Short-term Repeatability Research Articles

Surface acoustic wave humidity sensors based on uniform and thickness controllable graphene oxide thin films formed by surface tension

Graphene oxide (GO) is a promising candidate for humidity sensing, and the uniformity and thickness of GO films are important for the reproducibility and test signal strength of humidity sensors. In this paper, uniform and thickness-controllable GO films are first formed by the surface tension of different concentrations of GO solution and then transferred to surface acoustic wave (SAW) humidity sensors. This GO film formation and transfer process has very good repeatability and stability, as evidenced by the humidity response of the sensors. With the help of the uniform and highly oxidized GO film, the humidity sensors show a significantly high sensitivity (absolute sensitivity of 25.3 kHz/%RH and relative sensitivity of 111.7 p.p.m./%RH) in a wide test range from 10%RH to 90%RH with very little hysteresis (<1%RH). The sensors achieve good reversibility, excellent short-term repeatability and stability. Moreover, the humidity sensors also show a fast response and recovery time of <10 s.

Repeatability of Epitaxial Growth of n-Type 4H-SiC Films by High Speed Wafer Rotation Vertical CVD Tool

N-type 4H-SiC homo-epitaxial films were grown by high speed wafer rotation vertical CVD tool, and both short term repeatability and long term repeatability of epitaxial growth were investigated. In the short term repeatability investigated by 6 epitaxial wafers chosen from successively grown 12 epitaxial wafers using same recipe, it was found that total variation of thickness and carrier concentration for all measurement points of 6 wafers is 1.44 and 4.64 % respectively, which indicates excellent repeatability as well as high uniform thickness and carrier concentration. In the long term repeatability investigated by a very large number of growth experiments, probability achieving target uniformity of thickness and carrier concentration of the SiC films was increased up to 1.32 times by optimizing gas nozzle structure in gas inlet compared with in the case of conventional gas nozzles. Moreover, adjustment range of C/Si ratio necessary to achieve target uniformity of thickness and carrier concentration of the films was considerably reduced to 22 % by optimized gas nozzles.

Stable individual differences in vocalisation and motor activity during acute stress in the domestic cat

The behavioural assessment of individual animals in stressful situations should consider measures which are consistent across repeated testing, and therefore truly representative of an individual's behaviour. Here we report a study conducted on 40 neutered adult cats (Felis silvestris catus) of both sexes, originating from two animal shelters in Mexico and Hungary. We recorded the responses of the cats to repeated brief confinement trials that mimicked a common situation (confinement in a pet carrier). This test was repeated three times, leaving one week between trials, to assess short-term repeatability. Stable inter-individual differences in two behavioural measures, the number of separation calls and the duration of motor activity, were found, although the inter-individual differences in vocalisation were more pronounced than they were for motor activity. Additionally, the overall number of vocalisations emitted remained stable despite repeated testing, whereas motor activity tended to decrease week to week. There was a negative effect of age on vocalisation rate, and no effect of sex on either behaviour. No correlation between the two behavioural measures was found. We suggest that, in adult cats, vocalisation may be more reliable than motor activity as a behavioural measure of stress.

Performance evaluation and secondary monitor unit checkout for a dedicated accelerator in intraoperative electron radiotherapy

Quality assurance in intraoperative electron radiotherapy (IOERT) is a mandatory issue, because of single shot nature. Employed equipment for IOERT implementation, especially the treatment machine, should have a very stable performance for reliable treatment delivery. Calculated MUs is also an important factor which can affect the treatment quality. The aim of this study is to evaluate the performance characteristics of a dedicated accelerator in IOERT as well as a secondary MU check to ensure the validity of employed software for such purpose.The LIAC12 accelerator was considered in this study. The performance characteristics of accelerator including linearity, short term repeatability (STR) and Long term repeatability (LTR) were measured by ionometric dosimetry over a long time period of 48 weeks. LIAC Monitor Unit calculation (LMUCalculation) software is currently used for MU calculations of LIAC in IOERT. The validity of this software was evaluated through development of a secondary MU calculation worksheet and comparing the obtained results by two methods.The results showed that the LIAC accelerator fulfils the desired performance for IOERT. A perfect linear response was observed at different electron energies. The STR and LTR of LIAC response were less than 1% and 4%, respectively, at all of studied electron energies. The mean difference between calculated MUs by LMUCalculation and the developed manual approach was 1.23%.The obtained results guarantee the validity of LIAC performance for intraoperative radiotherapy purposes. Furthermore, accuracy of calculated MUs by LMUCalculation software was confirmed according to the recommended action level (2%) by AAPM TG-40 protocol.

Abstract P371: Short-term Repeatability of the Peguero Electrocardiographic Index of Left Ventricular Hypertrophy

Background: Electrocardiographic left ventricular hypertrophy (ECG-LVH) represents preclinical cardiovascular disease and predicts cardiovascular disease and mortality. Current criteria include the Cornell voltage, Sokolow-Lyon, and the newly developed Peguero index (S D + SV 4 ). While the Peguero index has been shown to have better prognostic prediction compared with current criteria, its short term repeatability remains uncertain. Objectives: Characterize the repeatability and minimal detectable change of the Peguero ECG-LVH index. Methods: Participants (n=63; mean age 50 years; 31 females) underwent two standardized visits one week apart. At each visit, trained and certified technicians obtained two ECGs following a standardized protocol. The Epidemiological Cardiology Research Center automatically processed the ECGs using GE Marquette GE 12-SL software (GE, Milwaukee, WI) to obtain the Peguero (S D + SV 4 ) LHV index, defined as the deepest S wave in any single lead S D + SV 4 . We created a dichotomous using the following cut points: &gt;2.3 mV for women and &gt;2.8 mV for men. Random effects, mixed models were used to parse the variance of the index into the between-participant, between-visit, and within-visit components. We then calculated the intra-class correlation coefficient (ICC), Kappa coefficients, and minimal detectable change (95% confidence) between repeat measures. Results: Between-participant variation accounted for 93.58% (262,958 out of 280,985 SD points) of the total variation of the Peguero LVH index, while between-visit variation and within-visit variation were 5.51% (15,480 out of 280,985 SD points) and 0.91% (2,547 out of 280,985 SD points), respectively. The index had an ICC (95% confidence interval) of 0.94 (0.91-0.97) and a minimum detectable change value of 372.16 mV. Within visit Kappas were 0.79 (0.40-1.00) for the first visit and 1.00 (1.00-1.00) for the second visit. Between visit Kappas were 0.77 (0.70-0.84) for the first measurements of each visit and 0.79 (0.72-0.86) for the second measurements of each visit. Conclusion: The Peguero LVH index shows excellent repeatability for both within and between visits. The ICC and resulting confidence interval of the continuous index suggests near perfect agreement between groups. The Kappa values also suggest concurrence between groups of the dichotomous index, although the measures are not as precise as the ICC measure. The repeatability of this measure can be used to inform clinical and epidemiological studies and expand research of this novel index of ECG-LVH.

Feasibility and accuracy of quantitative imaging on a 1.5 T MR-linear accelerator

PurposeSystems for magnetic resonance (MR-) guided radiotherapy enable daily MR imaging of cancer patients during treatment, which is of interest for treatment response monitoring and biomarker discovery using quantitative MRI (qMRI). Here, the performance of a 1.5 T MR-linac regarding qMRI was assessed on phantoms. Additionally, we show the feasibility of qMRI in a prostate cancer patient on this system for the first time. Materials and methodsFour 1.5 T MR-linac systems from four institutes were included in this study. T1 and T2 relaxation times, and apparent diffusion coefficient (ADC) maps, as well as dynamic contrast enhanced (DCE) images were acquired. Bland–Altman statistics were used, and accuracy, repeatability, and reproducibility were determined. ResultsMedian accuracy for T1 ranged over the four systems from 2.7 to 14.3%, for T2 from 10.4 to 14.1%, and for ADC from 1.9 to 2.7%. For DCE images, the accuracy ranged from 12.8 to 35.8% for a gadolinium concentration of 0.5 mM and deteriorated for higher concentrations. Median short-term repeatability for T1 ranged from 0.6 to 5.1%, for T2 from 0.4 to 1.2%, and for ADC from 1.3 to 2.2%. DCE acquisitions showed a coefficient of variation of 0.1–0.6% in the signal intensity. Long-term repeatability was 1.8% for T1, 1.4% for T2, 1.7% for ADC, and 17.9% for DCE. Reproducibility was 11.2% for T1, 2.9% for T2, 2.2% for ADC, and 18.4% for DCE. ConclusionThese results indicate that qMRI on the Unity MR-linac is feasible, accurate, and repeatable which is promising for treatment response monitoring and treatment plan adaptation based on daily qMRI.

Effects of Forward- and Emitted-Pressure Calibrations on the Variability of Otoacoustic Emission Measurements Across Repeated Probe Fits.

The stimuli used to evoke otoacoustic emissions (OAEs) are typically calibrated based on the total SPL measured at the probe microphone. However, due to the acoustics of the ear-canal space (i.e., standing-wave interference), this method can underestimate the stimulus pressure reaching the tympanic membrane at certain frequencies. To mitigate this effect, stimulus calibrations based on forward pressure level (FPL) can be applied. Furthermore, the influence of ear-canal acoustics on measured OAE levels can be compensated by expressing them in emitted pressure level (EPL). To date, studies have used artificial shallow versus deep probe fits to assess the effects of calibration method on changes in probe insertion. In an attempt to better simulate a clinical setting, the combined effects of FPL calibration of stimulus level and EPL compensation of OAE level on response variability during routine (noncontrived) probe fittings were examined. The distortion component of the distortion-product OAE (DPOAE) and the stimulus-frequency OAE (SFOAE) were recorded at low and moderate stimulus levels in 20 normal-hearing young-adult subjects across a five-octave range. In each subject, three different calibration approaches were compared: (1) the conventional SPL-based stimulus calibration with OAE levels expressed in SPL; (2) FPL stimulus calibration with OAEs expressed in SPL; and (3) FPL stimulus calibration with OAEs expressed in EPL. Test and retest measurements were obtained during the same session and, in a subset of subjects, several months after the initial test. The effects of these different procedures on the inter- and intra-subject variability of OAE levels were assessed across frequency and level. There were no significant differences in the inter-subject variability of OAE levels across the three calibration approaches. However, there was a significant effect on OAE intra-subject variability. The FPL/EPL approach resulted in the overall lowest test-rest differences in DPOAE level for frequencies above 4 kHz, where standing-wave interference is strongest. The benefit was modest, ranging on average from 0.5 to 2 dB and was strongest at the lower stimulus level. SFOAE level variability did not show significant differences among the three procedures, perhaps due to insufficient signal-to-noise ratio and nonoptimized stimulus levels. Correlations were found between the short-term replicability of DPOAEs and the benefit derived from the FPL/EPL procedure: the more variable the DPOAE, the stronger the benefit conferred by the advanced calibration methods. Stimulus and response calibration procedures designed to mitigate the effects of standing-wave interference on both the stimulus and the OAE enhance the repeatability of OAE measurements and reduce their dependence on probe position, even when probe shifts are small. Modest but significant improvements in short-term test-retest repeatability were observed in the mid- to high-frequency region when using combined FPL/EPL procedures. The authors posit that the benefit will be greater in a more heterogeneous group of subjects and when different testers participate in the fitting and refitting of subjects, which is a common practice in the audiology clinic. The impact of calibration approach on OAE inter-subject variability was not significant, possibly due to a homogeneous subject population and because factors other than probe position are at play.

Development of a Highly Sensitive Humidity Sensor Based on a Piezoelectric Micromachined Ultrasonic Transducer Array Functionalized with Graphene Oxide Thin Film.

A novel relative humidity sensor that is based on a linear piezoelectric micromachined ultrasonic transducer (pMUT) array was proposed and microfabricated for high sensitivity, fast response, and good stability. The humidity-sensitive graphene oxide (GO) film was deposited on the pMUT array with a facile drop-casting method and characterized by scanning electron microscope (SEM), atomic force microscope (AFM), and Fourier transform infrared spectrum (FTIR). With the humidity level ranging from 10% to 90% RH, the sensor exhibited a high sensitivity of 719 Hz/% RH and an extremely high relative sensitivity of 271.1 ppm/% RH. The humidity-sensing results also showed good short-term repeatability and long-term stability, fast response and recovery, and low hysteresis. Moreover, the temperature coefficient of frequency (TCF) of the present humidity sensor was investigated and it could be easily compensated owing to the pMUT array structure design. This work confirmed that the GO functionalized pMUT is an excellent candidate in humidity detection and it may enable many potential applications, such as ultrasensitive mass detection and simultaneous detection of multiple parameters.

Towards quantitative perfusion MRI of the lung in COPD: The problem of short-term repeatability.

Purpose4D perfusion magnetic resonance imaging (MRI) with intravenous injection of contrast agent allows for a radiation-free assessment of regional lung function. It is therefore a valuable method to monitor response to treatment in patients with chronic obstructive pulmonary disease (COPD). This study was designed to evaluate its potential for monitoring short-term response to hyperoxia in COPD patients.Materials and methods19 prospectively enrolled COPD patients (median age 66y) underwent paired dynamic contrast-enhanced 4D perfusion MRI within 35min, first breathing 100% oxygen (injection 1, O2) and then room air (injection 2, RA), which was repeated on two consecutive days (day 1 and 2). Post-processing software was employed to calculate mean transit time (MTT), pulmonary blood volume (PBV) and pulmonary blood flow (PBF), based on the indicator dilution theory, for the automatically segmented whole lung and 12 regions of equal volume.ResultsComparing O2 with RA conditions, PBF and PBV were found to be significantly lower at O2, consistently on both days (p<10–8). Comparing day 2 to day 1, MTT was shorter by 0.59±0.63 s (p<10–8), PBF was higher by 22±80 ml/min/100ml (p<3·10–4), and PBV tended to be lower by 0.2±7.2 ml/100ml (p = 0.159) at both, RA and O2, conditions.ConclusionThe second injection (RA) yielded higher PBF and PBV, which apparently contradicts the established hypothesis that hyperoxia increases lung perfusion. Quantification of 4D perfusion MRI by current software approaches may thus be limited by residual circulating contrast agent in the short-term and even the next day.

Humidity sensors based on AlN microcantilevers excited at high-order resonant modes and sensing layers of uniform graphene oxide

Resonant humidity sensors base on interdigital transducers (IDTs) excited microcantilevers are proposed for high sensitivity. The microcantilevers are coated with uniform graphene oxide (GO) thin films as sensing layers. For the first time, IDTs are used to excite piezoelectric microcantilevers to operate at very high-order resonant modes with intense signal. A small temperature coefficient of frequency (-23.6 ppm/˚C) of the microcantilvers is obtained by using AlN/Si (surface highly doped) layered structure. Uniform and thickness-controllable GO films covering the surface of microcantilevers are formed by vacuum filtration. Compared with the normal electrodes excited sensor with the same structure size, the sensitivity of the IDTs excited sensor is increased from 9.67 to 84.41 Hz/%RH. The thicker GO film, the higher sensitivity of the humidity sensor. Very little humidity hysteresis (< 3%RH) of the sensors is observed in a wide test range from 10%RH to 90%RH. Moreover, the sensors have excellent short term repeatability, fast response and short recovery time (about 10 s).

Calibration Tests of a 25-GHz Mode-spacing Broadband Astro-comb on the Fiber-fed High Resolution Spectrograph (HRS) of the Chinese 2.16-m Telescope

A 25-GHz mode-spacing astro-comb with 470–720 nm wavelength coverage has been installed as the calibration source on the fiber-fed High Resolution Spectrograph (HRS) of the Chinese 2.16-m telescope at Xinglong Observatory. The calibration tests were carried out based on the single-channel system of HRS. The results have achieved a 2–8 times (for different orders) higher wavelength solution accuracy than the thorium argon (ThAr) lamp, and a short-term repeatability of 0.1 m s−1, which is around the photon noise limit. It proved that the coupling system linking the astro-comb to HRS successfully suppressed the negative effects of laser speckles. The comb-line overlapping exists in the acquired spectrum of the astro-comb on HRS. We demonstrated that when determining the comb-line center, the comb-line overlapping leads to a systematic bias, which is caused by asymmetrical sampling, and meanwhile a larger uncertainty. The correction for the systematic bias is feasible by simulating the overlapping comb lines according to actual comb-line spacing and pixel phase and then calculating the difference of the fitted line center with the true line center. A higher accuracy of wavelength solution has been achieved after correction.

Comparison of methods of chemical loop gain measurement during tidal ventilation in awake healthy subjects.

The loop gain (LG) is defined as the ratio of a ventilatory response over the perturbation in ventilation, and it is used to analyze ventilatory control stability. The LG can be derived from minute ventilation (V̇e), end-tidal Pco2 ([Formula: see text]), and end-tidal Po2 ([Formula: see text]) values. Several methods of LG assessment have been developed, which have never been compared. We evaluated the computability, the short-term repeatability, and the agreement of six published (or slightly modified) models for LG determination. These models included three unconstrained autoregressive models, univariate (V̇e), bivariate (V̇e, [Formula: see text]), and trivariate (V̇e, [Formula: see text], and [Formula: see text]), and three analytical transfer function constrained models based on V̇e, V̇e and CO2-sensitivity, and V̇e and central and peripheral CO2 sensitivities, respectively. The models were tested with tidal breathing data in 37 awake healthy subjects (median age 35 yr; 23 women, 14 men). Modeling failed in 11, 0, and 0 subjects for the three unconstrained models, respectively, and 4, 1, and 9 subjects for the three constrained models, respectively. Bland and Altman analyses of the LG values in the medium frequency range of two separate recordings demonstrated good repeatability for four models, excluding univariate and trivariate unconstrained models. The four repeatable models gave LG values that were in agreement (medium frequency LG, median 0.100-0.210), although the constrained model based on V̇e systematically overestimated LG values. The variances explained by these models were ∼20%. In conclusion, model-based analyses of tidal breathing were performed with different approaches that gave comparable results for chemical LG and explained variance.NEW & NOTEWORTHY Several methods of chemical loop gain measurement have been published but never compared. We show that a better repeatability is obtained with analytical constrained models compared with autoregressive unconstrained models and that the repeatable models gave comparable results of loop gain, even if the calculation based on ventilation-only recording gave higher values than those obtained with both ventilation and end-tidal Pco2 recording. The explained variance of ventilation was similar whatever the model.

Assessing Biological and Methodological Aspects of Brain Volume Loss in Multiple Sclerosis

Before using brain volume loss (BVL) as a marker of therapeutic response in multiple sclerosis (MS), certain biological and methodological issues must be clarified. To assess the dynamics of BVL as MS progresses and to evaluate the repeatability and exchangeability of BVL estimates with Jacobian Integration (JI) and Functional Magnetic Resonance Imaging of the Brain (FMRIB) Software Library (FSL) (specifically, the Structural Image Evaluation, Using Normalisation, of Atrophy-Cross-Sectional [SIENA-X] tool or FMRIB's Integrated Registration and Segmentation Tool [FIRST]). A cohort of patients who had either clinically isolated syndrome or MS was enrolled from February 2011 through October 2015. All underwent a series of annual magnetic resonance imaging (MRI) scans. Images from 2 cohorts of healthy volunteers were used to evaluate short-term repeatability of the MRI measurements (n = 34) and annual BVL (n = 20). Data analysis occurred from January to May 2017. The goodness of fit of different models to the dynamics of BVL throughout the MS disease course was assessed. The short-term test-retest error was used as a measure of JI and FSL repeatability. The correlations (R2) of the changes quantified in the brain using JI and FSL, together with the accuracy of the annual BVL cutoffs to discriminate patients with MS from healthy volunteers, were used to measure compatibility of imaging methods. A total of 140 patients with clinically isolated syndrome or MS were enrolled, including 95 women (67.9%); the group had a median (interquartile range) age of 40.7 (33.6-48.1) years. Patients underwent 4 MRI scans with a median (interquartile range) interscan period of 364 (351-379) days. The 34 healthy volunteers (of whom 18 [53%] were women; median [IQR] age, 33.5 [26.2-42.5] years) and 20 healthy volunteers (of whom 10 [50%] were women; median [IQR] age, 33.0 [28.7-39.2] years) underwent 2 MRI scans within a median (IQR) of 24.5 (0.0-74.5) days and 384.5 (366.3-407.8) days for the short-term and long-term MRI follow-up, respectively. The BVL rates were higher in the first 5 years after MS onset (R2 = 0.65 for whole-brain volume change and R2 = 0.52 for gray matter volume change) with a direct association with steroids (β = 0.280; P = .02) and an inverse association with age at MS onset, particularly in the first 5 years (β = 0.015; P = .047). The reproducibility of FSL (SIENA) and JI was similar for whole-brain volume loss, while JI gave more precise, less biased estimates for specific brain regions than FSL (SIENA-X and FIRST). The correlation between whole-brain volume loss using JI and FSL was high (R2 = 0.92), but the same correlations were poor for specific brain regions. The area under curve of the whole-brain volume change to discriminate between patients with MS and healthy volunteers was similar, although the thresholds and accuracy index were distinct for JI and FSL. The proposed BVL threshold of less than 0.4% per year as a marker of therapeutic efficiency should be reconsidered because of the different dynamics of BVL as MS progresses and because of the limited reproducibility and variability of estimates using different imaging methods.

Cone photoreceptor macular function and recovery after photostress in early non-exudative age-related macular degeneration.

PurposeTo identify parameters from cone function and recovery after photostress that detect functional deficits in early non-exudative age-related macular degeneration (AMD) and to determine the repeatability of these parameters.MethodsCone-mediated visual function recovery after photostress was examined in three groups of subjects: young normal subjects (ages 20–29; N=8), older normal subjects (ages 50–90; N=9), and early non-exudative AMD subjects (ages 50–90; N=12). Eight AMD and four normal subjects were retested 1 year after the initial evaluation. Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity (VA) and parameters of cone function (baseline cone sensitivity and cone recovery half-life following photobleach) were measured and compared between AMD and normal subjects. Short-term repeatability was assessed for each subject’s initial evaluation. Long-term repeatability was assessed by comparing outcomes from the initial evaluation and 1-year follow-up.ResultsThe mean baseline cone threshold was significantly worse in subjects with early AMD compared to older normal subjects (−1.80±0.04 vs −1.57±0.06 log cd/m2 p=0.0027). Moreover, the baseline cone threshold parameter exhibited good short-term (intraclass correlation coefficient [ICC]=0.88) and long-term (ICC=0.85) repeatability in all subjects. The cone intercept parameter and ETDRS VA were not significantly different between AMD and older normal subject groups. Cone recovery half-life was significantly different between older normal and AMD subject groups (p=0.041). Neither ETDRS VA nor cone function parameters were significantly different for any group at the 1-year follow-up.ConclusionThe baseline cone threshold shows potential as a novel parameter to assess visual dysfunction in early AMD. This outcome consistently detected deficits in AMD subjects, and differentiated them from age-matched controls with high test–retest repeatability.

Sensitive and selective n-butanol gas detection based on ZnO nanocrystalline synthesized by a low-temperature solvothermal method

ZnO nanocrystalline with a few nanometers in size were synthesized by a low-temperature solvothermal method from zinc acetate dihydrate (Zn(CH3COO)2·2H2O), potassium hydroxide (KOH) and ethanol (C2H5OH). X ray diffraction (XRD), transmission electron microscopy (TEM) and X ray photoelectron spectroscopy (XPS) were used to characterize the structure, morphology, specific surface area and chemical state of the samples. The analyzed results indicate that the ZnO nanocrystalline with good dispersion are several nanometers in size about 10 nm. The ZnO nanocrystalline was used as sensing material to fabricate an indirect-heating structure sensor and its gas sensing properties are tested. At the optimal operating temperature (340 °C), its gas response toward 500 ppm n-butanol is 148.11 and the response and recovery time are 20 and 8 s, respectively. The test results show that the sensitivity of the as-prepared gas sensor has high selectivity to n-butanol and good response/recovery characteristics, linear response, short-term repeatability, as well as the long-term stability. The experimental results show that the gas sensor based on ZnO nanocrystalline can be used in the detection and real-time monitoring of toxic gases, especially n-butanol gas, which makes it to be highly promising candidate for practical detectors for n-butanol gas.

Design and Development of Strain Gauge Pressure Transducer Working in High Pressure Range of 500 MPa Using Autofrettage and Finite Element Method

Development of strain gauge based pressure transducers is very common but its development in high pressure range without sacrificing cost effectiveness and design simplicity is a challenge. While keeping this perspective, we have discussed the development of strain gauge based hydraulic pressure transducer working up to pressure of 500 MPa. The present paper describes the different design stages bearing own challenges and feasible solutions. For design considerations, stress analysis has been performed by using finite element method (FEM). A mathematical modeling is developed for determining the sensitivity of the transducer and is validated with the experimental results. We have also introduced the concept of using autofrettage technique first time in pressure transducer design and its validity for effectiveness in the proposed design is performed with the help of the finite element analysis which reveals that the autofrettage of sensing element, not only increase the pressure bearing capacity of the transducer but also improve the sensitivity. Finally, we have performed the calibration and performance testing experiments on this newly manufactured transducer which shows good linearity (R2=0.999), minimal hysteresis (0.18% of full scale), minimal short term repeatability (0.32% of full scale) and an overall accuracy better than 1% of full scale.

Short-Term Repeatability of Insulin Resistance Indexes in Older Adults: The Atherosclerosis Risk in Communities Study.

The homeostatic model assessment of insulin resistance (HOMA-IR) and triglyceride (TG)/high-density lipoprotein cholesterol (HDL-C) ratio (TG/HDL-C) are insulin resistance indexes routinely used in clinical and population-based studies; however, their short-term repeatability is not well characterized. To quantify the short-term repeatability of insulin resistance indexes and their analytes, consisting of fasting glucose and insulin for HOMA-IR and TG and HDL-C for TG/HDL-C. Prospective cohort study. A total of 102 adults 68 to 88 years old without diabetes attended an initial examination and repeated examination (mean, 46 days; range, 28 to 102 days). Blood samples were collected, processed, shipped, and assayed following a standardized protocol. Repeatability was quantified using the intraclass correlation coefficient (ICC) and within-person coefficient of variation (CV). Minimum detectable change (MDC95) and minimum detectable difference with 95% confidence (MDD95) were quantified. For HOMA-IR, insulin, and fasting glucose, the ICCs were 0.70, 0.68, and 0.70, respectively; their respective within-person CVs were 30.4%, 28.8%, and 5.6%. For TG/HDL-C, TG, and HDL-C, the ICCs were 0.80, 0.68, and 0.91, respectively; their respective within-person CVs were 23.0%, 20.6%, and 8.2%. The MDC95 was 2.3 for HOMA-IR and 1.4 for TG/HDL-C. The MDD95 for a sample of n = 100 was 0.8 for HOMA-IR and 0.6 for TG/HDL-C. Short-term repeatability was fair to good for HOMA-IR and excellent for TG/HDL-C according to suggested benchmarks, reflecting the short-term variability of their analytes. These measurement properties can inform the use of these indexes in clinical and population-based studies.

Abstract P366: Repeatability of Cardio-Ankle Vascular Index in Morbidly Obese Individuals

Background: The AHA 2016 Statement for arterial stiffness evaluation introduced several novel parameters. Cardio-ankle vascular index (CAVI) is one of them and has a unique property of being largely independent of blood pressure (BP) at the time of examination. The repeatability of CAVI has been confirmed in healthy population but not in morbidly obese individuals. Methods: We investigated 76 participants (mean age 44 years, and mean BMI 48 kg/m 2 [ranged from 36-70]) in the BARI-Heart Study, who underwent 2 standardized visits (1-10 months apart) before bariatric surgery. CAVI was measured twice 5-minute apart at each visit using oscillometric device VaSera VS-1500 (Fukuda Denshi, Tokyo, Japan) at a supine position. We calculated intra-class correlation coefficient (ICC), minimal detectable change (MDC 95 ) and minimal detectable difference (MDD) using a nested random-effects analysis of variance model for CAVI. As a contrast, we also calculated these repeatability statistics for brachial and ankle BP measured using the same device when CAVI was measured. Results: At the first visit, average CAVI was 6.2 (SD 1.1) and average brachial systolic and diastolic BP was 146 mmHg (SD 13) and 86 mmHg (SD 7). For short-term repeatability in 5 minutes at the first visit, the ICCs were very high for both CAVI and brachial and ankle BPs (all with ICC ≥ 0.82 bilaterally). When we observed longer term repeatability over several months, the ICCs were fair for BPs (ranged from 0.42-0.57) but remained very high for CAVI with ≥0.72 for both sides. The MDC 95 between repeated measures within an individual across two visits was 1.6-1.7 for CAVI and 15-35 mmHg for BP parameters. In this scenario, the MDD for two independent samples of 100 per group was ~0.5 for CAVI and 4-8 mmHg for BP parameters. Conclusion: The short- and longer-term repeatability of CAVI was overall good even among morbidly obese individuals. Our results suggest that a longitudinal change of CAVI by 1.6-1.7 indicates a change beyond the measurement error.

Gas Diffusion Cell Geometry for a Microfluidic Dissolved Inorganic Carbon Analyzer

Variable gas diffusion cell geometries were tested for the extraction of dissolved inorganic carbon (DIC) from a microfluidic (tens to hundreds of microliters) seawater sample. With a focus on optimization of diffusion cell geometry, we compare five unique diffusion cell designs. Using 3-D printing technology to streamline the prototyping and testing process, we were able to conceive, design, fabricate, and thoroughly evaluate each design over the course of about one month. In total, 1043 DIC measurements were carried out in 109 experiments for the five working manifolds. We find that a small diameter, cylindrical diffusion cell design offers several advantages over its planar counterparts and a larger diameter cylindrical cell, most notably the ability to increase the ratio of the exchange membrane’s contact surface area to solution volume (the “aspect ratio”) without sacrificing channel integrity. Multiple designs approached short-term repeatability of $\mu \text{L}$ of sample.

Variable flip angle 3D ultrashort echo time (UTE) T1 mapping of mouse lung: A repeatability assessment.

Lung T1 is a potential translational biomarker of lung disease. The precision and repeatability of variable flip angle (VFA) T1 mapping using modern 3D ultrashort echo time (UTE) imaging of the whole lung needs to be established before it can be used to assess response to disease and therapy. To evaluate the feasibility of regional lung T1 quantification with VFA 3D-UTE and to investigate long- and short-term T1 repeatability in the lungs of naive mice. Prospective preclinical animal study. Eight naive mice and phantoms. 3D free-breathing radial UTE (8 μs) at 4.7T. VFA 3D-UTE T1 calculations were validated against T1 values measured with inversion recovery (IR) in phantoms. Lung T1 and proton density (S0 ) measurements of whole lung and muscle were repeated five times over 1 month in free-breathing naive mice. Two consecutive T1 measurements were performed during one of the imaging sessions. Agreement in T1 between VFA 3D-UTE and IR in phantoms was assessed using Bland-Altman and Pearson 's correlation analysis. The T1 repeatability in mice was evaluated using coefficient of variation (CV), repeated-measures analysis of variance (ANOVA), and paired t-test. Good T1 agreement between the VFA 3D-UTE and IR methods was found in phantoms. T1 in lung and muscle showed a 5% and 3% CV (1255 ± 63 msec and 1432 ± 42 msec, respectively, mean ± SD) with no changes in T1 or S0 over a month. Consecutive measurements resulted in an increase of 2% in both lung T1 and S0 . VFA 3D-UTE shows promise as a reliable T1 mapping method that enables full lung coverage, high signal-to-noise ratio (∼25), and spatial resolution (300 μm) in freely breathing animals. The precision of the VFA 3D-UTE method will enable better design and powering of studies. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.