Jean L. Dietemann

Reconstruction of scattered data in fetal diffusion MRI.

In this paper we present a method for reconstructing diffusion-weighted MRI data on regular grids from scattered data. The proposed method has the advantage that no specific diffusion model needs to be assumed. Previous work assume the tensor model, but this is not suitable under certain conditions like intravoxel orientational heterogeneity (IVOH). Data reconstruction is particularly important when studying the fetal brain in utero, since registration methods applied for movement and distortion correction produce scattered data in spatial and diffusion domains. We propose the use of a groupwise registration method, and a dual spatio-angular interpolation by using radial basis functions (RBF). Leave-one-out experiments performed on adult data showed a high accuracy of the method. The application to fetal data showed an improvement in the quality of the sequences according to objective criteria based on fractional anisotropy (FA) maps, and differences in the tractography results.

Current and future imaging of the peripheral nervous system

Peripheral nervous system (PNS) imaging is usually carried out by ultrasound and MRI. Thanks to its wide availability and excellent spatial resolution, ultrasound is a mature investigation with clearly established indications, particularly in entrapment syndromes and tumors. MRI is generally a second-line examination, which provides decisive additional information thanks to its excellent contrast resolution and its multiplanar abilities. This review describes the current methods for imaging the PNS, concentrating on acquisition techniques, normal results and basic pathological semiology. Ongoing and future developments are described in order to underline the forthcoming changes in this very dynamic field of musculoskeletal radiology.

Glioblastoma multiforme presenting with ischemic stroke: Case report and review of the literature

A 58-year-old woman presented with acute onset of global aphasia. Imaging studies revealed a left frontotemporal enhancing tumor and ischemic stroke in the territory of the middle cerebral artery. The patient was operated on, and the diagnosis of glioblastoma multiforme was confirmed. At the time of surgery, several branches of the left middle cerebral artery were found embedded in the tumor. One branch, which was infiltrated by tumor and completely occluded, was resected to achieve complete resection. Postoperatively, the stroke area within the middle cerebral artery territory increased, together with worsening of the patients clinical status, thus requiring urgent decompressive craniectomy. Thereafter, the patient gradually improved, and received radiation therapy and chemotherapy with no recurrence after 24 months of follow-up. To our knowledge, glioblastomas presenting with ischemic stroke are rare, and such patients should be considered to be at high surgical risk.

Tumeur mélanocytaire méningée primitive de grade intermédiaire : confrontation radio-pathologique

Resume Un cas de tumeur melanocytaire meningee primitive de grade intermediaire interessant la racine droite de C2 est presente. Cette rare entite peut etre evoquee en presence d’une lesion extra-axiale situee dans la fosse posterieure ou le canal cervical et presentant un raccourcissement des T1 et T2. Le diagnostic de certitude repose sur l’histologie qui montre de maniere caracteristique une proliferation de cellules melanocytaires fusiformes marquees par la coloration de la melanine et positives pour l’antigene HMB45. La cellularite, l’index mitotique, l’index de proliferation et le caractere invasif sont les principaux criteres permettant de classer cette lesion au sein des tumeurs melanocytaires meningees dont le spectre s’etend du melanocytome au melanome malin.

Reconstruction of scattered data in fetal diffusion MRI

In this paper we present a method for reconstructing D-MRI data on regular grids from sparse data without assuming specific diffusion models. This is particularly important when studying the fetal brain in utero, since registration methods applied for movement and distortion correction produce scattered data in spatial and angular (gradient) domains. We propose the use of a groupwise registration method, and a dual spatio-angular interpolation by using radial basis functions (RBF). Experiments performed on adult data showed a high accuracy of the method when estimating diffusion images in unavailable directions. The application to fetal data showed an improvement in the quality of the sequences according to criteria based on fractional anisotropy (FA) maps, and differences in the tractography results.

Le bilan d'imagerie dans les traumatismes récents du rachis

Resume L’objectif de cette mise au point est de preciser la place actuelle des differentes modalites d’imagerie dans le bilan d’un traumatisme du rachis. Nous detaillons les differentes techniques disponibles en discutant leurs avantages et inconvenients respectifs, puis nous passons en revue le spectre des lesions observees, qu’elles soient osseuses, ligamentaires, vasculaires ou nerveuses. Enfin, nous proposons une strategie diagnostique integrant ces differents elements.

Case 173: Acute Disseminated Encephalomyelitis Confined to the Brainstem

Three diagnostic considerations should be offered for the cause of an isolated ring-enhancing lesion of the brainstem: primary or secondary brainstem tumors, abscesses, or acute disseminated encephalomyelitis; a first episode of multiple sclerosis also might be considered.

Anatomie fonctionnelle du lobe temporal et techniques d’exploration en IRM

Objectifs Connaitre l’anatomie corticale et des fibres d’association temporales. Connaitre les grandes fonctions temporales et limbiques. Savoir explorer la region temporale en IRM. Points cles Le lobe temporal est compose de 5 circonvolutions et de la region amygdalo-hippocampique. Il est relie aux regions occipitales, parietales et frontales par l’intermediaire de faisceaux d’association. Il participe aux fonctions auditives, du langage et a la memoire. Le lobe temporal s’explore dans le plan coronal perpendiculaire aux structures hippocampiques. Resume L’organisation anatomique du lobe temporal et son inclinaison conduisent a l’explorer de maniere optimale dans un plan coronal perpendiculaire aux structures hippocampiques. Mais l’ exploration doit egalement couvrir l’ensemble de l’encephale car les pathologies temporales peuvent impliquer d’autres regions cerebrales. Il est compose de 5 circonvolutions et de la region amygdalo-hippocampique. Il est connecte aux autres structures cerebrales par l’intermediaire de faisceaux d’association (faisceaux uncines et longitudinal inferieur) qui peuvent etre mis en evidence par les techniques de tenseur de diffusion et de tractographie. Il fait egalement partie du lobe limbique (circuit de Papez) et participe ainsi a la memoire. Il participe egalement au langage (aires de Wernicke) et a l’audition (gyrus de Heschl). La connaissance de l’anatomie et des fonctions temporales est indispensable a la reconnaissance des anomalies morphologiques et a la comprehension des pathologies regionales.

Subclinical haemorrhage in non-functional adenomas

AIM The prevalence and risk factors of subclinical haemorrhage on non-functional adenomas (NFA) remain controversial. The primary aim of our study was to assess the incidence of subclinical haemorrhage (SH) and the secondary objectives were to evaluate the risk factors of SH and the impact of SH on pituitary function at diagnosis. PATIENTS AND METHODS This retrospective transversal analysis included 95 patients between January 2012 and December 2014. The patients included in this series were all adults (>18 years of age), who presented a non-functional adenoma confirmed by an endocrinological evaluation and on dedicated MRI pituitary imaging. Sixty-four patients were eligible for this study. Subclinical haemorrhage was defined by the presence of haemorrhage within pituitary adenoma confirmed by pituitary MRI with no clinical symptoms. A senior neuroradiologist blinded to the diagnosis reviewed all MRI. The population was prospectively divided into two groups based on MRI results (SH group vs. group control) to determine risk factors. RESULTS SH was diagnosed in 22 patients (34.38%). No risk factors (age, sex, tumor size, chronic hypertension, diabetes mellitus, malignant disease, the use of anticoagulation or antithrombotic medication or Cabergoline treatment) were involved as regards the SH. At the diagnosis, pituitary deficiency was statistically significantly more frequent in the SH group (45.45%) than in the control group (19.04%) (P=0.04). CONCLUSION The SH within NFA was observed in 34.38% of cases without an association of risk factors.

Imagerie de l’epilepsie temporale

Objectifs Connaitre les principales etiologies d’epilepsie temporale. Connaitre leur semeiologie radiologique. Savoir reconnaitre une sclerose de l’hippocampe. Points cles La sclerose de l’hippocampe est la principale etiologie d’epilepsie temporale. Elle se traduit par un hypersignal T2 et une atrophie. Elle peut s’associer a d’autres anomalies temporales et limbiques. Les autres etiologies d’epilepsie temporale sont les causes retrouvees dans les epilepsies d’autre localisation, en particulier tumorales, malformatives, vasculaires ou post-traumatiques. Resume L’epilepsie temporale est la premiere cause d’epilepsie chirurgicale. L’anomalie la plus frequente est la sclerose de l’hippocampe. Elle se traduit par une atrophie et un hypersignal T2. Elle peut etre associee a des anomalies d’autres structures limbiques et temporales (atrophie du fornix, du tubercule mamillaire, gliose du pole). D’autres etiologies d’epilepsie peuvent etre rencontrees (tumorales, malformatives, vasculaires ou post-traumatiques). Les lesions tumorales sont le plus souvent des lesions peu ou pas evolutives et doivent etre distinguees des lesions oligodendrogliales et des lesions malformatives comme les dysplasies corticales. Les malformations vasculaires les plus frequentes sont les hemangiomes caverneux. Dans de rares cas, on peut rencontrer l’association de plusieurs de ces lesions (cavernome avec une sclerose de l’hippocampe par exemple). Ce sont des « dual pathologies ».