Gravity-Dependent Modulation of Downbeat Nystagmus and Subjective Visual Vertical in the Roll Plane.

Downbeat nystagmus (DBN) is the most common form of acquired central vestibular nystagmus. Gravity perception in patients with DBN has previously been investigated by means of subjective visual straight ahead (SVA) and subjective visual vertical (SVV) in the pitch and roll planes only during whole-body tilts. To our knowledge, the effect of head tilt in the roll plane on the SVV and on DBN has not yet been systematically studied in patients. In this study, we investigated static and dynamic graviceptive function in the roll-plane in patients with DBN (patients) and healthy-controls (controls) by assessment of the Subjective Visual Vertical (SVV) and the modulation of slow-phase-velocity (SPV) of DBN. SPV of DBN and SVV were tested at different head-on trunk-tilt positions in the roll-plane (0°,30° clockwise (cw) and 30° counterclockwise (ccw)) in 26 patients suffering from DBN and 13 controls. In patients, SPV of DBN did not show significant modulations at different head-tilt angles in the roll-plane. SVV ratings did not differ significantly between DBN patients vs. controls, however patients with DBN exhibited a higher variability in mean SVV estimates than controls. Our results show that the DBN does not exhibit any modulation in the roll-plane, in contrast to the pitch-plane. Furthermore, patients with DBN show a higher uncertainty in the perception of verticality in the roll-plane in form of a higher variability of responses.

Seasonality of benign paroxysmal positional vertigo : A retrospective study from Central Europe.

BACKGROUND: Although benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo in clinical practice, factors influencing the pathophysiology remain not fully understood. OBJECTIVE: Here we aim to investigate possible seasonal influences on the occurrence of BPPV in Vienna, a city located in a Central European country with pronounced seasonal fluctuations. METHODS: We retrospectively investigated data from 503 patients presenting with BPPV to the outpatient clinics of the Medical University of Vienna between 2007 and 2012. Analyses included age, gender, type of BPPV, seasonal assignment, as well as daylight hours and the temperature in Vienna at symptom onset. RESULTS: Out of 503 patients (159 male, 344 female, ratio 1:2.2; mean age 60 ± 15.80 years), most patients presented with posterior (89.7%) and left-sided (43.1%) BPPV. There was a significant seasonal difference (χ2 p = 0.036) with the majority of symptoms occurring in winter seasons (n = 142), followed by springtime (n = 139). Symptom onset did not correlate with the average temperature (p = 0.24) but on the other hand very well with daylight hours (p < 0.05), which ranged from 8.4 h per day in December, to an average of 15.6 h in July. CONCLUSION: Our results show a seasonal accumulation of BPPV during winter and springtime, which is in line with previous studies from other climatic zones, suggesting an association of this seasonality with varying vitamin D levels.

Cupulolithiasis as an Alternative Mechanism for Pseudo-spontaneous Nystagmus in Horizontal Canal Benign Paroxysmal Positional Vertigo.

Benign paroxysmal positional vertigo of the horizontal semicircular canal may present a differential diagnostic challenge. In addition to the classical positional nystagmus, a persistent nystagmus in a seated position occasionally occurs, so-called pseudo-spontaneous nystagmus (PSN), which can be mistaken for a central or peripheral spontaneous nystagmus. We report a case with cupulolithiasis of the horizontal semicircular canal presenting with horizontal PSN in a sitting position, with implications for a new pathomechanism of PSN.

Development of a method to create uniform phantoms for task-based assessment of CT image quality.

PURPOSE: To develop a customized method to produce uniform phantoms for task-based assessment of CT image quality. METHODS: Contrasts between polymethyl methacrylate (PMMA) and fructose solutions of different concentrations (240, 250, 260, 280, 290, 300, 310, 320, 330, and 340 mg/mL) were calculated. A phantom was produced by laser cutting PMMA slabs to the shape of a patient's neck. An opening of 10 mm diameter was cut into the left parapharyngeal space. An angioplasty balloon was inserted and filled with the fructose solutions to simulate low-contrast lesions. The phantom was scanned with six tube currents. Images were reconstructed with filtered back projection (FBP) and adaptive iterative dose reduction 3D (AIDR 3D). Calculated and measured contrasts were compared. The phantom was evaluated in a detectability experiment using images with 4 and 20 HU lesion contrast. RESULTS: Low-contrast lesions of 4, 9, 11, 13, 18, 20, 24, 30, 35, and 37 HU contrast were simulated. Calculated and measured contrasts correlated excellently (r = 0.998; 95% confidence interval: 0.991 to 1). The mean ± SD difference was 0.41 ± 2.32 HU (P < 0.0001). Detection accuracy and reader confidence were 62.9 ± 18.2% and 1.58 ± 0.68 for 4 HU lesion contrast and 99.6 ± 1.3% and 4.27 ± 0.92 for 20 HU lesion contrast (P < 0.0001), confirming that the method produced lesions at the threshold of detectability. CONCLUSION: A cost-effective and flexible approach was developed to create uniform phantoms with low-contrast signals. The method should facilitate access to customized phantoms for task-based image quality assessment.

Prescription patterns of antidementives in a high income country: A pharmacoepidemiologic study.

INTRODUCTION: Dementia is a leading and growing cause of morbidity and mortality. The aim of this study was to investigate real-world prescription patterns of antidementive medication in one of the largest cohorts published thus far to optimize use in this growing population. METHODS: Prescription claims from 2005 to 2016 were provided by Austrian sickness funds, covering 98% of the population of Austria. Patients treated with at least one of the four approved antidementive drugs (ADDs) were included. Prescription prevalence was calculated for 2014 and 2015, and prescription patterns were traced on an individual level during the entire study period. RESULTS: A total of 127,896 patients were treated with an ADD between 2005 and 2016. The prevalence was 0.93% in 2014 and 1% in 2015. The median age at initiation of treatment was 82.3 years, and 65% were female. Initial therapy was a cholinesterase inhibitor (ChEI) in 80% and memantine in 20%. The median duration of therapy was 13.3 months. Eighteen percent of patients switched medication: two thirds to receive memantine, and one third to a different cholinesterase inhibitor. More than 26% discontinued treatment early. CONCLUSION: We find that discontinuation of ADDs is more frequent than switching; memantine is a common starting drug and age at the start of treatment is rather high in this population. Interpretation should be cautious, but the data may suggest that treatment guidelines are followed inconsistently. Appropriate provision of the available options should be emphasized to optimize cognitive survival, comorbidity, quality of life, and health care expenditures.

Vertebral Bone Marrow and Endplate Assessment on MR Imaging for the Differentiation of Modic Type 1 Endplate Changes and Infectious Spondylodiscitis.

On magnetic resonance (MR) imaging, Modic type 1 (MT1) endplate changes and infectious spondylodiscitis share similar findings. Therefore, this study investigated vertebral bone marrow and endplate changes to enable their differentiation. The lumbar spine MR examinations of 91 adult patients were retrospectively included: 39 with MT1; 19 with early spondylodiscitis without abscess; and 33 with advanced spondylodiscitis with abscess. The assessment included percentage of bone marrow edema on sagittal short tau inversion recovery images, and the signal ratio of edema to unaffected bone and endplate contour (normal; irregular, yet intact; blurred; destructive) on sagittal unenhanced T1-weighted images. Differences were tested for statistical significance by Chi-square test and mixed model analysis of variance. The MR diagnostic accuracy in differentiating MT1 and spondylodiscitis was assessed by cross-tabulation and receiver-operating characteristic analysis. The endplate contours, edema extents, and T1-signal ratios of MT1 (extent, 31.96%; ratio, 0.83) were significantly different (p < 0.001) from early spondylodiscitis (56.42%; 0.60), and advanced spondylodiscitis (91.84%; 0.61). The highest diagnostic accuracy (sensitivity, 94.87%; specificity, 94.23%; accuracy, 94.51%) in identifying MT1 was provided by an irregular, yet intact endplate contour. This may be a useful MR feature for the differentiation between MT1 and spondylodiscitis, particularly in its early stage.

Lumbar Intervertebral Disc Degeneration as a Common Incidental Finding in Young Pregnant Women as Observed on Prenatal Magnetic Resonance Imaging.

Background: Obstetric imaging, subserving fetal evaluation, may yield incidental maternal findings. Based on prenatal magnetic resonance (MR) imaging, this study aims to investigate incidental intervertebral disc degeneration and displacement in young, pregnant women. Methods: This retrospective study included the sagittal 1.5 Tesla, T2-weighted lumbar spine images of 943 pregnant Central Europeans (age range, 18-47 years), who initially had undergone MR imaging because of sonographically suspected fetal abnormalities. Qualitatively, 4715 lumbar intervertebral discs were evaluated for degeneration using a modified Pfirrmann MR classification (nondegenerated, low-grade, moderate, and high-grade degeneration), as well as for displacement. In addition to descriptive statistics, an ordinal regression analysis was performed to analyze the relationship between degeneration and the women's age, and body weight. Results: With regard to the highest degree of degeneration in each woman, 578 (61.3%) showed low-grade, 211 (22.4%) moderate, and 154 (16.3%) high-grade degeneration, and no woman had entirely nondegenerated discs. For the span from 18 to 47 years of age, moderate and high-grade degeneration increased from 6.7% to 36.7% and from 13.3% to 22.4%, respectively. Of 943 women, 57 (6%) had disc displacements, of which 97% were in conjunction with high-grade degeneration. There was a statistically significant relationship (p < 0.001) between degeneration and age, and between degeneration and body weight. Conclusions: In young pregnant women, lumbar intervertebral disc degeneration is a ubiquitous, incidental finding, increasing from the late second decade of life onward, which may be part of physiological aging, as opposed to a small percentage of incidental disc displacements.

Scout-guided needle placement-a technical approach for dose reduction in CT-guided periradicular infiltration.

PURPOSE: To develop and evaluate a technical approach for CT-guided periradicular infiltration using quantitative needle access and guidance parameters extracted from CT scout images. METHODS: Five 3D-printed phantoms of the abdomen mimicking different patients were used to develop a technical approach for scout-guided periradicular infiltration. The needle access point, puncture depth, and needle angulation were calculated using measurements extracted from anterior-posterior and lateral CT scout images. Fifty needle placements were performed with the technique thus developed. Dose exposure and number of image acquisitions were compared with ten procedures performed using a conventional free-hand technique. Data were analyzed with the Mann-Whitney U test. RESULTS: Parameters derived solely from scout images provided adequate guidance for successful and reliable needle placement. Needle guidance was performed with the same equipment as the standard periradicular infiltration. Two scout images and 3.5 ± 2.3 (mean ± SD) single-shot images for needle positioning were acquired. Mean DLP ± SD was 3.8 ± 2.5 mGy cm. The number of single-shot acquisitions was reduced by 68% and the overall dose was reduced by 84% in comparison with the conventional free-hand technique (p < 0.0001). CONCLUSION: Scout-guided needle placement for periradicular infiltration is feasible and reduces radiation exposure significantly.

When an incidental MRI finding becomes a clinical issue : Posterior lumbar subcutaneous edema in degenerative, inflammatory, and infectious conditions of the lumbar spine.

BACKGROUND: On magnetic resonance imaging (MRI), posterior lumbar subcutaneous edema (PLSE) is a frequent incidental, yet unclear finding within the deep subcutaneous perifascial tissue. This study aimed to investigate PLSE in various pathological lumbar conditions. METHODS: This retrospective study included the MR images of the lumbar spine of 279 patients (age range 18-82 years) without cardiovascular, renal or hepatic diseases, 79 of whom had low-grade disc degeneration, 101 combined endplate and facet joint degeneration, 53 axial spondyloarthritis and 46 infectious spondylodiscitis. There were 232 patients with a body mass index (BMI) <30, and 47 with a BMI ≥30 (obese). For each group, the relationship between PLSE and BMI was analyzed using multiple logistic regression, and between PLSE extension and BMI using ordinal regression. RESULTS: A PLSE was found in 11/79 (13.9%) patients with disc degeneration, 37/101 (36.6%) with endplate and facet joint degeneration, 7/53 (13.2%) with spondyloarthritis, and 28/46 (60.9%) with spondylodiscitis. For each group, a statistically significant relationship was demonstrated between PLSE and BMI (P = 0.000-P = 0.031), except for spondylodiscitis (P = 0.054), as well as between PLSE extension and BMI (P = 0.000-P = 0.049). A PLSE was found in 21.1% of nonobese and 72.3% of obese patients (P = 0.000). CONCLUSION: The presence of PLSE seems to be associated with various lumbar conditions, particularly in obese patients. Its perifascial location may suggest a potential fascial origin; however, PLSE should not to be confused with posttraumatic, postsurgical or infectious edema or edema associated with internal diseases.

Characterization of office laser printers for 3-D printing of soft tissue CT phantoms.

The purpose of our study is to develop and evaluate a method for radiopaque 3-D printing (R3P) of soft tissue computed tomography (CT) phantoms with office laser printers. Five laser printers from different vendors are tested for toner CT attenuation. A liver phantom is created by printing CT images of a patient liver on office paper. One thousand eight hundred sixty paper sheets are printed with three repeated prints per page, resulting in a stack of 18.6 cm. The phantom is examined with 12 tube current settings. Images are reconstructed using filtered back projection (FBP) and iterative reconstruction [adaptive iterative dose reduction 3D (AIDR 3D)]. Seven radiologists rated image quality of all acquisitions. Toner attenuation of all investigated printers increased linearly with the print template grayscale. The liver phantom reproduced anatomic detail and attenuation values of the patient ( mean ± SD HU difference 12.68 ± 7.74 ). Image quality scores increased with dose but did not vary significantly above a threshold dose for AIDR 3D. Overall, AIDR 3D reconstructed images are rated superior to FBP reconstructions ( p < 0.001 ). In conclusion, R3P with standard office laser printers can generate soft tissue CT phantoms without hardware manipulations but with limited flexibility regarding attenuation properties of the printed toner material.

Paper-based 3D printing of anthropomorphic CT phantoms: Feasibility of two construction techniques.

OBJECTIVES: To develop and evaluate methods for assembling radiopaque printed paper sheets to realistic patient phantoms for CT dose and image quality testing. METHODS: CT images of two patients were radiopaque printed with aqueous potassium iodide solution (0.6 g/ml) on paper. Two methods were developed for assembling the paper sheets to head and neck phantoms. (1) Printed sheets were fed to a paper-based 3D printer along with corresponding 3D printable STL files. (2) Paper stacks of 5-mm thickness were glued with toner, cut to the patient shape and assembled to a phantom. In a sample application study, both phantoms were examined with five different tube current settings. Images were reconstructed using filtered-back projection (FBP) and iterative reconstruction (AIDR 3D) with three strength levels. Dose length product (DLP), signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNRs) were analysed. Data were analysed using 2-way analysis of variance (ANOVA). RESULTS: Both methods achieved anthropomorphic phantoms with detailed patient anatomy. The 3D printer yielded a precise reproduction of the external patient shape, but caused visible glue artefacts. Gluing with toner avoided these artefacts and yielded more flexibility with regard to phantom size. In the sample application study, non-inferior SNR and CNR and up to 83.7% lower DLP were achieved on the phantoms with AIDR 3D compared with FBP. CONCLUSIONS: Two methods for assembling radiopaque printed paper sheets to phantoms of individual patients are presented. The sample application demonstrates potential for simulation of patient imaging and systematic CT dose and image quality assessment. KEY POINTS: • Two methods were developed to create realistic CT phantoms of individual patients from radiopaque printed paper sheets. • Analysis of five tube current and four reconstruction settings on two radiopaque 3D printed patient phantoms yielded non-inferior SNR and CNR and up to 83.7% lower dose with iterative reconstruction in comparison with filtered back projection. • Radiopaque 3D printed phantoms can simulate patients and allow systematic analysis of CT dose and image quality parameters.

Strong Spatial and Spectral Localization of Surface Plasmons in Individual Randomly Disordered Gold Nanosponges.

Porous nanosponges, percolated with a three-dimensional network of 10 nm sized ligaments, recently emerged as promising substrates for plasmon-enhanced spectroscopy and (photo)catalysis. Experimental and theoretical work suggests surface plasmon localization in some hot-spot modes as the physical origin of their unusual optical properties, but so far the existence of such hot-spots has not been proven. Here we use scattering-type scanning near-field nanospectroscopy on individual gold nanosponges to reveal spatially and spectrally confined modes at 10 nm scale by recording local near-field scattering spectra. High quality factors of individual hot-spots of more than 40 are demonstrated, predicting high Purcell factors up to 106. The observed field localization and enhancement make such nanosponges an appealing platform for a variety of applications ranging from nonlinear optics to strong-coupling physics.

Visual advisory warnings about hidden dangers: Effects of specific symbols and spatial referencing on necessary and unnecessary warnings.

Augmented reality has the potential to improve the effectiveness of collision warnings in vehicles because they inherently convey spatial information about the hazard and can guide the attention of the driver towards it. For future warning systems, which can detect sight obstructed dangers, related work already revealed some advantages. In a driving simulator study with 80 participants, we investigated the effects of three corresponding design parameters which are commonly integrated at augmented reality warnings. This study analyzes the individual contribution of specific warning symbols, warning animation, and spatial referencing. Part one of the study concentrates on the effectiveness of necessary warnings and part two on the drivers' compliance despite false alarms. Compared to the control condition with static unspecific warning symbols, static specific warning symbols depicting the type and motion direction of the hazard led to several but inconsistent advantages. The scaling animation only improved subjective evaluation. However, spatial referencing of an (unspecific) warning symbol consistently improved drivers' reactions to as well as evaluations of necessary and unnecessary warnings. The results emphasize the potential of spatial referencing, particularly for in-vehicle warnings of future collision avoidance systems.

A radiopaque 3D printed, anthropomorphic phantom for simulation of CT-guided procedures.

OBJECTIVES: To develop an anthropomorphic phantom closely mimicking patient anatomy and to evaluate the phantom for the simulation of computed tomography (CT)-guided procedures. METHODS: Patient CT images were printed with aqueous potassium iodide solution (1 g/mL) on paper. The printed paper sheets were stacked in alternation with 1-mm thick polyethylene foam layers, cut to the patient shape and glued together to create an anthropomorphic abdomen phantom. Ten interventional radiologists performed periradicular infiltration on the phantom and rated the phantom procedure regarding different aspects of suitability for simulating CT-guided procedures. RESULTS: Radiopaque printing in combination with polyethylene foam layers achieved a phantom with detailed patient anatomy that allowed needle placement. CT-guided periradicular infiltration on the phantom was rated highly realistic for simulation of anatomy, needle navigation and overall course of the procedure. Haptics were rated as intermediately realistic. Participants strongly agreed that the phantom was suitable for training and learning purposes. CONCLUSIONS: A radiopaque 3D printed, anthropomorphic phantom provides a realistic platform for the simulation of CT-guided procedures. Future work will focus on application for training and procedure optimisation. KEY POINTS: • Radiopaque 3D printing combined with polyethylene foam achieves patient phantoms for CT-guided procedures. • Radiopaque 3D printed, anthropomorphic phantoms allow realistic simulation of CT-guided procedures. • Realistic visual guidance is a key aspect in simulation of CT-guided procedures. • Three-dimensional printed phantoms provide a platform for training and optimisation of CT-guided procedures.

Augmented reality warnings in vehicles: Effects of modality and specificity on effectiveness.

In the future, vehicles will be able to warn drivers of hidden dangers before they are visible. Specific warning information about these hazards could improve drivers' reactions and the warning effectiveness, but could also impair them, for example, by additional cognitive-processing costs. In a driving simulator study with 88 participants, we investigated the effects of modality (auditory vs. visual) and specificity (low vs. high) on warning effectiveness. For the specific warnings, we used augmented reality as an advanced technology to display the additional auditory or visual warning information. Part one of the study concentrates on the effectiveness of necessary warnings and part two on the drivers' compliance despite false alarms. For the first warning scenario, we found several positive main effects of specificity. However, subsequent effects of specificity were moderated by the modality of the warnings. The specific visual warnings were observed to have advantages over the three other warning designs concerning gaze and braking reaction times, passing speeds and collision rates. Besides the true alarms, braking reaction times as well as subjective evaluation after these warnings were still improved despite false alarms. The specific auditory warnings were revealed to have only a few advantages, but also several disadvantages. The results further indicate that the exact coding of additional information, beyond its mere amount and modality, plays an important role. Moreover, the observed advantages of the specific visual warnings highlight the potential benefit of augmented reality coding to improve future collision warnings.

Long-lived electron emission reveals localized plasmon modes in disordered nanosponge antennas.

We report long-lived, highly spatially localized plasmon states on the surface of nanoporous gold nanoparticles-nanosponges-with high excitation efficiency. It is well known that disorder on the nanometer scale, particularly in two-dimensional systems, can lead to plasmon localization and large field enhancements, which can, in turn, be used to enhance nonlinear optical effects and to study and exploit quantum optical processes. Here, we introduce promising, three-dimensional model systems for light capture and plasmon localization as gold nanosponges that are formed by the dewetting of gold/silver bilayers and dealloying. We study light-induced electron emission from single nanosponges, a nonlinear process with exponents of n≈5...7, using ultrashort laser pulse excitation to achieve femtosecond time resolution. The long-lived electron emission process proves, in combination with optical extinction measurements and finite-difference time-domain calculations, the existence of localized modes with lifetimes of more than 20 fs. These electrons couple efficiently to the dipole antenna mode of each individual nanosponge, which in turn couples to the far-field. Thus, individual gold nanosponges are cheap and robust disordered nanoantennas with strong local resonances, and an ensemble of nanosponges constitutes a meta material with a strong polarization independent, nonlinear response over a wide frequency range.

A photoswitchable rotaxane operating in monolayers on solid support.

A novel photoswitchable rotaxane was synthesised and its switching behaviour in solution was analysed with NMR and UV-Vis. A monolayer of rotaxanes was deposited on glass surfaces and the on-surface photoswitching was investigated. Angle-resolved NEXAFS spectra revealed a preferential orientation that reversibly changes upon switching.

Photocontrolled On-Surface Pseudorotaxane Formation with Well-Ordered Macrocycle Multilayers.

The photoinduced pseudorotaxane formation between a photoresponsive axle and a tetralactam macrocycle was investigated in solution and on glass surfaces with immobilized multilayers of macrocycles. In the course of this reaction, a novel photoswitchable binding station with azobenzene as the photoswitchable unit and diketopiperazine as the binding station was synthesized and studied by NMR and UV/Vis spectroscopy. Glass surfaces have been functionalized with pyridine-terminated SAMs and subsequently with multilayers of macrocycles through layer-by-layer self assembly. A preferred orientation of the macrocycles could be confirmed by NEXAFS spectroscopy. The photocontrolled deposition of the axle into the surface-bound macrocycle-multilayers was monitored by UV/Vis spectroscopy and led to an increase of the molecular order, as indicated by more substantial linear dichroism effects in angle-resolved NEXAFS spectra.

Catenation and encapsulation induce distinct reconstitutions within a dynamic library of mixed-ligand Zn4L6 cages.

Two new Zn4L6 cages composed of diamine subcomponents containing either naphthalene diimide (NDI) or porphyrin moieties are described. Their structural differences allow these cages to exhibit distinct interactions with different chemical stimuli, yielding different supramolecular products. The electron-poor NDI subunits of the first cage were observed to thread through electron-rich aromatic crown-ether macrocycles, forming mechanically-interlocked species up to a [3]catenane, whereas the porphyrin ligands of the second cage interacted favourably with C70, causing it to be bound as a guest. When mixed, the two cages were observed to form a dynamic combinatorial library (DCL) of seven constitutionally distinct mixed-ligand Zn4L6 cages. The DCL was observed to reconstitute in opposing ways when treated with either the crown ether or C70: the electron-rich macrocycle templated the formation of heteroleptic catenanes, whereas C70 caused the DCL to self-sort into homoleptic structures.