Search results for "Image"
showing 10 items of 6818 documents
Asymmetric modulation of human visual cortex activity during 10 degrees lateral gaze (fMRI study).
2005
We used BOLD fMRI to study the differential effects of the direction of gaze on the visual and the ocular motor systems. Fixation of a target straight ahead was compared to fixation of a target 10 degrees to the right and 10 degrees to the left from gaze straight ahead, and to eyes open in complete darkness in thirteen healthy volunteers. While retinotopic coordinates remained the same in all fixation conditions, the fixation target shifted with respect to a head-centered frame of reference. During lateral fixation, deactivations in higher-order visual areas (one ventral cluster in the lingual and fusiform gyri and one dorsal cluster in the postero-superior cuneus) and, as a trend, activati…
Eye closure in darkness animates sensory systems.
2003
Single subject and group analyses (n = 12) showed that the eyes-open and eyes-closed states in complete darkness considerably and consistently differ in the patterns of associated brain activation in fMRI. During nonchanging external stimulation, ocular motor and attentional systems were activated when the eyes were open; the visual, somatosensory, vestibular, and auditory systems were activated when the eyes were closed. These data suggest that there are two different states of mental activity: with the eyes closed, an "interoceptive" state characterized by imagination and multisensory activity and with the eyes open, an "exteroceptive" state characterized by attention and ocular motor act…
Evidence for cortical visual substitution of chronic bilateral vestibular failure (an fMRI study).
2007
Bilateral vestibular failure (BVF) is a rare disorder of the labyrinth or the eighth cranial nerve which has various aetiologies. BVF patients suffer from unsteadiness of gait combined with blurred vision due to oscillopsia. Functional MRI (fMRI) in healthy subjects has shown that stimulation of the visual system induces an activation of the visual cortex and ocular motor areas bilaterally as well as simultaneous deactivations of multisensory vestibular cortex areas. Our question was whether the chronic absence of bilateral vestibular input (BVF) causes a plastic cortical reorganization of the above-described visual-vestibular interaction. We used fMRI to measure the differential effects of…
Neural mechanisms of training an auditory event‐related potential task in a brain–computer interface context
2019
Effective use of brain-computer interfaces (BCIs) typically requires training. Improved understanding of the neural mechanisms underlying BCI training will facilitate optimisation of BCIs. The current study examined the neural mechanisms related to training for electroencephalography (EEG)-based communication with an auditory event-related potential (ERP) BCI. Neural mechanisms of training in 10 healthy volunteers were assessed with functional magnetic resonance imaging (fMRI) during an auditory ERP-based BCI task before (t1) and after (t5) three ERP-BCI training sessions outside the fMRI scanner (t2, t3, and t4). Attended stimuli were contrasted with ignored stimuli in the first-level fMRI…
Hippocampal subfields predict positive symptoms in schizophrenia : First evidence from brain morphometry
2012
Alterations of hippocampal anatomy have been reported consistently in schizophrenia. Within the present study, we used FreeSurfer to determine hippocampal subfield volumes in 21 schizophrenic patients. A negative correlation between PANSS-positive symptom score and bilateral hippocampal subfield CA2/3 as well as CA1 volume was found on high-resolution magnetic resonance images. Our observation opens the gate for advanced investigation of the commonly reported hippocampal abnormalities in schizophrenia in terms of specific subfields.
Quantitative analysis of emphysema in 3D using MDCT: Influence of different reconstruction algorithms
2008
Abstract Purpose The aim of the study was to compare the influence of different reconstruction algorithms on quantitative emphysema analysis in patients with severe emphysema. Material and methods Twenty-five patients suffering from severe emphysema were included in the study. All patients underwent inspiratory MDCT (Aquilion-16, slice thickness 1/0.8 mm). The raw data were reconstructed using six different algorithms: bone kernel with beam hardening correction (BHC), soft tissue kernel with BHC; standard soft tissue kernel, smooth soft tissue kernel (internal reference standard), standard lung kernel, and high-convolution kernel. The only difference between image data sets was the algorith…
Characterization of Small Incidental Indeterminate Hypoattenuating Hepatic Lesions: Added Value of Single-Phase Contrast-Enhanced Dual-Energy CT Mate…
2018
OBJECTIVE. The objective of this study is to determine whether single-phase contrast-enhanced dual-energy CT (DECT) material attenuation analysis improves the characterization of small (< 2.0 cm) incidental indeterminate hypoattenuating hepatic lesions, compared with conventional single-energy CT evaluation. MATERIALS AND METHODS. This retrospective study involved 55 patients (24 men and 31 women; mean [± SD] age, 63.9 ± 15.3 years) with 77 incidental hypoattenuating hepatic lesions (59 benign and 18 malignant lesions) measuring 0.5–2.0 cm who underwent single-phase contrast-enhanced DECT of the abdomen for pain. For each lesion, attenuation measurements were obtained using blended 120-k…
Perception of Occlusion, Psychological Impact of Dental Esthetics, History of Orthodontic Treatment and Their Relation to Oral Health in Naval Recrui…
2007
Abstract Objective: To investigate whether the oral health of young male adults was related to (1) the degree of self-perceived malocclusion, (2) the degree of experienced negative psychosocial impact of dental esthetics, and (3) the history of orthodontic treatment and its duration. Materials and Methods: The study subjects were 470 male naval recruits undergoing a routine dental health checkup. They answered the Perception of Occlusion Scale (POS) and Negative Impact of Dental Aesthetics Scale (NIDAS). The Approximal Plaque Index (API), the Sulcus Bleeding Index (SBI), and the number of decayed teeth (DT) and missing teeth (MT) were examined by a staff dentist. Statistical procedures were…
Quantitative myocardial perfusion imaging using different autocalibrated parallel acquisition techniques
2008
Purpose To compare three different autocalibrated parallel acquisition techniques (PAT) for quantitative and semiquantitative myocardial perfusion imaging. Materials and Methods Seven healthy volunteers underwent myocardial first-pass perfusion imaging at rest using an SR-TrueFISP pulse sequence without PAT and while using GRAPPA, mSENSE, and TSENSE. signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), normalized upslopes (NUS), and myocardial blood flow (MBF) were calculated. Artifacts, image noise, and overall image quality were qualitatively assessed. Furthermore, the relation between signal intensity (SI) and contrast medium (CM) concentration was determined in phantoms. Results …
Focal nodular hyperplasia-like lesions in patients with cavernous transformation of the portal vein: prevalence, MR findings and natural history.
2011
PURPOSE: To retrospectively investigate the prevalence, MR findings, natural history, and association with other hepatic lesions of focal nodular hyperplasia (FNH)-like lesions in a cohort of consecutive patients with cavernous transformation of the portal vein (CTPV). MATERIALS AND METHODS: This retrospective IRB-approved study comprised 58 patients (32 men, 26 women; average age, 50 years) with CTPV who underwent liver MR imaging between 2000 and 2008. MR images were assessed by two radiologists in consensus for the presence of (a) FNH-like lesions and other liver lesions, and (b) other imaging findings. Patients were assigned to a stable or progressive clinical course based on lesion cha…