Coefficient Of Repeatability Research Articles

Children treated for developmental dysplasia of the hip at birth and with normal acetabular index at 1 year: How many had residual dysplasia at 5 years?

Purpose:The purpose of the study was to assess the effect of further follow-up for children treated for developmental dysplasia of the hip, with normal clinical and radiological findings at 1-year time point. The effect was quantified by the number of hips with a pathologic deterioration up to 5 years.Methods:Among 47,289 children born in Sør-Trøndelag county in Norway between 2003 and 2015, 265 children had developmental dysplasia of the hip. Of these, 164 children (239 hips) treated for developmental dysplasia of the hip with normal clinical findings and normal acetabular index at the 1-year time point were included in the study. The number of hips with pathologic acetabular index at the 5-year time point were reported. The diagnostic uncertainty related to radiological measurements was quantified together with the effect of introducing a second radiographic measurement, the center edge angle.Results:A total of 239 treated hips were normal at the 1-year time point. At 5-year time point, 10 (4.2%) hips had a pathologic acetabular index measurement and none classified to have developmental dysplasia of the hip caused by measurement inaccuracy. Eight (3.3%) hips had pathologic center edge angle measurement. Four hips had both pathologic acetabular index and center edge angle measurements, with three later treated with surgery. The intra- and interobserver repeatability coefficients were within 3.1°–6.6°.Conclusion:The repeatability coefficient of the acetabular index measurements was high and no hips could be classified to have developmental dysplasia of the hip at the 5-year time point when taking this repeatability into account. Hips classified as pathologic combining acetabular index and center edge angle measurements were likely to be treated with surgery for residual dysplasia. We recommend further follow-up for these children.Level of evidence:level II.

Comparison of corneal tomography using a novel swept-source optical coherence tomographer and rotating Scheimpflug system in normal and keratoconus eyes: repeatability and agreement analysis

BackgroundTo determine the repeatability and agreement using corneal tomography of a swept-source optical coherence tomographer (SS-OCT) compared to a rotating Scheimpflug camera (RSC) in normal eyes and keratoconus (KC) eyes.MethodsThis prospective repeatability analysis was performed at the Department of Ophthalmology of University Hospital Carl Gustav Carus, Dresden, Germany. Forty-three normal and 57 KC eyes were enrolled in the study. Three consecutive measurements were performed by the same operator on each device. Corneal parameters of anterior and posterior corneal surface, such as simulated keratometry (SimK), as well as central and thinnest corneal thickness were evaluated. Repeatability and agreement were assessed by using the coefficient of repeatability and Bland-Altman analysis.ResultsThe repeatability of anterior corneal parameters was comparable between RSC and SS-OCT in normal eyes (repeatability < 0.5 D). Repeatability was increased in mild and moderate KC for all parameters using both devices. In moderate KC, repeatability of Kmax was 1.33 D and 0.78 D for RSC and SS-OCT, respectively. Repeatability of posterior corneal parameters was consistently better for SS-OCT. Significant offsets and wide ranges of limits of agreement were found between the devices for SimK and corneal thickness values.ConclusionsSS-OCT showed highly repeatable measurements of anterior and posterior corneal parameters in normal and KC eyes. Compared to RSC, the SS-OCT had a better repeatability of anterior corneal parameters in mild and moderate KC as well as posterior corneal parameters in all groups. Both devices should not be used interchangeably in the diagnostic process of patients.Trial registration NCT04251143 at Clinicaltrials.gov, registered on 12 March 2018, https://clinicaltrials.gov/ct2/show/NCT04251143?cond=Keratoconus&cntry=DE&city=Dresden&draw=2&rank=1

Reliability of relaxation properties of knee-extensor muscles induced by transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS)-induced relaxation rate reflects intrinsic muscle contractile properties by interrupting the drive from the central nervous system during voluntary muscle contractions. To determine the appropriateness of knee-extensor muscle relaxation measurements induced by TMS, this study aimed to establish both the within- and between-session reliability before and after a fatiguing exercise bout. Eighteen participants (9 females, 9 males, age 25 ± 2 years, height 171 ± 9 cm, body mass 68.5 ± 13.5 kg) volunteered to participate in two identical sessions approximately 30 days apart. Maximal and submaximal neuromuscular evaluations were performed with TMS six times before (PRE) and at the end (POST) of a 2-min sustained maximal voluntary isometric contraction. Within- and between-session reliability of PRE values were assessed with intraclass correlation coefficient (ICC2,1, relative reliability), repeatability coefficient (absolute reliability), and coefficient of variation (variability). Test-retest reliability of post-exercise muscle relaxation rates was assessed with Bland-Altman plots. For both the absolute and normalized peak relaxation rates and time to peak relaxation, data demonstrated low variability (e.g. coefficient of variation ≤ 7.8%) and high reliability (e.g. ICC2,1 ≥ 0.963). Bland-Altman plots showed low systematic errors. These findings establish the reliability of TMS-induced muscle relaxation rates in unfatigued and fatigued knee-extensor muscles, showing that TMS is a useful technique that researchers can use when investigating changes in muscle relaxation rates both in unfatigued and fatigued knee-extensor muscles.

Characterizing Visual Fields in RPGR Related Retinitis Pigmentosa Using Octopus Static-Automated Perimetry.

PurposePeripheral visual fields have not been as well defined by static automated perimetry as kinetic perimetry in RPGR-related retinitis pigmentosa. This study explores the pattern and sensitivities of peripheral visual fields, which may provide an important end point when assessing interventional clinical trials.MethodsA retrospective observational cross-sectional study of 10 genetically confirmed RPGR subjects was performed. Visual fields were obtained using the Octopus 900 perimeter. Interocular symmetry and repeatability were quantified. Visual fields were subdivided into central and peripheral subfields for analysis.ResultsMean patient age was 32 years old (20 to 49 years old). Average mean sensitivity was 7 dB (SD = 3.67 dB) and 6.8 dB (SD = 3.4 dB) for the right and left eyes, respectively, demonstrating interocular symmetry. Coefficient of repeatability for overall mean sensitivity: <2 dB. Nine out of 10 subjects had a preserved inferotemporal subfield, whose mean sensitivity was highly correlated to the central field (r2 = 0.78, P = 0.002 and r2 = 0.72, P = 0.002 for the right and left eyes, respectively). Within the central field, sensitivities were greater in the temporal than the nasal half (t-test, P = 0.01 and P = 0.03 for the right and left eyes, respectively).ConclusionsOctopus static-automated perimeter demonstrates good repeatability. Interocular symmetry permits use of the noninterventional eye as an internal control. In this cohort, the inferotemporal and central visual fields are preserved into later disease stages likely mapping to populations of surviving cones.Translational RelevanceA consistently preserved inferotemporal island of vision highly correlated to that of the central visual field may have significance as a possible future therapeutic site.

Phenotypic Variability in the Induction of Alpha Acids in Hops (Humulus lupulus L.) in Brazil

Hops (Humulus lupulus L.) is a key ingredient in beer, with great significance for the Brazilian industry. The economically viable production of hops in Brazil depends on the genetic variability available to be used in the selection and development of high-as performance photo-neutral cultivars and their interaction with the environment. The objective of this research was to evaluate the phenotypic variability of alpha-effective character in relation to the environmental variation in different Brazilian regions. Alpha-acids tests were performed through the American Society of Brewing Chemists (ASBC-HOPS 6. B-Conductometric titration methodology). Phenotypic variation assessment showed that 30% of the variation occurred among clones, while 47% was attributed to the environmental components of cultivation. The repeatability coefficient (t) was below 0.25, demonstrating that interaction between genotype and environment inflicted on alpha-acid levels. Results showed variability in the alpha-acid contents depending on the hops growing regions. According to the results, clones 9 (8.22%), 26 (12.95%) and 27 (9.94%) added the highest levels of alpha-acids. Therefore, there is variability available for the genetic improvement of the culture in Brazil and its effects must be evaluated in each microclimate of cultivation.

The repeatability and agreement of biometric measurements by dual Scheimpflug device with integrated optical biometer

To determine the repeatability of biometric measurements by dual Scheimpflug Devices with Integrated Optical Biometers and its agreement with partial coherence interferometry according to the axial length (AL), and the presence of cataracts. The present population-based cross-sectional study was conducted on the geriatric population in Tehran. For participants, imaging was performed by dual Scheimpflug Devices with Integrated Optical Biometers (Galilei G6) and partial coherence interferometry (IOL Master 500). All measurements were performed by one person. In both normal and cataractous eyes, the ICC values were above 0.99 for three measurements of AL, intraocular lens (IOL) power target, anterior chamber depth (ACD), central corneal thickness (CCT), flat and steep keratometry readings, and mean total corneal power (MTCP). The repeatability coefficient for the AL measurements was 0.003 and 0.002 in eyes with and without cataracts, respectively. The mean difference of AL between IOL Master 500 and Galilei G6 in normal and cataractous eyes was 0.015 and −0.003 mm, respectively. The 95% limits of agreement (LoA) of AL between these two devices were −0.09 to 0.12 mm in normal and −0.09 to 0.08 mm in cataractous eyes. The 95% LoA of ACD between the two devices was −0.13 to 0.36 mm and −0.10 to 0.31 mm in eyes without and with cataracts, respectively. The 95% LoA of steep K between the two devices was −0.63 to 0.32 and −1.04 to 0.89 diopter in normal and cataractous eyes, respectively. The results of the present study indicate the high repeatability of Galilei G6 in ocular biometric measurements. Galilei biometric measurements, had a very high agreement with the IOL Master 500.

TiB2‐Modified Polymer‐Derived Ceramic SiCN Double‐Layer Thin Films Fabricated by Direct Writing for High‐Temperature Application

The thermal stability at high temperatures is the first design principle of high‐temperature thin‐film sensors. To improve the thermal stability of the thin‐film sensor, a TiB2‐modified SiCN double‐layer thin‐film resistor grid with a thickness of 18 μm is fabricated on an alumina substrate via direct writing. Owing to their in situ–generated SiO2–B2O3–TiO2 thermally grown oxide protective layer on the surface and TiB2 percolation paths inside, the produced films exhibit large high‐temperature oxidation resistance, electrical conductivity and high‐temperature‐resistance stability. In the thermal cycling test up to 800 °C, the TiB2‐modified SiCN films exhibit a negative‐temperature coefficient of resistance and excellent repeatability and stability. The resistance change rate at 800 °C for 1 h is only 1.1%. With the flexible manufacturing and high‐temperature stability of such ceramic films, this work on double‐layer ceramic films can be applied to in situ monitoring of hot components at high temperature.

Design of a novel smartphone-based photostress recovery time test for detecting abnormalities in the macula. A cross-sectional study

BackgroundThe study aims to present a new smartphone-based photostress recovery time test (K-PSRT test) that measures the stimulus-specific loss of visual sensitivity, as well as the differentiation between normal from abnormal macular function. This novel test defines a new standardized photostress application as an alternative tool for incorporation into clinical practice. Materials and methodsA total of 48 visually impaired eyes and 47 normal sighted age-matched controls eyes were enrolled in the study. The median age in subjects with impairment was 71.0 years, while the median age in normal subjects was 70.0 years. A light produced by the smartphone camera at approximately 5 cm distance, perpendicular to the eye up 10 s filled the pupil. The photostress recovery time was assessed immediately after the exposure by asking the subjects to read correctly at least three successive letters of size corresponding to the previous line of the BCVA line at a distance of 40 cm. The digital photostress testing was performed with the best-corrected visual acuity (BCVA). The patients were examined twice within 2 weeks. Correlations among the recovery times, the visual acuity, and the contrast sensitivity function as well as correlations concerning each specific ocular disease were also performed. Furthermore, correlations among technology, usability, and ease of performance in both groups were analyzed. ResultsThe initial median photostress recovery time in patients with impaired eyes was 83.5 (68.5, 126.0), while in the normal individuals was 39.0 (14.0, 43.0). The median visual acuity in individuals with impairment was 0.59 logMAR (0.40, 0.90), whereas in the normal individuals was −0,06 logMAR. Test-retest reliability study was performed on 26 eyes (16 males, 10 females) for visually impaired eyes as well as on 35 normal eyes (19 males, 16 females). Concerning the reliability, the average Intraclass Correlation Coefficients (with 95% confidence intervals) ICC (95% CI) = 0,99 (0,98–1,00), indicating significant correlation between them (p < 0.01). The coefficient of repeatability for eye measurements reaches clinically acceptable levels, which is demonstrated with increased repeatability and consistency. The recovery time in patients with diabetic retinopathy was statistically significantly lower than in those with dry age-related macular degeneration (p = 0.027) and those with wet age-related macular degeneration (p = 0.032). The patient group has lower scores concerning technology, usability, and ease of performance compared to the normal. ConclusionsThis new testing modality (K-Photostress Recovery time test), is designed to be an easily implemented measurement in ophthalmic practice, and it can expand our understanding of macular function. The above findings support the usefulness of a novel reproducible photostress application as an indicator of macular pathology.

Determination of Zn2+ in Solid Pharmaceutical Dosage Forms by Means of Spectrophotometry in Micellar Media: Method Validation

In this study, a spectrophotometric method for the quantitative determination of zinc in a dietary supplement was validated. Zinc forms a ternary complex with Xylenol Orange and cetylpyridinium chloride in acetate buffer at pH = 5.5. The complex exhibits an absorption maximum at 560 nm. Linearity (range was 0.5–1.5 µg/mL, and correlation coefficient of the calibration curve was 0.9998), precision (repeatability variation coefficient and reproducibility variation coefficient were 1.57% and 1.77%, respectively), and accuracy (confidence interval of the mean recovery was 98.29–100.55%) of this method fulfil current pharmacopeial requests. Results obtained by spectrophotometric method were statistically compared with ones obtained by atomic absorption spectrometry and good agreement was found. The method can be applied routinely for quality control of solid pharmaceutical dosage forms containing zinc.

Repeatability of lung clearance index in infants with cystic fibrosis and recurrent wheeze.

To describe the short- and medium-term repeatability of lung clearance index at 2.5%(LCI2.5 ) in infants and calculate the number of patients needed to enroll in a study (N) using LCI2.5 as a primary outcome. An 8-month follow-up observational study was employed for assessing short-term [coefficient of repeatability (CR) and intraclass correlation (ICC)]and medium-term repeatability (Bland-Altman method) of LCI2.5 in infants with cystic fibrosis (CF) or recurrent wheeze (RW) measured by the nitrogen multiple-breath washout test (N2 -MBW). Using these variability data, the N to reach 90% test power at the level of statistical significance (0.05) was calculated. Forty infants with CF and 21 with RW were enrolled. Initial N2 -MBW testing was successful in 33 and 17 patients, respectively. Follow-up data were available for 23 and 11 infants, respectively. Short-term repeatability of LCI2.5 was high (CR = 1.10 and 1.04 in CF and RW patients, respectively; ICC = 0.88 and 0.83 in CF and RW patients, respectively). The between-subject standard deviation was <13% of the actual LCI2.5 value. In clinically stable patients, LCI2.5 did not significantly change during the 8-month follow-up. Mean LCI2.5 change was -0.08 (1% of baseline) in CF and -0.05 (0.6%) in RW, with 95% limits of agreement being (-1.70; 1.53) in CF and (-1.51; 1.40) in RW patients. N = 23 infants if both intragroup differences of LCI2.5 and minimal difference to be detected would be 2.0. N2 -MBW may be a reproducible tool with reasonable test power to detect differences in infant studies.

Effects of weighing phase duration on vertical force-time analyses and repeatability

ABSTRACT Force plate analyses of various activities sometimes require the average (WPav) and standard deviation (WPsd) of force across the Weighing Phase (i.e., quiet period) to calculate kinetic, temporal and kinematic metrics. Yet, the influence of weighing phase duration on these analyses has been scarcely investigated. This study investigated the effects of weighing phase duration on the agreement between vertical force-time variables and the repeatability of WPav and WPsd. Durations of 0.5, 1.0 and 1.5 s were compared to 2.0 s. Limits of agreement (LOA) for system weight, onset threshold, onset time, net impulse, take-off velocity and take-off displacement were calculated for 137 counter-movement, squat and single leg jumps. Repeatability coefficients for WPav and WPsd estimated the consistency between repeated trials. Shorter weighing phase durations produced small differences in WPav (LOA < ±0.25%), which accumulated during integration, affecting net impulse, take-off velocity (LOA ±2%) and take-off displacement (LOA ±23%). Differences were substantial using 5xWPsd as the onset threshold (LOA approximately ±25% to ±72%), consequently influencing onset time (LOA approximately ±6% to ±18%). WPav repeatability was high but the within-trial differences could augment with integration, requiring weighing phases longer than 2 s. WPsd had poor repeatability and its use requires further investigation.

In Vivo Corneal Biomechanical Properties in a Selected Chinese Population, Measured Using the Corneal Visualization Scheimpflug Technology.

Purpose: To evaluate the repeatability and reproducibility of recalculated dynamic corneal response (DCR) parameters and the biomechanical-compensated intraocular pressure (bIOP) derived from the Corneal Visualization Scheimpflug Technology (Corvis ST), as well as to study the variations of DCR parameters and their relationship with demographic, and ocular characteristics. Methods: A total of 544 healthy subjects were recruited in this study and a series of ophthalmological examinations were performed on their right eyes. Three repeated measurements were obtained at 3-min intervals for 291 of the participants to ensure repeatability. A sum of 100 participants was examined twice within 2-h intervals using two different Corvis ST in the reproducibility study. The repeatability and reproducibility of 37 parameters, including 36 DCR parameters and bIOP, were assessed by the coefficient of repeatability (CR), coefficient of variation (CV), intraclass correlation coefficient (ICC), and within-subject standard deviation (sw). Pearson’s correlation coefficients and stepwise multivariate linear regression models were performed to investigate whether the DCR parameters were related to demographic and ocular characteristics. Results: Of all the 37 parameters, 34 showed excellent (ICC ≥0.90) or good (ICC ≥0.75) repeatability while 27 of the 37 parameters showed excellent (ICC ≥0.90) or good (ICC ≥0.75) reproducibility. In particular, a CV of less than 20% was found for all DCR parameters and bIOP. A fraction of 14 out of 36 DCR parameters was selected for correlation analysis, based on measurement reliability and clinical relevance in referring to previous literature. Age was negatively associated with the Highest concavity delta arc length (HCdArcL) and peak distance (PD) but it positively correlated with the Whole Eye Movement Max Length (WEMML). Intraocular pressure (IOP) and central corneal thickness (CCT) were negatively associated with the deformation amplitude ratio (DARM) [1 mm], A1 Velocity (A1V), and PD, while positively related to the stiffness parameter at applanation 1 (SP-A1). The bIOP was negatively associated with A1V but positively associated with A2 Velocity (A2V). The anterior chamber volume (ACV) was negatively associated with the pachy slope (PS), WEMML, and SP-A1. Conclusion. The Corvis ST showed good precision for the repeatability and reproducibility of 36 DCR parameters and bIOP parameters in healthy eyes. The IOP, CCT, bIOP, Km, and ACV significantly influenced the DCR parameters of the eyes.

Intrasession Repeatability and Intersession Reproducibility of Macular Vessel Parameters on Optical Coherence Tomography Angiography in Glaucomatous and Non-Glaucomatous Eyes

Purpose Using optical coherence tomography angiography (OCTA), this study compared intrasession repeatability versus intersession reproducibility of macular vessel parameters in glaucoma and non-glaucoma subjects. Methods 6 × 6 mm2 macular OCTA scans (Cirrus HD-OCT 5000) were acquired from glaucomatous and non-glaucomatous subjects as part of an observational, longitudinal study. Vessel area density (VAD) and vessel skeleton density (VSD) were calculated using research-based quantification software while perfusion density (PDZ) and vessel density (VDZ) were calculated using commercially developed software (Cirrus 11.0, Carl Zeiss Meditec). Intrasession repeatability and intersession reproducibility were determined using within-eye standard deviation (SW), within-eye coefficient of repeatability (CRW), within-eye coefficient of variation (CVW), and intraclass correlation coefficients (ICC). Results The intrasession repeatability and intersession reproducibility for macular OCTA parameters were similar to one another for both non-glaucomatous and glaucomatous eyes. Intrasession CVW from the non-glaucoma group (n = 73) was 1.097% for VAD, 1.007% for VSD, 2.980% for PDZ, and 2.714% for VDZ. Intersession CVW from the non-glaucoma group (n = 55) was 1.389% for VAD, 1.279% for VSD, 2.935% for PDZ, and 2.695% for VDZ. Intrasession CVW from the glaucoma group (n = 59) was 1.189% for VAD, 0.970% for VSD, 3.827% for PDZ, and 3.542% for VDZ. Intersession CVW from the glaucoma group (n = 45) was 1.412% for VAD, 1.132% for VSD, 3.915% for PDZ, and 3.654% for VDZ. Non-glaucomatous intrasession ICC ranged from 0.711 to 0.824, non-glaucomatous intersession ICC ranged from 0.649 to 0.762, glaucomatous intrasession ICC ranged from 0.710 to 0.853, and glaucomatous intersession ICC ranged from 0.661 to 0.827. Conclusions Macular OCTA scans can be a useful tool in monitoring the longitudinal progression of glaucoma due to their high repeatability and reproducibility.

Repeatability of i.Profiler for measuring wavefront aberrations in healthy eyes.

To evaluate the repeatability of wavefront aberration measurements and the correlation between corneal aberration and pupil size in normal eyes using a wavefront-based autorefractor (i.ProfilerPlus; Carl Zeiss Vision, Germany). A prospective cross-sectional study. Wavefront aberrations, including spherical aberration (SA) (Z40), coma (Z3-1, Z31), trefoil (Z3-3, Z33) and total higher-order aberrations (tHOA), were measured at different pupil diameters. The repeatability was evaluated using one-way ANOVA method, and statistical indicators including within-subject standard deviation (Sw), test-retest repeatability (TRT), and intra-class correlation coefficient (ICC). The correlations between corneal aberrations and pupil sizes were evaluated by Pearson correlation analysis. A total of 96 healthy young volunteers were enrolled. Corneal and ocular higher-order aberrations (HOA) measured by i.Profiler showed Sw < 0.01μm, TRT < 0.10μm, ICC > 0.90. There was a linear positive correlation between the corneal HOA and pupil size. The correlation coefficient between SA and tHOA was the largest (r = 0.996, P < 0.001). The measurements of wavefront aberrations by i.Profiler are highly repeatable. Corneal HOA was significantly dependent on pupil size. SA was the most influential aberration for visual quality in this study.

Comparison of preoperative angle kappa measurements in the eyes of cataract patients obtained from Pentacam Scheimpflug system, optical low-coherence reflectometry, and ray-tracing aberrometry

BackgroundAngle kappa plays a vital role in the implantation of multifocal intraocular lens (MIOL). Large angle kappa is related to a higher risk of postoperative photic phenomena. This study aims to compare preoperative angle kappa in the eyes of cataract patients obtained from the Pentacam Scheimpflug system (Pentacam), optical low-coherence reflectometry (Lenstar), and ray-tracing aberrometry (iTrace).MethodsOne hundred thirteen eyes of 113 patients with cataracts were included. Each eye was examined 3 times using all devices to obtain angle kappa and pupil diameter. When considering dependent eyes for one individual, angle kappa in both right eyes and left eyes should be analysed separately. The repeatability and reproducibility were evaluated using the within-subject standard deviation (Sw), repeatability (2.77 Sw), and intraclass correlation coefficient (ICC). The difference, correlation, and agreement between devices were evaluated by paired t-tests, Pearson tests, and Bland-Altman analysis, respectively.ResultsIntraoperator repeatability and interoperator and intersession reproducibility of angle kappa showed an Sw of less than 0.05 mm, a 2.77 Sw of 0.14 mm or less, and an ICC of more than 0.96. Angle kappa was not significantly different between Pentacam and Lenstar (P > 0.05), while angle kappa was significantly different between Pentacam and iTrace and between Lenstar and iTrace (P < 0.05). There was a strong correlation between Pentacam and Lenstar for angle kappa (r =0.907 to 0.918) and a weak or moderate correlation between Pentacam and iTrace and between Lenstar and iTrace (r =0.292 to 0.618). There were narrow 95% limits of agreement (LoA) between Pentacam and Lenstar for angle kappa and wide 95% LoA between Pentacam and iTrace and between Lenstar and iTrace. No significant differences in pupil diameter were found between Pentacam and Lenstar in either eye (P > 0.05). Positive angle kappa (nasal light reflex) was found in most cataract patients (79.25% to 84.91%) through 3 different devices in both eyes.ConclusionsThe 3 devices provided high intraoperator repeatability and interoperator and intersession reproducibility for angle kappa measurements. The measurement of preoperative angle kappa in the eyes of patients with cataracts by Pentacam and Lenstar has good agreement.

Quantitative analysis of liver function: 3D variable-flip-angle versus Look-Locker T1 relaxometry in hepatocyte-specific contrast-enhanced liver MRI.

Gd-EOB-DTPA, a liver specific contrast agent with T1- shortening effects, is routinely used in clinical magnetic resonance imaging (MRI) for detection and characterization of focal liver lesions. Gd-EOB-DTPA-enhanced T1 relaxometry has recently received increasing attention as a tool for the quantitative analyses of liver function. However, this T1 relaxometry technique is limited due to various artifacts caused by B1 inhomogeneities and motion artifacts. This study aims to compare two different T1 relaxometry techniques for evaluating liver function as determined using a 13C-methacetin-based breath test (13C-MBT). Ninety-six patients underwent gadoxetic acid-enhanced MRI of the liver at 3T and a 13C-MBT. Two different prototype sequences for T1 relaxometry were used, a 3D VIBE sequence using Dixon water-fat separation and variable-flip-angles (VFA), as well as a 2D Look-Locker sequence (LL). Images were acquired before (T1 pre) and 20 minutes after (T1 post) administration of liver-specific contrast agent to evaluate the reduction rates of T1 relaxation time (rrT1) in accordance with the 13C-MBT outcome. To analyze both MR sequences' performance, the intraclass correlation coefficient (ICC) between four ROI measurements within the same liver and the coefficient of repeatability (CR) were calculated. T1 relaxometry measurements based on MR sequences, VFA, and LL show a constant change in line with impaired liver function progression. Simple regression models showed a log-linear correlation of 13C-MBT values with all evaluated T1 relaxometry measurements (VFA T1post, VFA rrT1, LL T1post, LL rrT1, P<0.001). Both ICC (VFA T1post, LL T1post; 0.75, 0.95) and CR (VFA T1 post, LL T1 post; 179, 101) showed a better agreement between ROI measurements using the LL sequence. Both T1 relaxometry sequences are suitable for the evaluation of liver function based on 13C-MBT. However, the Look-Locker sequence is less susceptible to artifacts and might be more advantageous, especially in patients with impaired liver function.

Comparison of the Near Eye Tool for Refractive Assessment (NETRA) and non-cycloplegic subjective refraction

ObjectiveThe NETRA (Near Eye Tool for Refractive Assessment) is a smartphone-based refractive tool that allows for self-evaluation of refractive error. This study investigates the validity of the NETRA with and...

Disease-specific assessment of Vision Impairment in Low Luminance in age-related macular degeneration – a MACUSTAR study report

Background/aimsTo further validate the Vision Impairment in Low Luminance (VILL) questionnaire, which captures visual functioning and vision-related quality of life (VRQoL) under low luminance, low-contrast conditions relevant to age-related macular...

Ganglion Cell Layer Thickness Variance Using SPECTRALIS Optical Coherence Tomography.

To determine the normal variance of the mean macular ganglion cell layer (GCL) volume among subjects without significant ocular pathology using SPECTRALIS optical coherence tomography (OCT). Fifty subjects underwent a baseline scan using SPECTRALIS OCT followed by 2 more studies with (reg-ON) and without (reg-OFF) eye registration all taken at the same session. The mean GCL volume was measured using built-in SPECTRALIS software. Eyes with macular pathology were excluded. The reproducibility of the measurements of the GCL volume was evaluated with Bland-Altman plots and limits of agreement, intraclass correlation coefficient (ICC), and the coefficient of repeatability (CR). A total of 98 eyes met criteria for the analysis. The mean GCL volume difference was 0.0002 ± 0.029 and -0.0005 ± 0.035 mm 3 for scans 1 versus 2 (baseline vs reg-ON) and 3 (baseline vs reg-OFF), respectively. The ICCs were 0.985 and 0.977 for the baseline vs reg-ON and reg-OFF groups. The CR for baseline vs reg-ON was 0.056 while CR for baseline vs reg-OFF was 0.069. Ninety percent of eyes fell within 0.04 mm 3 of test-retest reliability. Our model found a predictable threshold of 0.07 mm 3 or less for SPECTRALIS OCT mean GCL volume variance, which did not significantly change with eye registration in eyes without macular pathology. Clinicians may also consider a threshold of 0.04 mm 3 when determining stable vs progressive changes in mean GCL volume using this device.

Colour assessment of bleaching effect on orthodontically treated teeth.

To assess whether the efficacy of external tooth bleaching differs between untreated and orthodontically treated teeth. Three groups of subjects were formed; group Debonded included 24 consecutive orthodontically treated patients evaluated immediately after removal of fixed appliances. The Retention group included 24 consecutive orthodontically treated patients in the phase of retention. The Untreated group consisted of 24 arbitrarily selected undergraduate dental students without history of fixed-appliances orthodontic therapy. Each of the above three groups was further randomized into two subgroups, Bleaching and Placebo. Each subgroup received either a 38% hydrogen peroxide bleaching treatment or a placebo agent, respectively. Tooth colour changes were assessed at seven timepoints: 1 day before intervention; on the day of intervention before and after treatment; and at 7, 14, 21, and 90 days for parameters L*, a*, b*, and ΔΕ in all upper incisors and canines with the use of a reflectance spectrophotometer. Intra-rater agreement was estimated with the Intra-class Correlation Coefficient and method's error was calculated using the Repeatability Coefficient. Regarding tooth colour changes, an analysis of variance was used to assess differences between groups. Bleaching was associated with an increase of the L* value and decrease of b* and a* values in both orthodontically treated and untreated teeth. Parameters ΔE, L*, and b* exhibited statistically significant differences between the Bleaching-Untreated and Bleaching-Retention subgroups. In the Bleaching subgroups, statistically significant differences were found between different teeth for all parameters. Previous exposure to fixed orthodontic appliance influenced the efficacy of external tooth bleaching. The effect of bleaching was higher after orthodontic treatment and with longer period in retention. Canines changed in colour more than incisors, and the effect was reduced over time.