Advanced Neuroimaging with Computed Tomography Scanning

International audienceThe x-ray computed tomography (CT) is well known as a useful imaging method and thus CT images have continuingly been used for many applications, especially in medical fields. This book discloses recent advances and new ideas in theories and applications for CT imaging and its analysis. The 16 chapters selected in this book cover not only the major topics of CT imaging and analysis in medical fields, but also some advanced applications for forensic and industrial purposes. These chapters propose state-of-the-art approaches and cutting-edge research results

Early Deformation of Deep Brain Stimulation Electrodes Following Surgical Implantation: Intracranial, Brain, and Electrode Mechanics

IntroductionAlthough deep brain stimulation is nowadays performed worldwide, the biomechanical aspects of electrode implantation received little attention, mainly as physicians focused on the medical aspects, such as the optimal indication of the surgical procedure, the positive and adverse effects, and the long-term follow-up. We aimed to describe electrode deformations and brain shift immediately after implantation, as it may highlight our comprehension of intracranial and intracerebral mechanics.Materials and MethodsSixty electrodes of 30 patients suffering from severe symptoms of Parkinson’s disease and essential tremor were studied. They consisted of 30 non-directional electrodes and 30 directional electrodes, implanted 42 times in the subthalamus and 18 times in the ventrolateral thalamus. We computed the x (transversal), y (anteroposterior), z (depth), torsion, and curvature deformations, along the electrodes from the entrance point in the braincase. The electrodes were modelized from the immediate postoperative CT scan using automatic voxel thresholding segmentation, manual subtraction of artifacts, and automatic skeletonization. The deformation parameters were computed from the curve of electrodes using a third-order polynomial regression. We studied these deformations according to the type of electrodes, the clinical parameters, the surgical-related accuracy, the brain shift, the hemisphere and three tissue layers, the gyration layer, the white matter stem layer, and the deep brain layer (type I error set at 5%).ResultsWe found that the implanted first hemisphere coupled to the brain shift and the stiffness of the type of electrode impacted on the electrode deformations. The deformations were also different according to the tissue layers, to the electrode type, and to the first-hemisphere-brain-shift effect.ConclusionOur findings provide information on the intracranial and brain biomechanics and should help further developments on intracerebral electrode design and surgical issues

Apport diagnostique des séquences IRM de diffusion, perfusion et spectroscopie dans le bilan initial des tumeurs cérébrales intra-axiales de l'adulte

L'objectif est de définir l'intérêt diagnostique des séquences IRM de diffusion, de perfusion et de spectroscopie dans le bilan initial des tumeurs cérébrales intra-axiales de l'adulte. 57 patients ont été inclus de novembre 2009 à octobre 2010. Il s'agissait de 7 gliomes de bas grade (7 oligodendrogliomes), 35 gliomes de haut grade (13 oligodendrogliomes anaplasiques, 12 oligoastrocytomes mixtes anaplasiques et 10 glioblastomes), 7 lymphomes cérébraux primitifs et 8 métastases. Nous avons étudié les valeurs du coefficient apparent de diffusion (ADC) sur les séquences de diffusion, le volume sanguin cérébral relatif (rCBV) de la tumeur et de l'œdème sur les séquences de perfusion, et différents rapports de métabolites en spectroscopie monovoxel à écho court et à écho long. L'ADC moyen est de 0.77+/-0.19 pour les lymphomes, 0.97+/-0.18 pour les métastases, 1.06+/-0.21 pour les gliomes de haut grade et 1.22+/-0.17 pour les gliomes de bas grade. En perfusion le rCBV tumoral moyen est de 0.89+/-0.5 pour les lymphomes, 6.21+/-3.1 pour les métastases, 6.5+/-2.5 pour les gliomes de haut grade et 1.28+/-0.5 pour les gliomes de bas grade. Le rCBV de l'œdème moyen est de 0.74+/-0.5 pour les lymphomes, 0.29+/-0.06 pour les métastases et 0.95+/-0.5 pour les gliomes de haut grade. En spectroscopie, les rapports Cho/Cr et Cho/Naa sont respectivement de 4.14 et 4.7 pour les lymphomes, 2.71 et 1.54 pour les métastases, 3.38 et 3.8 pour les gliomes de haut grade et de 1.47 et 1.44 pour les gliomes de bas grade. Les résultats de notre étude concordent avec les données de la littérature. Les lymphomes se caractérisent par une restriction de diffusion et un rCBV non augmenté. L'étude du rCBV de l'œdème péri lésionnel permet la distinction entre métastases et gliomes de haut grade (p<0.001) avec une valeur seuil de 0.4. Les 3 techniques apportent des différences significatives entre les gliomes de bas grade et les gliomes de haut grade avec des valeurs seuils de 1.2x10-3 mm /s pour l'ADC (sensibilité de 75% et spécificité 84%), de 2.5 pour le rCBV (Se et Sp de 100%) et de 1.8 pour le rapport Cho/Cr (Se=82% et Sp=75%). Les séquences IRM de diffusion, perfusion et spectroscopie apparaissent dorénavant comme indispensables au bilan initial des tumeurs cérébrales intra-axiales de l'adulte. Elles permettent d'approcher le diagnostic histologique, d'aider au grading des tumeurs gliales, et ainsi d'améliorer la prise en charge initiale des patients. De plus, elles pourraient permettre de réduire le nombre de biopsies stéréotaxiques, de cibler au mieux le site biopsique et le champ d'irradiation, et améliorer le suivi thérapeutique.CLERMONT FD-BCIU-Santé (631132104) / SudocSudocFranceF

Using High Spatial Resolution to Improve BOLD fMRI Detection at 3T.

For different functional magnetic resonance imaging experiments using blood oxygenation level-dependent (BOLD) contrast, the acquisition of T2*-weighted scans at a high spatial resolution may be advantageous in terms of time-course signal-to-noise ratio and of BOLD sensitivity when the regions are prone to susceptibility artifacts. In this study, we explore this solution by examining how spatial resolution influences activations elicited when appetizing food pictures are viewed. Twenty subjects were imaged at 3 T with two different voxel volumes, 3.4 μl and 27 μl. Despite the diminution of brain coverage, we found that high-resolution acquisition led to a better detection of activations. Though known to suffer to different degrees from susceptibility artifacts, the activations detected by high spatial resolution were notably consistent with those reported in published activation likelihood estimation meta-analyses, corresponding to taste-responsive regions. Furthermore, these regions were found activated bilaterally, in contrast with previous findings. Both the reduction of partial volume effect, which improves BOLD contrast, and the mitigation of susceptibility artifact, which boosts the signal to noise ratio in certain regions, explained the better detection noted with high resolution. The present study provides further evidences that high spatial resolution is a valuable solution for human BOLD fMRI, especially for studying food-related stimuli

Disrupted Pallido-Thalamo-Cortical Functional Connectivity in Chronic Disorders of Consciousness

International audienceChronic disorders of consciousness (DOC) encompass unresponsive wakefulness syndrome and a minimally conscious state. Their anatomo-functional correlates are not clearly defined yet, although impairments of functional cortical networks have been reported, as well as the implication of the thalamus and deep brain structures. However, the pallidal functional connectivity with the thalamus and the cortical networks has not been studied so far. Using resting-state functional MRI, we conducted a functional connectivity study between the pallidum, the thalamus and the cortical networks in 13 patients with chronic DOC and 19 healthy subjects. We observed in chronic DOC patients that the thalami were no longer connected to the cortical networks, nor to the pallidums. Concerning the functional connectivity of pallidums, we reported an abolition of the negative correlation with the default mode network, and of the positive correlation with the salience network. The disrupted functional connectivity observed in chronic DOC patients between subcortical structures and cortical networks could be related to the mesocircuit model. A better understanding of the DOC underlying physiopathology could provide food for thought for future therapeutic proposals

Is R2* a new MRI biomarker for the progression of parkinson's disease? A longitudinal follow-up

International audienceTo study changes of iron content in basal ganglia in Parkinson's disease (PD) through a three-year longitudinal follow-up of the effective transverse relaxation rate R-2*, a validated MRI marker of brain iron content which can be rapidly measured under clinical conditions.Twenty-seven PD patients and 26 controls were investigated by a first MRI (t(0)). Longitudinal analysis was conducted among the 18 controls and 14 PD patients who underwent a second MRI (t(1)) 3 years after. The imaging protocol consisted in 6 gradient echo images obtained at different echo-times for mapping R-2*. Quantitative exploration of basal ganglia was performed by measuring the variation of R-2* [R-2*(t(1)) - R-2*(t(0))] in several regions of interest. Results: During the three-year evolution of PD, R-2* increased in Substantia nigra (SN) (by 10.2% in pars compacta, p = 0.001, and 8.1% in pars reticulata, p = 0.013) and in the caudal putamen (11.4%, p = 0.011), without significant change in controls. Furthermore, we showed a positive correlation between the variation of R-2* and the worsening of motor symptoms of PD (p = 0.028). Significant variation of R-2* was longitudinally observed in the SN and caudal putamen of patients with PD evolving over a three-year period, emphasizing its interest as a biomarker of disease progression. Our results suggest that R-2* MRI follow-up could be an interesting tool for individual assessment of neurodegeneration due to PD, and also be useful for testing the efficiency of disease-modifying treatment

Toxoplasmic pachymeningitis with visual field impairment in a single-eyed patient and a literature review

To describe the clinical features of a patient with toxoplasmic pachymeningitis and provide a review of the recent cases of pachymeningitis in the literature.Retrospective, observational case report. A one-eyed patient who presented to our institution with blurred vision, floaters, and visual field shrinkage. Review of clinical, laboratory, perimetric, and radiologic records of the patient and description of the efficacy of antibiotic therapy. The signs of ocular impairment, including visual acuity, visual field, and magnetic resonance imaging (MRI) changes. A one-eyed patient who complained of blurred vision and unexplained visual field shrinkage was evaluated. The diagnosis of toxoplasmic pachymeningitis was confirmed by existence of a toxoplasmic seroconversion, cerebrospinal fluid abnormalities, radiological features, absence of other diagnoses, improvement of symptoms, and resolution of pachymeningitis in MRI with oral trimethoprim–sulfamethoxazole combination

How is salt taste intensity encoded within the human brain? The responses of BOLD fMRI using food models

Functional MRI (fMRI) allows understanding the mechanisms by which sensations induced by food cues are perceived and processed within the brain, under the influence of various external (e.g. visual stimuli) and internal factors (e.g. body state). In particular, it allows analyzing at neurophysiological level how food formulations influence their sensory qualities and the pleasure experienced. Here, we used fMRI to infer several neural correlates of the perceived salty intensity produced by rewarding food models. Subjects received different savory solutions on their tongue using an MR-compatible gustatometer. The activations were mapped from smoothed high-resolution data, an imaging protocol providing good functional sensitivity in the gustatory cortex [1]. Two primary areas for taste processing were presumed in the human brain, intercepting the operculo-insular cortex and the lesser-known postcentral gyrus. We found highly significant neural correlates of salt taste intensity at the base of the postcentral gyrus bilaterally and to a lesser extent in the insula and the overlying operculi. This finding suggests that both primary areas were involved in salt taste intensity coding in human brain, which contrasts with previous results obtained with unpleasant salty solutions. We speculate that it may result from the use of rewarding food models, making it necessary to take specific account of the stimulation context for mimicking the brain’s integration of sensory rewards during normal feeding.[1] Iranpour J, Morrot G, Claise B, Jean B, Bonny J-M. Using high resolution to improve BOLD fMRI detection in gustatory cortices. Human Brain Mapping. Submitted

Glioblastomas extension on DTI: prospective and comparative study versus metastases and healthy subjects

Rationale Occult tumor cell invasion along white matter fibers is inapparent in conventional MRI. We aimed to precise glioblastomas extension on Diffusion Tensor Imaging (DTI) through a prospective and comparative study. Patients, material and methods Glioblastomas (n=15), metastases (n=9) and healthy controls (n=15) were included. DTI parameters were analyzed, particularly in the normal appearing white matter (NAWM) beyond peritumoral area. Results Specific DTI abnormalities were found in glioblastomas such as hyperanisotropia and morphological modifications in the NAWM

Interest of local intra-arterial fibrinolysis in acute central retinal artery occlusion: Clinical experience in 16 patients

Central retinal artery occlusion (CRAO) is a rare disease with poor visual prognosis. We evaluated clinical effectiveness of in situ fibrinolysis with original angiographic scores describing the aspect of carotid siphon, proximal ophthalmic artery, and choroid blush