Sven Haller

To investigate neuronal activations during processing of radiologic and nonradiologic images by experienced radiologists and nonradiologist subjects by using event-related functional magnetic resonance (MR) imaging. Study was approved by local ethics committee, and informed consent was obtained. Radiologic and control images were presented to 12 experienced radiologists (mean age, 35.8 years +/- 3.6 [standard deviation]) and 12 nonradiologist subjects (mean age, 33.0 years +/- 6.9). Half of the images were artificially manipulated-that is, for example, a local shadow was introduced. Subjects had to indicate whether a visually presented image was original or manipulated, while neuronal activity was assessed by using event-related functional MR imaging. Analysis was performed on the basis of fixed-effects general linear models with correction for multiple comparisons (false discovery rate). Radiologic images, when compared with control images, evoked stronger activations exclusively in the group of radiologists, notably in the bilateral middle and inferior temporal gyrus, bilateral medial and middle frontal gyrus, and left superior and inferior frontal gyrus (P < .001, corrected). Additionally, visual processing of control images (ie, nonradiologic images) differed significantly between experienced radiologists and nonradiologist subjects (P < .001, corrected). Radiologists showed strongest activation in the left-dominant more posterior superior and inferior parietal lobule, while nonradiologist subjects showed strongest activation in the right-dominant more anterior superior and inferior parietal lobule and postcentral gyrus. With radiologic experience, there is selective enhancement of brain activation with radiologic images, and the visual system is modified in general.

We present the case of a 45-year-old woman with a history of multiple back surgeries to illustrate the feasibility of combining CT myelography (myeloCT) and Tc-HDP SPECT/CT bone scan in a 1-step procedure to realize a combined SPECT-myeloCT. Myelography CT and SPECT/CT were required to assess nerve root compression and pseudarthrosis, respectively. The proposed combined acquisition protocol provides information about nervous compression as well as pseudarthrosis in a 1 examination, optimizing radiation dose and patient comfort.

An increasing number of studies using real-time fMRI neurofeedback have demonstrated that successful regulation of neural activity is possible in various brain regions. Since these studies focused on the regulated region(s), little is known about the target-independent mechanisms associated with neurofeedback-guided control of brain activation, i.e. the regulating network. While the specificity of the activation during self-regulation is an important factor, no study has effectively determined the network involved in self-regulation in general. In an effort to detect regions that are responsible for the act of brain regulation, we performed a post-hoc analysis of data involving different target regions based on studies from different research groups. We included twelve suitable studies that examined eight different target regions amounting to a total of 175 subjects and 899 neurofeedback runs. Data analysis included a standard first- (single subject, extracting main paradigm) and second-level (single subject, all runs) general linear model (GLM) analysis of all participants taking into account the individual timing. Subsequently, at the third level, a random effects model GLM included all subjects of all studies, resulting in an overall mixed effects model. Since four of the twelve studies had a reduced field of view (FoV), we repeated the same analysis in a subsample of eight studies that had a well-overlapping FoV to obtain a more global picture of self-regulation. The GLM analysis revealed that the anterior insula as well as the basal ganglia, notably the striatum, were consistently active during the regulation of brain activation across the studies. The anterior insula has been implicated in interoceptive awareness of the body and cognitive control. Basal ganglia are involved in procedural learning, visuomotor integration and other higher cognitive processes including motivation. The larger FoV analysis yielded additional activations in the anterior cingulate cortex, the dorsolateral and ventrolateral prefrontal cortex, the temporo-parietal area and the visual association areas including the temporo-occipital junction. In conclusion, we demonstrate that several key regions, such as the anterior insula and the basal ganglia, are consistently activated during self-regulation in real-time fMRI neurofeedback independent of the targeted region-of-interest. Our results imply that if the real-time fMRI neurofeedback studies target regions of this regulation network, such as the anterior insula, care should be given whether activation changes are related to successful regulation, or related to the regulation process per se. Furthermore, future research is needed to determine how activation within this regulation network is related to neurofeedback success.

To assess correlations between the degree of dopaminergic depletion measured using single-photon emission computed tomography (SPECT) and different clinical parameters of disease progression in Parkinson's disease (PD). This retrospective study included 970 consecutive patients undergoing (123)I-ioflupane SPECT scans in our institution between 2003 and 2013, from which we selected a study population of 411 patients according to their clinical diagnosis: 301 patients with PD (69.4 ± 11.0 years, of age, 163 men) and 110 patients with nondegenerative conditions included as controls (72.7 ± 8.0 years of age, 55 men). Comprehensive and operator-independent data analysis included spatial normalization into standard space, estimation of the mean uptake values in the striatum (caudate nucleus + putamen) and voxel-wise correlation between SPECT signal intensity and disease stage as well as disease duration in order to investigate the spatiotemporal pattern of the dopaminergic nigrostriat...

Although many smokers try to quit smoking, only about 20-25 percent will achieve abstinence despite 6 months or more of gold-standard treatment. This low success rate suggests long-term changes in the brain related to smoking, which remain poorly understood. We compared ex-smokers to both active smokers and non-smokers using functional magnetic resonance imaging (fMRI) to explore persistent modifications in brain activity and network organization. This prospective and consecutive study includes 18 non-smokers (29.5 ± 6.7 years of age, 11 women), 14 smokers (≥10 cigarettes a day >2 years of smoking, 29.3 ± 6.0 years of age, 10 women) and 14 ex-smokers (>1 year of quitting 30.5 ± 5.7 years of age, 10 women). Participants underwent a block-design fMRI study contrasting smoking cue with control (neutral cue) videos. Data analyses included task-related general linear model, seed-based functional connectivity, voxel-based morphometry (VBM) of gray matter and tract-based spatial statistics (TBSS) of white matter. Smoking cue videos versus control videos activated the right anterior insula in ex-smokers compared with smokers, an effect correlating with cumulative nicotine intake (pack-years). Moreover, ex-smokers had a persistent decrease in functional connectivity between right anterior insula and anterior cingulate cortex (ACC) compared with control participants, but similar to active smokers. Potentially confounding alterations in gray or white matter were excluded in VBM and TBSS analyses. In summary, ex-smokers with long-term nicotine abstinence have persistent and dose-dependent brain network changes notably in the right anterior insula and its connection to the ACC.

Anterior shoulder apprehension is a commonly reported complaint in anterior shoulder instability, which may lead to patient morbidity and impede shoulder function. It is the result of a cognitively complex mechanism, which includes anxiety, salience, fear and anticipation. The aim of this prospective case-control study was to correlate five clinically established scores using fMRI to assess brain activation patterns in patients with apprehension related to anterior shoulder instability. This study includes 28 consecutive right-handed, male patients (26.8 ± 1.2 years) with positive shoulder apprehension test and ten healthy matched control participants without apprehension or a history of instability. Task-related and functional connectivity fMRI activation patterns occuring during apprehension video cue stimulation were correlated to five clinical tests and scores: Visual Analog Scale (VAS), Rowe score for instability (Rowe), Simple Shoulder Test (SST), Subjective Shoulder Value (SS...

This article reviews the most relevant state-of-the-art magnetic resonance (MR) techniques, which are clinically available to investigate brain diseases. MR acquisition techniques addressed include notably diffusion imaging (diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), and diffusion kurtosis imaging (DKI)) as well as perfusion imaging (dynamic susceptibility contrast (DSC), arterial spin labeling (ASL), and dynamic contrast enhanced (DCE)). The underlying models used to process these images are described, as well as the theoretic underpinnings of quantitative diffusion and perfusion MR imaging-based methods. The technical requirements and how they may help to understand, classify, or follow-up neurological pathologies are briefly summarized. Techniques, principles, advantages but also intrinsic limitations, typical artifacts, and alternative solutions developed to overcome them are discussed. In this article, we also review routinely available three-dimensional ...

Palatal tremor (PT), also known as palatal myoclonus, is defined by short rhythmic contractions of the palatal musculature. Functional MR imaging (fMRI) revealed prominent bilateral neuronal activation in the putamen associated with essential palatal tremor (EPT) in a 41-year-old man. This implies a central role of the putamen in EPT, most likely as a consequence of diminished inhibition in an afferent pathway. Because fMRI primarily detects activations, dysfunctional areas remain obscure. The present functional study complements previous pathologic studies, which associated PT with lesions to dentate nucleus, red nucleus, and the inferior olive (Guillain-Mollaret triangle).

Real-time functional magnetic resonance imaging (rt-fMRI) neurofeedback allows learning voluntary control over specific brain areas by means of operant conditioning and has been shown to decrease pain perception. To further increase the effect of rt-fMRI neurofeedback on pain, we directly compared two different target regions of the pain network, notably the anterior insular cortex (AIC) and the anterior cingulate cortex (ACC). Participants for this prospective study were randomly assigned to two age-matched groups of 14 participants each (7 females per group) for AIC and ACC feedback. First, a functional localizer using block-design heat pain stimulation was performed to define the pain-sensitive target region within the AIC or ACC. Second, subjects were asked to down-regulate the BOLD activation in four neurofeedback runs during identical pain stimulation. Data analysis included task-related and functional connectivity analysis. At the behavioral level, pain ratings significantly ...

Discrimination between radiation necrosis and tumor progression after radiation therapy represents a radiologic challenge. The aim of our investigation is to identify patterns of radiation necrosis on brain magnetic resonance imaging (MRI) and positron emission tomography (PET) with Fluoroethyltyrosin (FET) after proton beam therapy (PBT) for skull base tumors. Five consecutive patients with extra-axial neoplasms were included, presenting a total of eight radiation necrosis lesions (three clival chordomas; two petroclival chondrosarcomas; two women; mean age: 49 ± 18.2 years). Radiation necrosis was defined as the appearance of abnormal enhancement on MRI after PBT decreasing over time, and additional histopathologic confirmation in one patient. MRI and PET imaging were retrospectively analyzed by two experienced radiologists in consensus. All lesions were localized close to the primary tumor in the field of irradiation. Three patients showed bilateral symmetrical lesions. All lesions showed T2 hyperintensity and T1 hypointensity. Cerebral blood volume (CBV) was reduced in all available studies. None of the lesions showed a restricted diffusion. FET-PET (three patients) showed a higher uptake in four out of five lesions; three of which had a mean tumor-to-background (TBRmean) uptake lower than 1.95 and FET uptake increasing over time and were correctly classified into radiation necrosis. Most radiation necroses were in direct continuity with the primary tumor mimicking tumor progression. The most consistent imaging findings for PBT radiation necrosis are low CBV without restricted diffusion and FET-PET TBRmean lower than 1.95 or increasing uptake over time. Bilateral symmetric involvement may be another indicator of radiation necrosis.

ABSTRACT Natalizumab (NTZ) is a recombinant humanised immunoglobulin G4 monoclonal antibody that selectively inhibits adhesion of α4-β1 receptor on the surface of lymphocytes and hinders circulating cells from leaving the vascular compartment of the brain.1 NTZ is associated with a risk of developing progressive multifocal leukoencephalopathy (PML), estimated at approximately 1/200 in JCV-positive patients after 24 months treatment duration.1 The overall survival rate is 71% in PML secondary to NTZ treatment, which is substantially better than the often-fatal course of PML in other immunosuppressed patients.2 This reflects the fact that immune reconstitution is more easily obtained in NTZ patient by treatment cessation.3 Immune reconstitution inflammatory syndrome (IRIS), characterised by contrast-enhancing MRI lesions with clinical deterioration, is observed in almost all PML patients after NTZ cessation.2 Plasma exchange (PLEX) is usually initiated after NTZ cessation to remove remaining circulating NTZ levels, which favours the immune reconstitution, whereas intravenous corticosteroids (CS) are given to suppress IRIS development.1 Nevertheless, the increased peripheral functional T-cell expansion following PLEX can be seen as an accelerator for IRIS, and the negative impact of CS on JCV-specific CD8 T cell response is also at risk of inhibiting the physiological immune response against the JC virus (JCV). Report of a case A patient was diagnosed with relapsing-remitting MS at the age of 46 years. Her JCV IgG serum status was positive 6 months after NTZ treatment initiation. After 22 infusions, she presented …

ABSTRACT The hybrid Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) is a newly available imaging modality combining the molecular and metabolic PET information with the morphological and functional data provided by MRI. Integrated PET/MRI tomographs were conceived in analogy to the current PET/Computed Tomography (PET/CT) technology, with specific properties linked to the intrinsic differences of MRI and CT imaging. In the field of neuro-imaging, in particular, MRI provides a larger panel of information, as compared with CT, and is already systematically fused and used as a support for PET images for diagnostic and research purposes. We summarize here our current experience with the first integrated PET/MRI tomograph installed in Switzerland, concerning specifically three clinical applications: brain tumors characterization, the diagnosis of neurodegenerative dementias and the presurgical evaluation of pharmaco-resistant epilepsy. With this sequential tomograph, we could combine the full range of diagnostic MR sequences (including diffusion tensor imaging, tractography, spectroscopy, functional MR) with PET imaging of brain glucose metabolism (by 18F-Fluorodeoxyglucose–FDG) and of amino acid transport (by 18F-Fluoroethyltyrosine–FET). We also summarize the main results obtained in neuro-imaging by the different groups working with these new hybrid tomographs. These data show that PET/MRI, acquired in a single imaging session, may represent the modality of choice for neuro-imaging.

Infections of the nervous system are a common and serious occurrence. Neuroimaging has allowed to improve early detection and thus to initiate treatment earlier. Magnetic resonance (MR) imaging has become the method of choice in investigating a patient with suspicion of an infection of the central nervous system. Newer modalities such as MR spectroscopy and MR diffusion and perfusion will further help to improve diagnostic accuracy of the technique. For the investigation of infections of white matter, techniques such as diffusion imaging are essential.

In order to further improve the impact of the continuously evolving neurointerventional techniques, the interventional neuroradiologist needs to have at his disposal more powerful techniques to image the central nervous system. With the recent development of diagnostics techniques that are computed tomography and magnetic resonance based we are now able to assess not just morphology, but also physiology, physiopathology and function. This review discusses the place of diagnostic techniques in the evaluation that the interventional neuroradiologist hast to make when confronted with patients. We provide an overview of current techniques for the brain and spine.

Acute ischemic stroke is now clearly recognized as a medical emergency. As such diagnosis has to be done quickly and in a precise way during the therapeutic window. Both computed tomography and magnetic resonance imaging are tools that can adequately demonstrate ischemia really very early on. MRI using diffusion techniques has a much higher sensitivity for acute lesions but its implementation has not been unproblematic due to initial resistance and some technical problems. Thus, very often CT is still preferred with MR used for situations where the answer given is not sufficient as well as for follow-up of lesions. However, the parallel development of new therapeutic strategies have rendered the precision of the tools more and more sophisticated and their combined use can help to improve patient outcomes in ways never imagined previously. No matter which technique is used, be it alone or in combination, the idea is to speed up and optimize management in order to provide early revasc...

Magnetic resonance imaging plays an important role in the diagnosis and management of cerebrovascular diseases. In addition to stroke, it can also demonstrate changes apparent in the white matter such as leukoaraiosis. These as well as other changes occurring with increasing age can be visualized. Among others, there is an increase in the number and size of perivascular spaces. Although many of these alterations may be clinically silent, with increasing load they may become symptomatic. Other vascular pathological findings such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy and the posterior reversible encephalopathy syndrome can also provoke changes in the cerebral white matter that are visible on magnetic resonance imaging and are discussed.

Resting-state (RS) functional magnetic resonance (MR) imaging constitutes a novel paradigm that examines spontaneous brain function by using blood oxygen level-dependent contrast in the absence of a task. Spatially distributed networks of temporal synchronization can be detected that can characterize RS networks (RSNs). With a short acquisition time of less than 10 minutes, RS functional MR imaging can be applied in special populations such as children and patients with dementia. Some RSNs are already present in utero, while others mature in childhood. Around 10 major RSNs are consistently found in adults, but their exact spatial extent and strength of coherence are affected by physiologic parameters and drugs. Though the acquisition and analysis methods are still evolving, new disease insights are emerging in a variety of neurologic and psychiatric disorders. The default mode network is affected in Alzheimer disease and various other diseases of cognitive impairment. Alterations in...

The neural correlate of anterograde amnesia in Wernicke-Korsakoff syndrome (WKS) is still debated. While the capacity to learn new information has been associated with integrity of the medial temporal lobe (MTL), previous studies indicated that the WKS is associated with diencephalic lesions, mainly in the mammillary bodies and anterior or dorsomedial thalamic nuclei. The present study tested the hypothesis that amnesia in WKS is associated with a disrupted neural circuit between diencephalic and hippocampal structures. High-density evoked potentials were recorded in four severely amnesic patients with chronic WKS, in five patients with chronic alcoholism without WKS, and in ten age matched controls. Participants performed a continuous recognition task of pictures previously shown to induce a left medial temporal lobe dependent positive potential between 250 and 350 ms. In addition, the integrity of the fornix was assessed using diffusion tensor imaging (DTI). WKS, but not alcoholic patients without WKS, showed absence of the early, left MTL dependent positive potential following immediate picture repetitions. DTI indicated disruption of the fornix, which connects diencephalic and hippocampal structures. The findings support an interpretation of anterograde amnesia in WKS as a consequence of a disconnection between diencephalic and MTL structures with deficient contribution of the MTL to rapid consolidation.

Metabolic diseases of the brain are a rare occurrence. They may be either occurring as inherited diseases causing a destruction of myelin, or they may be the result of toxicity. Neuroimaging, especially magnetic resonance imaging, plays an important role in the detection and classification of these rare diseases. Magnetic resonance spectroscopy is an important tool in the characterization and diagnosis of inherited metabolic diseases.

Although cross-sectional diffusion tensor imaging (DTI) studies revealed significant white matter changes in mild cognitive impairment (MCI), the utility of this technique in predicting further cognitive decline is debated. Thirty-five healthy controls (HC) and 67 MCI subjects with DTI baseline data were neuropsychologically assessed at one year. Among them, there were 40 stable (sMCI; 9 single domain amnestic, 7 single domain frontal, 24 multiple domain) and 27 were progressive (pMCI; 7 single domain amnestic, 4 single domain frontal, 16 multiple domain). Fractional anisotropy (FA) and longitudinal, radial, and mean diffusivity were measured using Tract-Based Spatial Statistics. Statistics included group comparisons and individual classification of MCI cases using support vector machines (SVM). FA was significantly higher in HC compared to MCI in a distributed network including the ventral part of the corpus callosum, right temporal and frontal pathways. There were no significant g...