An evolution of low-field strength MRI.

The paper describes the evolution of low-field MRI from the very early pioneering days in the late 70 s until today. It is not meant to give a comprehensive historical account of the development of MRI, but rather to highlight the different research environments then and now. In the early 90 s, when low-field systems below 1.5 T essentially vanished, there were just no reasonable means available to make up for the factor of roughly three in signal-to-noise-ratio (SNR) between 0.5 and 1.5 T. This has drastically changed. Improvements in hardware-closed Helium-free magnets, RF receiver systems and especially much faster gradients, much more flexible sampling schemes including parallel imaging and compressed sensing and especially the use of AI at all stages of the imaging process have made low-field MRI a clinically viable supplement to conventional MRI. Ultralow-field MRI with magnets around 0.05 T are also back and constitute a bold and courageous endeavor to bring MRI to communities, which have neither the means nor the infrastructure to sustain a current standard of care MRI.

Single shot spiral TSE with annulated segmentation.

PURPOSE: To develop, optimize, and implement a single shot spiral turbo spin echo (TSE) sequence at 3T and to demonstrate its feasibility to acquire artifact free images of the central nervous system with 1 mm spatial resolution in <200 ms. THEORY AND METHODS: Spiral TSE sequences with annulated spiral segmentation have been implemented with different acquisition modes. In fixed mode, the duration of each spiral segment is fixed to fill the available acquisition time tacq . In tangential mode, the beginning of each spiral segment is reached via a straight tangential trajectory. Tangential mode allows faster transition and thus longer tacq for a given echo spacing (ESP), but less data points can be acquired per acquisition interval. Alternating between spiral-in and spiral-out readout in alternating echoes leads to a somewhat different point spread function for off-resonant spins. RESULTS: Images of the brain with 1 mm spatial resolution acquired with a variable density spiral with ∼40% undersampling can be acquired in a single shot. All acquisition modes produce comparable image quality. Only mild artifacts in regions of strong susceptibility effects can be observed for ESP of 10 ms and below. The use of variable flip angle schemes allows seamless acquisition of consecutive slices and/or dynamic scans without waiting time between consecutive acquisitions. Comparison with images acquired at 1.5T shows reduced susceptibility artifacts within the brain and facial structures. CONCLUSION: Single shot spiral TSE has been demonstrated to enable highly efficient acquisition of high-resolution images of the brain in <200 ms per slice.

Neuroprotective effects of dynamic bubble trap use in patients undergoing pulmonary endarterectomy: a two-arm randomized controlled trial.

BACKGROUND: During cardiosurgical procedures that use extracorporeal circulation (ECC), a variety of neurological complications can occur, and postoperative cognitive deficits remain an unsolved problem. Among the sources of these complications are intraoperatively detectable cerebral microemboli, which mainly consist of air. This study's purpose was to assess neuroprotective effects of reducing these gaseous microemboli using a dynamic bubble trap (DBT) in patients undergoing pulmonary endarterectomy (PEA) for the treatment of chronic thromboembolic pulmonary hypertension (CTEPH). METHODS: Patients undergoing PEA were randomly assigned to receive either a DBT (n=47) or no additional device (controls, n=46) during ECC. Neuropsychological testing was performed before and 3 months after PEA. The primary endpoint was cognitive improvement in the DBT group (n=29) compared with the control group (n=42). As secondary endpoint, ischemic brain micro-lesions were analyzed on postoperative days 6 through 10 using diffusion-weighted magnetic resonance imaging (MRI). RESULTS: Analysis of interaction effects revealed improved performance in visual long-term memory (P=0.008, η2=0.099), verbal long-term memory (P=0.030, η2=0.067), verbal short-term memory (P=0.014, η2=0.083), and attention and processing speed (P=0.043, η2=0.056) from pre- to post-testing in the DBT group compared to control group. In MRI, postoperative ischemic micro-lesions could only be detected in one patient; another patient suffered a severe bihemispheric embolic stroke. CONCLUSIONS: DBT positively influences memory function after PEA. This effect is most likely caused by the reduction of gaseous microemboli. TRIAL REGISTRATION: This study is registered in the German Clinical Trials Register, ID: DRKS00021499.

Positive psychology interventions in in-patients with depression: influences of comorbidity and subjective evaluation of the training programme.

BACKGROUND: Studies on positive psychology interventions (PPIs) have frequently demonstrated benefits for healthy participants and patients. However, effect sizes are moderate, and underlying inter-individual differences in responses were rarely investigated. AIMS: We investigated whether severity of depression and subjective evaluation of PPIs are relevant sources of variance in this respect. METHOD: A 4-week group PPI programme (one 45-min session per week) was offered to 38 in-patients with depression. The control group (n = 38) was carefully matched and received treatment as usual. In the PPI group, emotional states were recorded before and after each session (responsiveness). Beck Depression Inventory-II scores at hospital admission and discharge were used to evaluate clinical effectiveness. The number of comorbidities (as an indicator of severity of disease) and patients' evaluations of the PPI sessions were used as additional independent factors for overall treatment outcome. RESULTS: The PPI induced a highly significant improvement in positive emotional state and decrease in negative emotional state, indicating responsiveness. Moreover, positive affectivity increased from week to week only in patients with a low number of comorbidities (indicating effectiveness). With respect to overall treatment outcome (Beck Depression Inventory-II scores), positive attitude toward the PPI resulted in the largest improvement. CONCLUSIONS: The results partly explain the variance in the effectiveness of PPIs. Moreover, they support the idea of personalised psychotherapy, and may inform discussion on whether patients with depression should be included in PPIs. However, additional individual characteristics should increase knowledge about individual predictors for effectiveness.

Event-Related Potentials in Women on the Pill: Neural Correlates of Positive and Erotic Stimulus Processing in Oral Contraceptive Users.

Background/Aims: Exposure toward positive emotional cues with - and without - reproductive significance plays a crucial role in daily life and regarding well-being as well as mental health. While possible adverse effects of oral contraceptive (OC) use on female mental and sexual health are widely discussed, neural processing of positive emotional stimuli has not been systematically investigated in association with OC use. Considering reported effects on mood, well-being and sexual function, and proposed associations with depression, it was hypothesized that OC users showed reduced neural reactivity toward positive and erotic emotional stimuli during early as well as later stages of emotional processing and also rated these stimuli as less pleasant and less arousing compared to naturally cycling (NC) women. Method: Sixty-two female subjects (29 NC and 33 OC) were assessed at three time points across the natural menstrual cycle and corresponding time points of the OC regimen. Early (early posterior negativity, EPN) and late (late positive potential, LPP) event-related potentials in reaction to positive, erotic and neutral stimuli were collected during an Emotional Picture Stroop Paradigm (EPSP). At each appointment, subjects provided saliva samples for analysis of gonadal steroid concentration. Valence and arousal ratings were collected at the last appointment. Results: Oral contraceptive users had significantly lower endogenous estradiol and progesterone concentrations compared to NC women. No significant group differences in either subjective stimulus evaluations or neural reactivity toward positive and erotic emotional stimuli were observed. For the OC group, LPP amplitudes in reaction to erotic vs. neutral pictures differed significantly between measurement times across the OC regimen. Discussion: In this study, no evidence regarding alterations of neural reactivity toward positive and erotic stimuli in OC users compared to NC was found. Possible confounding factors and lines for future research are elaborated and discussed.

15 Years MR-encephalography.

OBJECTIVE: This review article gives an account of the development of the MR-encephalography (MREG) method, which started as a mere 'Gedankenexperiment' in 2005 and gradually developed into a method for ultrafast measurement of physiological activities in the brain. After going through different approaches covering k-space with radial, rosette, and concentric shell trajectories we have settled on a stack-of-spiral trajectory, which allows full brain coverage with (nominal) 3 mm isotropic resolution in 100 ms. The very high acceleration factor is facilitated by the near-isotropic k-space coverage, which allows high acceleration in all three spatial dimensions. METHODS: The methodological section covers the basic sequence design as well as recent advances in image reconstruction including the targeted reconstruction, which allows real-time feedback applications, and-most recently-the time-domain principal component reconstruction (tPCR), which applies a principal component analysis of the acquired time domain data as a sparsifying transformation to improve reconstruction speed as well as quality. APPLICATIONS: Although the BOLD-response is rather slow, the high speed acquisition of MREG allows separation of BOLD-effects from cardiac and breathing related pulsatility. The increased sensitivity enables direct detection of the dynamic variability of resting state networks as well as localization of single interictal events in epilepsy patients. A separate and highly intriguing application is aimed at the investigation of the glymphatic system by assessment of the spatiotemporal patterns of cardiac and breathing related pulsatility. DISCUSSION: MREG has been developed to push the speed limits of fMRI. Compared to multiband-EPI this allows considerably faster acquisition at the cost of reduced image quality and spatial resolution.

The variability of functional MRI brain signal increases in Alzheimer's disease at cardiorespiratory frequencies.

Biomarkers sensitive to prodromal or early pathophysiological changes in Alzheimer's disease (AD) symptoms could improve disease detection and enable timely interventions. Changes in brain hemodynamics may be associated with the main clinical AD symptoms. To test this possibility, we measured the variability of blood oxygen level-dependent (BOLD) signal in individuals from three independent datasets (totaling 80 AD patients and 90 controls). We detected a replicable increase in brain BOLD signal variability in the AD populations, which constituted a robust biomarker for clearly differentiating AD cases from controls. Fast BOLD scans showed that the elevated BOLD signal variability in AD arises mainly from cardiovascular brain pulsations. Manifesting in abnormal cerebral perfusion and cerebrospinal fluid convection, present observation presents a mechanism explaining earlier observations of impaired glymphatic clearance associated with AD in humans.

Covid-19-Beyond virology: Potentials for maintaining mental health during lockdown.

BACKGROUND: The current study aimed to assess prevalence of mental disorders during Covid-19 pandemic- and respective lockdown in Germany, and potential behaviors/states that can have protective functions on preventing severe mental problems. Assessing prevalence of mental disorders, as well as to find potential protective variables is very important in order to determine people's psychological suffering. It provides the basis for teaching possible coping styles in order to prevent a major breakdown on mental health. Prevalence on mental disorders was expected to increase during the pandemic, especially depression, (general-/and health-) anxiety, panic attacks- and disorder, as well as obsessive-compulsive disorder. Additionally, potentially protective variables, such as resilience and coping, were included. METHODS: N = 949 subjects completed an online-survey that asked for symptoms regarding depression, (health) anxiety, panic disorder, obsessive-compulsive disorder, and lock-down related behavior-starting 14 days after lockdown in Germany. RESULTS: Prevalence of mental disorders in the current sample was much higher than usual prevalence of mental disorders, with 50.6% expressing at least one mental disorder. Resilience was associated with lower risks for any mental disorder (OR = 4.23, p < .0001, 95%CI = 3.21-5.57), as well as with any other measured mental illness (all ORs between = 2.82 for obsessive-compulsive disorder and OR = 41.44 for panic disorder, all p < .001). Similar results were obtained regarding coping (focus on positive). CONCLUSION: Results are highly relevant in order to provide a glance on what substantial influence the current pandemic- and lockdown situation has on mental health across the country, and possibly across the world. Possible ways in order to prevent deterioration and help coping with the current situation are being elaborated and discussed.

Analysis of accelerated 4D flow MRI in the murine aorta by radial acquisition and compressed sensing reconstruction.

Preclinical 4D flow MRI remains challenging and is restricted for parallel imaging acceleration due to the limited number of available receive channels. A radial acquisition with combined parallel imaging and temporal compressed sensing reconstruction was implemented to achieve accelerated preclinical 4D flow MRI. In order to increase the accuracy of the measured velocities, a quantitative evaluation of different temporal regularization weights for the compressed sensing reconstruction based on velocity instead of magnitude data is performed. A 3D radial retrospectively triggered phase contrast sequence with a combined parallel imaging and compressed sensing reconstruction with temporal regularization was developed. It was validated in a phantom and in vivo (C57BL/6 J mice), against an established fully sampled Cartesian sequence. Different undersampling factors (USFs [12, 15, 20, 30, 60]) were evaluated, and the effect of undersampling was analyzed in detail for magnitude and velocity data. Temporal regularization weights λ were evaluated for different USFs. Acceleration factors of up to 20 compared with full Nyquist sampling were achieved. The peak flow differences compared with the Cartesian measurement were the following: USF 12, 3.38%; USF 15, 4.68%; USF 20, 0.95%. The combination of 3D radial center-out trajectories and compressed sensing reconstruction is robust against motion and flow artifacts and can significantly reduce measurement time to 30 min at a resolution of 180 µm3 . Concisely, radial acquisition with combined compressed sensing and parallel imaging proved to be an excellent method for analyzing complex flow patterns in mice.

Common and dissociable effects of oxytocin and lorazepam on the neurocircuitry of fear.

Benzodiazepines (BZDs) represent the gold standard of anxiolytic pharmacotherapy; however, their clinical benefit is limited by side effects and addictive potential. Consequently, there is an urgent need to develop novel and safe anxiolytics. The peptide hormone oxytocin (OXT) exhibits anxiolytic-like properties in animals and humans, but whether OXT and BZDs share similar effects on the neural circuitry of fear is unclear. Therefore, the rationale of this ultra-high-field functional MRI (fMRI) study was to test OXT against the clinical comparator lorazepam (LZP) with regard to their neuromodulatory effects on local and network responses to fear-related stimuli. One hundred twenty-eight healthy male participants volunteered in this randomized double-blind, placebo-controlled, between-group study. Before scanning using an emotional face-matching paradigm, participants were randomly administered a single dose of OXT (24 IU), LZP (1 mg), or placebo. On the behavioral level, LZP, but not OXT, caused mild sedation, as evidenced by a 19% increase in reaction times. On the neural level, both OXT and LZP inhibited responses to fearful faces vs. neutral faces within the centromedial amygdala (cmA). In contrast, they had different effects on intra-amygdalar connectivity; OXT strengthened the coupling between the cmA and basolateral amygdala, whereas LZP increased the interplay between the cmA and superficial amygdala. Furthermore, OXT, but not LZP, enhanced the coupling between the cmA and the precuneus and dorsomedial prefrontal cortex. These data implicate inhibition of the cmA as a common denominator of anxiolytic action, with only OXT inducing large-scale connectivity changes of potential therapeutic relevance.

Females' menstrual cycle and incentive salience: Insights on neural reaction towards erotic pictures and effects of gonadal hormones.

Background: Studies in regard to womens' neural reactivity to erotic and other positive emotional cues in association with sexual hormones are relatively rare and findings rather inconclusive. Concerning the neural reactions towards erotic stimuli, the late positive potential (LPP) is seen as the most relevant ERP-component: More positive amplitudes are supposed to reflect larger motivational salience and higher arousal in reaction to the presented stimuli. Therefore, it was expected that the LPP in reaction to erotic pictures would be more pronounced during fertile periods of the menstrual cycle around ovulation, as well as to be associated with estradiol-levels. A similar pattern was hypothesized to be present with testosterone-levels, whereas no association with progesterone was expected. Method: N â€‹= â€‹35 free-cycling women completed an Erotic picture Stroop task (neutral, positive, and erotic stimuli, with three neutral- and three erotic subcategories) during follicular phase, ovulation and luteal phase, while EEG was recorded. Subjects provided saliva samples in order to determine estradiol-, progesterone-, and testosterone levels at each measuring time, and affective states were assessed using the Positive and Negative Affect Scale (PANAS). Results: LPPs in reaction to erotic-compared to positive- and neutral pictures were larger in every cycle phase. LPPs in reaction to erotic couples were strongest in comparison to every other (sub-) category. During ovulation, higher estradiol-concentrations were associated with lower LPP-amplitudes towards erotic-couples- than to neutral pictures. No effects of progesterone, no direct effect of testosterone, as well as no effects of cycle phase, were evident. Conclusion: Results partly contradict our hypotheses, as estradiol was expected to be positively associated with LPP during fertile stages. Possible differences between stimulus-entities (words v. pictures) and ideas for further research are being discussed.

Schizotypy, social stress and the emergence of psychotic-like states - A case for benign schizotypy?

Schizotypy is a personality-organisation related to schizophrenia-liability as well as the emergence of psychotic symptoms and psychotic-like experiences (PLEs) in non-schizophrenic individuals. It has been suggested that some non-schizophrenic individuals may exhibit PLEs frequently, but in a fashion that is not distressing but life-enhancing ("benign schizotypy"). In schizophrenia and at-risk individuals, however, psychotic symptoms are not only distressing, but also triggered stress. To further investigate questions of causality and examine how PLEs may present as distressing symptoms in some individuals and as benign experiences in others, we explored how schizotypy-facets moderated PLEs-variability under experimentally induced social stress.We performed a standardised social stress-paradigm in 107 healthy adults (77 female, 30 male; average age 22,5 years), measuring changes in psychometrically assessed PLEs and the moderation of changes under stress through positive, negative and disorganised schizotypy. Results suggest two discrete effects: On the one hand, individuals high in disorganised and negative schizotypy showed stress-dependent increases in PLEs; without added effects of positive schizotypy. On the other, individuals low in negative and disorganised schizotypy showed higher levels of PLEs solely as a function of positive schizotypy but not stress. We discuss these findings in light of the fully-dimensional model of schizotypy and hypothesize that PLEs in individuals high in schizotypy-facets suggested to convey risk-for-schizophrenia (negative and disorganised) may reflect qualitatively different entities than PLEs in individuals with low values in these facets, but high expressions of positive schizotypy ("happy schizotypes"). Additionally, we emphasize the importance of not overlooking the disorganised schizotypy-facet in related research.

Oxytocin enhances the pain-relieving effects of social support in romantic couples.

Social support plays a vital role in physical and mental well-being. The neuropeptide hormone oxytocin (OXT) has been implicated in modulating pair-bonding and affiliative behaviors, but whether OXT contributes to the analgesic effects of a romantic partner's touch remains elusive. In the present randomized placebo-controlled, between-group, functional magnetic resonance imaging study involving 194 healthy volunteers (97 heterosexual couples), we tested the effects of intranasal OXT (24 IU) on handholding as a common mode of expressing emotional support in romantic couples. We scanned the subjects while brief electric shocks were administered. The subjects assumed that they received social support from either their romantic partner or an unfamiliar person. Unbeknown to the subject, in the partner and stranger support conditions, the same male experimenter always held the subject's left hand. Partner support was most effective in reducing the unpleasantness of electric shocks, and OXT further attenuated the unpleasantness across conditions. On the neural level, OXT significantly augmented the beneficial effects of partner support, as evidenced by a stronger decrease of neural responses to shocks in the anterior insula (AI), a stronger activity increase in the middle frontal gyrus (MFG), and a strengthened functional coupling between the AI and MFG. Our results support the notion that OXT specifically modulates the beneficial effects of social support in romantic couples by concomitantly reducing pain-associated activity and increasing activity linked to cognitive control and pain inhibition. We hypothesize that impaired OXT signaling may contribute to the experience of a lack of partner support.

Fearfulness, neuroticism/anxiety, and COMT Val158Met in long-term fear conditioning and extinction.

Individual differences in long-term stability of fear memories are of potential relevance for stable dispositions related to threat processing, such as neuroticism/anxiety and fearfulness. As previous research suggests a prominent role of dopamine for the retention of conditioned and extinguished fear, dopaminergic gene polymorphisms may also relate to individual differences in fear stability. While the COMT Val158Met polymorphism causes individual differences in prefrontal dopamine, its associations with human long-term fear extinction are currently unknown. Here, n = 30/29/28 healthy male Val/Val, Val/Met and Met/Met carriers, respectively, underwent a two-day differential conditioning paradigm with fear acquisition and extinction on Day 1 and a recall test on Day 2 with recordings of EEG and ECG. Fearfulness but not neuroticism/anxiety predicted fear bradycardia (i.e., heart period slowing) during Day 1 fear acquisition while it did not affect extinction or Day 2 fear recall. In contrast, COMT Val158Met significantly modulated Day 2 fear recall as evident in fear bradycardia and Late Positive Potential (LPP) amplitudes while it did not affect Day 1 fear or extinction learning. Furthermore, exploratory analyses revealed that individual differences in fear bradycardia during Day 2 extinction recall depended on Day 1 extinction success. Importantly, this contingency was (a) modulated by COMT Val158Met and (b) significantly reduced in high vs. low neuroticism/anxiety. The present study indicates that (a) individual differences in dopaminergic genotypes may affect the long-term stability of fear memories and (b) fearfulness vs. neuroticism/anxiety might play distinct roles in initial fear reactions vs. long-term stability of fear memories, respectively.

Preoperative Assessment of Neural Elements in Lumbar Spinal Stenosis by Upright Magnetic Resonance Imaging: An Implication for Routine Practice?

Introduction Lumbar spinal stenosis (LSS) is a kinetic-dependent disease typically aggravating during spinal loading. To date, assessment of LSS is usually performed with magnetic resonance imaging (MRI). However, conventional supine MRI is associated with significant drawbacks as it does not truly reflect physiological loads, experienced by discoligamentous structures during erect posture. Consequently, supine MRI often fails to reveal the source of pain and/or disability caused by LSS. The present study sought to assess neural dimensions via MRI in supine, upright, and upright-hyperlordotic position in order to evaluate the impact of patient positioning on neural narrowing. Therefore, radiological measures such as neuroforaminal dimensions, central canal volume, sagittal listhesis, and lumbar lordosis at spinal level L4/5 were extracted and stratified according to patient posture. Materials and methods Overall, 10 subjects were enclosed in this experimental study. MRI was performed in three different positions: (1) 0° supine (SP), (2) 80° upright (UP), and (3) 80° upright + hyperlordotic (HY) posture. Upright MRI was conducted utilizing a 0.25T open-configuration scanner equipped with a rotatable examination bed allowing for true standing MRI. Radiographic outcome of upright MRI imaging was extracted and evaluated according to patient positioning. Results Upright MRI-based assessment of neural dimensions was successfully accomplished in all subjects. Overall, radiographic parameters revealed a significant decrease of neural dimensions from supine to upright position: Specifically, mean foraminal area decreased from SP to UP by 13.3% (P ≤ 0.05) as well as from SP to HY position by 21% (P ≤ 0.05). Supplementation of hyperlordosis did not result in additional narrowing of neural elements (P ≥ 0.05). Furthermore, central canal volume revealed a decrease of 7% at HY and 8% at UP compared to SP position (P ≥ 0.05). Assessment of lumbar lordosis yielded in a significant increase when assessed at HY (+22.1%) or UP (+8.7%) compared to SP (P ≤ 0.05). Conclusions Our data suggest that neuroforaminal dimensions assessed by conventional supine MRI are potentially overestimated in patients with LSS. Especially, in patients having occult disease not visualized on conventional imaging modalities, upright MRI allows for a precise, clinically relevant, and at the same time non-invasive evaluation of neural elements in LSS when neural decompression is considered.

A positive-psychological intervention reduces acute psychosis-proneness.

BACKGROUND: While individuals at ultra-risk for schizophrenia are characterized by high negative/disorganised but low positive schizotypy, schizophrenia patients are usually high in all three schizotypy facets. Thus, avoiding increases in positive schizotypy in ultra-high risk individuals may constitute of form of schizophrenia-prevention. A possible method of reducing positive schizotypy could be Positive-Psychological intervention (PI). METHODS: We present results from 2 independent studies, including a 12-month follow-up from study 1, using an easy-to-perform intervention based on Positive Psychology to reduce positive schizotypy. RESULTS: A PI can significantly and sustainably reduce positive schizotypy compared to a placebo-condition. Furthermore, our results show very high response-rates to said intervention, with responsiveness to the intervention increasing significantly with disorganised schizotypic traits. CONCLUSIONS: As especially disorganised schizotypy is of relevance for the risk of transition from high benign schizotypy to schizophrenia and is found most closely associated to familial schizophrenia-risk and highly elevated in at-risk mental states, our results are encouraging. We suggest, thus, that positive psychology can not only reduce positive schizotypy, but may be increasingly useful with rising schizophrenia-risk and, thus, be worthy of further investigation regarding it potential in schizophrenia-prevention.

Fluctuations of estradiol during women's menstrual cycle: Influences on reactivity towards erotic stimuli in the late positive potential.

BACKGROUND: While several studies examined the reactivity towards negative emotional stimuli across women's menstrual cycle, only few investigated responses to positive emotional cues in association with sexual hormones on a neural level. Therefore, the aim of the current EEG-experiment was to study the differential reactivity towards positive (erotic) words during the menstrual cycle (i.e. with fluctuations in the steroids estradiol and progesterone) in the late positive potential (LPP). Regarding reactivity towards erotic stimuli, the LPP is seen as the most relevant ERP-component, as more positive amplitudes in the LPP reflect larger incentive salience and higher arousal. The LPP towards erotic words was expected to be more pronounced during fertile phases of the menstrual cycle (around ovulation). Furthermore, associations with hormonal concentrations of estradiol and progesterone were investigated. METHOD: 19 young, free cycling women were tested in an Erotic Stroop paradigm during the follicular phase, ovulation, and the luteal phase in a balanced cross-over design, while electroencephalogram (EEG) was recorded. RESULTS: LPPs in reaction to erotic compared to neutral words were larger in every phase. During the follicular phase and ovulation, higher estradiol-concentrations were associated with more positive LPP-amplitudes towards erotic- than to neutral words. No effects of progesterone, as well as no effects of cycle phase, were evident. Results are being discussed regarding implications for further research.

Image-based assessment of uncertainty in quantification of carotid lumen.

Measurements of the vessel lumen diameter are often used to determine the degree of atherosclerotic disease in carotid arteries. However, quantification results vary with imaging technique and acquisition settings. We aim at providing a tool that quantifies the lumen diameter on different image datasets and gives an estimate of quantification uncertainties, so that they can be taken into consideration when evaluating and comparing measurements. For the segmentation of the vessel lumen, we present an algorithm using ray-casting techniques and partial volume correction. We furthermore propose a scheme for the analysis and exploration of the lumen diameter. Finally, we present a clinically relevant application scenario, in which we explore agreement between lumen diameter estimations in corresponding computed tomography angiography, contrast-enhanced magnetic resonance angiography, time-of-flight, and subtraction images of carotid vessels with severe carotid atherosclerotic plaques.

Preclinical 4D-flow magnetic resonance phase contrast imaging of the murine aortic arch.

PURPOSE: Cardiovascular diseases remain the number one death cause worldwide. Preclinical 4D flow phase contrast magnetic resonance imaging can provide substantial insights in the analysis of aortic pathophysiologies in various animal models. These insights may allow a better understanding of pathophysiologies, therapy monitoring, and can possibly be translated to humans. This study provides a framework to acquire the velocity field within the aortic arch. It analyses important flow values at different locations within the aortic arch. Imaging parameters with high temporal and spatial resolution are provided, that still allow combining this time-consuming method with other necessary imaging-protocols. METHODS: A new setup was established where a prospectively gated 4D phase contrast sequence is combined with a highly sensitive cryogenic coil on a preclinical magnetic resonance scanner. The sequence was redesigned to maintain a close to steady state condition of the longitudinal magnetization and hence to overcome steady state artifacts. Imaging parameters were optimized to provide high spatial and temporal resolution. Pathline visualizations were generated from the acquired velocity data in order to display complex flow patterns. RESULTS: Our setup allows data acquisition with at least two times the rate than that of previous publications based on Cartesian encoding, at an improved image quality. The "steady state" sequence reduces observed artifacts and provides uniform image intensity over the heart cycle. This made possible quantification of blood speed and wall shear stress (WSS) within the aorta and its branches. The highest velocities were observed in the ascending aorta with 137.5 ± 8 cm/s. Peak velocity values in the Brachiocephalic trunk were 57 ± 12 cm/s. Quantification showed that the peak flow occurs around 20 ms post R-wave in the ascending aorta. The highest mean axial wall shear stress was observed in the analysis plane between the left common carotid artery (LCCA) and the left subclavian artery. A stable image quality allows visualizing complex flow patterns by means of streamlines and for the first time, to the best of our knowledge, pathline visualizations from 4D flow MRI in mice. CONCLUSION: The described setup allows analyzing pathophysiologies in mouse models of cardiovascular diseases in the aorta and its branches with better image quality and higher spatial and temporal resolution than previous Cartesian publications. Pathlines provide an advanced analysis of complex flow patterns in the murine aorta. An imaging protocol is provided that offers the possibility to acquire the aortic arch at sufficiently high resolution in less than one hour. This allows the combination of the flow assessment with other multifunctional imaging protocols.