Development and validation of an assessment index for quantifying cognitive task load in pilots under simulated flight conditions using heart rate variability and principal component analysis.

To investigate whether high cognitive task load (CTL) for aircraft pilots can be identified by analysing heart-rate variability, electrocardiograms were recorded while cadet pilots (n = 68) performed the plane tracking, anti-gravity pedalling, and reaction tasks during simulated flight missions. Data for standard electrocardiogram parameters were extracted from the R-R-interval series. In the research phase, low frequency power (LF), high frequency power (HF), normalised HF, and LF/HF differed significantly between high and low CTL conditions (p < .05 for all). A principal component analysis identified three components contributing 90.62% of cumulative heart-rate variance. These principal components were incorporated into a composite index. Validation in a separate group of cadet pilots (n = 139) under similar conditions showed that the index value significantly increased with increasing CTL (p < .05). The heart-rate variability index can be used to objectively identify high CTL flight conditions.Practitioner summary: We used principal component analysis of electrocardiogram data to construct a composite index for identifying high cognitive task load in pilots during simulated flight. We validated the index in a separate group of pilots under similar conditions. The index can be used to improve cadet training and flight safety.Abbreviations: ANOVA: a one-way analysis of variance; AP: anti-gravity pedaling task; CTL: cognitive task load; ECG: electrocardiograms; HR: heart rate; HRV: heart-rate variability; HRVI: heart-rate variability index; PT: plane-tracking task; RMSSD: root-mean square of differences between consecutive R-R intervals; RT: reaction task; SDNN: standard deviation of R-R intervals; HF: high frequency power; HFnu: normalized HF; LF: low frequency power; LFnu: normalized LF; PCA: principal component analysis.

Screen Content Video Quality Assessment: Subjective and Objective Study.

In this paper, we make the first attempt to study the subjective and objective quality assessment for the screen content videos (SCVs). For that, we construct the first large-scale video quality assessment (VQA) database specifically for the SCVs, called the screen content video database (SCVD). This SCVD provides 16 reference SCVs, 800 distorted SCVs, and their corresponding subjective scores, and it is made publicly available for research usage. The distorted SCVs are generated from each reference SCV with 10 distortion types and 5 degradation levels for each distortion type. Each distorted SCV is rated by at least 32 subjects in the subjective test. Furthermore, we propose the first full-reference VQA model for the SCVs, called the spatiotemporal Gabor feature tensor-based model (SGFTM), to objectively evaluate the perceptual quality of the distorted SCVs. This is motivated by the observation that 3D-Gabor filter can well stimulate the visual functions of the human visual system (HVS) on perceiving videos, being more sensitive to the edge and motion information that are often-encountered in the SCVs. Specifically, the proposed SGFTM exploits 3D-Gabor filter to individually extract the spatiotemporal Gabor feature tensors from the reference and distorted SCVs, followed by measuring their similarities and later combining them together through the developed spatiotemporal feature tensor pooling strategy to obtain the final SGFTM score. Experimental results on SCVD have shown that the proposed SGFTM yields a high consistency on the subjective perception of SCV quality and consistently outperforms multiple classical and state-of-the-art image/video quality assessment models.

Quantitative Assessment of Keloids Using Ultrasound Shear Wave Elastography.

This study was aimed at investigating the value of shear wave elastography (SWE) in quantitative evaluation of keloids. A total of 87 patients with 139 keloids were enrolled. Vancouver scar scale (VSS) scores were recorded. Thickness and blood flow grade were evaluated using high-frequency ultrasound. Skin stiffness (mean speed of shear wave, Cmean) was evaluated using SWE in both transverse and longitudinal sections. All measurements were performed in both keloids and site-matched unaffected skin (normal controls). The reliability of measurements was evaluated using intra- and inter-class correlation coefficients by two observers. Inter- and intra-observer repeatability was excellent (correlation coefficient > 0.99, p < 0.01). The SWE results revealed a significant increase in Cmean in keloids (p < 0.001) compared with the normal controls. Cmean in the longitudinal section was greater than that in the transverse section for keloids (p < 0.001). Cmean was highly positively correlated with VSS score (r = 0.904, p < 0.001), moderately positively correlated with thickness (r = 0.490, p < 0.001) and less positively correlated with blood flow (r = 0.231, p < 0.01). This non-invasive, tolerable and convenient imaging technique could be an effective tool for objectively evaluating keloid stiffness in the future, thus laying a foundation for the treatment and evaluation of keloids.

Ultrasound assessment in psoriatic arthritis (PsA) and psoriasis vulgaris (non-PsA): which sites are most commonly involved and what features are more important in PsA?

BACKGROUND: The aim of this study was to find out the most commonly involved sites and the most important ultrasonic features in psoriatic arthritis (PsA). METHODS: In total, 120 PsA patients and 320 psoriasis vulgaris (non-PsA) patients were assessed by grayscale and power Doppler (PD) ultrasound (US). Joints, tendons, enthesis, and bursa changes were observed. Weights of affected anatomical sites of PsA patients (overall weights >90%) were calculated. Affected anatomical sites between PsA and non-PsA patients were compared. Ultrasonic features of joint, tendon, entheses, and bursa changes between PsA and non-PsA patients were also compared. Finally, the test performance of ultrasonic features for the diagnosis of PsA was calculated. RESULTS: The anatomical sites with the highest weights were the Achilles tendon, quadriceps tendon, and knee; weights of these anatomical sites were all more than 5%. Among the affected anatomical sites of PsA patients, most of the anatomical sites were more greatly affected in the PsA patients than in the non-PsA patients (all P<0.05). The comparison of the affected Achilles tendon, quadriceps tendon, MTP1, subacromial-subdeltoid bursa, MCP4, and MCP3 showed no significance between PsA and non-PsA patients (all P>0.05). Joint synovial thickening, joint PD signal grades, joint bone erosions, tendon sheath synovial thickening, tendon sheath PD signals, enthesis bone erosions, and enthesis PD signals in PsA patients were higher than in non-PsA patients (all P<0.05). Joint PD signal grades, joint bone erosions, enthesis bone erosions, and enthesis PD signals showed the highest specificities, which were 96.06%, 95.15%, 96.93%, and 94.63% respectively. CONCLUSIONS: The most common involvement sites of PsA were the Achilles tendon, quadriceps tendon, and knee, and some sites in non-PsA patients were also highly involved. The most important features in PsA included joint PD signal grades, joint bone erosion, entheses bone erosions, and entheses PD signals in US assessment.

Quantitative assessment of treatment efficacy in keloids using high-frequency ultrasound and shear wave elastography: a preliminary study.

The purpose of this study was to investigate the performance of high-frequency ultrasound (HFUS) and shear wave elastography (SWE) in the quantitative evaluation of therapeutic responses of keloids. 43 patients with 76 keloids were recruited into this study. In keloids and symmetrical sites, the skin thickness was measured using HFUS and skin stiffness expressed as elastic moduli (Young's modulus and shear wave velocity) was measured using SWE. The coefficient of variation values were calculated by using difference values of skin elastic moduli and skin thickness. A significant increase of both skin stiffness and thickness appeared in pre-treated keloids compared with post-treated keloids (P < 0.001) and normal controls (P < 0.001), respectively. Stiffness in post-treated keloids and normal skins was significantly different (P < 0.001), while the difference in thickness measurements showed no significance (P = 0.56, >0.05). The coefficient of variation of Young's modulus was the highest when compared between (i) pre-treated keloids and theirs site-matched areas; (ii) pre-treated and post-treated keloids. SWE, which showed greater ability in determining the extent of keloids recovery, may provide an ideal tool to assess the stiffness of keloids and theirs therapeutic response.

Assessment of the static upright balance index and brain blood oxygen levels as parameters to evaluate pilot workload.

OBJECTIVE: To investigate the potential for static upright balance function and brain-blood oxygen parameters to evaluate pilot workload. METHODS: Phase 1: The NASA Task Load Index (NASA-TLX) was used to compare the workloads of real flights with flight simulator simulated flight tasks in 15 pilots (Cohort 1). Phase 2: To determine the effects of workload, 50 cadets were divided equally into simulated flight task load (experimental) and control groups (Cohort 2). The experimental group underwent 2 h of simulated flight tasks, while the control group rested for 2 h. Their static upright balance function was evaluated using balance index-1 (BI-1), before and after the tasks, with balance system posturography equipment and cerebral blood oxygen parameters monitored with near infrared spectroscopy (NIRS) in real time. Sternberg dual-task and reaction time tests were performed in the experimental and control groups before and after the simulated flight tasks. RESULTS: (Phase1) There was a significant correlation between the workload caused by real flight and simulated flight tasks (P<0.01), indicating that NASA-TLX scales were also a tool for measuring workloads of the stimulated flight tasks. (Phase 2) For the simulated flight task experiments, the NASA-TLX total scores were significantly different between the two groups (P<0.001) and (pre-to-post) changes of the BI-1 index were greater in the experimental group than in controls (P<0.001). The cerebral blood oxygen saturation levels (rsO2) (P<0.01) and ΔHb reductions (P<0.05) were significantly higher in the experimental, compared to the control group, during the simulated flight task. In contrast to the control group the error rates (P = 0.002) and accuracy (P<0.001) changed significantly in the experimental group after the simulated flight tasks. CONCLUSIONS: The simulated flight task model could simulate the real flight task load and static balance and NIRS were useful for evaluating pilots' workload/fatigue.

Posturographic Balance's Validity in Mental and Physical Fatigue Assessment Among Cadet Pilots.

BACKGROUND: Postural control is adversely affected by mental and physical fatigue, but its validity in fatigue assessment has not been investigated systemically among pilots. We explored the correlations of posturographic balance with physiological and psychological signals among cadet pilots.METHODS: In experiment 1, 37 cadet pilots performed a posturographic balance test, heart rate variability (HRV), and profile of mood states (POMS) during 40 h of sleep deprivation. For experiment 2, physiological signals of 60 subjects, including breathing rate (BR), systolic blood pressure (SBP), and heart rate (HR) were measured under the effects of physical fatigue. Then correlations with a mental and physical fatigue index based on effective posturographic parameters with those subjective and objective methods were analyzed by linear regression.RESULTS: The mental fatigue index correlated linearly with the depression score of the POMS (r = 0.212), standard deviation of normal to normal beats (r = 0.286), and square root of the mean differences of successive beat intervals (r = 0.207). Meanwhile, linear correlations with frequency-domain parameters of HRV such as total power, low frequency power, and high frequency power were also statistically significant. With the increase in the physical fatigue index, physiological signals such as SBP (r = 0.300), HR (r = 0.349), and BR (r = 0.266) increased linearly.CONCLUSIONS: Impairment of postural stability can reflect the aggravation of mental and physical fatigue among cadet pilots, which provides a potential method for assessing fatigue level before flight tasks and preventing errors by pilots.Cheng S, Sun J, Ma J, Dang W, Tang M, Hui D, Zhang L, Hu W. Posturographic balance's validity in mental and physical fatigue assessment among cadet pilots. Aerosp Med Hum Perform. 2018; 89(11):961-966.

Simultaneous determination of six analytes by HPLC-UV for high throughput analysis in permeability assessment.

A methodology for the simultaneous determination of six control analytes, including carbamazepine, desipramine, guanabenz, methotrexate, propranolol, and warfarin, was developed and validated utilizing reversed-phase high-performance liquid chromatography with ultraviolet detection for high throughput analysis for permeability assessment. The analytes were separated on Agilent Zorbax SB-C18 (50 × 4.6 mm I.D., 5 µm) with a gradient mobile phase consisting of water (containing 1% isopropyl alcohol and 0.01% heptafluorobutyric acid) and acetonitrile (containing 1% isopropyl alcohol and 0.01% heptafluorobutyric acid). The flow rate was 2.0 mL/min and the eluent was monitored at 280 nm. A linear response was found for all six analytes over a broad concentration range (1.00-200 µM). The correlation coefficient for each analyte was greater than 0.999. The limit of detection and limit of quantitation were 0.03 and 0.10 µM, 0.10 and 0.30 µM, 0.05 and 0.15 µM, 0.03 and 0.10 µM, 0.05 and 0.15 µM, 0.10 and 0.30 µM for carbamazepine, desipramine, guanabenz, methotrexate, propranolol, and warfarin, respectively. The optimized method was further successfully applied to high throughput analysis for parallel artificial permeability assay.

Cost-effectiveness of screening for recurrent hepatocellular carcinoma after liver transplantation.

The effectiveness of screening and treatment of recurrent hepatocellular carcinoma (HCC) after liver transplantation (LT) remains undefined. Our aim was to evaluate the potential cost-effectiveness of screening for recurrent HCC after LT. We constructed a Markov model of the natural history after LT for HCC. We superimposed screening with computed tomography, alpha-fetoprotein, and chest X-ray every six months for 1-5 yr after LT, with resection for treatable recurrence. Screening only those whose explant pathology exceeded Milan Criteria (MC) for two yr cost $ 138,000/life-yr gained, and the incremental cost of screening all patients was $ 340,000/life-yr gained. Screening for longer than two yr incurred progressively higher incremental costs/life-yr gained. The most critical variable in sensitivity analyses was the survival benefit of finding a resectable recurrence. With the most favorable assumptions for a two-yr screening duration, screening those whose explant pathology exceeded MC cost $ 91,000/life-yr gained. In conclusion, screening for HCC recurrence after LT would probably yield most of its benefit in the first two yr, but at a relatively high cost/life-yr gained. Screening for two yr in only those whose explant pathology exceeds MC may be relatively cost-effective depending on the survival benefit of resection.