONCLUSIONS: We conclude that a time lag in AQP4 expression occurs such that the more significant upregulation was achieved only after a delay period. This change in AQP4 expression appears to act as an important determinant in the exacerbation of edema, considering that AQP4 expression is insufficient to counter the water influx during the build-up phase, while the second more pronounced but delayed upregulation is involved in the resolution phase. A better pathophysiological understanding of edema exacerbation, which is observed in many clinical situations, is crucial in pursuing new therapeutic strategies.




2010 | Cerebrovasc Dis   IF 2.7
Reliability of the ECASS radiological classification of postthrombolysis brain haemorrhage: a comparison of CT and three MRI sequences.
Renou P , Sibon I , Tourdias T , Rouanet F , Rosso C , Galanaud D , Drier A , Coudert M , Deltour S , Crozier S , Dormont D , Samson Y

Abstract:
BACKGROUND: Postthrombolysis brain haemorrhagic transformations (HT) are often categorized with the CT-based classification of the European Cooperative Acute Stroke Study (ECASS). However, little is known about the reliability of this classification and its extension to MRI. Our objective was to compare the inter- and intraobserver reliability of this classification on CT and 3 MRI sequences. METHODS: Forty-three patients with postthrombolysis HT on CT or at least 1 of the 3 MRI sequences: fluid-attenuation inversion recovery (FLAIR), diffusion-weighted imaging (DWI), and T2* gradient recalled echo (T2*GRE) were selected. Twelve control patients without any bleeding were added to avoid a bias based on a pure HT-positive cohort. Each series of images were independently classified with the ECASS method by 6 blinded observers. Inter- and intraobserver reproducibility was categorized from poor to excellent depending on kappa values. RESULTS: The inter- and intraobserver overall concordance of the classification was good for T2*GRE, DWI and CT (kappa > 0.6) and moderate for FLAIR (kappa < 0.6). The interobserver concordance for parenchymal haematomas was excellent for T2*GRE (kappa > 0.8) and moderate for CT, FLAIR and DWI. CONCLUSION: The T2*GRE sequence is the most reproducible method to categorize postthrombolysis HT and has an excellent reliability for the severe parenchymal haematoma category, suggesting that this sequence should be used to assess HT in thrombolytic therapy trials.




12/2009 | Cancer Radiother   IF 1.3
[Molecular imaging of tumor hypoxia].
Huchet A , Fernandez P , Allard M , Belkacemi Y , Maire JP , Trouette R , Eimer S , Tourdias T , Loiseau H

Abstract:
By allowing an earlier diagnosis and a more exhaustive assessment of extension of the disease, the tomography by emission of positrons (TEP) transforms the care of numerous cancers. At present, (18)F-fluorodesoxyglucose ([(18)F]-FDG) imaging appears as the only one available but new molecular markers are being developed. In the next future they would modify the approach of cancers. In this context, the molecular imaging of the hypoxia and especially the (18)Ffluoromisonidazole TEP ([(18)F]-MISO TEP) can give supplementary information allowing the mapping of hypoxic regions within the tumour. Because of the links, which exist between tumour hypoxia and treatment resistance of very numerous cancers, this information can have an interest, for determination of prognosis as well as for the delineation, volumes to be irradiated. Head and neck tumours are doubtless those for which the literature gives the most elements on the therapeutic impact of tumour hypoxia. Targeted therapies, based on hypoxia, already exist and the contribution of the molecular imaging could be decisive in the evaluation of the impact of such treatment. Molecular imaging of brain tumours remains to be developed. The potential contributions of the [(18)F]-MISO TEP for the care of these patients need to be confirmed. In this context, we propose a review of hypoxia molecular imaging taking as examples head and neck tumours and glioblastomas (GB), two tumours for which hypoxia is one of the key factors to overcome in order to increase therapeutics results.




15/08/2009 | Neuroimage   IF 5.8
Aquaporin 4 correlates with apparent diffusion coefficient and hydrocephalus severity in the rat brain: a combined MRI-histological study.
Tourdias T , Dragonu I , Fushimi Y , Deloire MS , Boiziau C , Brochet B , Moonen C , Petry KG , Dousset V

Abstract:
Hydrocephalus features include ventricular dilatation and periventricular edema due to transependymal resorption of cerebrospinal fluid (CSF). Aquaporin 4 (AQP4), a water channel protein located at the blood-brain barrier, might facilitate the removal of this excess of water from the parenchyma into the blood. First, we hypothesized a link between AQP4 expression and the severity of hydrocephalus. We further hypothesized that movements of water through AQP4 could affect apparent diffusion coefficient (ADC) measurements. Communicating inflammatory hydrocephalus was induced in 45 rats, and at various stages, magnetic resonance imaging (MRI) was used to measure CSF volume and periventricular ADC, with immunostaining being used to determine periventricular AQP4. We found an up-regulation of periventricular AQP4 in hydrocephalic rats that was strongly correlated with both CSF volume (Pearson=0.87, p<0.00001) and periventricular ADC (Pearson=0.85, p<0.00001). AQP4 were first located on astrocyte endfeet, but later on the whole membrane of astrocytes that became hypertrophic in the most severe and chronic hydrocephalic rats. These results show that AQP4 expression follows an adaptative profile to the severity of hydrocephalus, which is probably a protective response mechanism. They also suggest that ADC, on top of informing about cell sizes and interstitial bulk water, might also indirectly reflect quantitative water channel expression.




06/2009 | J Magn Reson Imaging   IF 3.7
Inter- and intraobserver reliability of five MRI sequences in the evaluation of the final volume of cerebral infarct.
Sibon I , Menegon P , Orgogozo JM , Asselineau J , Rouanet F , Renou P , Tourdias T , Pachai C , Chene G , Dousset V

Abstract:
PURPOSE: To evaluate the reproducibility of fluid attenuated inversion recovery (FLAIR) and four other magnetic resonance imaging (MRI) sequences in the quantitative assessment of final cerebral infarct volume. MATERIALS AND METHODS: FLAIR, T1-3D, magnetization transfer ratio (MTR)-map, diffusion-weighted trace (DWI)-trace, and apparent diffusion coefficient (ADC)-map, were acquired and measured in 33 patients 30-45 days after onset of a first-ever ischemic stroke. The infarct area was visually detected and manually delineated two times by two readers separately after images and sequences randomization. The reliability was assessed by using an intraclass correlation coefficient (ICC) and its two-sided 95% confidence interval (95% CI). RESULTS: DWI-trace had the best reliability, with an ICC of 0.96 (95% CI = 0.93-0.98). FLAIR had an ICC of 0.86 (95% CI = 0.73-0.93), and a much higher volume. T1-3D, MTR-map and ADC-map had lower reliability or excessive volume values equal to 0 in comparison to DWI-trace. CONCLUSION: DWI-trace performed within 30th and 45th day following onset of acute ischemic stroke was the most reliable sequence for final infarct volume quantification. This sequence should be added to FLAIR evaluation to strengthen the statistical results of the pharmacological trials and reduce their variability.




05/2009 | Rev Neurol (Paris)   IF 2.2
[Magnetic resonance imaging of central nervous system inflammation].
Tourdias T, Brochet B , Petry KG , Dousset V

Abstract:
Magnetic resonance imaging (MRI) is widely used to explore central nervous system inflammatory disorders, especially multiple sclerosis (MS). Advanced MRI methods are bringing more sensitive and specific tools for each step of the inflammatory process. In this review, we discuss the different MRI approaches for inflammatory disorders exploration, especially MS. We give particular emphasize on sensibility and specificity of each MRI approach and we also discuss the current knowledge concerning biological and histopathological substratum that could explain MRI signal with each modality.




01/2009 | Clin Transl Oncol   IF 2.4
Radiofrequency thermocoagulation of lung tumours. Where we are, where we are headed.
Gomez FM , Palussiere J , Santos E , Tourdias T , Cornelis F , Saiz V , Montes H , Eker O

Abstract:
Only 25% of all lung cancers are diagnosed in an early stage allowing surgical treatment. Primary tumours usually concerning lung metastasis are breast, colon, kidney, uterus/cervix, prostate, and head and neck tumours. During recent years many publications have confirmed the effectiveness and reliability of lung radiofrequency ablation (RFA) alone or together with other techniques (chemotherapy, radiotherapy...). Results suggest that survival increase and curative rates of lung radiofrequency are similar to those achieved by more aggressive procedures and present lower rates of complications. Pneumothorax, pleural effusion and alveolar haemorrhage are the most frequent complications. Indications for lung RFA must be individually evaluated by lung cancer committees. Percutaneous lung RFA may be useful in patients with pulmonary primary tumours and metastases, especially in those with nodules smaller than 3 cm and a peripheral location (>1 cm from the hilum). PET/CT seems to be the most accurate technique in patient follow up.