Intrasession Repeatability Research Articles

MVP‐VSASL: measuring MicroVascular Pulsatility using velocity‐selective arterial spin labeling

AbstractPurposeBy leveraging the small‐vessel specificity of velocity‐selective arterial spin labeling (VSASL), we present a novel technique for measuring cerebral MicroVascular Pulsatility named MVP‐VSASL.Theory and MethodsWe present a theoretical model relating the pulsatile, cerebral blood flow‐driven VSASL signal to the microvascular pulsatility index (), a widely used metric for quantifying cardiac‐dependent fluctuations. The model describes the dependence of the of VSASL signal (denoted ) on bolus duration (an adjustable VSASL sequence parameter) and provides guidance for selecting a value of that maximizes the SNR of the measurement. The model predictions were assessed in humans using data acquired with retrospectively cardiac‐gated VSASL sequences over a broad range of values. In vivo measurements were also used to demonstrate the feasibility of whole‐brain voxel‐wise pulsatility mapping, assess intrasession repeatability of , and illustrate the potential of this method to explore an association with age.ResultsThe theoretical model showed excellent agreement to the empirical data in a gray matter region of interest (average value of 0.898 0.107 across six subjects). We further showed excellent intrasession repeatability of the pulsatility measurement (, ) and the potential to characterize associations with age (, ).ConclusionWe have introduced a novel, VSASL‐based cerebral microvascular pulsatility technique, which may facilitate investigation of cognitive disorders where damage to the microvasculature has been implicated.

Slice-specific B1 + shimming improves the repeatability of multishot DWI at 7 T.

Compared with lower field strengths, DWI at 7 T faces the combined challenges of increased distortion and blurring due to B0 inhomogeneity, and increased signal dropouts due to B1 + inhomogeneity. This study addresses the B1 + limitations using slice-specific static parallel transmission (pTx) in a multi-shot, readout-segmented EPI diffusion imaging sequence. DWI was performed in 7 healthy subjects using MRI at 7 T and readout-segmented EPI. Data were acquired with non-pTx circular-polarized (CP) pulses (CP-DWI) and static pTx pulses (pTx-DWI) using slice-specific B1 + shim coefficients. Each volunteer underwent two scan sessions on the same day, with two runs of each sequence in the first session and one run in the second. The sequences were evaluated by assessing image quality, flip-angle homogeneity, and intrasession and intersession repeatability in ADC estimates. pTx-DWI significantly reduced signal voids compared with CP-DWI, particularly in inferior brain regions. The use of pTx also improved RF uniformity and symmetry across the brain. These effects translated into improved intrasession and intersession repeatability for pTx-DWI. Additionally, re-optimizing the pTx pulse between repeat scans did not have a negative effect on ADC repeatability. The study demonstrates that pTx provides a reproducible image-quality increase in multishot DWI at 7 T. The benefits of pTx also extend to quantitative ADC estimation with regard to the improvement in intrasession and intersession repeatability. Overall, the combination of multishot imaging and pTx can support the development of reliable, high-resolution DWI for clinical studies at 7 T.

A New Method to Measure Ocular Surface Sensitivity: Repeatability and Reproducibility of the Liquid Jet Esthesiometer.

To assess the reliability of the liquid jet esthesiometer (LJA) for measurement of corneal sensitivity. Two separate studies were conducted to assess intrasession repeatability (study 1) and intersession reproducibility (study 2) of corneal sensitivity measured using the LJA. Thirty participants (13 female and 17 male participants, age 23±6 years) participated in study 1 and another 30 (18 female and 12 male participants, 35±10 years) participated in study 2. For study 1, mechanical sensation threshold of the central cornea was measured three times on the same day, with a 30-min break between repeats. For study 2, central corneal sensation threshold was measured on five different days by one of eight randomly assigned examiners. Corneal sensation thresholds obtained in studies 1 and 2 were 2.3±1.0 and 2.5±1.2 μL, respectively. No significant differences between repeated measurements were obtained in either study (P≥0.19). Thresholds were lower (i.e., corneal sensitivity was higher) in female than male participants (2.1±1.0 vs. 2.7±0.9 μL in male participants, P=0.02) but were not affected by contact lens wear. Clinical reliability of the LJA was good for intrasession repeatability (coefficient of repeatability ±1.6 μL, intraclass correlation coefficient 0.74, within-subject coefficient of variation (CVW) 24%) and moderate for intersession reproducibility (Coefficient of Reproducibility ±2.2 μL, CVW 32%). Measurement variability was independent of threshold level (P=0.84). The LJA offers good clinical repeatability and is a reliable tool to measure corneal sensitivity in different population groups, regardless of stimulus thresholds. Day-to-day fluctuations in corneal sensitivity probably account for the relatively lower reproducibility.

Factors Associated With Ocular Perfusion Measurements as Obtained With Laser Speckle Contrast Imaging.

To study the ocular and systemic factors affecting optic nerve head (ONH) perfusion data as obtained using a commercially available laser speckle flowgraphy (LSFG) device in a cohort of Caucasian subjects without ocular diseases. Also, to assess the intrasession repeatability and intersession reproducibility of ONH, macular, retinal, and choroidal perfusion. Seventy-five healthy eyes of 75 Caucasian participants underwent LSFG and spectral-domain optical coherence tomography (SD-OCT) on the same visit. Perfusion of the ONH was assessed with LSFG, and SD-OCT was used to measure peripapillary retinal nerve fiber layer thickness (RNFLT) and macular ganglion cell plus inner plexiform layer thickness (GCIPLT). The intrasession repeatability and intersession reproducibility of ONH and macular perfusion and retinal and choroidal relative flow volume (RFV) were evaluated in 20 participants measured on three different days over a 6-month period. Intrasession and intersession intraclass correlation coefficients of LSFG parameters ranged from 0.787 to 0.967 and from 0.776 to 0.935, respectively. Intersession 95% prediction intervals for the ratio of two measurements were wider for RFV indices than for ONH and macular perfusion parameters. The multiple regression analysis indicated that higher ONH perfusion was associated with younger age, female sex, smaller optic disc area, and higher RNFLT. RNFLT was an independent predictor of ONH perfusion, whereas GCIPLT was not. Each 1-µm increase in RNFLT was associated with a 0.272 arbitrary unit increase in ONH perfusion. LSFG measurements of optic disc perfusion are influenced by sex, age, and anatomical variations in optic disc area and RNFLT. Better evaluation of ocular blood flow will result in better diagnosis and treatment of various ocular diseases.

Repeatability and Reproducibility of pseudo-Continuous Arterial Spin Labeling Measured Brain Perfusion in Healthy Volunteers and Glioblastoma Patients.

Arterial spin labeled (ASL) MRI has gained recognition as a quantitative perfusion imaging method for managing patients with brain tumors. Limited studies have so far investigated the reproducibility of ASL-derived perfusion in patients with brain tumors. This study aims to evaluate intrasession repeatability and intersession reproducibility of perfusion measurements using 3D pseudo-continuous ASL (pCASL) with Cartesian TSE (TSE-CASPR) in healthy volunteers (HV) and glioblastoma (GBM) patients at 3 Tesla and compare against 3D pCASL with GRASE. This prospective study (NCT03922984) was approved by the institutional review board and written informed consent was obtained from all subjects. HV underwent repeated pCASL evaluations 2-4 weeks apart between November 2021 and October 2022. GBM patients were recruited for longitudinal MRI from September 2019 to February 2023. Intrasession repeatability (HV and GBM) and intersession reproducibility (HV only) of pCASL were assessed using linear regression, Bland-Altman analyses, intraclass correlation coefficient (ICC) with 95% confidence interval (CI), and within-subject coefficients of variation (wsCV). Twenty HV (9 men, age: 25.1±1.7 years, range 23-30 years) and 21 GBM patients (15 men; age: 59.8±14.3 years, range 28-81 years) were enrolled. Within imaging session, 3D pCASL measured perfusion with TSE-CASPR and GRASE respectively achieved high R2 values (0.88-0.95; 0.93-0.96), minimal biases (-0.46 to 0.81; -0.08 to 0.35 mL/100g/min), high ICC [95% CI] (0.96-0.98 [0.94-0.98]; 0.96-0.98 [0.92-0.99]), and low wsCV (6.64%-9.07%; 5.20%-8.16%) in HV (N=20) and GBM patients (N=21). Across imaging session, 3D pCASL in HV (N=20) achieved high R2 values (0.71; 0.82), minimal biases (-1.2; -0.90 mL/100g/min), high ICC [95% CI] values (0.85 [0.81-0.89]; 0.90 [0.87-0.93]), and low wsCV values (13.82%; 9.98%). Our study demonstrated excellent intrasession repeatability of 3D pCASL measured cerebral perfusion in HV and GBM patients and good to excellent intersession reproducibility in HV. 3D pCASL with GRASE performed slightly better than 3D pCASL with TSE-CASPR in HV; however, in GBM patients, 3D pCASL with TSE-CASPR showed better performance in tumor regions with nearly twofold higher SNR. ASL measured perfusion could serve as a non-contrast quantitative imaging biomarker to facilitate the management of GBM patients. ASL = arterial spin labeling; pCASL = pseudo-continuous arterial spin labeling; GBM = glioblastoma; CBF = cerebral blood flow; CASPR = Cartesian acquisition with spiral profile reordering; GRASE = gradient and spin echo; NAGM = normal-appearing gray matter.

Evaluation of the SpotChecks contrast sensitivity test in healthy adults.

SpotChecks is a new contrast sensitivity (CS) test designed for self-monitoring of vision. This study assessed the test-retest repeatability of take-home SpotChecks, in-office SpotChecks and near Pelli-Robson charts in healthy adults. One eye of 61 healthy adults with near visual acuity (VA) of 6/9 or better (age range 22-84, mean 49 [18] years) was tested during two office visits (mean 10 [8] days apart). Each visit included high-contrast VA, then 12 randomly ordered CS tests (6 different SpotChecks and 6 different Pelli-Robson) under the same lighting (luminance 110 cd/m2), all at near in the same eye with habitual correction. The same eye was self-tested with take-home SpotChecks once a day on 6 days between the office visits. SpotChecks was scored by the logCS at the highest line with ≥2 errors. Pelli-Robson was scored by [0.05 × number of letters read correctly - 0.15]. Repeatability of logCS was defined as 1.96 Sw, Sw representing within-subject standard deviation. Comparison for repeatability was performed with Bootstrap hypothesis test. SpotChecks and Pelli-Robson showed similar intra-session or inter-visit repeatability (p = 0.14-0.81). Inter-day repeatability for take-home SpotChecks was 0.18 logCS, the same as that from the first measurements of two office visits with SpotChecks or Pelli-Robson. Inter-visit repeatability improved to 0.15 by using the average of two repeated measurements for SpotChecks (p = 0.02) or three repeated measurements for Pelli-Robson (p = 0.04). Age showed a small effect on logCS (-0.015/decade, p = 0.02) for both SpotChecks and Pelli-Robson. Mean logCS was 0.05 lower in those ≥50 years (SpotChecks 1.84 [0.10] and Pelli-Robson 1.77 [0.10]) compared with those <50 years of age (SpotChecks 1.89 [0.07] and Pelli-Robson 1.83 [0.07]). SpotChecks showed good repeatability with take-home and in-office testing in healthy adults, making it a promising tool for monitoring disease progression at home.

Repeatability of a Combined Adaptive Optics Visual Simulator and Hartman-Shack Aberrometer in Pseudophakic Eyes With and Without Previous Corneal Refractive Surgery.

To evaluate the intrasession repeatability of wavefront aberrations obtained by a combined adaptive optics visual simulator and Hartman-Shack aberrometer in pseudophakic eyes with and without previous corneal refractive surgery. Three consecutive measurements were performed in one eye of each individual. Total ocular aberrations were recorded up to the 5th Zernike order for a 4.5-mm pupil. Repeatability was assessed by calculating the within-subject standard deviation (Sw), the repeatability limit (R), and the intraclass correlation coefficient (ICC). Vector analysis was performed to assess astigmatism variability between scans. The study enrolled 32 normal individuals and 24 individuals with a history of refractive surgery. In normal and eyes that had previous refractive surgery, respectively, the Sw values were 0.155 and 0.176 diopters (D) for sphere and 0.184 and 0.265 D for cylinder. The Sw values for all 3rd order terms ranged from 0.037 to 0.047 µm in normal eyes and 0.044 to 0.063 µm in eyes that had previous refractive surgery. The Sw for primary spherical aberration was 0.020 µm in normal eyes and 0.026 µm in eyes that had previous refractive surgery. ICC values for measurements of astigmatism yielded larger variability (ICC = 0.751 and 0.879). However, both groups demonstrated excellent repeatability (ICC > 0.9) for root mean square higher order aberrations (RMS-HOA) and total RMS values. In pseudophakic eyes, the adaptive optics Hartmann-Shack device demonstrated acceptable repeatability for measurement of sphere and 3rd and 4th order HOAs with higher variability for astigmatism measurements, especially in eyes with a prior history of corneal refractive surgery. [J Refract Surg. 2024;40(9):e645-e653.].

Self-Gated Radial Free-Breathing Liver MR Elastography: Assessment of Technical Performance in Children at 3 T.

Conventional liver magnetic resonance elastography (MRE) requires breath-holding (BH) to avoid motion artifacts, which is challenging for children. While radial free-breathing (FB)-MRE is an alternative for quantifying liver stiffness (LS), previous methods had limitations of long scan times, acquiring two slices in 5 minutes, and not resolving motion during reconstruction. To reduce FB-MRE scan time to 4 minutes for four slices and to investigate the impact of self-gated (SG) motion compensation on FB-MRE LS quantification in terms of agreement, intrasession repeatability, and technical quality compared to conventional BH-MRE. Prospective. Twenty-six children without fibrosis (median age: 12.9 years, 15 females). 3 T; Cartesian gradient-echo (GRE) BH-MRE, research application radial GRE FB-MRE. Participants were scanned twice to measure repeatability, without moving the table or changing the participants' position. LS was measured in areas of the liver with numerical confidence ≥90%. Technical quality was examined using measurable liver area (%). Agreement of LS between BH-MRE and FB-MRE was evaluated using Bland-Altman analysis for SG acceptance rates of 40%, 60%, 80%, and 100%. LS repeatability was assessed using within-subject coefficient of variation (wCV). The differences in LS and measurable liver area were examined using Kruskal-Wallis and Wilcoxon signed-rank tests. P < 0.05 was considered significant. FB-MRE with 60% SG achieved the closest agreement with BH-MRE (mean difference 0.00 kPa). The LS ranged from 1.70 to 1.83 kPa with no significant differences between BH-MRE and FB-MRE with varying SG rates (P = 0.52). All tested methods produced repeatable LS with wCV from 4.4% to 6.5%. The median measurable liver area was smaller for FB-MRE (32%-45%) than that for BH-MRE (91%-93%) (P < 0.05). FB-MRE with 60% SG can quantify LS with close agreement and comparable repeatability with respect to BH-MRE in children. 2 TECHNICAL EFFICACY: Stage 1.

Post mortem analysis of hepatic volume and lipid content by magnetic resonance imaging and spectroscopy in fixed murine neonates.

Maternal obesity and hyperglycemia are linked to an elevated risk for obesity, diabetes, and steatotic liver disease in the adult offspring. To establish and validate a noninvasive workflow for perinatal metabolic phenotyping, fixed neonates of common mouse strains were analyzed postmortem via magnetic resonance imaging (MRI)/magnetic resonance spectroscopy (MRS) to assess liver volume and hepatic lipid (HL) content. The key advantage of nondestructive MRI/MRS analysis is the possibility of further tissue analyses, such as immunohistochemistry, RNA extraction, and even proteomics, maximizing the data that can be gained per individual and therefore facilitating comprehensive correlation analyses. This study employed an MRI and 1H-MRS workflow to measure liver volume and HL content in 65 paraformaldehyde-fixed murine neonates at 11.7 T. Liver volume was obtained using semiautomatic segmentation of MRI acquired by a RARE sequence with 0.5-mm slice thickness. HL content was measured by a STEAM sequence, applied with and without water suppression. T1 and T2 relaxation times of lipids and water were measured for respective correction of signal intensity. The HL content, given as CH2/(CH2+ H2O), was calculated, and the intrasession repeatability of the method was tested. The established workflow yielded robust results with a variation of ~3% in repeated measurements for HL content determination. HL content measurements were further validated by correlation analysis with biochemically assessed triglyceride contents (R2= 0.795) that were measured in littermates. In addition, image quality also allowed quantification of subcutaneous adipose tissue and stomach diameter. The highest HL content was measured in C57Bl/6N (4.2%) and the largest liver volume and stomach diameter in CBA (53.1 mm3 and 6.73 mm) and NMRI (51.4 mm3 and 5.96 mm) neonates, which also had the most subcutaneous adipose tissue. The observed effects were independent of sex and litter size. In conclusion, we have successfully tested and validated a robust MRI/MRS workflow that allows assessment of morphology and HL content and further enables paraformaldehyde-fixed tissue-compatible subsequent analyses in murine neonates.

Intrasession repeatability and agreement of the anterior corneal assessment provided by a multidiagnostic device

ABSTRACT Clinical relevance Multidiagnostic systems have recently appeared on the market. Knowledge of the repeatability and validity of any instrument is mandatory before its introduction in clinical practice. Background The aim of this work is to examine the intrasession repeatability of anterior pole measurements provided by the multidiagnostic device Wave Analyzer Medica 700 (WAM700) and agreement with Pentacam measurements in normal eyes. Methods In the right eyes of 113 participants, three repeat measurements of central keratometry, central corneal thickness, anterior chamber depth and corneal eccentricity were made with the WAM700 and Pentacam in random order. Intrasession repeatability and agreement were determined. Results Employing WAM700, intrasession repeatability for keratometry, central corneal thickness and anterior chamber depth was good (ICCs ≥ 0.992; CV 0.48–0.98%), yet worse than the values obtained for the Pentacam (ICCs ≥ 0.998; CV 0–0.33%). WAM700 showed excellent intrasession repeatability when used to measure the anterior chamber depth (Sw 0.03 mm). However, the repeatability of this device was inferior for central corneal thickness (Sw 4.24 μm) and keratometry measurements (Sw < 0.21 D) and was poor for corneal eccentricity (Sw 0.07; ICC 0.908; CV 14.58%). Agreement between WAM700 and Pentacam showed a high ICC for the keratometry measurements, central corneal thickness and anterior chamber depth (>0.972) but lower for corneal eccentricity (ICC 0.762). Conclusions In healthy eyes, the WAM700 multidiagnostic device showed good intrasession repeatability for keratometry, central corneal thickness and anterior chamber depth measurements. Agreement between WAM700 and Pentacam was good for the anterior chamber depth measurement. However, these instruments cannot be considered interchangeable for keratometry, central corneal thickness and eccentricity readings.

Clinical Evaluation of a New Spectral-Domain Optical Coherence Tomography-Based Biometer.

The VEMoS-AXL system is a new optical biometer based on spectral domain optical coherence tomography (SD-OCT) that has been tested in terms of intrasession repeatability and compared with a swept-source optical coherence tomography biometer (SS-OCT), which is recognized as the gold standard for the performance of an agreement analysis. A biometric analysis was performed three consecutive times in 120 healthy eyes of 120 patients aged between 18 and 40 years with the SD-OCT system, and afterwards, a single measurement was obtained with the SS-OCT system. Within-subject standard deviations were 0.004 mm, 4.394 µm, and 0.017 mm for axial length (AL), central corneal thickness (CCT), and anterior chamber depth (ACD) measures obtained with the SD-OCT biometer, respectively. The agreement between devices was good for AL (limits of agreement, LoA: -0.04 to 0.03 mm) and CCT (LoA: -4.36 to 14.38 µm), whereas differences between devices were clinically relevant for ACD (LoA: 0.03 to 0.21 mm). In conclusion, the VEMoS-AXL system provides consistent measures of anatomical parameters, being most of them interchangeable with those provided by the SS-OCT-based gold standard.

Repeatability of swept-source optical coherence tomography angiography automated macular vessel density.

Optical Coherence Tomography Angiography Ratio Analysis (OCTARA) is capable of visualizing inner and outer retinal vascular plexuses, choriocapillaris, and larger choroidal vasculature in vivo without contrast injection. The aim of this study was to assess the intrasession repeatability of automated vessel density measurements using Triton Swept-Source Optical Coherence Tomography Angiography (OCTA) innovative algorithm OCTARA in retinal and choroidal vasculature. To study population between 65-90 years old with no eye diseases. For each subject measurements were performed four times. The intraclass correlation coefficient and the coefficient of variation were calculated to analyze repeatability of the OCTARA automatically generated vessel density measurements. A total of 35 eyes were included in the study. The intraclass correlation coefficient of the global vessel density in the superficial capillary plexus and the deep capillary plexus were 0.963 and 0.975, respectively, and the coefficient of variation were 5.4% and 4.4%, respectively. The intraclass correlation coefficient of the rest of the global measurements was indicative of good reliability with the exception of the deep choroid layer with an intraclass correlation coefficient of 0.6 indicative of moderate reliability. Our results proved excellent repeatability of automated vessel density measurements in the superficial and deep capillary plexus layers in our cohort using a OCTARA algorithm indicating that it may be a reliable diagnostic tool. It also showed good reliability in choriocapillary and mid choroid layer. These findings may be of value in assessing the significance of differences in capillary density measurements over time and across different settings.

Unraveling diurnal and technical variability in cerebral hemodynamics from neurovascular 4D-Flow MRI

Neurovascular 4D-Flow MRI enables non-invasive evaluation of cerebral hemodynamics including measures of cerebral blood flow (CBF), vessel pulsatility index (PI), and cerebral pulse wave velocity (PWV). 4D-Flow measures have been linked to various neurovascular disorders including small vessel disease and Alzheimer’s disease; however, physiological and technical sources of variability are not well established. Here, we characterized sources of diurnal physiological and technical variability in cerebral hemodynamics using 4D-Flow in a retrospective study of cognitively unimpaired older adults (N = 750) and a prospective study of younger adults (N = 10). Younger participants underwent repeated MRI sessions at 7am, 4 pm, and 10 pm. In the older cohort, having an MRI earlier on the day was significantly associated with higher CBF and lower PI. In prospective experiments, time of day significantly explained variability in CBF and PI; however, not in PWV. Test-retest experiments showed high CBF intra-session repeatability (repeatability coefficient (RPC) =7.2%), compared to lower diurnal repeatability (RPC = 40%). PI and PWV displayed similar intra-session and diurnal variability (PI intra-session RPC = 22%, RPC = 24% 7am vs 4 pm; PWV intra-session RPC = 17%, RPC = 21% 7am vs 4 pm). Overall, CBF measures showed low technical variability, supporting diurnal variability is from physiology. PI and PWV showed higher technical variability but less diurnal variability.

Evaluation of contrast sensitivity in visually impaired individuals using K-CS test. A novel smartphone-based contrast sensitivity test-Design and validation.

To describe the development and investigate the accuracy of a novel smartphone-based Contrast Sensitivity (CS) application, the K-CS test. A total of 67 visually impaired and 50 normal participants were examined monocularly using the novel digital K-CS test and the Pelli-Robson (PR) chart. The K-CS test examines letter contrast sensitivity in logarithmic units, using eight levels of contrast from logCS = ~0,1 to logCS = ~2,1 at two spatial frequencies of 1.5 and 3 cycles per degree (cpd). The K-CS test was compared to the gold standard, PR test and intra-session test repeatability was also examined. The K-CS test in normally sighted was found to agree well with the PR, providing comparable mean scores in logCS (±SD) (K-CS = 1.908 ± 0.06 versus PR = 1.93 ± 0.05) at 1.5 cpd and mean (± SD) logCS at 3 cpd (K-CS = 1.83 ± 0.13 versus PR = 1.86 ± 0.07). The mean best corrected visual acuity of visually impaired participants was 0.67 LogMAR (SD = 0.21) and the K-CS was also found to agree well with the Pelli-Robson in this group, with an equivalent mean (±SD) logCS at 1.5 cpd: (K-CS = 1.19 ± 0.27, PR = 1.15 ± 0.31), 3 cpd: K-CS = 1.01 ± 0.33, PR = 0.94 ± 0.34. Regarding the intra-session test repeatability, both the K-CS test and the PR test showed good repeatability in terms of the 95% limits of agreement (LoA): K-CS = ±0.112 at 1.5 cpd and ±0.133 at 3 cpd, PR = ±0.143 at 1.5 cpd and ±0.183 in 3 cpd in visually impaired individuals. The K-CS test provides a quick assessment of the CS both in normally sighted and visually impaired individuals. The K-CS could serve as an alternative tool to assess contrast sensitivity function using a smartphone and provides results that agree well with the commonly used PR test.

Biometry-Based Technique for Determining the Anterior Scleral Thickness: Validation Using Optical Coherence Tomography Landmarks.

Considering the potential role of anterior scleral thickness (AST) in myopia and the ubiquitous use of optical biometers, we applied and validated a biometry-based technique for estimating AST using optical coherence tomography (OCT) landmarks. The AST was determined across four meridians in 62 participants (aged 20-37years) with a swept-source OCT and a noncontact optical biometer at a mean ± SD distance of 3.13 ± 0.88mm from the limbus. The biometer's graticule was focused and aligned with the anterior scleral reflex, which led to the generation of four prominent A-scan peaks: P1 (anterior bulbar conjunctiva), P2 (anterior episclera), P3 (anterior margin of anterior sclera), and P4 (posterior margin of anterior sclera), which were analyzed and compared with the corresponding OCT landmarks to determine tissue thickness. The AST measurements between biometer and OCT correlated for all meridians (r ≥ 0.70, overall r = 0.82; coefficient of variation [CV], 9%-12%; P < 0.01). The mean difference ± SD between two instruments for overall AST measures was 3 ± 2.8 µm (range, -18 to +16µm; lower limits of agreement, -89 to +83 µm; P = 0.23) across all meridians. The mean ± SE AST with both instruments was found to be thickest at the inferior (562 ± 7µm and 578 ± 7µm) and thinnest at the superior (451 ± 7µm and 433 ± 6µm) meridian. The biometer demonstrated good intrasession (CV, 8.4%-9.6%) and intersession (CV, 7.9%-13.3%) repeatability for AST measurements across all meridians. The noncontact optical biometer, which is typically used to determine axial length, is capable of accurately estimating AST based on OCT landmarks. The high-resolution optical biometers can demonstrate wider application in the field of myopia research and practice to determine AST.

Targeted High-Density Microperimetry Testing of Nascent Geographic Atrophy in Age-Related Macular Degeneration

To examine the effectiveness of a targeted high-density microperimetry testing strategy for detecting visual sensitivity abnormalities in eyes with nascent geographic atrophy (nGA) when compared with standard central microperimetry testing. Observational study. Three-hundred and twenty-one eyes from 176 individuals with nonneovascular age-related macular degeneration (AMD). Thirty-five eyes from 33 participants underwent targeted high-density microperimetry testing of atrophic lesions (either nGA or geographic atrophy [GA]) within a 1.75° radius (or approximately 1000 μm diameter) region. Another cohort of 286 eyes from 143 participants with bilateral large drusen at baseline underwent standard microperimetry testing of the central 6° radius region at 6-monthly intervals for up to 36 months and thus included eyes that developed nGA and GA over the follow-up. All eyes underwent 2 tests at each visit to evaluate intrasession measurement repeatability. Magnitude of visual sensitivity abnormalities based on mean sensitivity (MS), pointwise sensitivity standard deviation (PSD), and the number of test locations with a threshold of ≤ 10 decibels (dB; or deep defects) in eyes with nGA, compared between eyes that underwent targeted high-density microperimetry testing and standard central microperimetry testing. The magnitude of visual sensitivity abnormalities based on MS, PSD and the number of deep defects were all significantly greater in eyes with nGA using targeted, high-density microperimetry testing compared with eyes with nGA using standard central microperimetry testing (all P < 0.001) and were all significantly less than eyes with GA using targeted, high-density microperimetry testing (all P ≤ 0.004). The intrasession coefficient of repeatability, where 95% of the test-retest differences are expected to occur, for MS in eyes with atrophic changes was 0.9 dB with the targeted, high-density microperimetry testing, and 1.8 dB with standard central microperimetry testing. Targeted, high-density microperimetry testing enabled the detection of a significantly greater magnitude of visual sensitivity abnormalities in eyes with nGA than standard microperimetry testing. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Ultrasonographic reliability and repeatability of simultaneous bilateral assessment of diaphragm muscle thickness during normal breathing.

The diaphragm is considered the main muscle involved in breathing and also linked to trunk stabilization functions. Up to date, rehabilitative ultrasound imaging (RUSI) has been the most used technique to evaluate unilaterally the transcostal diaphragm thickness. Nevertheless, the inspiratory activity of both hemi-diaphragms is bilaterally performed at the same time, and its simultaneous evaluation with a thoracic orthosis could improve its assessment as well as its re-education with visual biofeedback of both hemi-diaphragms at the same time. The purpose was to evaluate the reliability and repeatability of simultaneous thickness measurements of both hemi-diaphragms bilaterally during normal breathing using a thoracic orthosis that allowed bilateral fixation of both right and left ultrasound probes. The study was conducted in 46 healthy subjects, whose diaphragm thickness was measured bilaterally and simultaneously in the anterior axillary line during relaxed breathing with a designed thoracic orthosis and 2 ultrasound tools. Intra-examiner (same examiner), inter-examiner (2 examiners), intra-session (1 hour) and inter-session (1 week) reliability and repeatability between each pair of measurements of diaphragm muscle thickness were analyzed during normal breathing. Reliability and repeatability for intra-session evaluations using the thoracic orthosis were excellent to evaluate simultaneous thickness of both hemi-diaphragms by bilateral probes fixation (intraclass correlation coefficient =0.919-0.997; standard error of measurement =0.002-0.007 cm; minimum detectable change =0.006-0.020 cm), without systematic errors (P>0.05) between each pair of measurements. Nevertheless, inter-session evaluations varied from good to excellent using the bilateral probes fixation (intraclass correlation coefficient =0.614-0.984; standard error of measurement =0.006-0.028 cm; minimum detectable change =0.017-0.079 cm), although some systematic errors were presented (P<0.05). Good to excellent reliability and repeatability was shown for simultaneous thickness measurements of both hemi-diaphragms bilaterally during normal breathing. Despite systematic errors were presented for some inter-examiner assessments, the use of the thoracic orthosis that allowed bilateral fixation of ultrasound probes could be recommended for simultaneous hemi-diaphragms breathing re-education by visual biofeedback.

Medium-term repeatability for airwave oscillometry in patients with severe asthma taking benralizumab.

The effort-independent tidal breathing test used by oscillometry presents a viable alternative for following up patients whose condition is stable while they are receiving biologic therapy. We aimed to determine intrasession and intersession repeatability values for airwave oscillometry (AOS) and spirometry in patients who were already taking benralizumab. In all, 21 patients with severe eosinophilic asthma attended the Scottish Centre for Respiratory Research as partof a clinical trial (EudraCT identification number 2019-003763-22). Paired AOS and spirometry values were obtained at 3 separate visits (baseline and days 28 and 56) with no change in asthma therapy. Intrasession agreement between repeated measurements for AOS and spirometry was excellent (intraclass correlation coefficient≥ 0.90) at all 3 visits. Intersession agreement was also excellent (intraclass correlation coefficient≥ 0.80). In this study we report medium-term intrasession and intersession repeatability values for airwave oscillometry and spirometry in a cohort of severely asthmatic patients receiving benralizumab therapy. Oscillometry can be used to follow up patients with asthma who are taking biologics.

Reliability and Agreement of Keratometry Measurements Obtained With Eye Surface Profilometry and Partial Coherence Interferometry.

The aim of this study was to assess the repeatability of keratometry parameters obtained using the Eye Surface Profiler (ESP) system and their agreement with the IOL Master 500 device. Seventy-one eyes of 71 healthy participants were evaluated. Three repeated measurements were performed using the ESP system. Simulated keratometry in the flat (SimKf) and steep (SimKs) meridians, astigmatism, and axis were obtained. The same parameters were measured using the IOL Master 500 device. The J0 and J45 vector components of the astigmatism were calculated. The intrasession repeatability was analyzed using within-subject SD (Sw) and intraclass correlation coefficient (ICC). Agreement was assessed using paired statistical tests and the Bland-Altman method. The Sw was 0.07 mm, 0.04 mm, 0.51 D, 0.33 D, and 0.22 D, and the ICC was 0.96, 0.98, 0.74, 0.61, and 0.55 for SimKf, SimKs, astigmatism, J0, and J45, respectively. The mean difference and limits of agreement when comparing the ESP system with the IOL Master 500 device were 0.37 mm (0.08/0.66) for SimKf ( P < 0.001), 0.18 mm (0.00/0.35) for SimKs ( P < 0.001), -0.93 D (-2.42/0.56) for astigmatism ( P < 0.001), 0.51 D (-0.22/1.24) for J0 ( P < 0.001), and 0.06 D (-0.48/0.60) for J45 ( P = 0.09). The ESP system provides consistent values for simulated keratometry, showing moderate consistency for astigmatism parameters. Contact lens practitioners should be aware that the ESP system and IOL Master 500 device provide different simulated keratometry from a clinically viewpoint.

Intrasession Repeatability of OCT Angiography Parameters in Neurodegenerative Disease.

To assess the intrasession repeatability of macular OCT angiography (OCTA) parameters in Alzheimer's disease (AD), mild cognitive impairment (MCI), Parkinson's disease (PD), and normal cognition (NC). Cross sectional study. Patients with a clinical diagnosis of AD, PD, MCI, or NC were imaged. Images with poor quality and of those with diabetes mellitus, glaucoma, or vitreoretinal disease were excluded from analysis. All participants were imaged using the Zeiss Cirrus HD-5000 with AngioPlex (Carl Zeiss Meditec, Software Version 11.0.0.29946) and repeat OCTA images were obtained for both eyes. Perfusion density (PFD), vessel density (VD), and Foveal avascular zone (FAZ) area were measured from 3×3 mm and 6×6 mm OCTA images centered on the fovea using an ETDRS grid overlay. Intraclass correlation coefficients were used to quantify repeatability of PFD, VD, and FAZ area measurements obtained from imaging. 3×3 mm scans of 22 AD, 40 MCI, 21 PD, and 26 NC participants and 6×6 mm scans of 29 AD, 44 MCI, 29 PD, and 30 NC participants were analyzed. Repeatability values ranged from 0.64 (0.49-0.82) for 6×6 mm PFD in AD participants to 0.87 (0.67-0.92) for 3×3 mm PFD in AD participants. No significant differences were observed in repeatability between NC participants and those with neurodegenerative disease. Overall, similar OCTA repeatability was observed between NC participants and those with neurodegeneration. Regardless of diagnostic group, macular OCTA metrics demonstrated moderate to good repeatability. The authors have no proprietary or commercial interest in any materials discussed in this article.