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L’épilepsie bénigne à pointes centrotemporales (EPCT) est la forme la plus fréquente des épilepsies idiopathiques chez l’enfant (Fastenau et al., 2009). Le pronostic de ces patients est bon, notamment en raison de la rémission spontanée de cette épilepsie à l’adolescence; toutefois plusieurs études suggèrent la présence de troubles cognitifs et de spécificités neuroanatomiques. Il n’existe pas actuellement de consensus sur les liens entre leurs troubles cognitifs et leurs particularités neuroanatomiques et neurofonctionnelles. Dans cette thèse, notre but est de préciser le profil des enfants ayant une épilepsie bénigne à pointes centro-temporales, en investiguant les caractéristiques des patients à plusieurs niveaux: cognitif, fonctionnel, structurel. La thèse est composée de quatre articles, dont deux articles empiriques. Notre premier article a pour objectif de recenser les difficultés cognitives et affectives rapportées par les études s’intéressant aux caractéristiques des enfants ayant une épilepsie bénigne. Bien qu’une certaine variabilité soit retrouvée dans la littérature, cette revue démontre qu’une histoire d’épilepsie, même bénigne, peut être un facteur de risque pour le développement cognitif et socio-affectif des enfants. Notre revue de littérature a indiqué des troubles particuliers du langage chez ces enfants, mais aucune étude n’avait auparavant investigué spécifiquement la compréhension de lecture chez les enfants ayant une EPCT, une compétence essentielle dans le cheminement scolaire des enfants. Ainsi, nous avons développé une tâche novatrice de compréhension de lecture de phrases en imagerie par résonnance magnétique fonctionnelle (IRMf), adaptée à la population pédiatrique. Dans notre second article, nous avons validé cette tâche auprès d’enfants sains et nous avons mis en évidence une mobilisation des régions cérébrales généralement engagées dans des tâches langagières chez l’enfant sain, y compris les régions impliquées dans le traitement sémantique (Berl et al., 2010; Blumenfeld, Booth et Burman, 2006). Le troisième article de cette thèse rapporte notre investigation du réseau cérébral activé durant cette nouvelle tâche de compréhension de lecture de phrases en IRMf chez les enfants ayant une EPCT. Nos résultats suggèrent que ces derniers ont recours à l’activation d’un réseau cérébral plus large, présentant des similarités avec celui retrouvé chez les enfants dyslexiques. Par ailleurs, l’activation du striatum gauche, structure généralement associée à la réalisation de processus cognitifs complexes est uniquement retrouvée chez les enfants épileptiques. Étant donné que les enfants ayant une EPCT obtiennent des performances à la tâche d’IRMf équivalentes à celles des enfants sains, il est possible d’émettre l’hypothèse que ces différences d’activations cérébrales soient adaptatives. L’étude des relations entre les résultats neuropsychologiques, la performance à la tâche et les activations cérébrales a mis en évidence des prédicteurs différents entre les deux groupes d’enfants, suggérant qu’ils ne s’appuient pas exactement sur les mêmes processus cognitifs pour réussir la tâche. De plus, nous avons réalisé un travail d’intégration des diverses méthodologies utilisées dans les études en imagerie pondérée en diffusion chez l’enfant épileptique, ce qui constitue le quatrième article de cette thèse. Nous rapportons les diverses applications de cette méthode dans la caractérisation des anomalies structurelles subtiles de la matière blanche chez les enfants épileptiques en général. Les différentes méthodologies employées, les enjeux, et les biais potentiels relatifs aux traitements des données de diffusion y sont discutés. Enfin, pour mieux comprendre l’origine et les marqueurs de cette épilepsie, nous avons étudié les spécificités structurelles des cerveaux des enfants ayant une EPCT à l’aide d’analyses sur les données d’imagerie par résonnance magnétique. Aucune différence n’a été mise en évidence au niveau de la matière grise entre les cerveaux d’enfants sains et ceux ayant une EPCT. À l’inverse, nous rapportons des différences subtiles au niveau de la matière blanche dans notre population d’enfants épileptiques, avec une diminution de l’anisotropie fractionnelle (FA) au niveau temporal inférieur/moyen de l’hémisphère gauche, ainsi que dans l’hémisphère droit dans les régions frontales moyennes et occipitales inférieures. Ces résultats suggèrent la présence d’altérations de la matière blanche subtiles et diffuses dans le cerveau des enfants ayant une EPCT et concordent avec ceux d’autres études récentes (Ciumas et al., 2014)., Benign epilepsy with centrotemporal spikes (BECTS) is the most common idiopathic epilepsy in children. Owing to its spontaneous remission during adolescence, prognosis is usually good. However, studies have recently demonstrated cognitive deficits and neuroanatomical abnormalities in BECTS. To date, the relationship between cognitive impairment and brain function and structure in BECTS is unclear owing to a lack of consensus in the literature. The aim of the present thesis was to establish a multidimensional profile of children with BECTS, investigating impairments on a cognitive, functional and structural level as compared to healthy controls. The present thesis is composed of four articles, including two review articles and two empirical articles. Our first review article summarizes the cognitive and behavioural impairments reported by studies investigating the characteristics of children with BECTS. Although some variability was found in the literature, our review demonstrates that a history of childhood epilepsy, even if benign, can be considered as a risk factor for both cognitive and socio-affective development in children. More precisely, our review showed that children with BECTS present specific language impairments. However, none of the studies reviewed investigated reading comprehension in these children, which represent an essential academic skill. Thus, we developed an innovative functional magnetic resonance imaging (fMRI) sentence reading comprehension task, adapted to a pediatric population. In our first empirical article, we validated this task in healthy children. Our results were concordant with those of other studies investigating semantic processing in children (Berl et al., 2010; Blumenfeld et al., 2006). The second empirical article aimed at investigating cerebral reading networks activated in BECTS children during our fMRI sentence-reading comprehension task. Our results suggest that these children activate a larger cerebral reading network as compared to healthy controls, showing similar activation patterns to children with dyslexia while performing a similar task. Moreover, activations in the left striatum, a region generally associated with complex cognitive processes, were found in BECTS children. Given that the performance of these children on the fMRI task was similar to that of healthy controls, we hypothesize that these differences in brain reading network activations are adaptive. We further studied relationships between neuropsychological results, task performance and brain activations. Our results suggest that BECTS children rely on slightly different cognitive processes during task performance as compared to healthy controls. In addition, we performed an integrated review of various methodologies used in diffusion magnetic resonance imaging (dMRI) studies of epileptic children, which constitutes the second review article in the present thesis. We reported various applications of this method in the characterisation of subtle white matter abnormalities in epileptic children in general. The different methodologies utilized, the challenges and the potential biases associated with data processing were discussed. Finally, we investigated structural abnormalities in children with BECTS using MRI data in order to better understand the origin and markers of this epilepsy. No grey matter differences were found between BECTS children and healthy controls. However, we reported subtle white matter differences between groups, such that children with BECTS demonstrated a decreased fractional anisotropy (FA) in the middle/superior temporal region of the left hemisphere as well as in the middle frontal and inferior occipital regions of the right hemisphere. These results suggest subtle and diffuse white matter alterations in BECTS, supporting recently reported results (Ciumas et al., 2014).

Radiotherapy based on functional imaging consists to deliver a heterogeneity dose based on biological proprieties. This approach is termed biologically conformal radiotherapy or dose painting with biological target volume inside the gross tumor volume. Diffusion-weighted magnetic resonance imaging (MRI) and dynamic contrast-enhanced MRI can also be used to define a specific biological target volume. Three main tracers are used: ((18)F)-fluorodeoxyglucose to target the hypermetabolism, ((18)F)-fluoromizonidazole and ((18)F)- fluoroazomycin arabinoside to target areas of hypoxia. In this review, we give a practical approach to achieving a treatment-guided radiotherapy molecular and the main issues raised by this imaging technique. Despite the provision of all the technological tools to the radiotherapist, this new therapeutic approach is still evaluated in clinical studies to demonstrate a real clinical benefit compared to radiotherapy based on anatomic imaging.

According to the criteria of Hodges and Warlow, transient global amnesia is defined by sudden onset of isolated anterograde amnesia of spontaneous resolution within one to twenty-four hours. Its pathophysiological mechanisms are still uncertain.In a retrospective study, we have analyzed epidemiological, clinical and MRI data from twelve patients admitted to the only neurological department of French Polynesia for transient global amnesia corresponding to the criteria of Hodges and Warlow between January 2010 and December 2013.The median age of the cohort was 61.5 (53-72), the sex ratio was 1. Ten patients had one or more cardiovascular risk factors, 3 had migraine headaches and 3 had anxiodepressive disorders. Among triggers found, the occurrence during the rest was noted in one case. Retrograde amnesia was observed in 42% of cases, repetitive questioning in 75% of cases, anxious bewilderment in 67% of cases and disorientation in 33% of cases. The median episode duration was 9 hours and the duration of hospitalization was 3 days. Three patients had a recurrence. MRI was abnormal in all patients and showed diffusion-weighted hyperintensities in right (n=8), left (n=3) and bilateral (n=1) hippocampi.Epidemiological, clinical and MRI data from our cohort are similar to those from the literature except for the highest prevalence of cardiovascular risk factors and the most frequent right hippocampus involvement. Transient global amnesia occurring exceptionally while sleeping was also observed in one of our patients.

In the last decades, schizophrenia has intensively been studied using various brain imaging techniques. However, several potential confounding factors limited their interpretation power (e.g. chronicity, the impact of antipsychotic medication). By considering psychosis as a continuum of changes starting from mild cognitive impairments to serious psychotic symptoms, it became possible to provide deeper insight in the neurobiological mechanisms underlying the onset of psychosis by focusing on at-risk individuals and first-episodes. Recent brain imaging meta-analyses of the first episode psychosis (FEP), noteworthy reported conjoint bilateral structural and functional differences at the level of the insula, the superior temporal gyrus and the medial frontal gyrus, encompassing the anterior cingulate cortex. In the present review, we thus provide an update of brain imaging studies of FEP with a particular emphasis on more recent anatomical, functional and molecular explorations. Specifically, we provide 1) a review of the common features observed in individuals with high risk for psychosis and changes characterizing the transition to psychosis, 2) a description of the environmental and drug factors influencing these abnormalities, 3) how these findings in FEP may differ from those observed in chronic individuals with schizophrenia, and 4) a short overview of new classification algorithms able to use MRI findings as valuable biomarkers to guide early detection in the prodromal phase of psychosis.

Bipolar disorder is a complex pathology which has a strong heritability component. Epidemiologic studies have pinpointed the contribution of genetic factors to the heritability component. The molecular studies, that have used classical genetic approaches, have been inconclusive at indentifying genes involved in the etiology of this disorder. To overcome these difficulties, a number of strategies have been developed. One of them is the endophenotypic approach. Its main scope is to identify biological markers that are influenced by genetic factors that are less complex than those involved in the clinical expression of the disorder. Thus, it is likely these markers will be more readily linked to specific genetic loci. In this article, we describe the main phenotypes of neuro-anatomic measurements that are widely used in research, and report data on their heritability in the general population. Then, we focus on the results of the few structural neuro-imaging studies that have been carried out in families of patients suffering of bipolar disorders. The current data converge to indicate that subtle structural abnormalities, particularly at the level white matter tracts, seem to be promising endophenotype candidates for bipolar disorder.

We report the case of a 70-year-old man who developed probable unilateral Creutzfeldt-Jakob disease. Clinically, he presented with right hemiparesis, progressive aphasia, temporospatial disorientation and cerebellar ataxia and later on, myoclonia. The MRI showed a hypersignal from the left caudate in DWI with decreased ADC. Repeated electroencephalograms showed a slow background rhythm in the left hemisphere with superimposed periodic, biphasic and triphasic sharp-wave complexes in the left temporal region. Death occurred after 5weeks. Although exceptional, unilateral Creutzfeldt-Jakob disease was retained as possible.

Biomarkers can be used to describe and quantify a biological process related to pathology or to the effect of a treatment. In bipolar depression, progresses in the fields of structural and functional imaging, but also in biological research help to identify such biomarkers. Results in structural imaging are heterogeneous. Using functional imaging, in bipolar depression we can identify an hyperactivity of limbic and striatal regions with a specific implication of the lateral part of the orbito-frontal cortex. Bipolar depression is also associated with a modification of neurotrophic factors and of factors involved in the inflammatory process. Modifications in circadian rhythms have also be described but their level of specificity have to be demonstrated. The identification of biomarkers for bipolar depression seems to be an interesting field, but it still remains in the domain of research.

International audience; The standard technique for brain activation functional MRI (fMRI) is the BOLD sequence. Two new techniques have emerged: arterial spin labeling (ASL) MRI and diffusion MRI. Both have the theoretical advantage of more accurately directly demonstrating neuronal activation compared to BOLD imaging, resulting in improved spatial and temporal resolution. ASL is a perfusion sequence using labeled arterial protons as an endogenous perfusion agent. In spite of methodological difficulties, quantitative CBF measurements are possible. ASL is less susceptible to venous contamination than BOLD and more reproducible. Diffusion MRI evaluates neuronal activation at the cellular level with the prospect of excellent spatial resolution. The main limitations for both techniques are the technical difficulties in the acquisition and the low SNR. AS such, ASL is not widely used clinically and diffusion remains in the field of research. However, the increasing availability of 3T MR systems coupled with multi-channel surface coils and improved postprocessing techniques should improve the detection of the brain activation signal. It is thus possible that these techniques could become clinically available either in complement to or as a replacement for BOLD imaging.

Lateral ventricular neoplasms are rare, and account for 50% of all intraventricular tumors in adults and 25% in children. Although these neoplasms are easily detected with computed tomography (CT) and magnetic resonance imaging (MRI), both techniques are relatively unspecific in identifying the type of tumor. However, few imaging patterns are specific for a particular pathological process and useful conclusions can be made from the morphological appearance of the lesion, its location and enhancement pattern. The aim of this article was to review and illustrate the CT and MRI findings of a wide spectrum of tumors of the lateral ventricle. We reviewed choroid plexus tumors, meningioma, subependymal giant cell astrocytoma, central neurocytoma, and less frequent lesion such as lymphoma and metastases.

This study's purpose was to demonstrate a relationship between growth of stroke volume measured on Diffusion-Weighted MRI (DWI) at admission (baseline) and 24 hours later (follow-up) and functional outcome at 90 days evaluated by the modified Rankin Scale (mRS).DWI infarct volumes were calculated, using an Analyze Software. Clinical outcomes were assessed at 90 days by the mRS. Univariate regression analysis was performed to assess the relationship between changes in DWI lesion volume and mRS less or equal to 1.Sixty-nine cases had serial DWI scans with a measurable lesion at baseline and follow-up. The median baseline National Institutes of Health Stroke Scale (NIHSS) was 10, 5 and 7 at 24 hours. At 90 days, the proportion of patients with Rankin less or equal to 1 was 51.7%. The average baseline volume was 19.7 cm(3) and average follow-up volume was 46.1 cm(3). For each 10 cm(3) of growth in DWI infarct volume, the odds ratio for a mRS less or equal to 1 was 10,1 (IC 95%, 3-33.9).The results of this study provide evidence of a significant inverse relationship between infarct growth measured by DWI and good functional clinical outcome at 90 days.

The kidney performs multiple functions. Glomerular filtration is the most studied of these functions. In clinical practice, the surgical indication for patients with unilateral uropathy is frequently based on the split renal function as demonstrated by scintigraphy. MRI is not yet validated as a technique but nonetheless offers an interesting non-radiating alternative to achieve both morphological and functional renal evaluation. Recent pulse sequences such as diffusion, arterial spin labeling, and blood oxygenation dependent imaging may also provide additional information. CT and US remain of limited value for the evaluation of renal function.

Multiple chronic renal diseases evolve to end-stage kidney disease due to progressive renal tissue fibrosis at the level of the interstitium or glomeruli. Fibrosis often results from transformation of the extracellular matrix by cytokines and chemokines released by activated cells in the setting of recurrent episodes of acute inflammation. Newer techniques to image intrarenal inflammation and fibrosis are mandatory for the non-invasive evaluation of these processes to improve follow-up and monitoring of drug therapy. These techniques are based on methods of cellular and molecular imaging, and methods of functional, such as diffusion weighted imaging, and structural, such as elastography.

The frequency of neuropsychiatric symptoms in systemic lupus varies between 14 and 75%. Their mechanisms are multiple and their non-specificity makes the etiological diagnosis more difficult. The MRI lesions are dominated by small white matter hyperintensities.We report a case of 17-year-old girl without medical, surgical or familial past, who presented an acute psychotic episode with fever. The neurological examination showed a pyramidal syndrome. The brain MRI objectified diffuse, bilateral and symmetrical white and gray matter hyperintensities. The diagnosis of neuropsychiatric lupus was retained with association of more than four criteria among the 11 ARA revised criteria: pleural effusion, neuropsychiatric manifestations, anemia, lymphopenia and positive ANA. The treatment was based on corticosteroids. The evolution was fatal.Psychiatric disorders are polymorphic and appear during the course of the disease or at diagnosis; they can be seen in 20% of cases and are a sign of a poor prognosis. Most often these disorders are a non-specific reaction, but severe clinical forms can be observed as suicidal risk or mood disorders (depression, mania...), or acute psychotic episode.The diagnosis of neuropsychiatric lupus must be evoked systematically in atypical neuropsychiatric disorders especially when confronted with minimal biological and brain imaging abnormalities.

Meningococcal disease can manifest in very different clinical situations. Meningococcal meningitis and fulminant meningococcemia (or purpura fulminans) are the most common forms of these infections, but many other manifestations can be seen including septic arthritis, pericarditis, pleurisy and conjunctivitis. Brain abscesses have also been described; they are a rare complication of meningococcal disease. We report the case of a 28-year-old immunocompetent patient who developed meningococcal infection associated with brain abscesses and oligo-arthritis.

Evaluate diffusion MRI in the multiparametric assessment of prostate cancer before needle biopsy.One hundred eleven patients with suspected prostate cancer (mean age: 63 years old, median PSA: 7 ng/mL) were examined before undergoing needle biopsy (59 patients with a history of a negative biopsy and 52 without a history of biopsy). A diffusion sequence type SS SE-EPI (TR/TE: 5357/58, fEPI: 73, b 0 and 1000 s/mm², axial) with a qualitative analysis of the ADC map was performed in addition to T2 and T1 gadolinium enhanced sequences on 3 T MRI with an endorectal coil. The histological correlations were obtained by ultrasound guided needle biopsy (85 patients) or radical prostatectomy (26 patients).The correlation of the results of the diffusion sequence in the series of the 111 patients and the biopsies of the entire prostate or the hemiprostate had a sensitivity of: 92%, 77%; a specificity of: 55%, 70%; a positive predictive value of: 77%, 62%; a negative predictive value of: 84%, 80% and an efficacy of 78%, 75% respectively. The agreement of the three sequences had a specificity of 84.3%.The sensitivity of diffusion MRI is high for the detection of cancer of the prostate. Specificity of sequences is good. The results of simple visual assessment of the ADC map are good.

There is a wide range of spinal cord pathologies (vascular, inflammatory, infectious, metabolic, degenerative). They present clinically as acute partial or complete cord syndromes, or chronic myelopathies (more than 4 weeks in duration). MRI examination should be undertaken with a very strict protocol. Spinal cord lesions should be evaluated with regards to their T1W and T2W signal characteristics, involvement of grey and/or white matter, axial and sagittal extension, cord volume changes, contrast uptake and associated lesions (perimedullary, radicular or brain). The correlation of MR imaging features with clinical and biological data (blood and CSF) should suggest a differential diagnosis.

Cord injuries are frequent and severe lesions resulting in significant disability, most frequently in younger subjects. The area of cord injured results in clinical syndromes (Brown-Sequard, motor and/or sensory deficit...). Cord and rootlet injuries are best depicted on MRI. Diffusion tensor imaging with tractography enables depiction of the most severe cord lesions and some prediction of tissue viability which may provide an idea of the potential functional prognosis and patient recovery. MRI is optimal to demonstrate areas of cord hemorrhage or compression, partial or complete cord transsection, nerve root avulsion...

The spinal canal is divided into epidural, subdural and subarachnoid spaces. Intraspinal processes should be correctly placed into their space of origin. MRI is the best imaging modality to achieve this task. Accurate determination of the space of origin routinely requires the acquisition of two different pulse sequences, typically T1W and T2W images, in two orthogonal planes, usually axial and sagittal. Simple imaging features can assist in determining the site of origin: changes to the epidural fat, compression or widening of subarachnoid spaces. The epidural space, bordered medially by dura, contains fat and vascular structures. The subdural space is a virtual space in between the dura and arachnoid membrane. The subarachnoid space is home to the CSF, spinal cord and nerve rootlets. An epidural process replaces the epidural fat, displaces the dura and narrows the subarachnoid space. A subarachnoid process widens the subarachnoid space and spares the epidural fat. Epidural processes usually are infectious or tumoral, either primary or secondary to spinal involvement. Subarachnoid processes include primary tumors, leptomeningeal metastases, arachnoiditis and hemorrhage. Nerve sheath tumors and meningiomas are the most frequent intradural extramedullary tumors.

To determine the reliability and variations of apparent diffusion coefficient (ADC) values in normal fetuses. Materials and methods. Retrospective study (2007-2008) on 22 normal fetal MR examinations, performed between 30 and 34 of gestation, using a routine protocol (T1W and T2W images in 3 planes, b=1,000 diffusion-weighted imaging) without sedation. ADC values were measured by placing 3 adjacent regions of interest (ROI) including a centrally located ROI over the right frontal and occipital white matter (6 ROI).reproducibility of adjacent ADC values (intraclass correlation coefficient: ICC) and comparison between frontal and occipital ADC values (Wilcoxon).The mean ADC value was 1.78 mm(2)/s for the frontal white matter (+ or - 0.10) and 1.66 mm(2)/s for the occipital white matter (+ or - 0.12) with excellent reproducibility (ICC=0.91 in the frontal lobe) and good reproducibility for adjacent measurements (ICC=0.7). A linear inverse correlation existed between ADC values and gestational age in the occipital lobes, and a significant fronto-occipital gradient existed after 32 weeks of gestational age.ADC value measurements are reliable and inversely correlated with gestational age due to fetal brain maturation. The existence of a fronto-occipital gradient after 32 weeks of gestational age could be a marker of normal maturation used in clinical practice.

Imaging of water diffusion or diffusion-weighted MR imaging provides physiological information about brain diseases that cannot be obtained from conventional sequences. This technique is very sensitive for the detection of cerebral ischemia from arterial origin and can distinguish cerebral ischemia from other non-vascular brain pathologies in patients presenting with abrupt onset of focal neurological deficit. Diffusion-weighted imaging is used for the evaluation of non-vascular diseases as well. Combined with conventional sequences, it is helpful to differentiate brain abscesses from necrotic tumors. Quantitative diffusion-weighted imaging provides additional information in the characterization of tumors or inflammatory, degenerative and metabolic lesions. Finally, diffusion-weighted imaging data also has prognostic value.

Due to technical advances (parallel imaging and new phased-array coils), diffusion-weighted MR imaging can be used to image the female pelvis. Diffusion-weighted (b=1000) images are now acquired as a complement to conventional sequences (T2W, dynamic T1W images after intravenous injection of gadolinium). Diffusion weighted imaging improves the detection of small uterine tumors and the visualization of small implants of peritoneal carcinomatosis, which could play a significant role for tumor staging. It is helpful for characterization of complex ovarian tumors: the absence of hyperintensity on b=1000 diffusion-weighted images has an excellent positive predictive value for a benign etiology. It could also be helpful to characterize endometrial lesions, to differentiate between endometrial polyp and carcinoma when hysteroscopy is not possible, and to differentiate uterine fibroid from sarcoma. Finally, diffusion-weighted imaging could be helpful to assess the response of uterine tumors to therapy and could confirm a good outcome following uterine artery embolization of uterine fibroids.

Diffusion-weighted imaging studies the motion of water molecules within a given tissue. Initially used for neuroradiological applications, it is now routinely used for abdominal imaging, especially liver imaging. The diffusion pulse sequence is a T2 echo-planar sequence where diffusion gradients are applied. In this article, we will review the sequence itself and the parameters used to optimize the sequence, quantitative and qualitative image evaluation, and the main applications for liver imaging: characterization of focal lesions, detection of focal lesions, evaluation of response to therapy and quantification of liver fibrosis.

Diffusion-weighted imaging is helpful to further characterize lesions that remain indeterminate after morphological and dynamic MR evaluation. Suspicious lesions are hyperintense on diffusion-weighted images with corresponding low ADC values, indicating restricted diffusion and hypercellularity. Benign lesions and tumors responding to treatment usually have no diffusion restriction. ADC maps are useful for T2W hyperintense lesions that could mask the presence of restricted diffusion. Image fusion is sometimes needed to accurately localize enhancing lesions on ADC maps. For indeterminate lesions, a hypocellular appearance suggests a lower ACR category whereas the presence of restricted diffusion suggests a higher category.

Functional imaging complements T2-weighted imaging in the evaluation of the prostate. The most frequently used techniques are diffusion-weighted imaging and perfusion imaging following the intravenous administration of contrast material. Perfusion imaging has high sensitivity and moderate specificity, even when using a quantitative technique, because contrast kinetics in some cases of peripheral zone prostatitis and benign transition zone hyperplasia may simulate cancer. Diffusion-weighted imaging is currently under evaluation but appears to be preferable to dynamic perfusion MR imaging because of its higher specificity and simpler acquisition. Functional imaging of the prostate is performed to detect cancers missed on biopsies or evaluate the volume of a newly diagnosed clinically localized cancer to assist in therapy selection. Future applications for image-guidance of targeted therapies to the tumor are currently investigational.

After being first used for liver imaging, diffusion-weighted imaging of the kidney is in development. The kidney is the only anisotropic organ in the abdomen. It is a complex organ, with different types of flow, that is the subject of multiple research projects. Diffusion-weighted imaging is very sensitive for the detection of tumors, especially small ones. It also facilitates lesion characterization with the help of ADC values. Diffusion restriction indicates hypercellularity, which suggests malignancy. Diffusion-weighted imaging is currently available on clinical scanners. Characterization of different types of collections is possible. The characterization of nephropathies remains investigational.

Diffusion weighted MR imaging is increasingly being used for the imaging of head and neck pathology. This imaging technique now replaces CT and conventional MR imaging for the initial diagnosis of cholesteatoma and detection of recurrent disease. Diffusion weighted imaging has also proven to be valuable for additional head and neck pathologies and currently has three main indications: detection and characterization of tumors, regional tumor staging, and prediction of tumor response to treatment and follow-up. In the recent months, several publications have discussed the use of diffusion weighted imaging for head and neck pathology and this technique has become virtually indispensable for the MR imaging evaluation of the head and neck.

Due to its excellent sensitivity, MR imaging is invaluable for the evaluation of lesions of the cord and spine. Several studies dedicated to diffusion-weighted MR evaluation of the cord and spine have been published. While diffusion-weighted MR imaging of the brain is routinely performed, it is seldom performed when imaging the spine due to serious limitations. While anatomical limitations may not be changed, the voxel size, phase-encoding direction, mode of k-space filling, and acceleration factor are all parameters that can be optimized in order to routinely obtain diffusion-weighted imaging of the spine on 1.5T and 3T scanners.

Hemato-oncologic imaging combines anatomical and functional imaging data for optimal staging and follow-up of patients. It is currently possible to achieve high spatial resolution and functional evaluation at whole body MR imaging. Functional imaging may be achieved with two techniques: dynamic imaging following intravenous contrast injection and diffusion-weighted imaging. The purpose of this article is to demonstrate how both functional imaging techniques can be combined with whole body MR imaging for the evaluation of multiple myeloma and lymphomas.

Mild cognitive impairment (MCI) is considered as a strong risk factor for Alzheimer's disease (AD) or other dementia syndromes. Since the last decade, numerous publications have been aimed to characterize early detectable brain changes in vivo, using more and more efficient neuroimaging techniques. This review is devoted to the brain damages detectable in MCI patients according to the MRI techniques available to date. The greatest number of studies, using structural and functional imaging, report many abnormalities principally located in the medial temporal lobe. They show, especially in this region, cortical atrophy, reduction of glucose metabolism, decrease in regional cerebral blood flew and biochemical changes. Moreover, progresses in the functional methods allow to detect brain activity during memory tasks, trying to specify whether this activity increases or decreases according to the task and the severity of cognitive impairment. The contribution of each RMI technique (morphologic, metabolic, and functional) is addressed in order to reveal how relevant they are to distinguish subjects with MCI from patients with early AD. Furthermore, their relevance to discriminate between MCI with different degrees of cognitive deficit and their power to predict the risk of conversion to AD is discussed. Finally, we review the main assumptions made to explain the underlying mechanisms of cognitive decline and present evidences in favor of dynamic compensatory processes, existence of cognitive reserve and disconnection processes. Many neuroimaging data support the pattern of installation and evolution of brain damages found in AD, reinforcing the idea that a part of amnesic MCI is probably a prodromal state of AD.

International audience; Due to ongoing technological advances, the range of clinical applications for diffusion-weighted MR imaging has expanded to now include abdominal pathology. Current applications for liver pathology include two main directions. First, oncologic imaging with detection, characterization and follow-up of lesions. Second, evaluation of diffuse liver diseases, including hepatic fibrosis. The diagnostic impact and role of diffusion-weighted MR imaging remain under investigation, but appear promising. Because of its short acquisition time, sensitivity, and additional information it provides, diffusion-weighted MR imaging should be included in routine liver imaging protocols.

To determine the value of diffusion-weighted imaging (DWI) in the evaluation of adnexal tumors, especially to distinguish between malignant and benign tumors. Materials and methods. Fifty-four patients with pelvic tumors (32 malignant and 22 benign) were referred for MRI of the pelvis. DWI was obtained in all patients. Histological correlation was available in all cases. The signal of solid and cystic tumor components was evaluated on T2W and b=1000 DWI, and ADC values were obtained.T2W hypointensity or absence of hyperintense signal on b=1000 DWI sequences was suggestive of a benign tumor. Hyperintensity on b=1000 DWI sequences was strongly correlated with malignant lesions. ADC values did not appear to discriminate between malignant and benign tumors. Also, the signal intensity of cystic tumor components on DWI sequences was not helpful to distinguish between malignant and benign tumor.The evaluation of solid tumor components on DWI appears to be helpful for adnexal tumor characterization.

To use diffusion weighted MR imaging (DWI), a technique routinely used in patients with stroke, for diagnosis of myocardial infarction (MI).A breath hold ECG gated DWI sequence (b = 300 sec/mm2) was developped and applied to 7 patients with recent MI (3-15 days), 3 patients with chronic MI (6 months) and 4 patients with valvular heart disease without MI (control cases). DWI data were correlated to T2W, first pass perfusion and delayed enhancement data.In all patients with recent MI, DWI showed an area of increased signal with reduction of ADC relative to normal myocardium. Hyperintense lesion on DWI corresponded to areas of delayed enhancement. The diffusion images were normal in patients with chronic MI or no MI.Even though no animal model or other reference method is available, these preliminary results indicate that DWI could assist clinicians in detecting recent MI.

The treatment of advanced cervix is concomitant radiochemotherapy. Local prognosis and global survival depend on tumoral volume, locoregional extension and radio sensitivity of the lesion. This one is function of tumoral hypoxia, tumoral interstitial pressure and existence of an anaemia. DCE-MRI allows to quantify pilot vascular parameters of the first two factors. Combined analysis: tumoral volume, anaemia and vascular parameters before and in the course of treatment allows a strong correlation with the risk of local recurrence and global survival.

Because of its excellent diagnostic performance, whole-body MRI will probably become an alternative to or replacement for positron emission tomography and computed tomography (PET-CT). The sensitivity of diffusion sequences is high. Whole body MRI is used increasingly often in oncology, for initial or follow-up staging, finding primary tumors after identifying metastases, staging for pregnant woman and children, and therapeutic follow-up. Advantages of whole-body MRI over PET-CT include the absence of irradiation as well as the greater availability, and lower cost of MRI.

This article shows that functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) are very useful in the in vivo description of the visual pathways using today's most advanced techniques and allowing fusion between fMRI and tractography. Two complementary techniques were combined: (1) DTI coupled with the tractography and (2) fMRI.A group of 205 cases, normal and pathological, children and adults, were studied for tractographic reconstitution of visual pathways. In addition, 11 patients underwent an acquisition in fMRI (BOLD effect), with a stimulation of a black-and-white flickering checkerboard. Acquisition was carried out on a 3.0 Tesla GEHC MRI unit. Activated arrays of fMRI are overlaid with those of neurotractography (neural tractography) having like results a functional neurotractography.The main components of the visual pathways were successfully reconstructed in tractography: the optic nerves, optic chiasm, optic tracts, and optic radiations. It was also possible to visualize fiber decussation within the chiasma (possible direct pathways to the hypothalamus and thalamus were also identified).The tensor of diffusion is increasingly used and is a promising technology to improve the diagnosis of neurological diseases. Sophisticated algorithms contribute a new vision of the anatomy, with the possibility of isolating distinct anatomical entities. With the software used, the charts of fMRI activation are overlaid on the anisotropy charts. The tractograms that link two regions of the same functional network thus provide information on subjacent structural connectivity. Consequently, one speaks about functional neurotractography.

Susac syndrome is a rare microangiopathy, responsible for small cerebral, retinal and cochlear infarcts. The classic clinical triad includes multiple neurologic signs (from headaches to coma), retinal branch occlusions and sensorineural hearing loss.We report a series of five patients with Susac syndrome followed in our department from 1997 to 2007.There were four women and one man (mean age at onset: 35.2 years). Clinical symptoms at onset were neurological (n=1), ophthalmological (n=1), auditory (n=1) and clinical triad (n=2). Neurologic symptoms included encephalopathy (n=2), headache (n=5), transient ischemic attacks (n=1). Brain MRI showed T2 lesions in the white and grey matter, corpus callosum and gadolinium-enhanced punctiform lesions. Cerebrospinal fluid contained an elevated protein level in three cases. Immunologic treatments (steroids [n=4], cylophosphamid [n=3], intravenous immunoglobulins [n=5]) associated with aspirin and/or oral anticoagulants, despite early relapses (n=2), led to dramatic clinical improvement (n=5).Due to its polymorphism the SS is difficult to diagnose when the clinical triad is lacking. In the absence of clinical trial and consensus treatment is empiric and based on supposed pathogenesis.

Star-fruit ingestion has been previously reported to cause severe neurotoxicity in uremic patients with symptoms ranging from hiccups, vomiting and consciousness disturbances to refractory status epilepticus, coma and death. MRI examinations of five uremic patients with severe neurological disturbances following star-fruit intoxication were reviewed. At the time of MRI, all patients presented with a confusional state, preceded by seizures in three cases. MRI showed focal (four patients) and diffuse (one patient) cortical hyperintensity on diffusion-weighted sequences, with a corresponding low apparent diffusion coefficient. An additional area of increased diffusion intensity was observed in the pulvinar (two patients) and hippocampus (two patients). MRI and diffusion-weighted imaging may be useful for the diagnosis of star-fruit neuro-intoxication which is associated with a poor prognosis and requires acute and appropriate treatment.

CNS tuberculosis remains relatively frequent in endemic regions. Both CT and MRI are valuable for diagnosis. Even though non-specific, MRI including diffusion-weighted imaging and proton spectroscopy is more sensitive than CT for detection of some lesions. The purpose of this paper is to illustrate the imaging features of CNS tuberculosis.

To describe the CT and MRI features of 3 cases of arachnoid cyst of the petrous apex.Three patients with isolated trigeminal neuralgia, trigeminal hypoesthesia, and sinusitis. Axial and coronal CT images were obtained. T1W, FSE T2W, FLAIR, T2*W and diffusion-weighted MR sequences were obtained.In all cases, both CT and MRI showed expansile lesions eroding the petrous apex. Lesions were hypodense on CT and isointense to CSF on MRI, without contrast enhancement. In one case, the lesion was contiguous with Meckel's cave with temporal fossa and sphenoid sinus extension. CT and MR imaging features are useful to distinguish arachnoid cysts of the petrous apex from other benign lesions of the petrous apex.CT and MRI imaging features allow diagnosis of arachnoid cyst of the petrous apex because its imaging features, especially on DWI, are different from other cystic lesions of the petrous apex, namely cholesteatoma. It should be considered in patients with trigeminal involvement, especially trigeminal neuralgia.

To describe subtle brain abnormalities detected on MRI in adult patients with adrenomyeloneuropathy (AMN). Materials and methods. Retrospective evaluation of data acquired prospectively as part of a clinical trial (Riluzole) in 66 adult patients with AMN without obvious brain lesion on MR. All patients underwent brain MR including T1W, T2W, FLAIR and spectroscopy. After a review had been validated by three different reviewers, review of MR images was performed by consensus using a semi-quantitative scale.Preliminary analysis of MR images confirmed the presence of signal abnormalities involving the corticospinal tracts in 36 patients (54.6%). Additional subtle abnormalities were also detected: white matter palor, mainly parieto-occipital in location, with patchy hyperintensity in 36 patients (54.6%), hyperintense pontocerebellar fibers on T2W and FLAIR in 25 patients (41.7%). The presence of elevated Cho/Cr and mI/Cr ratios, described in the literature, were confirmed.This retrospective study allows the description of an AMN pattern on MRI in patients without white matter or callosal abnormalities.

Imaging plays a crucial role in oncology to assist in the management of patients and selection of drug regimen. Recent advances in imaging techniques allowing to predict and evaluate response to treatments in oncology will be reviewed. The standard in the evaluation of response to treatment is based on the measurement of lesion size. Functional imaging assesses physiological or molecular processes that may be earlier indicators of early response to treatment. Dynamic imaging of tumor vascularization assesses the biodistribution of a contrast agent within tumoral tissues. Diffusion-weighted MR imaging can differentiate free water from water restricted by tissues, providing an assessment of tumor cellularity. MR spectroscopy assesses the relative quantity of specific chemical components within normal and tumoral tissues. 18 FDG PET imaging provides an assessment of the metabolic activity of tissues. FDG uptake is proportional to cellular proliferation and number of viable cells within a tumor. Results from studies assessing the role of these emerging imaging techniques remain preliminary and the medical community must determine their respective role in the routine evaluation of response to treatment in oncological patients.

Conventional MRI with T1, T2 and FLAIR sequences has an important role for the diagnosis of Creutzfeldt-Jakob disease, but the usual examination does not exclude the disease. The objective of this study is to report on the role of diffusion-weighted imaging (DWI) in the diagnostic strategy. From 2002 to 2006, four patients with a suspected diagnosis of sporadic Creutzfeldt-Jakob disease, which was retrospectively confirmed, underwent DWI. In all patients, MRI demonstrated high-signal intensities on FLAIR sequences and on spin-echo T2-weighted MRI, with restricted diffusion of caudate and lenticular nuclei. In one patient, DWI revealed cortical high-signal intensities that were not visualized on either FLAIR or T2-weighted MRI. In two other patients, MRI showed restricted thalamic diffusion, which is a classic sign of the new variant of the disease. Thus, thalamic involvement can be found in the sporadic form of the disease. It can be revealed on DWI and by apparent diffusion coefficient (ADC) mapping or detected only by ADC measurement.