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

81 publication(s) depuis Décembre 2006:

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2010 | Cerebrovasc Dis
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

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
[Molecular imaging of tumor hypoxia].
Huchet A , Fernandez P , Allard M , Belkacemi Y , Maire JP , Trouette R , Eimer S , Tourdias T , Loiseau H

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
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

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
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

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)
[Magnetic resonance imaging of central nervous system inflammation].
Tourdias T, Brochet B , Petry KG , Dousset V

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
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

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.

05/2008 | j Neuroradiol
Pulsed arterial spin labeling applications in brain tumors: practical review.
Tourdias T , Rodrigo S , Oppenheim C , Naggara O , Varlet P , Amoussa S , Calmon G , Roux FX , Meder JF

Few institutions use MRI perfusion without contrast injection called arterial spins labeling (ASL) routinely in clinical setting. After general considerations concerning the different ASL techniques and quantitative issues, we will detail a pulsed sequence that can be used on a clinical 1.5-T MR unit. We will discuss and illustrate the use of ASL in tumoral diseases for diagnosis, gliomas grading, stereotactic biopsy guidance and for follow-up after treatment.

15/02/2008 | J Neurol Sci
How to trace stem cells for MRI evaluation?
Dousset V, Tourdias T, Brochet B, Boiziau C, Petry KG

Applications of imaging techniques to visualize stem cells for monitoring, control and treatment of biological systems, in particular the brain, is at the forefront of investigations. These approaches involve the identification of stem and precursor cells that may be of various origins, but are related to specific clinical conditions, and the choice of the appropriate markers to achieve the required imaging while minimizing the side effects. This article will review examples of the contrast agent design for rational approaches in stem cell imaging. Potential pitfalls or side effects associated with contrast agents, in particular iron oxide nanoparticles, for cell labelling are also discussed.

12/2007 | Stroke
Magnetization transfer imaging shows tissue abnormalities in the reversible penumbra.
Tourdias T , Dousset V , Sibon I , Pele E , Menegon P , Asselineau J , Pachai C , Rouanet F , Robinson P , Chene G , Orgogozo JM

BACKGROUND AND PURPOSE: In the concept of ischemic penumbra, the volume of salvaged penumbra is considered as the volume of FLAIR normalization on follow-up MRI compared with early diffusion and perfusion abnormalities. Using magnetization transfer imaging, very sensitive to macromolecular disruption, we investigated whether FLAIR normalization was a good marker for tissue full recovery. METHODS: We prospectively included 30 patients with acute middle cerebral artery stroke. Diffusion-weighted imaging (DWI) and perfusion-weighted imaging were performed within 12 hours after onset (MRI.1), and the final infarct was documented by MRI with FLAIR and magnetization transfer at 1-month follow-up (MRI.2). We compared magnetic transfer ratio of a normal region with values measured at 1 month (MRI.2) in 4 regions of interest: (1) the initial DWI hypersignal (CORE=DWI MRI.1); (2) the infarct growth area (infarct growth=FLAIR MRI.2-DWI MRI.1); (3) the hypoperfused area that normalized (reversible perfusion abnormalities=perfusion-weighted imaging MRI.1-FLAIR_ MRI.2); and (4) the early DWI abnormalities that normalized (reversible diffusion abnormalities=DWI MRI.1- FLAIR_MRI.2). RESULTS: In comparison with values obtained in normal tissue (magnetic transfer ratio=49.8%, SD=1.9), magnetic transfer ratio at 1 month was significantly decreased in reversible perfusion abnormalities (45.2%, SD=2.5; P<0.0001) and reversible diffusion abnormalities (43.2%, SD=2.8; P=0.0156). It was also markedly reduced, as expected, in the CORE (40.9%, SD=5.2) and infarct growth regions (43.1%, SD=2.0). CONCLUSIONS: Magnetic transfer ratio assessed presence of microstructural damages in the MRI-defined salvaged penumbra. This may imply cellular loss and partial infarction. Evaluation of the efficacy of therapies that promote reperfusion or neuroprotection may benefit from this additional information.

03/2007 | J Radiol
[Diffusion tensor imaging and tractography of the brain and spinal cord].
Oppenheim C , Ducreux D , Rodrigo S , Hodel J , Tourdias T , Charbonneau F , Pierrefitte S , Meder J

Diffusion tensor imaging is a magnetic resonance imaging technique that provides details on tissue microstructure and organization well beyond the usual image resolution. With diffusion tensor imaging, diffusion anisotropy can be quantified and subtle white matter changes not normally seen on conventional MRI can be detected. The aim of this article is to review the principles of diffusion tensor imaging and fiber tracking and their applications to the study of the brain, including Alzheimer disease, neuropsychiatric disorders, strokes, multiple sclerosis, brain tumors, and intractable seizures. Emerging applications to spinal cord disorders are also presented.