Absence Of Motion Research Articles

Influence of appearance and motion interaction on emotional state attribution to objects: The example of hugging shimeji mushrooms

Feeling that a non-human object has emotions (hereinafter referred to as emotional state attribution) is generally known as animacy perception. Previous studies have considered appearance and motion separately as factors that evoke emotional state attribution. Then, if both the degree of human likeness in shape and the presence or absence of motion are considered simultaneously, is there a possibility of strong emotional state attribution even for objects that are not human-like in terms of shape? In this study, we experimentally investigated the influence of human likeness in shape and movements evoking social relations on emotional state attribution, including their interaction, using three types of objects (human figure, shimeji mushroom, and match) that were assumed to differ from humans in terms of shape. We conducted three experiments. In Experiment 1, although the human figure was rated as more human-like than the shimeji mushroom in terms of shape, emotions were attributed more strongly to the shimeji mushroom than to the human figure when accompanied by movements that evoked social relationships. In Experiment 2, a follow-up to Experiment 1 was conducted by eliminating the influence of three-dimensionality, and similar results to Experiment 1 were obtained. In Experiment 3, the influence of face parts was examined, and emotions were attributed more strongly when motion was given to an object without face parts. The results suggest that people may attribute emotions more strongly to faceless objects that resemble humans only to a certain extent in shape when they show movements that evoke social relations.

Facilitating diffusion tensor imaging of the brain during continuous gross head motion with first and second order motion compensating diffusion gradients.

To demonstrate the feasibility of motion compensating diffusion gradient schemes in the acquisition of quality diffusion tensor images (DTI) of the brain during continuous gross head motion. Five healthy subjects were scanned using a clinical 3 T MRI with and without continuous head motion. For one volunteer, DTI data was acquired using standard (M0) diffusion-weighted (DW) gradients, and first (M1) and second (M2) order gradient schemes that were previously developed for use in cardiac DTI. In four additional volunteers, DTI data was acquired with M0 and M2 gradients. DTI parameters were calculated and compared with established retrospective motion corrections. In the absence of motion, DTI parameters calculated from M0, M1, and M2 data were consistent. In the presence of motion, up to 44% of DW images acquired with M0 gradients were corrupted by signal dropout, compared to 0% of the M2 images. In voxelwise comparisons, DTI parameters calculated using motion-M0 data were elevated compared to reference data. Retrospective corrections for extreme motion applied to motion-M0 data did not improve consistency with reference data in cases where motion corrupted >15% of DW images. In contrast, DTI parameters calculated with motion-M2 data were consistent with reference data. This proof-of-principle study demonstrates that motion compensating diffusion gradients can mitigate artifacts because of continuous motion in DTI of the brain and offers promise for improved DTI accessibility. Further study will be necessary to determine the robustness of the approach in patient populations with high susceptibility to head motion.

Prospective motion correction for cervical spinal cord MRS.

To develop prospective motion correction for single-voxel MRS in the human cervical spinal cord. A motion MR navigator was implemented using reduced field-of-view 2D-selective RF excitation together with EPI readout. A short-echo semi-LASER sequence (TE = 30 ms) was updated to incorporate this real-time image-based motion navigator, as well as real-time shim and frequency navigators. Five healthy participants were studied at 3 T with a 64-channel head-neck receive coil. Single-voxel MRS data were measured in a voxel located at the C3-5 vertebrae level. The motion navigator was used to correct for translations in the X-Y plane and was validated by assessing spectral quality with and without prospective correction in the presence of subject motion. Without prospective correction, motion resulted in severe lipid contamination in the MR spectra. With prospective correction, the quality of spinal cord MR spectra in the presence of motion was similar to that obtained in the absence of motion, with comparable spectral signal-to-noise ratio and linewidth and no significant lipid contamination. Prospective motion and B0 correction allow acquisition of good-quality MR spectra in the human cervical spinal cord in the presence of motion. This new technique should facilitate reliable acquisition of spinal cord MR spectra in both research and clinical settings.

Epidemic processes on self-propelled particles: Continuum and agent-based modeling

Most spreading processes require spatial proximity between agents. The stationary state of spreading dynamics in a population of mobile agents thus depends on the interplay between the time and length scales involved in the epidemic process and their motion in space. We analyze the steady properties resulting from such interplay in a simple model describing epidemic spreading (modeled as a susceptible-infected-susceptible process) on self-propelled particles (performing run-and-tumble motion). Focusing our attention on the diffusive long-time regime, we find that the agents' motion changes qualitatively the nature of the epidemic transition from an inactive phase to an active one, characterized by the emergence of a macroscopic fraction of infected agents. Indeed, the transition becomes of the mean-field type for agents diffusing in one, two, and three dimensions, while, in the absence of motion, the epidemic outbreak depends on the dimension of the underlying static network determined by the agents' fixed locations. The insights obtained from a continuum description of the system are validated by numerical simulations of an agent-based model. Our work aims at establishing a connection between the research fields of soft active matter physics and theoretical epidemiology, and may be of interest for both communities.

Shoulder injury related to vaccine administration following SARS-CoV-2 inoculation: Case series and review of literature

IntroductionShoulder Injuries Related to Vaccine Administration (SIRVA), describes those cases of shoulder severe post-inoculation complications, including pain and prolonged disability. Most of the reported cases have been secondary to influenza vaccination. This study retrospectively describes a series of 18 patients following SARS-CoV-2 inoculation and compares the findings with those previously reported for other vaccines. Materials and methodsInclusion criteria was onset of symptoms within 48 h after injection, symptoms duration of at least seven days, and restricted range of motion in absence of symptoms prior to vaccination. Average age was 59.4 years old (38–76), and 72.2% were women. ResultsIn many cases (58%) the initial diagnosis was not clear, which lead to incorrect treatment. The most common pathological finding was subacromial-subdeltoid bursitis (66.6%). All patients who received depot corticosteroids followed by a gentle rehabilitation program showed strong clinical improvement but did not completely resolve the symptoms at 7.2 months average final follow-up. Surgical intervention was necessary in one of the patients due to the persistence of symptoms despite conservative treatment. ConclusionsShoulder injury related to vaccine administration is rare, but when present, its torpid evolution makes it difficult to treat. We have found in our case series a similar pattern to that already described for other vaccines. A high index of suspicion helps to pick up the condition promptly and early treatment can bring satisfactory outcome.

Narrative Comprehension Guides Eye Movements in the Absence of Motion.

Viewers' attentional selection while looking at scenes is affected by both top-down and bottom-up factors. However, when watching film, viewers typically attend to the movie similarly irrespective of top-down factors-a phenomenon we call the tyranny of film. A key difference between still pictures and film is that film contains motion, which is a strong attractor of attention and highly predictive of gaze during film viewing. The goal of the present study was to test if the tyranny of film is driven by motion. To do this, we created a slideshow presentation of the opening scene of Touch of Evil. Context condition participants watched the full slideshow. No-context condition participants did not see the opening portion of the scene, which showed someone placing a time bomb into the trunk of a car. In prior research, we showed that despite producing very different understandings of the clip, this manipulation did not affect viewers' attention (i.e., the tyranny of film), as both context and no-context participants were equally likely to fixate on the car with the bomb when the scene was presented as a film. The current study found that when the scene was shown as a slideshow, the context manipulation produced differences in attentional selection (i.e., it attenuated attentional synchrony). We discuss these results in the context of the Scene Perception and Event Comprehension Theory, which specifies the relationship between event comprehension and attentional selection in the context of visual narratives.

Self-navigated prospective motion correction for 3D-EPI acquisition.

Although 3D EPI is more susceptible to motion artifacts than 2D EPI, it presents some benefits for functional MRI, including the absence of spin-history artifacts, greater potential for parallel imaging acceleration, and better functional sensitivity in high-resolution imaging. Here we present a self-navigated 3D-EPI sequence suitable for prospective motion-corrected functional MRI without additional hardware or pulses. For each volume acquisition, the first 24 of the 52 partitions being acquired are accumulated to a new feedback block that was added to the image reconstruction pipeline. After zero-filling the remaining partitions, the feedback block constructs a volumetric self-navigator (vSNav), co-registers it to the reference vSNav acquired during the first volume acquisition, and sends motion estimates to the sequence. The sequence then updates its FOV and acquires subsequent partitions with the adjusted FOV, until the next update is received. The sequence was validated without and with intentional motion in phantom and in vivo on a 3T Skyra. For phantom scans, the FOV was updated 0.704 s after acquisition of the vSNav partitions, and for in vivo scans after 0.768 s. Both phantom and in vivo data demonstrated stable motion estimates in the absence of motion. For in vivo acquisitions, prospective head-pose estimates using the vSNav's and retrospective estimates with FLIRT (FMRIB's Linear Image Registration Tool) agreed to within 0.23 mm (< 10% of the slice thickness) and 0.14° in all directions. Depending when motion occurs during a volume acquisition, the proposed method fully corrects the FOV and recovers image quality within one volume acquisition.

Study of self-charging features in hybrid vehicle

Pollution and energy crises become more and more visible, and Hybrid Electric Vehicles (HEVs) are gaining more and more popularity around the world. To study the perception of alternative technology in an automobile, the project "Hybrid Vehicle Using Self-Charging Functions" is being carried out. A hybrid vehicle uses two or more different types of energy and combines it with electrical power. When the motor is started, the magnetic coil present in the crank starts to rotate. The rotation creates a higher voltage flux. In this case, an additional alternative magnet coil is connected in parallel with the magnet coil using gears. As the coil rotates, the energy generated in the main coil is used for ignition, while the energy generated in the alternate coil is sent to the rectifier and stored in the battery. While the car runs out of fuel, the hybrid switch is activated, then the energy stored in the battery is transferred to the wheel hub, and it starts to work. Since ancient times, people have been using vehicles for transportation and some personal needs. It pollutes the environment with gasoline and diesel fuel. It is burned in the engine for energy, but as some unburned gases come out, it affects the human respiratory system. Therefore, the automotive industry has introduced a battery vehicle (hybrid vehicle). It consumes zero emissions and is environmentally friendly. For a while, it only appeared in cars, not two-wheelers, so for a change, if it creates a hybrid two-wheeler combined with a motor and battery, it will have power, fuel efficiency, and fewer emissions. It has power and environmental fixes in a two-wheeler. When driving at an average speed of 0 to 50 mph, it consumes more fuel due to high torque instead of power from the engine. It receives power from the battery above 50 to 100, and when the engine comes to work, there is power from the engine at that time with low torque, so the motorcycle will not consume much fuel, which means that in motion, the two-wheeler is running on battery, and in the absence of motion, in an engine with such low emissions.

Efficacy and Pharmacological Appropriateness of Cinnarizine and Dimenhydrinate in the Treatment of Vertigo and Related Symptoms.

Vertigo is not itself a disease, but rather a symptom of various syndromes and disorders that jeopardize balance function, which is essential for daily activities. It is an abnormal sensation of motion that usually occurs in the absence of motion, or when a motion is sensed inaccurately. Due to the complexity of the etiopathogenesis of vertigo, many pharmacological treatments have been tested for efficacy on vertigo. Among these drugs, cinnarizine, usually given together with dimenhydrinate, appears to be the first-line pharmacotherapy for the management of vertigo and inner ear disorders. Based on these considerations, the present non-interventional study aimed to investigate the clinical efficacy and tolerability of a fixed combination of cinnarizine (20 mg) and dimenhydrinate (40 mg) in patients suffering from vertigo-related symptoms. To this end, we enrolled 120 adults—70 males, and 50 females—with an average age of 64 years. Before beginning pharmacological treatment, all patients were screened for the intensity of vertigo, dizziness, and concomitant symptoms through the Visual Scale of Dizziness Disorders and Dizziness Handicap Inventory scales. At the end of the anamnestic evaluation, patients received the fixed-dose combination of cinnarizine (20 mg) plus dimenhydrinate (40 mg) 3 times daily, for 60 days. The results of this study provide further insight regarding the efficacy of the fixed combination when used to reduce symptoms of vestibular vertigo of central and/or peripheral origin, after both the 15- and 60-day therapies. Independent of the type of vertigo, the fixed combination was able to reduce dizziness- and vertigo-associated symptoms in more than 75% of all patients treated, starting from 15 days of therapy, and improving 60 days after starting the therapy. Interestingly, we also found differences between male and female patients in the framework of the pharmacological effects of therapy. This study provides further details concerning the therapeutic efficacy of the fixed combination of cinnarizine and dimenhydrinate, and also focuses attention on the possibility that these drugs could act in a gender-specific manner, paving the way for further research.

Accuracy of heart rate variability estimated with reflective wrist-PPG in elderly vascular patients

Optical heart rate monitoring (OHR) with reflective wrist photoplethysmography is a technique mainly used in the wellness application domain for monitoring heart rate levels during exercise. In the absence of motion, OHR technique is also able to estimate individual beat-to-beat intervals relatively well and can therefore also be used, for example, in monitoring of cardiac arrhythmias, stress, or sleep quality through heart rate variability (HRV) analysis. HRV analysis has also potential in monitoring the recovery of patients, e.g. after a medical intervention. However, in order to detect subtle changes, the calculated HRV parameters should be sufficiently accurate and very few studies exist that asses the accuracy of OHR derived HRV in non-healthy subjects. In this paper, we present a method to estimate beat-to-beat-intervals (BBIs) from reflective wrist PPG signal and evaluated the accuracy of the proposed method in estimating BBIs in a cross-sectional study with 29 hospitalized patients (mean age 70.6 years) in 24-h recordings performed after peripheral vascular surgery or endovascular interventions. Finally, we evaluate the accuracy of more than 30 commonly used HRV parameters and find that the accuracy of certain metrics, for example SDNN and triangular index, shown in the literature to be associated with the deterioration of the status of the patients during recovery from surgical intervention, could be adequate for patient monitoring. On the other hand, the parameters more affected by the high-frequency content of the HRV and especially the LF/HF-ratio should be used with caution.

Effects of motion and b-value on apparent temperature measurement by diffusion-based thermometry MRI: eye vitreous study.

To make noninvasive measurements of temperature in the posterior chamber (vitreous) of the eye using diffusion-based thermometry (DBT) magnetic resonance imaging (MRI) and to explain variability in these measurements due to choice of b-value and the effects of motion. Phantom studies of human vitreous and distilled water were performed using b-values from 0 to 1500s/mm2 to determine the liquid-specific calibration factor for vitreous as well as to determine the temperature offsets due to sampling the diffusion curve using three higher routine clinical b-values (b=0, 500, 1000s/mm2 ) or four lower b-values (b=0, 200, 400, 600s/mm2 ), thought to be optimized for fluids. Retrospective ROI-based measurements of apparent diffusion coefficient on single slices as well as multi-slice histograms of the eyes were made in six patients with peri-orbital cellulitis and 11 age-matched controls, to assess for temperature changes in the presence of peri-orbital inflammation. A prospective study of ten repeated measurements of eye temperature using both high and lower b-value sampling was performed in ten asymptomatic volunteers to determine the reproducibility of eye temperature measurements in-vivo as well as to estimate vitreous temperature in the absence of motion. The diffusion coefficient of vitreous (2,088±13×10-6 mm2 /s) was significantly lower (-1.9%, P<0.001) compared to distilled water (2,128±12×10-6 mm2 /s). The calibration factor for temperature measurements of vitreous using DBT is +0.74±0.06°C. Temperature offsets were smaller (<-0.2°C, P<0.01) when using larger routine clinical b-values to estimate the diffusion coefficient compared to using a series of lower b-values (<-1.0°C, P<0.001). Two-dimensional single-slice ROI-based measurement showed significant temperature differences (ΔTI-C =2.5±1.2°C, P<0.001) between the eyes of patient with peri-orbital cellulitis, higher on the side of inflammation. There was no significant difference in eye temperature when using the 3D histogram (which is likely due to motion averaging as significant slice-to-slice variation was present). However, significant differences in the 3D temperature histograms between the two eyes was observed in one out of six patients. Prospective eye temperature measurements in healthy volunteers showed significant intra- and inter-subject variability (33.8-41.6°C), which was caused by eye motion. This resulted in +2.4°C cohort-wide elevation in temperature when three b-values were used and +4.7°C when four b-values were used. Using a pattern of elevated temperature at the periphery of the eye to detect motion, eye temperature is the absence of motion was estimated to be 34.5±0.4°C with three higher b-values and 34.6±1.9°C with four lower b-values; this temperature corresponds with prior mathematical simulations of eye temperature as well as boundary conditions. Globe vitreous temperature has been measured noninvasively using DBT MRI. Using routine clinical b-values of b=0, 500 and 1000s/mm2 produces acceptable (<-0.2°C) temperature offsets. Although DBT measurements are highly susceptible to motion, methods such as temperature differences or regression can be used to reduce or eliminate the effects of motion. Using a single clinical diffusion-weighted MRI, globe temperature difference of 1.6°C is pathological. Using a series of ten measurements, globe temperature differences larger than 0.6°C are abnormal. This study suggests CSF flow likely artifactually increases core brain temperature measured by DBT MRI.

The Clinical Significance of the Failure to Perceive Vertigo in the Postcaloric Period Despite a Robust Caloric Response.

Purpose The purpose of this project was to explore the association between the perception of motion during caloric testing and two tasks associated with central vestibular processing: postural stability and visuospatial memory. Method This was a prospective study of 25 patients who were found to have nonvestibular etiologies of their symptoms and normal vestibular function test results and who underwent caloric testing with a mean maximum slow phase eye velocity for each irrigation of 15° or greater. Following each caloric irrigation, patients were asked whether they had any sensation of movement. Patients were grouped based on the presence or absence of motion during the caloric exam (motion perception vs. absent perception). Postural stability was assessed using computerized dynamic posturography, and visuospatial memory was assessed using a memory match card game application. Results There were no significant differences between groups on any measures of peripheral vestibular function. However, the Absent Perception Group showed greater postural instability during Condition 5 of posturography and performed significantly worse on a task of visuospatial working memory. Both age and absence of motion perception predicted abnormal performance on measures of postural stability and visuospatial working memory. Conclusions There appears to be clinical implications to a lack of motion perception during the caloric exam in patients with an otherwise normal peripheral vestibular system. Based on the current findings, we are unable to determine whether differences in postural stability and visuospatial memory were due to age or a central vestibular processing deficit.

Real-Time Epileptic Seizure Detection During Sleep Using Passive Infrared Sensors

This paper addresses the problem of detecting epileptic seizures experienced by a human subject during sleep. Commonly used solutions to this problem mostly rely on detecting motion due to seizures using contact-based sensors or video-based sensors. We seek a low-cost, low-power alternative that can sense motion without making direct contact with the subject and provides high detection accuracy. We investigate the use of Passive InfraRed (PIR) sensors to sense human body motion caused by epileptic seizures during sleep which makes the body shake and causes the PIR sensor to generate an oscillatory output signal. This signal can be distinguished from that of ordinary motions during sleep using analysis with machine learning algorithms. The supervised hidden Markov model algorithm (HMM) and a 1-D and 2-D convolutional neural network (ConvNet) are used to classify the data set of the PIR sensor output into the occurrence of epileptic seizures, ordinary motions, or absence of motion. The method was tested on the PIR signals captured at 1 m from 33 recruited healthy subjects who, after watching seizure videos, either moved their body on a bed to simulate a seizure, ordinary motion, or lay still. The HMM algorithm attained 97.03% accuracy, while 1D-ConvNet and 2D-ConvNet attained an accuracy of 96.97% and 98.98%, respectively. All simulated seizures were successfully detected, with errors occurring only in distinguishing between ordinary motion and no motion, thereby demonstrating the potential for using PIR sensors in the epileptic seizure detection.

To move or not to move? Analyzing motion cueing in vehicle simulators by means of massive simulations

Motion platforms and motion cueing algorithms (MCA) have been included in virtual reality applications for several decades. They are necessary to provide suitable inertial cues in vehicle simulators. However, the great number of operational constraints that these devices and algorithms suffer, namely limited physical space, elevated costs, absence of sufficient power, difficulty of tuning and lack of standardized assessment methods, have hindered their widespread use. This work tries to clarify open questions in the field, such as: How important is MCA tuning? How much does size, number of DOF and power/latency matter? Can the absence of motion be better than poor motion cueing? What are the key factors that should be addressed to enhance the design of these devices? Although absolute certain answers cannot be given, this paper tries to clarify these research questions by performing massive experiments with simulated motion platforms of different types, sizes and powers. The information obtained from these experiments will be important to customize the design of real devices for this particular use. Ideally, subjective experiments with human experts would have been preferred. However, the use of simulated devices allows comparing many different motion platforms. In this paper, forty of these devices are simulated, optimized by means of a heuristic algorithm and compared with objective indicators in order to measure their relative performance using the classical MCA, something that would require an unreasonable amount of effort with real users and real devices. The obtained results show that MCA tuning is of the utmost importance in motion cueing. They also suggest that high power can usually compensate for lack of size and that a 6-DOF motion platform slightly improves the performance of a 3-DOF motion platform.

Dynamics of magnetic flux tubes in accretion discs of T Tauri stars

Abstract Dynamics of slender magnetic flux tubes (MFTs) in the accretion discs of T Tauri stars is investigated. We perform simulations taking into account buoyant, aerodynamic, and turbulent drag forces, radiative heat exchange between MFT and ambient gas, and magnetic field of the disc. The equations of MFT dynamics are solved using Runge–Kutta method of the fourth order. The simulations show that there are two regimes of MFT motion in absence of external magnetic field. In the region r &lt; 0.2 au, the MFTs of radii $0.05 \le a_0 \le 0.16\, H$ (H is the scale height of the disc) with initial plasma beta of 1 experience thermal oscillations above the disc. The oscillations decay over some time, and MFTs continue upward motion afterwards. Thinner or thicker MFTs do not oscillate. MFT velocity increases with initial radius and magnetic field strength. MFTs rise periodically with velocities up to 5–15 km s−1 and periods of 0.5–10 yr determined by the toroidal magnetic field generation time. Approximately 20 per cent of disc mass and magnetic flux can escape to disc atmosphere via the magnetic buoyancy over characteristic time of disc evolution. MFTs dispersal forms expanding magnetized corona of the disc. External magnetic field causes MFT oscillations near the disc surface. These magnetic oscillations have periods from several days to 1–3 months at r &lt; 0.6 au. The magnetic oscillations decay over few periods. We simulate MFT dynamics in accretion discs in the Chameleon I cluster. The simulations demonstrate that MFT oscillations can produce observed IR-variability of T Tauri stars.

Characteristics of the paralysed diaphragm studied by M‐mode ultrasonography

M-mode ultrasonography might be useful for detecting hemidiaphragm paralysis. The objective of the present study was to describe the motion recorded by M-mode ultrasonography of both diaphragmatic leaves in patients with a pre-established diagnosis of hemidiaphragm paralysis. A study was conducted in 26 patients (18 men, 8 women) with unilateral diaphragmatic paralysis. They were referred to two different rehabilitation centres after thoracic surgery in 23 cases and cardiac interventional procedures in three cases. The pulmonary function tests and the study of the diaphragmatic motion using M-mode ultrasonography were recorded. The pulmonary function tests showed a restrictive pattern. The M-mode ultrasonography reported either the absence of motion or a weak paradoxical (cranial) displacement (less than 0·5cm) of the paralysed hemidiaphragm during quiet breathing. A paradoxical motion was recorded in all patients during voluntary sniffing, reaching around -1cm. During deep breathing, a paradoxical motion at the beginning of the inspiration was observed. Thereafter, a re-establishment of the motion in the craniocaudal direction was recorded. The excursions measured on the healthy side, during quiet breathing and voluntary sniffing, were increased in patients suffering from contralateral hemidiaphragm paralysis, when compared with 170 healthy volunteers. To detect diaphragmatic dysfunction in patients at risk, it would be useful to study diaphragmatic motion by M-mode ultrasonography during quiet breathing, voluntary sniffing and deep breathing.

Plenoptic Image Motion Deblurring.

We propose a method to remove motion blur in a single light field captured with a moving plenoptic camera. Since motion is unknown, we resort to a blind deconvolution formulation, where one aims to identify both the blur point spread function and the latent sharp image. Even in the absence of motion, light field images captured by a plenoptic camera are affected by a non-trivial combination of both aliasing and defocus, which depends on the 3D geometry of the scene. Therefore, motion deblurring algorithms designed for standard cameras are not directly applicable. Moreover, many state of the art blind deconvolution algorithms are based on iterative schemes, where blurry images are synthesized through the imaging model. However, current imaging models for plenoptic images are impractical due to their high dimensionality. We observe that plenoptic cameras introduce periodic patterns that can be exploited to obtain highly parallelizable numerical schemes to synthesize images. These schemes allow extremely efficient GPU implementations that enable the use of iterative methods. We can then cast blind deconvolution of a blurry light field image as a regularized energy minimization to recover a sharp high-resolution scene texture and the camera motion. Furthermore, the proposed formulation can handle non-uniform motion blur due to camera shake as demonstrated on both synthetic and real light field data.

Management of extravasation injuries in upper extremity

Introduction: When contrast agents and chemotherapeutic agents used for diagnosis and treatment through vascular access are extravasated, they may cause many complications, ranging from tissue necrosis to amputation. In this study, extravasation of certain agents was evaluated. Material and methods: Five cases that developed from vancomycin, isotonic sodium, contrast agent and teicoplanin extravasation were examined. Results: Three of the patients were female and two were male. Their mean age was 42.8 years. One of them had complications seen in the right and four had complications observed in the left upper extremity. One of these cases underwent wrist amputation, three had fasciotomy and repair, and one had fasciotomy, recurrent debridement and reconstruction with a split-thickness skin graft. Conclusion: When extravasation is seen, the agent should stop being administered and the case should be monitored closely. In the situation of an increase in swelling and stiffness and absence of motion in the muscles and tendons, compartment syndrome should be considered and urgent fasciotomy should be performed. Early fasciotomy can be a savior while in where there is development of necrosis during late periods, amputation may be necessary.

Machined cervical interfacet allograft spacers for the management of atlantoaxial instability.

Background:The use of cervical interfacet spacers (CISs) to augment stability and provide solid arthrodesis at the atlantoaxial joint has not been studied in detail. The aim of this work is to report the outcomes with the use of machined allograft CISs at C1-2.Methods:A retrospective review of 19 patients who underwent an atlantoaxial fusion with the use of CISs was performed. All patients had instability documented with flexion and extension lateral radiographs. This instability was due to trauma, degenerative stenosis, symptomatic C1-2 arthropathy, and os odontoideum. Clinical and radiological outcomes were assessed. Fusion was determined based on a lack of hardware failure, absence of motion on flexion and extension plain X-ray films, and presence of bridging trabecular bone which was most often demonstrated by a computed tomography.Results:The mean age was 69.1 ± 12.9 years. Eight patients had traumatic fractures, six patients had degenerative stenosis, two patients had C2 neuralgia due to C1-2 arthropathy, two patients had C1-2 ligamentous subluxation, and one patient had an unstable os odontoideum. The occiput or subaxial spine was included in the arthrodesis in 10 patients. Rib autograft was utilized in most patients. No patient had postoperative neurological worsening, malposition of hardware, or vertebral artery injury and there were no mortalities. The fusion rate was 95%. The mean follow-up was 12.1 ± 5.5 months.Conclusions:CIS is a promising adjuvant for the treatment of atlantoaxial instability.

O52. Magnetic field inhomogeneity in the MRI scanner and image quality dependence

Introduction Different elements in the human body can be used as the source of magnetism. However, due to the abundance of hydrogen (1H) in the human body, 1H is the most commonly used element in clinical MRI. 1H nuclei in the presence of a magnetic field, B0, precess at the Larmor frequency ( ω 0 ) which is field dependent (127 MHz at 3 Tesla). To maintain a constant ω 0 for all nuclei, the B0 field must be homogeneous. Functional MRI (fMRI) generates contrast in the images based on tiny changes in the magnetic properties of 1H in haemoglobin. An fMRI acquisition requires repeatedly imaging the brain more than 150 times. Each measurement takes ∼ 2 seconds. Due to the prolonged fMRI acquisition, several factors distort the B0 field ( Δ B0) including subject motion. This results in corrupted fMRI data. In this work, we present a novel technique to measure and perform correction (shimming) in real time for Δ B0 in the presence and absence of motion during an fMRI scan. Materials and methods A navigation technique was inserted after each fMRI measurement to create a B0 field map. From the map, Δ B0 could be evaluated and corrected in real time. Three healthy subjects were scanned with the navigated fMRI sequence. In some scans subjects were instructed to move at specific times. Results The drift in the B0 field during the acquisitions exceeded 30 Hz even in the absence of head motion. Δ B0 resulted in noisy brain activation data. The navigated fMRI was able to accurately correct for Δ B0 and motion. Conclusion MRI scanners are not equipped with tools to alert us to changes in the B0 field during fMRI acquisition. The navigated fMRI sequence is able to correct in real time for Δ B0 and motion.