Using Digital and Physical Simulation to Focus on Human Factors and Ergonomics in Aviation Maintainability.

OBJECTIVE: This research aimed to evaluate the differences in the assessments made by three simulation tools used in a maintainability design office to perform human factor/ergonomics (HFE) analysis: digital human modeling (DHM), virtual reality (VR), and physical mock-up (PMU). BACKGROUND: Maintainability engineers use digital/physical simulation tools in the early design phase to analyze whether the design is well adapted for maintenance operators. Knowing the potential of these simulation tools would encourage maintainability stakeholders to integrate HFE in the design process more efficiently. METHOD: Eleven maintenance tasks were analyzed from the participation of six maintenance operators. Various HFE indicators including physical, cognitive, and organizational indicators were assessed. Each operator repeated 11 maintenance tasks on VR and PMU. Based on the anthropometric parameters, six manikins were created to analyze 11 maintenance tasks on DHM. RESULTS: A significant difference was found for the organizational indicators between VR and PMU, whereas the physical and cognitive indicators are similar. DHM, VR, and PMU are compared with the common HFE indicators for the physical dimension and present a significant difference for individual tasks. CONCLUSION: To reduce the gap between simulation tools, a better physical representation is requested on the VR platform, improving the perception of work sequences in the virtual world. Concerning DHM, a new paradigm is proposed to study a few tasks per work area instead of studying each task independently. APPLICATION: This study will help develop a new methodology and tools specifically for non-HFE experts in the maintainability department.

Comparison of outcomes for pediatric paraphimosis reduction using topical anesthetic versus intravenous procedural sedation.

BACKGROUND: Paraphimosis is an acute urologic emergency requiring urgent manual reduction, frequently necessitating procedural sedation (PS) in the pediatric population. The present study sought to compare outcomes among pediatric patients undergoing paraphimosis reduction using a novel topical anesthetic (TA) technique versus PS. METHODS: We performed a retrospective analysis of all patients <18years old, presenting to a tertiary pediatric ED requiring analgesia for paraphimosis reduction between October 2013 and September 2016. The primary outcome was reduction first attempt success; secondary outcomes included Emergency Department length of stay (ED LOS), adverse events and return visits. Dichotomous outcomes were analyzed by Chi-square testing and multivariate linear regression was used to compare continuous variables. RESULTS: Forty-six patients were included; 35 underwent reduction using TA, 11 by PS. Patient age and duration of paraphimosis at ED presentation did not differ between groups. There was no difference in first attempt success between TA (32/35, 91.4%) and PS groups (9/11, 81.8%; p=0.37). Mean ED LOS was 209min shorter for TA patients (148min vs. 357min, p=0.001) and remained significantly shorter after controlling for age and duration of paraphimosis (adjusted mean difference -198min, p=0.003). There were no return visits or major adverse events in either group, however, among successful reduction attempts, PS patients more frequently experienced minor adverse events (7/9 vs. 0/32, p<0.001). CONCLUSIONS: Paraphimosis reduction using TA was safe and effective. Compared to PS, TA was associated with a reduced ED LOS and fewer adverse events. TA could potentially allow more timely reduction with improved patient experience and resource utilization.

Field inhomogeneity correction for gradient echo myelin water fraction imaging.

PURPOSE: Recently, the multi-echo gradient echo (MGRE) sequence has been proposed for multicomponent T2* (MC T2*) based myelin water fraction (MWF) mapping. This approach has appeal because it can provide fast whole-brain coverage, has low specific absorption rate, and short echo spacing. However, the MGRE signal requires correction for accurate MWF mapping, because of its sensitivity to magnetic field inhomogeneities (ΔB0 ). We propose a ΔB0 correction method for 2D MGRE data obtained for MWF mapping. THEORY AND METHODS: Latter-echo MGRE data were fit to estimate B0 gradients in the slice-select direction ( Gz). The decay signal was corrected for the effects of Gz, and MC T2* analysis was performed using nonnegative least-squares fitting. The method was evaluated using simulations and its performance demonstrated in healthy volunteers. RESULTS: Simulations showed that MWFs are significantly biased in the presence of Gz and that our correction method leads to accurate MWF estimates. In vivo MWF maps obtained from corrected data showed recovery of MWF estimates in areas of high ΔB0, and overall good agreement with literature values obtained with the reference MC T2-based method. CONCLUSION: A new algorithm was presented for ΔB0 correction of 2D MGRE echo data acquired for MWF imaging. Simulations and in vivo data showed an improvement in MWF estimates. Magn Reson Med 78:49-57, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Frequency and phase drift correction of magnetic resonance spectroscopy data by spectral registration in the time domain.

PURPOSE: Frequency and phase drifts are a common problem in the acquisition of in vivo magnetic resonance spectroscopy (MRS) data. If not accounted for, frequency and phase drifts will result in artifactual broadening of spectral peaks, distortion of spectral lineshapes, and a reduction in signal-to-noise ratio (SNR). We present herein a new method for estimating and correcting frequency and phase drifts in in vivo MRS data. METHODS: We used a simple method of fitting each spectral average to a reference scan (often the first average in the series) in the time domain through adjustment of frequency and phase terms. Due to the similarity with image registration, this method is referred to as "spectral registration." Using simulated data with known frequency and phase drifts, the performance of spectral registration was compared with two existing methods at various SNR levels. RESULTS: Spectral registration performed well in comparison with the other methods tested in terms of both frequency and phase drift estimation. CONCLUSIONS: Spectral registration provides an effective method for frequency and phase drift correction. It does not involve the collection of navigator echoes, and does not rely on any specific resonances, such as residual water or creatine, making it highly versatile.

In vivo 1H MRS study in microlitre voxels in the hippocampus of a mouse model of Down syndrome at 11.7 T.

In this article, we report in vivo (1)H MRS performed in 1.8-µL voxels in a mouse model of Down syndrome (DS). To characterise the excitation-inhibition imbalance observed in DS, metabolite concentrations in the hippocampi of adult Ts65Dn mice, which recapitulate features of DS, were compared with those of their euploid littermates at a voxel 42-fold smaller than in a previously published study. Quantification of the metabolites was performed using a linear combination model. We detected 16 metabolites in the right and left hippocampi. Principal component analysis revealed that the absolute concentrations of the 16 detected metabolites could differentiate between Ts65Dn and euploid hippocampi. Although measurements in the left and right hippocampi were highly correlated, the concentration of individual metabolites was sometimes significantly different in the left and right structures. Thus, bilateral values from Ts65Dn and euploid mice were further compared with Hotelling's test. The level of glutamine was found to be significantly lower, whereas myo-inositol was significantly higher, in the hippocampi of Ts65Dn relative to euploid mice. However, γ-aminobutyric acid (GABA) and glutamate levels remained similar between the groups. Thus, the excitation-inhibition imbalance described in DS does not appear to be related to a radical change in the levels of either GABA or glutamate in the hippocampus. In conclusion, microliter MRS appears to be a valuable tool to detect changes associated with DS, which may be useful in investigating whether differences can be rescued after pharmacological treatments or supplementation with glutamine.

Keyhole acceleration for magnetic resonance acoustic radiation force imaging (MR ARFI).

MR ARFI measures the displacement induced by the ultrasonic radiation force and provides the location of the focal spot without significant heating effects. Displacements maps obtained with MR ARFI provide an indirect estimation of the acoustic beam intensity at the target. This measure is essential for dose estimation prior to focused ultrasound treatments (FUS) and adaptive focusing procedures of MR-guided transcranial and transribs FUS. In the latter case, the beam correction is achieved by maximizing the displacement at focus. A significant number of serial MR ARFI images are required and thus, a partial k-space updating method, such as keyhole appears as a method of choice. The purpose of this work is to demonstrate via simulations and experiments the efficiency of the keyhole technique combined with a two-dimensional spin-echo MR ARFI pulse sequence. The method was implemented in an ex vivo calf brain taking advantage of the a priori knowledge of the focal spot profile. The coincidence of the phase-encoding axis with the longest axis of the focal spot makes the best use of the technique. Our approach rapidly provides the focal spot localization with accuracy, and with a substantial increase to the signal-to-noise ratio, while reducing ultrasound energy needed during MR-guided adaptive focusing procedures.

Magnetic resonance imaging of the substantia nigra in Parkinson's disease.

Until recently, conventional magnetic resonance imaging (MRI) was most often negative in Parkinson's disease or showed nonspecific findings. Recent developments in structural MRI, including relaxometry, magnetization transfer, and neuromelanin imaging, have demonstrated improved contrast and enabled more accurate visualization of deep brain nuclei, in particular, the substantia nigra. Meanwhile, diffusion imaging has provided useful biomarkers of substantia nigra degeneration, showing reduced anisotropy and anatomical connectivity with the striatum and thalamus. These advances in structural imaging are complemented by findings of magnetic resonance spectroscopy on brain metabolism and resting-state functional MRI on functional connectivity. This article presents an overview of these new structural, metabolic, and resting-state functional MRI techniques and their implications for Parkinson's disease. The techniques are reviewed in the context of their potential for better understanding the disease in terms of diagnosis and pathophysiology and as biomarkers of its progression.

Methods to determine slow diffusion coefficients of biomolecules: applications to Engrailed 2, a partially disordered protein.

We present new NMR methods to measure slow translational diffusion coefficients of biomolecules. Like the heteronuclear stimulated echo experiment (XSTE), these new methods rely on the storage of information about spatial localization during the diffusion delay as longitudinal polarization of nuclei with long T(1) such as nitrogen-15. The new BEST-XSTE sequence combines features of Band-selective Excitation Short-Transient (BEST) and XSTE methods. By avoiding the saturation of all protons except those of amide groups, one can increase the sensitivity by 45% in small proteins. The new experiment which combines band-Selective Optimized Flip-Angle Short-Transient with XSTE (SOFAST-XSTE) offers an alternative when very short recovery delays are desired. A modification of the HSQC-edited version of the XSTE experiment offers enhanced sensitivity and access to higher resolution in the indirect dimension. These new methods have been applied to detect changes in diffusion coefficients due to dimerization or proteolysis of Engrailed 2, a partially disordered protein.

Determination of the antisymmetric part of the chemical shift anisotropy tensor via spin relaxation in nuclear magnetic resonance.

Relaxation processes induced by the antisymmetric part of the chemical shift anisotropy tensor (henceforth called anti-CSA) are usually neglected in NMR relaxation studies. It is shown here that anti-CSA components contribute to longitudinal relaxation rates of the indole (15)N nucleus in tryptophan in solution at different magnetic fields and temperatures. To determine the parameters of several models for rotational diffusion and internal dynamics, we measured the longitudinal relaxation rates R(1)=1/T(1) of (15)N, the (15)N-(1)H dipole-dipole (DD) cross-relaxation rates (Overhauser effects), and the cross-correlated CSA/DD relaxation rates involving the second-rank symmetric part of the CSA tensor of (15)N at four magnetic fields B(0)=9.4, 14.1, 18.8, and 22.3 T (400, 600, 800, and 950 MHz for protons) over a temperature range of 270

Cross-encoded magnetic resonance imaging in inhomogeneous fields.

In magnetic resonance imaging (MRI), it is possible to cancel the effects of severe inhomogeneities of the magnetic field even if the field profile is unknown. The new 'cross-encoded' method is based on adiabatic frequency-modulated pulses combined with two orthogonal gradients that are applied simultaneously during encoding and decoding. Undistorted two- and three-dimensional images can be obtained in inhomogeneous fields where the breadth of the water resonance extends over several kHz.

Multiple-timescale dynamics of side-chain carboxyl and carbonyl groups in proteins by 13C nuclear spin relaxation.

Side-chain carboxyl and carbonyl groups play a major role in protein interactions and enzyme catalysis. A series of (13)C relaxation experiments is introduced to study the dynamics of carboxyl and carbonyl groups in protein side chains on both fast (sub-ns) and slower (micros-ms) time scales. This approach is illustrated on the protein calbindin D(9k). Fast dynamics features correlate with hydrogen- and ion-binding patterns. We also identify chemical dynamics on micros time scales in solvent-exposed carboxyl groups, most probably due to exchange between the carboxylate and carboxylic acid forms.