Papez Circuit Observed by in vivo Human Brain With 7.0T MRI Super-Resolution Track Density Imaging and Track Tracing

The Papez circuit has been considered as an important anatomical substrate involved in emotional experience. However, the circuit remains difficult to elucidate in the human brain due to the resolution limit of current neuroimaging modalities. In this article, for the first time, we report the direct visualization of the Papez circuit with 7-Tesla super-resolution magnetic resonance tractography. Two healthy, young male subjects (aged 30 and 35 years) were recruited as volunteers following the guidelines of the institutional review board (IRB). Track density imaging (TDI) generation with track tracing was performed using MRtrix software package. With these tools, we were able to visualize the entire Papez circuit. We believe this is the first study to visualize the complete loop of the Papez circuit, including the perforant path (PP), thalamocortical fibers of the anterior nucleus (AN), and mammillothalamic tract (MTT), which were hitherto difficult to visualize by conventional imaging techniques

Mapa anisotrópico estadístico de imágenes de resonancia magnética funcional

En este trabajo presentamos un nuevo método para procesar imágenes de Resonancia Magnética Funcional (IRMf) del cerebro. El nuevo procedimiento esta basado en aplicar difusión anisotrópica robusta (DAR) a imágenes de resonancia magnética funcional ruidosa, para obtener mapas estadísticos de mayor relevancia. Las IRMf utilizan una serie de imágenes de resonancia magnética para mapear de forma no invasiva las áreas de actividad neuronal aumentada del cerebro humano. La baja relación señal ruido de las imágenes funcionales, hace necesario el uso de técnicas de procesamiento de imágenes sofisticadas como mapas estadísticos paramétricos (MEP). La aplicación del método propuesto permite obtener MEPs que incluyen valiosa información con respecto a la interrelación entre las series temporales correspondientes a cada elemento de volumen en un espacio 3-D (voxel) en el correspondiente MEP. Presentamos resultados de la técnica propuesta tanto en imágenes artificiales como en imágenes reales de resonancia magnética funcional de una experiencia basada en un estimulo visual en bloques.Eje: II - Workshop de computación gráfica, imágenes y visualizaciónRed de Universidades con Carreras en Informática (RedUNCI

Mapa anisotrópico estadístico de imágenes de resonancia magnética funcional

En este trabajo presentamos un nuevo método para procesar imágenes de Resonancia Magnética Funcional (IRMf) del cerebro. El nuevo procedimiento esta basado en aplicar difusión anisotrópica robusta (DAR) a imágenes de resonancia magnética funcional ruidosa, para obtener mapas estadísticos de mayor relevancia. Las IRMf utilizan una serie de imágenes de resonancia magnética para mapear de forma no invasiva las áreas de actividad neuronal aumentada del cerebro humano. La baja relación señal ruido de las imágenes funcionales, hace necesario el uso de técnicas de procesamiento de imágenes sofisticadas como mapas estadísticos paramétricos (MEP). La aplicación del método propuesto permite obtener MEPs que incluyen valiosa información con respecto a la interrelación entre las series temporales correspondientes a cada elemento de volumen en un espacio 3-D (voxel) en el correspondiente MEP. Presentamos resultados de la técnica propuesta tanto en imágenes artificiales como en imágenes reales de resonancia magnética funcional de una experiencia basada en un estimulo visual en bloques.Eje: II - Workshop de computación gráfica, imágenes y visualizaciónRed de Universidades con Carreras en Informática (RedUNCI

Automatic hippocampus segmentation of 7.0Tesla MR images by combining multiple atlases and auto-context models

In many neuroscience and clinical studies, accurate measurement of hippocampus is very important to reveal the inter-subject anatomical differences or the subtle intra-subject longitudinal changes due to aging or dementia. Although many automatic segmentation methods have been developed, their performances are still challenged by the poor image contrast of hippocampus in the MR images acquired especially from 1.5 or 3.0 Tesla (T) scanners. With the recent advance of imaging technology, 7.0 T scanner provides much higher image contrast and resolution for hippocampus study. However, the previous methods developed for segmentation of hippocampus from 1.5 T or 3.0 T images do not work for the 7.0 T images, due to different levels of imaging contrast and texture information. In this paper, we present a learning-based algorithm for automatic segmentation of hippocampi from 7.0 T images, by taking advantages of the state-of-the-art multi-atlas framework and also the auto-context model (ACM). Specifically, ACM is performed in each atlas domain to iteratively construct sequences of location-adaptive classifiers by integrating both image appearance and local context features. Due to the plenty texture information in 7.0 T images, more advanced texture features are also extracted and incorporated into the ACM during the training stage. Then, under the multi-atlas segmentation framework, multiple sequences of ACM-based classifiers are trained for all atlases to incorporate the anatomical variability. In the application stage, for a new image, its hippocampus segmentation can be achieved by fusing the labeling results from all atlases, each of which is obtained by applying the atlas-specific ACM-based classifiers. Experimental results on twenty 7.0 T images with the voxel size of 0.35 × 0.35 × 0.35 mm3 show very promising hippocampus segmentations (in terms of Dice overlap ratio 89.1 ± 0.020), indicating high applicability for the future clinical and neuroscience studies

Magnetic Resonance Imaging Compatibility of the Polymer-based Cochlear Implant

ObjectivesIn this study, we compared the magnetic resonance (MR) image artifacts caused by a conventional metal-based cochlear implant and a newly developed liquid crystal polymer (LCP)-based device.MethodsThe metal-based cochlear implant system (Nurobiosys Co.) was attached to side of the head of a subject and the LCP-based device was attached to opposite side. In both devices, alignment magnets were removed for safety. Magnetic resonance imaging (MRI) was performed on a widely used 3.0 T and an ultra-high 7.0 T MRI machine. 3.0 and 7.0 T MR images were acquired using T1- and T2*-weighted gradient echo sequences, respectively.ResultsIn the 3.0 T images, the metal-based device on the left side generated the significant amount of artifacts. The MR images in the proximity of the metal package were obscured by the artifacts in both axial and sagittal views. On the other hand, the MR images near the LCP-based device were relatively free from the artifacts and clearly showed the brain structures. 7.0 T MR images showed the more severe distortion in the both sides but the metal-based cochlear implant system caused a much larger obscure area than the LCP-based system.ConclusionThe novel LCP-based cochlear implant provides a good MRI compatibility beyond present-day cochlear implants. Thus, MR images can be obtained from the subjects even with the implanted LCP-based neural prosthetic systems providing useful diagnostic information. Furthermore, it will be also useful for functional MRI studies of the auditory perception mechanism after cochlear implantations as well as for positron emission tomography-MRI hybrid imaging

Clinical Application of 7.0 T Magnetic Resonance Images in Gamma Knife Radiosurgery for a Patient with Brain Metastases

In the study we assessed the distortion of 7.0 T magnetic resonance (MR) images in reference to 1.5 T MR images in the radiosurgery of metastatic brain tumors. Radiosurgery with Gamma Knife Perfexion® was performed for the treatment of a 54-yr-old female patient with multiple brain metastases by the co-registered images of the 7.0 T and 1.5 T magnetic resonance images (MRI). There was no significant discrepancy in the positions of anterior and posterior commissures as well as the locations of four metastatic brain tumors in the co-registered images between 7.0 T and 1.5 T MRI with better visualization of the anatomical details in 7.0 T MR images. This study demonstrates for the first time that 7.0 T MR images can be safely utilized in Perfexion® Gamma Knife radiosurgery for the treatment of metastatic brain tumors. Furthermore 7.0 T MR images provide better visualization of brain tumors without image distortion in comparison to 1.5 T MR images

A Proposal of New Reference System for the Standard Axial, Sagittal, Coronal Planes of Brain Based on the Serially-Sectioned Images

Sectional anatomy of human brain is useful to examine the diseased brain as well as normal brain. However, intracerebral reference points for the axial, sagittal, and coronal planes of brain have not been standardized in anatomical sections or radiological images. We made 2,343 serially-sectioned images of a cadaver head with 0.1 mm intervals, 0.1 mm pixel size, and 48 bit color and obtained axial, sagittal, and coronal images based on the proposed reference system. This reference system consists of one principal reference point and two ancillary reference points. The two ancillary reference points are the anterior commissure and the posterior commissure. And the principal reference point is the midpoint of two ancillary reference points. It resides in the center of whole brain. From the principal reference point, Cartesian coordinate of x, y, z could be made to be the standard axial, sagittal, and coronal planes

Canine model of ischemic stroke with permanent middle cerebral artery occlusion: clinical and histopathological findings

The aim of the present study was to assess the clinical and histopathological findings in a canine model of ischemic stroke. Cerebral ischemic stroke was induced by middle cerebral artery occlusion in four healthy beagle dogs using silicone plugs. They showed neurological signs of forebrain dysfunction such as reduced responsiveness, head turning, circling, postural reaction deficits, perceptual deficits, and hemianopsia. These signs gradually regressed within 4 weeks without therapy. On magnetic resonance imaging, T2 hyperintensity and T1 hypointensity were found in the cerebral cortex and basal ganglia. These lesions were well-defined and sharply demarcated from adjacent brain parenchyma with a homogenous appearance. No abnormalities of the cerebrospinal fluid were observed. At necropsy, atrophic and necrotic lesions were observed in the cerebral cortex. The cerebral cortex, basal ganglia, and thalamus were partially unstained with triphenyl-tetrazolium chloride. Histopathologically, typical features of infarction were identified in cortical and thalamic lesions. This study demonstrates that our canine model resembles the conditions of real stroke patients

An Investigation of Lateral Geniculate Nucleus Volume in Patients With Primary Open-Angle Glaucoma Using 7 Tesla Magnetic Resonance Imaging

PURPOSE. To investigate lateral geniculate nucleus (LGN) volume of primary open-angle glaucoma (POAG) patients compared with age-and sex-matched controls using ultra-high field 7.0-T magnetic resonance imaging (MRI). METHODS. The study included 18 patients with POAG and 18 age-and sex-matched healthy volunteers. All subjects underwent imaging on a high-resolution 7.0-T MRI system. Bilateral LGNs were identified and manually delineated, and LGN volumes were compared. Peripapillary retinal nerve fiber layer (pRNFL) thickness, optic nerve head parameters (including optic disc size, rim area, and cup-to-disc ratio), and combined thickness of the ganglion cell layer and inner plexus layer (GC-IPL) were measured by Cirrus high-definition optical coherence tomography (OCT). Correlations between OCT parameters and LGN volume were investigated. RESULTS. CONCLUSIONS. On high-resolution 7.0-T MRI, LGN volumes in POAG patients are significantly smaller than those of healthy subjects. Furthermore, in patients, LGN volume was found to be significantly correlated with GC-IPL thickness of the contralateral eye. Keywords: glaucoma, lateral geniculate nucleus, retinal nerve fiber layer thickness, ganglion cell layer, inner plexiform layer, GC-IPL, optical coherence tomography, 7 tesla magnetic resonance imaging R etinal ganglion cell (RGC) degeneration is the major pathogenetic characteristic of glaucoma. 1-18 Most RGCs synapse the next neurons in the lateral geniculate nucleus (LGN), which serves as an important relay station to visual cortex