Quantifying 3D MR fingerprinting (3D-MRF) reproducibility across subjects, sessions, and scanners automatically using MNI atlases

PURPOSE

Quantitative MRI techniques such as MR fingerprinting (MRF) promise more objective and comparable measurements of tissue properties at the point-of-care than weighted imaging. However, few direct cross-modal comparisons of MRF's repeatability and reproducibility versus weighted acquisitions have been performed. This work proposes a novel fully automated pipeline for quantitatively comparing cross-modal imaging performance in vivo via atlas-based sampling.

METHODS

We acquire whole-brain 3D-MRF, turbo spin echo, and MPRAGE sequences three times each on two scanners across 10 subjects, for a total of 60 multimodal datasets. The proposed automated registration and analysis pipeline uses linear and nonlinear registration to align all qualitative and quantitative DICOM stacks to Montreal Neurological Institute (MNI) 152 space, then samples each dataset's native space through transformation inversion to compare performance within atlas regions across subjects, scanners, and repetitions.

RESULTS

Voxel values within MRF-derived maps were found to be more repeatable (σT1  = 1.90, σT2  = 3.20) across sessions than vendor-reconstructed MPRAGE (σT1w  = 6.04) or turbo spin echo (σT2w  = 5.66) images. Additionally, MRF was found to be more reproducible across scanners (σT1  = 2.21, σT2  = 3.89) than either qualitative modality (σT1w  = 7.84, σT2w  = 7.76). Notably, differences between repeatability and reproducibility of in vivo MRF were insignificant, unlike the weighted images.

CONCLUSION

MRF data from many sessions and scanners can potentially be treated as a single dataset for harmonized analysis or longitudinal comparisons without the additional regularization steps needed for qualitative modalities.

The size distribution of the agitated saline microbubbles for contrast transcranial Doppler generated using standard manual methods

Agitated saline microbubbles (MBs) are a common contrast agent for determining right-to-left shunt (RLS) by the contrast transcranial Doppler (c-TCD). The size of the generated bubbles is not standardized in clinical practice. MBs were generated using the recommended manual method by reciprocating motion through two syringes. The bubble size distributions (BSD) were measured using the microscopic shadow imaging technique. The results show that the diameter of MBs is mainly distributed between 10 and 100 μm, the mean bubble size is between 21 and 34 μm, the Sauter mean diameter (D32) is primarily between 50 and 300 μm, and the standard deviation (SD) is between 6 and 17 μm in 80 experiments. It provides a more accurate basis for the recommended manual method instability. The high variance values of the BSD indicate that the manual method has low stability and repeatability. The results of this study can be useful for further improvement of the reliability of c-TCD in detecting RLS. RESEARCH HIGHLIGHTS: This study provided the first detailed descriptions of the MBs size distribution in a flowing contrast agent by the microscopic shadow imaging technique. It reveals significant differences in the bubble size of manual foaming during repeated manipulations for each individual and between individuals.

Effects of Cheliped Amputation on the Personality of Crayfish

Animal personality, which describes inter-individual differences and intra-individual consistency in behaviors across time and contexts, has been widely observed and has significance for both ecology and evolution. Morphological modifications, particularly during early life stages, may highly influence animal behavior in adulthood; thus, exploring this relationship can elucidate personality development throughout ontogeny. In this study, we reared juvenile crayfish (Procambarus clarkii) with different degrees of cheliped mutilation and explored their personality patterns, including exploration and aggression, when they reached sexual maturity. Male crayfish showed repeatability in exploration, and both sexes showed repeatability in aggression. We observed no significant correlation between the two behavioral traits, indicating the absence of behavioral syndromes. Moreover, exploration did not differ according to the type of mutilation, but crayfish with more intact chelipeds were more aggressive, and males were more aggressive than females. These results indicate that cheliped mutilation may modify the average levels of personality traits associated with competition or self-defense. Our study provides insights into how morphological modifications may shape animal personalities in adulthood.

Accuracy, Repeatability, and Reproducibility of a Hand-Held Structured-Light 3D Scanner across Multi-Site Settings in Lower Limb Prosthetics

The aim of this work was to assess the accuracy, repeatability, and reproducibility of a hand-held, structured-light 3D scanner (EINScan Pro 2X Plus with High Definition Prime Pack, SHINING 3D Tech. Co., Ltd., Hangzhou, China), to support its potential use in multi-site settings on lower limb prosthetics. Four limb models with different shapes were fabricated and scanned with a metrological 3D scanner (EINScan Laser FreeScan 5X, SHINING 3D Tech. Co., Ltd., Hangzhou, China) by a professional operator (OP0). Limb models were then mailed to three sites where two operators (OP1, OP2) scanned them using their own structured-light 3D scanner (same model). OP1 scanned limb models twice (OP1-A, OP1-B). OP0, OP1-A, and OP2 scans were compared for accuracy, OP1-A and OP1-B for repeatability, and OP1-A and OP2 for reproducibility. Among all comparisons, the mean radial error was <0.25 mm, mean angular error was <4°, and root mean square error of the radial distance was <1 mm. Moreover, limits of agreement were <3.5% for perimeters and volumes. By comparing these results with respect to clinically-relevant thresholds and to the literature available on other 3D scanners, we conclude that the EINScan Pro 2X Plus 3D Scanner with High Definition Prime Pack has good accuracy, repeatability, and reproducibility, supporting its use in multi-site settings.

Quantitative analysis of liver standardized uptake value repeatability in SPECT/CT implications for clinical practice

Purpose. The aim of this study was to assess the repeatability of the SUV normalized by liver volume (SUVL) between two liver receptor SPECT/CT studies performed on different days in patients with ICG-R15 values within normal range.Methods. 935 patients who underwent liver receptor scintigraphy between January 2010 and August 2018 were included. Patients who underwent liver resection, hepatic arterial embolization or had ICG-R15 >10% between scans were excluded, and 38 patients were finally included in the analysis. The repeatability of SUVL between scans was assessed using the intraclass correlation coefficient (ICC) (1.1) between SUVLmax, SUVLpeak and SUVLmean at the first and second scan and the additive and proportional errors from the Bland-Altman analysis.Results. In ICC (1,1), SUVLmax, SUVLpeak and SUVLmean were all greater than 0.8, indicating almost perfect repeatability; neither additive nor proportional errors were observed in the Bland-Altman analysis.Conclusions. In patients with ICG-R15 values within the normal range, the SUV Liver (SUVL) between two liver receptor SPECT/CT studies performed on different days was repeatability over time. It was suggested that the SUVL of liver receptor scintigraphy could be an indicator that could be used for follow-up over time in the assessment of liver fibrosis.

Partitioning variance in a signaling trade-off under sexual selection reveals among-individual covariance in trait allocation

Understanding the evolution of traits subject to trade-offs is challenging because phenotypes can (co)vary at both the among- and within-individual levels. Among-individual covariation indicates consistent, possibly genetic, differences in how individuals resolve the trade-off, while within-individual covariation indicates trait plasticity. There is also the potential for consistent among-individual differences in behavioral plasticity, although this has rarely been investigated. We studied the sources of (co)variance in two characteristics of an acoustic advertisement signal that trade off with one another and are under sexual selection in the gray treefrog, Hyla chrysoscelis: call duration and call rate. We recorded males on multiple nights calling spontaneously and in response to playbacks simulating different competition levels. Call duration, call rate, and their product, call effort, were all repeatable both within and across social contexts. Call duration and call rate covaried negatively, and the largest covariance was at the among-individual level. There was extensive plasticity in calling with changes in social competition, and we found some evidence for among-individual variance in call rate plasticity. The significant negative among-individual covariance in trait values is perpendicular to the primary direction of sexual selection in this species, indicating potential limits on the response to selection.

Repeatability of Open-MOLLI: An open-source inversion recovery myocardial T1 mapping sequence for fast prototyping

PURPOSE

To develop an open-source prototype of myocardial T1 mapping (Open-MOLLI) to improve accessibility to cardiac T1 mapping and evaluate its repeatability. With Open-MOLLI, we aim to enable faster implementation and testing of sequence modifications and to facilitate inter-scanner and cross-vendor reproducibility studies.

METHODS

Open-MOLLI is an inversion-recovery sequence using a balanced SSFP (bSSFP) readout, with inversion and triggering schemes based on the 5(3)3 MOLLI sequence, developed in Pulseq. Open-MOLLI and MOLLI sequences were acquired in the ISMRM/NIST phantom and 21 healthy volunteers. In 18 of those subjects, Open-MOLLI and MOLLI were repeated in the same session (test-retest).

RESULTS

Phantom T1 values were comparable between methods, specifically for the vial with reference T1 value most similar to healthy myocardium T1 (T1vial3 = 1027 ms): T1MOLLI = 1011 ± 24 ms versus T1Open-MOLLI = 1009 ± 20 ms. In vivo T1 estimates were similar between Open-MOLLI and MOLLI (T1MOLLI = 1004 ± 33 ms vs. T1Open-MOLLI = 998 ± 52 ms), with a mean difference of -17 ms (p = 0.20), despite noisier Open-MOLLI weighted images and maps. Repeatability measures were slightly higher for Open-MOLLI (RCMOLLI = 3.0% vs. RCOpen-MOLLI = 4.4%).

CONCLUSION

The open-source sequence Open-MOLLI can be used for T1 mapping in vivo with similar mean T1 values to the MOLLI method. Open-MOLLI increases the accessibility to cardiac T1 mapping, providing also a base sequence to which further improvements can easily be added and tested.

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

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.

A Comparative Study of Three Systems for Liver Magnetic Resonance Elastography

BACKGROUND

Different MR elastography (MRE) systems may produce different stiffness measurements, making direct comparison difficult in multi-center investigations.

PURPOSE

To assess the repeatability and reproducibility of liver stiffness measured by three typical MRE systems.

STUDY TYPE

Prospective.

POPULATION/PHANTOMS

Thirty volunteers without liver disease history (20 males, aged 21-28)/5 gel phantoms.

FIELD STRENGTH/SEQUENCE

3.0 T United Imaging Healthcare (UIH), 1.5 T Siemens Healthcare, 3.0 T General Electric Healthcare (GE)/Echo planar imaging-based MRE sequence.

ASSESSMENT

Wave images of volunteers and phantoms were acquired by three MRE systems. Tissue stiffness was evaluated by two observers, while phantom stiffness was assessed automatically by code. The reproducibility across three MRE systems was quantified based on the mean stiffness of each volunteer and phantom.

STATISTICAL TESTS

Intraclass correlation coefficients (ICC), coefficients of variation (CV), and Bland-Altman analyses were used to assess the interobserver reproducibility, the interscan repeatability, and the intersystem reproducibility. Paired t-tests were performed to assess the interobserver and interscan variation. Friedman tests with Dunn's multiple comparison correction were performed to assess the intersystem variation. P values less than 0.05 indicated significant difference.

RESULTS

The reproducibility of stiffness measured by the two observers demonstrated consistency with ICC > 0.92, CV < 4.32%, Mean bias < 2.23%, and P > 0.06. The repeatability of measurements obtained using the electromagnetic system for the liver revealed ICC > 0.96, CV < 3.86%, Mean bias < 0.19%, P > 0.90. When considering the range of reproducibility across the three systems for liver evaluations, results ranged with ICCs from 0.70 to 0.87, CVs from 6.46% to 10.99%, and Mean biases between 1.89% and 6.30%. Phantom studies showed similar results. The values of measured stiffness differed across all three systems significantly.

DATA CONCLUSION

Liver stiffness values measured from different MRE systems can be different, but the measurements across the three MRE systems produced consistent results with excellent reproducibility.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

In-vivo repeatability of three intra-oral spectrophotometers

OBJECTIVE

The objective was to assess the repeatability of three spectrophotometers, based on the CIELCh factors and shadeguide reference measurements.

MATERIALS AND METHODS

Color analysis was performed using three devices: Rayplicker, Easyshade 4, and Easyshade V. Five repeated measures were performed by the same operator, on the right central maxillary incisor of 30 patients. The CIELCh factors were retrieved and the intra-class correlation was calculated. The Vita Classical and Vita 3D Master shadeguides were used to evaluate the respective Fleiss' Kappa factors.

RESULTS

Rayplicker and Easyshade V demonstrated strong intra-class correlation based on the CIELCh factors: 0.98, 0.99, and 0.91 for Rayplicker, and 0.95, 0.99, and 0.93 for Easyshade V, for the L*, C*, and h* parameters, respectively. Regarding the repeatability of the shadeguide data, while Easyshade 4 had the best repeatability when using the Vita Classical as a reference, Rayplicker and Easyshade V showed better repeatability when using the Vita 3D Master.

CONCLUSION

These findings suggest that both Rayplicker and Easyshade V are reliable devices for measuring CIELCh parameters. In terms of shadeguide references, the reliability of spectrophotometers is generally lower compared to the CIELCh measurements.

CLINICAL SIGNIFICANCE

Given their good repeatability, both the Rayplicker and the Easyshade V spectrophotometers are reliable tools for prosthetic dental practices.

Role of sureness in evaluating AI/CADx: Lesion-based repeatability of machine learning classification performance on breast MRI

BACKGROUND

Artificial intelligence/computer-aided diagnosis (AI/CADx) and its use of radiomics have shown potential in diagnosis and prognosis of breast cancer. Performance metrics such as the area under the receiver operating characteristic (ROC) curve (AUC) are frequently used as figures of merit for the evaluation of CADx. Methods for evaluating lesion-based measures of performance may enhance the assessment of AI/CADx pipelines, particularly in the situation of comparing performances by classifier.

PURPOSE

The purpose of this study was to investigate the use case of two standard classifiers to (1) compare overall classification performance of the classifiers in the task of distinguishing between benign and malignant breast lesions using radiomic features extracted from dynamic contrast-enhanced magnetic resonance (DCE-MR) images, (2) define a new repeatability metric (termed sureness), and (3) use sureness to examine if one classifier provides an advantage in AI diagnostic performance by lesion when using radiomic features.

METHODS

Images of 1052 breast lesions (201 benign, 851 cancers) had been retrospectively collected under HIPAA/IRB compliance. The lesions had been segmented automatically using a fuzzy c-means method and thirty-two radiomic features had been extracted. Classification was investigated for the task of malignant lesions (81% of the dataset) versus benign lesions (19%). Two classifiers (linear discriminant analysis, LDA and support vector machines, SVM) were trained and tested within 0.632 bootstrap analyses (2000 iterations). Whole-set classification performance was evaluated at two levels: (1) the 0.632+ bias-corrected area under the ROC curve (AUC) and (2) performance metric curves which give variability in operating sensitivity and specificity at a target operating point (95% target sensitivity). Sureness was defined as 1-95% confidence interval of the classifier output for each lesion for each classifier. Lesion-based repeatability was evaluated at two levels: (1) repeatability profiles, which represent the distribution of sureness across the decision threshold and (2) sureness of each lesion. The latter was used to identify lesions with better sureness with one classifier over another while maintaining lesion-based performance across the bootstrap iterations.

RESULTS

In classification performance assessment, the median and 95% CI of difference in AUC between the two classifiers did not show evidence of difference (ΔAUC = -0.003 [-0.031, 0.018]). Both classifiers achieved the target sensitivity. Sureness was more consistent across the classifier output range for the SVM classifier than the LDA classifier. The SVM resulted in a net gain of 33 benign lesions and 307 cancers with higher sureness and maintained lesion-based performance. However, with the LDA there was a notable percentage of benign lesions (42%) with better sureness but lower lesion-based performance.

CONCLUSIONS

When there is no evidence for difference in performance between classifiers using AUC or other performance summary measures, a lesion-based sureness metric may provide additional insight into AI pipeline design. These findings present and emphasize the utility of lesion-based repeatability via sureness in AI/CADx as a complementary enhancement to other evaluation measures.

Feasibility of dynamic T2 *-based oxygen-enhanced lung MRI at 3T

PURPOSE

To demonstrate proof-of-concept of a T2 *-sensitized oxygen-enhanced MRI (OE-MRI) method at 3T by assessing signal characteristics, repeatability, and reproducibility of dynamic lung OE-MRI metrics in healthy volunteers.

METHODS

We performed sequence-specific simulations for protocol optimisation and acquired free-breathing OE-MRI data from 16 healthy subjects using a dual-echo RF-spoiled gradient echo approach at 3T across two institutions. Non-linear registration and tissue density correction were applied. Derived metrics included percent signal enhancement (PSE), ∆R2 * and wash-in time normalized for breathing rate (τ-nBR). Inter-scanner reproducibility and intra-scanner repeatability were evaluated using intra-class correlation coefficient (ICC), repeatability coefficient, reproducibility coefficient, and Bland-Altman analysis.

RESULTS

Simulations and experimental data show negative contrast upon oxygen inhalation, due to substantial dominance of ∆R2 * at TE > 0.2 ms. Density correction improved signal fluctuations. Density-corrected mean PSE values, aligned with simulations, display TE-dependence, and an anterior-to-posterior PSE reduction trend at TE1 . ∆R2 * maps exhibit spatial heterogeneity in oxygen delivery, featuring anterior-to-posterior R2 * increase. Mean T2 * values across 32 scans were 0.68 and 0.62 ms for pre- and post-O2 inhalation, respectively. Excellent or good agreement emerged from all intra-, inter-scanner and inter-rater variability tests for PSE and ∆R2 *. However, ICC values for τ-nBR demonstrated limited agreement between repeated measures.

CONCLUSION

Our results demonstrate the feasibility of a T2 *-weighted method utilizing a dual-echo RF-spoiled gradient echo approach, simultaneously capturing PSE, ∆R2 * changes, and oxygen wash-in during free-breathing. The excellent or good repeatability and reproducibility on intra- and inter-scanner PSE and ∆R2 * suggest potential utility in multi-center clinical applications.

Independent component analysis (ICA) applied to dynamic oxygen-enhanced MRI (OE-MRI) for robust functional lung imaging at 3 T

PURPOSE

Dynamic lung oxygen-enhanced MRI (OE-MRI) is challenging due to the presence of confounding signals and poor signal-to-noise ratio, particularly at 3 T. We have created a robust pipeline utilizing independent component analysis (ICA) to automatically extract the oxygen-induced signal change from confounding factors to improve the accuracy and sensitivity of lung OE-MRI.

METHODS

Dynamic OE-MRI was performed on healthy participants using a dual-echo multi-slice spoiled gradient echo sequence at 3 T and cyclical gas delivery. ICA was applied to each echo within a thoracic mask. The ICA component relating to the oxygen-enhancement signal was automatically identified using correlation analysis. The oxygen-enhancement component was reconstructed, and the percentage signal enhancement (PSE) was calculated. The lung PSE of current smokers was compared with nonsmokers; scan-rescan repeatability, ICA pipeline repeatability, and reproducibility between two vendors were assessed.

RESULTS

ICA successfully extracted a consistent oxygen-enhancement component for all participants. Lung tissue and oxygenated blood displayed the opposite oxygen-induced signal enhancements. A significant difference in PSE was observed between the lungs of current smokers and nonsmokers. The scan-rescan repeatability and the ICA pipeline repeatability were good.

CONCLUSION

The developed pipeline demonstrated sensitivity to the signal enhancements of the lung tissue and oxygenated blood at 3 T. The difference in lung PSE between current smokers and nonsmokers indicates a likely sensitivity to lung function alterations that may be seen in mild pathology, supporting future use of our methods in patient studies.

Individual variation in thermally induced plasticity of metabolic rates: ecological and evolutionary implications for a warming world

Energy metabolism is a fundamental property of life providing the energy for all processes and functions within an organism. As it is temperature-dependent, it mediates the effects of changing climate on ectotherm fitness and population dynamics. Though resting metabolic rate is a highly labile trait, part of its variation is individually consistent. Recent findings show that resting metabolic rate contains consistent variation not only in the elevations (intercepts) but also in the slopes of individual thermal dependence curves, challenging the thermal dependence assumption for this trait in several ectotherm taxa. I argue that among-individual variation in thermal metabolic curves represents a previously undetected component of ectotherm response to climate change, potentially affecting their adaptive capacity and population resilience under increasing stochasticity of thermal environment. Future studies need to examine not only the amount of among-individual variation in thermal metabolic curves across phylogenetic contexts but also other aspects concerning its mechanisms and adaptive significance to improve predictions about the impact of climate change on ectotherm population dynamics. This article is part of the theme issue 'The evolutionary significance of variation in metabolic rates'.

Non-lethal sampling for assessment of mitochondrial function does not affect metabolic rate and swimming performance

A fundamental issue in the metabolic field is whether it is possible to understand underlying mechanisms that characterize individual variation. Whole-animal performance relies on mitochondrial function as it produces energy for cellular processes. However, our lack of longitudinal measures to evaluate how mitochondrial function can change within and among individuals and with environmental context makes it difficult to assess individual variation in mitochondrial traits. The aims of this study were to test the repeatability of muscle mitochondrial metabolism by performing two biopsies of red muscle, and to evaluate the effects of biopsies on whole-animal performance in goldfish Carassius auratus. Our results show that basal mitochondrial respiration and net phosphorylation efficiency are repeatable at 14-day intervals. We also show that swimming performance (optimal cost of transport and critical swimming speed) was repeatable in biopsied fish, whereas the repeatability of individual oxygen consumption (standard and maximal metabolic rates) seemed unstable over time. However, we noted that the means of individual and mitochondrial traits did not change over time in biopsied fish. This study shows that muscle biopsies allow the measurement of mitochondrial metabolism without sacrificing animals and that two muscle biopsies 14 days apart affect the intraspecific variation in fish performance without affecting average performance of individuals. This article is part of the theme issue 'The evolutionary significance of variation in metabolic rates'.

Multiparametric Quantitative MRI of Peripheral Nerves in the Leg: A Reliability Study

BACKGROUND

Patients with polyneuropathies typically have demyelination and/or axonal degeneration in peripheral nerves. Currently, there is a lack of imaging biomarkers to track the changes in these pathologies.

PURPOSE

To develop and evaluate the reliability of a multiparametric quantitative magnetic resonance imaging (qMRI) method of peripheral nerves in the leg.

STUDY TYPE

Prospective.

SUBJECTS

Seventeen healthy volunteers (36.2 ± 13.8 years old, 9 males) with 10 of them scanned twice for test-retest.

FIELD STRENGTH/SEQUENCE

3 T, three-dimensional gradient echo and diffusion tensor imaging.

ASSESSMENT

A qMRI protocol and processing pipeline was established for quantifying the following nerve parameters that are sensitive to myelin and axonal pathologies: magnetization transfer (MT) ratio (MTR), MT saturation index (MTsat), T2 *, T1 , proton density (PD), fractional anisotropy (FA), and mean/axial/radial diffusivities (MD, AD, and RD). The qMRI protocol also measures the volume of nerve fascicles (fVOL) and the fat fraction (FF) of muscles.

STATISTICAL TESTS

The intersession reproducibility and inter-rater reliability of each qMRI parameter were assessed by Bland-Altman analysis and intraclass correlation coefficient (ICC). Pairwise Pearson correlation analyses were performed to investigate the intrinsic association between qMRI parameters. Distal-to-proximal variations were evaluated by paired t-tests with Bonferroni-Holm multiple comparison corrections. P < 0.05 was considered statistically significant.

RESULTS

The MTR, MTsat, T2 *, T1 , PD, FA, AD, and fVOL of the sciatic and tibial nerves, and the FF of leg muscles, had an overall good-to-excellent test-retest agreement (ICC varying from 0.78 to 0.99). All the qMRI parameters had good-to-excellent inter-rater reliability (ICC > 0.80). The data demonstrated a pattern of distal-to-proximal changes of an increased nerve MTsat and FA, and a decreased nerve T1 , PD, MD, and RD, as well as a significantly increased muscle FF.

DATA CONCLUSION

The proposed multiparametric qMRI method of the peripheral nerves is highly reproducible and provided healthy control data which will be used in developing monitoring biomarkers in patients with polyneuropathies.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 2.

On the function of a female-like signal type in the vibrational repertoire of Enchenopa male treehoppers (Hemiptera: Membracidae)

Animals often mimic the behaviours or signals of conspecifics of the opposite sex while courting. We explored the potential functions of a novel female-like signal type in the courtship displays of male Enchenopa treehoppers. In these plant-feeding insects, males produce plant-borne vibrational advertisement signals, to which females respond with their own duetting signals. Males also produce a signal type that resembles the female duetting responses. We experimentally tested whether this signal modifies the behaviour of receivers. First, we tested whether the female-like signal would increase the likelihood of a female response. However, females were as likely to respond to playbacks with or without them. Second, we tested whether the female-like signal would inhibit competing males, but males were as likely to produce displays after playbacks with or without them. Hence, we found no evidence that this signal has an adaptive function, despite its presence in the courtship display, where sexual selection affects signal features. Given these findings, we also explored whether the behavioural and morphological factors of the males were associated with the production of the female-like signal. Males that produced this signal had higher signalling effort (longer and more frequent signals) than males that did not produce it, despite being in worse body condition. Lastly, most males were consistent over time in producing the female-like signal or not. These findings suggest that condition-dependent or motivational factors explain the presence of the female-like signal. Alternatively, this signal might not bear an adaptive function, and it could be a way for males to warm up or practice signalling, or even be a by-product of how signals are transmitted through the plant. We suggest further work that might explain our puzzling finding that a signal in the reproductive context might not have an adaptive function.

Repeatability of 18F-FDG uptake in metastatic bone lesions of breast cancer patients and implications for accrual to clinical trials

BACKGROUND

Standard measures of response such as Response Evaluation Criteria in Solid Tumors are ineffective for bone lesions, often making breast cancer patients with bone-dominant metastases ineligible for clinical trials with potentially helpful therapies. In this study we prospectively evaluated the test-retest uptake variability of 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) in a cohort of breast cancer patients with bone-dominant metastases to determine response criteria. The thresholds for 95% specificity of change versus no-change were then applied to a second cohort of breast cancer patients with bone-dominant metastases.In this study, nine patients with 38 bone lesions were imaged with 18F-FDG in the same calibrated scanner twice within 14 days. Tumor uptake was quantified as the maximum tumor voxel normalized by dose and body weight (SUVmax) and the mean of a 1-cc maximal uptake volume normalized by dose and lean-body-mass (SULpeak). The asymmetric repeatability coefficients with confidence intervals of SUVmax and SULpeak were used to determine limits of 18F-FDG uptake variability. A second cohort of 28 breast cancer patients with bone-dominant metastases that had 146 metastatic bone lesions was imaged with 18F-FDG before and after standard-of-care therapy for response assessment.

RESULTS

The mean relative difference of SUVmax in 38 bone tumors of the first cohort was 4.3%. The upper and lower asymmetric limits of the repeatability coefficient were 19.4% and -16.3%, respectively. The 18F-FDG repeatability coefficient confidence intervals resulted in the following patient stratification for the second patient cohort: 11-progressive disease, 5-stable disease, 7-partial response, and 1-complete response with three inevaluable patients. The asymmetric repeatability coefficients response criteria changed the status of 3 patients compared to standard the standard Positron Emission Tomography Response Criteria in Solid Tumors of ±30% SULpeak.

CONCLUSIONS

In evaluating bone tumor response for breast cancer patients with bone-dominant metastases using 18F-FDG uptake, the repeatability coefficients from test-retest studies show that reductions of more than 17% and increases of more than 20% are unlikely to be due to measurement variability. Serial 18F-FDG imaging in clinical trials investigating bone lesions from these patients, such as the ECOG-ACRIN EA1183 trial, benefit from confidence limits that allow interpretation of response.

Reliability and agreement of subjective and objective non-invasive break-up time measurements in contact lens wearers

PURPOSE

To assess the reliability and agreement of non-invasive break-up time (NIBUT) in symptomatic and asymptomatic contact lens (CL) wearers using automatic objective and conventional subjective techniques.

METHODS

In this prospective cross-sectional study, soft CL wearers, classified into symptomatic and asymptomatic based on the Contact Lens Dry Eye Questionnaire-8, underwent NIBUT assessment with the CL in situ. The CA-800 Corneal Analyzer and the EasyTear® VIEW+ Tearscope were used for objective and subjective evaluation, respectively. The within-subject repeatability and intraclass correlation coefficient (ICC) were calculated. The agreement between the devices was compared using the Bland-Altman method.

RESULTS

A total of 141 CL wearers (51 male and 90 female) with a mean age of 33.6 (SD = 12.2) years were included. The repeatability and ICC values obtained with the CA-800 device when measuring NIBUT were 5.4 s and 58.6% across the whole sample, 4.2 s and 48.8% for the asymptomatic group and 7.1 s and 68.4% for the symptomatic group. When using the subjective method (EasyTear®), the respective repeatability and ICC values were 7.3 s and 32.7% for the whole sample, 6.5 s and 30.4% for the asymptomatic group and 8.6 s and 35.9% for the symptomatic group. The CA-800 device provided significantly (p < 0.001) shorter NIBUT values compared with EasyTear® for the whole sample (3.3 [2.9] vs. 8.1 [3.4] s), the asymptomatic (3.3 [3.0] vs. 7.7 [3.6] s) and the symptomatic (3.8 [2.9] vs. 8.6 [3.0] s) groups.

CONCLUSION

Objective (CA-800) NIBUT assessment provides more reliable measurements than the conventional subjective technique using the EasyTear® device. However, CL practitioners should also be aware that the objective method indicates shorter NIBUT values. Symptomatic CL wearers may also need a higher number of NIBUT measurements to obtain reliable estimations.

Lung ultrasound score in dogs and cats: A reliability study

BACKGROUND

Lung ultrasound (LUS) is a noninvasive tool for examining respiratory distress patients. The lung ultrasound score (LUSS) can be used to quantify and monitor lung aeration loss with good reliability.

HYPOTHESIS/OBJECTIVES

Assess the reliability of a new LUSS among raters with different levels of experience and determine how well the same raters agree on identifying patterns of LUS abnormalities.

ANIMALS

Forty LUS examinations of dogs and cats and 320 videos were reviewed from a digital database.

METHODS

Retrospective reliability study with post hoc analysis. Protocolized LUS were randomly selected; intrarater and interrater reliability of the LUSS and pattern recognition agreement among 4 raters with different levels of experience in LUS were tested.

RESULTS

The intrarater intraclass correlation coefficient (ICC) single measurement, absolute agreement, and 2-way mixed effects model was 0.967 for the high-experience rater (H-Exp), 0.963 and 0.952 for the medium-experience raters (M-Exp-1; M-Exp-2), and 0.950 for the low-experience rater (L-Exp). The interrater ICC average measurement, absolute agreement, and 2-way random effects model among the observers was 0.980. The Fleiss' kappa (k) values showed almost perfect agreement (k = 1) among raters in identifying pleural effusion and translobar tissue-like pattern, strong agreement for A-lines (k = 0.881) and B-lines (k = 0.806), moderate agreement (k = 0.693) for subpleural loss of aeration, and weak agreement (k = 0.474) for irregularities of the pleural line.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our results indicate excellent intra- and interrater reliability for LUS scoring and pattern identification, providing a foundation for the use of the LUSS in emergency medicine and intensive care.

Agreement, repeatability, and reproducibility of quantitative retinal layer assessment using swept-source and spectral-domain optical coherence tomography in eyes with retinal diseases

Purpose

To evaluate the agreement and precision of retinal thickness measurements obtained using swept-source optical coherence tomography (SS-OCT) and spectral-domain OCT (SD-OCT) in healthy eyes and eyes with retinopathy.

Methods

This cross-sectional prospective study involved three DRI-OCT Triton (SS-OCT) and three 3D-OCT-1 Maestro (SD-OCT) devices. One of each device (Maestro and Triton) was paired with a single operator. Healthy subjects and patients with retinal diseases were recruited, with study eye and testing order randomized. At least 3 scans per eye were captured for wide scan (12 mm × 9 mm-Triton and Maestro) and macular cube scan (7 mm × 7 mm-Triton, 6 mm × 6 mm-Maestro). Thickness of the full retina, ganglion cell layer + inner plexiform layer (GCL+), and ganglion cell complex (GCL++) were obtained from wide scan and cube scans. Agreement of the measurements between the Triton and Maestro was evaluated by Bland-Altman analysis and Deming regression for each group. Repeatability and reproducibility were assessed using a two-way random effect analysis of variance (ANOVA) model for each parameter by group.

Results

Twenty-five healthy subjects (25 eyes) and 26 patients with retinal diseases (26 eyes), including, but not limited to, age-related macular degeneration, macular hole, and diabetic retinopathy were recruited. Overall, the measurement differences between Triton and Maestro were <6 μm (mean differences of full retina, GCL++, and GCL+ thickness were ≤5.5 μm, 1.3 μm, and 2.8 μm, respectively) and not statistically significant across the parameters. The repeatability and reproducibility estimates indicate high precision in both devices and groups. Across all the parameters, the repeatability limit was ≤7.6 μm for Triton and ≤12.7 μm for Maestro; reproducibility limit was ≤9.2 μm for Triton and ≤14.4 μm for Maestro. In eyes with retinal pathology, the repeatability coefficient of variation (CV)% was ≤2.6% for Triton and ≤3.4% for Maestro; reproducibility CV% was ≤3.3% for Triton and ≤3.5% for Maestro.

Conclusion

Both Triton SS-OCT and Maestro SD-OCT provide reliable measurements of retinal thickness in healthy eyes and eyes with retinal diseases. Excellent agreement between the two devices indicates interoperability when testing healthy eyes or eyes with retinal pathology. These findings support the use of thickness measurements from Triton SS-OCT and Maestro SD-OCT in clinical practice.

Repeatabilities of individual measures of feed intake and body weight on in-house commercial dairy cattle using a 3-dimensional camera system

In this study a 3-dimensional (3D) camera system was set up to measure individual feed intake of dairy cows in a commercial in-house setting. The system was developed to identify the cows while eating, predict body weight based on the curvature of the back of the cow, and quantify the amount of feed eaten by the cow at each visit of eating. The identification of the cow was based on recognizing the patterns, colors, and curvatures of the back from a reference database obtained in a corridor after milking, where images were taken of all cows with a simultaneous reading of the electronic ear tag. Body weight is predicted using the curvatures of the back of the cow. Feed intake is quantified as the difference in surface of the feed a cow can reach before and after a visit is initiated. This estimate is in liters but converted to kilograms, using the density of the feed in the specific herd. A total of 9,142 cows were measured in 19 herds across 3 breeds: Jersey (2,513 cows), Red Dairy Cattle (2,813 cows), and Holstein (3,816 cows). Mean daily feed intake was higher for Red Dairy Cattle (61.72 kg) and Holstein (64.59 kg) than for Jersey (55.74 kg). Repeatability estimates for daily feed intake as a weekly average was 0.62, 0.65, and 0.63 for Jersey, Red Dairy, and Holstein cattle, respectively. Mean body weight was higher for Red Dairy (647.9 kg) and Holstein (683.8 kg) than for Jersey (469.6 kg). Repeatability estimates for body weight as a weekly average was 0.83, 0.85, and 0.88 for Jersey, Red Dairy, and Holstein, respectively. The perspectives in having such records available is huge both for the farmer and for the dairy industry. The records can both be used for improving management in farms on an individual cow level and herd level, but also for genetic evaluation and selection as well as testing feeding regimens. Feed intake can be measured on an individual level using a 3D camera system.

Validity and reliability of self-reported and neural measures of listening effort

Listening effort can be defined as a measure of cognitive resources used by listeners to perform a listening task. Various methods have been proposed to measure this effort, yet their reliability remains unestablished, a crucial step before their application in research or clinical settings. This study encompassed 32 participants undertaking speech-in-noise tasks across two sessions, approximately a week apart. They listened to sentences and word lists at varying signal-to-noise ratios (SNRs) (-9, -6, -3 and 0 dB), then retaining them for roughly 3 s. We evaluated the test-retest reliability of self-reported effort ratings, theta (4-7 Hz) and alpha (8-13 Hz) oscillatory power, suggested previously as neural markers of listening effort. Additionally, we examined the reliability of correct word percentages. Both relative and absolute reliability were assessed using intraclass correlation coefficients (ICC) and Bland-Altman analysis. We also computed the standard error of measurement (SEM) and smallest detectable change (SDC). Our findings indicated heightened frontal midline theta power for word lists compared to sentences during the retention phase under high SNRs (0 dB, -3 dB), likely indicating a greater memory load for word lists. We observed SNR's impact on alpha power in the right central region during the listening phase and frontal theta power during the retention phase in sentences. Overall, the reliability analysis demonstrated satisfactory between-session variability for correct words and effort ratings. However, neural measures (frontal midline theta power and right central alpha power) displayed substantial variability, even though group-level outcomes appeared consistent across sessions.

Exploring behavioral traits over different contexts in four species of Australian funnel-web spiders

Australian funnel-web spiders are arguably the most venomous spiders in the world, with much research focusing on this aspect of their biology. However, other aspects related to their life history, ecology and behaviour have been overlooked. For the first time, we assessed repeatability, namely risk-taking behaviour, aggressiveness and activity in the contexts of predation, conspecific tolerance and exploration of a new territory in four species of Australian funnel-web spiders: two are closely related, Hadronyche valida and H. infensa, and two have overlapping distributions but occupy different habitats, H. cerberea and Atrax robustus. We also compared behaviors between species. At the species level, we found that H. valida showed consistency in risk-taking behavior when exposed to a predator stimulus, aggressiveness against conspecifics, and exploration of a new territory. In contrast, in the other species, only A. robustus showed repeatability in the context of exploration of a new territory. These results suggest that some behavioral traits are likely more flexible than others, and that the repeatability of behaviors may be species-specific in funnel-webs. When we compared species, we found differences in risk-taking behavior and defensiveness. This study provides novel insights to understanding variation in behavioral traits within and between species of funnel-web spiders, suggesting that some behavioral traits are likely context and/or species dependent, as a result of their evolutionary history. These findings provide key insights for understanding the ecological role of behavior and venom deployment in venomous animals, and a greater understanding of behavior in these medically significant and iconic spiders that are of conservation concern.

Determining the effects of elevated partial pressure of oxygen on hypercapnia-induced cerebrovascular reactivity

Evaluation of cerebrovascular reactivity (CVR) to hypo- and hypercapnia is a valuable test for the assessment of vasodilatory reserve. While hypercapnia-induced CVR testing is usually performed at normoxia, mild hyperoxia may increase tolerability of hypercapnia by reducing the ventilatory distress. However, the effects of mild hyperoxia on CVR was unknown. We therefore recruited 21 patients with a range of steno-occlusive diseases and 12 healthy participants who underwent a standardized 13-minute step plus ramp CVR test with a carbon dioxide gas challenge at the subject's resting end-tidal partial pressure of oxygen or at mild hyperoxia (PetO2 = 150 mmHg) depending on to which group they were assigned. In 11 patients, the second CVR test was at normoxia to examine test-retest differences. CVR was defined as % Δ Signal/ΔPetCO2. We found that there was no significant difference between CVR test results conducted at normoxia and at mild hyperoxia for participants in Groups 1 and 2 for the step and ramp portion. We also found no difference between test and retest CVR at normoxia for patients with cerebrovascular pathology (Group 3) for step and ramp portion. We concluded normoxic CVR is repeatable, and that mild hyperoxia does not affect CVR.

Regression models for partially localized fMRI connectivity analyses

Background

Brain functional connectivity analysis of resting-state functional magnetic resonance imaging (fMRI) data is typically performed in a standardized template space assuming consistency of connections across subjects. Analysis methods can come in the form of one-edge-at-a-time analyses or dimension reduction/decomposition methods. Common to these approaches is an assumption that brain regions are functionally aligned across subjects; however, it is known that this functional alignment assumption is often violated.

Methods

In this paper, we use subject-level regression models to explain intra-subject variability in connectivity. Covariates can include factors such as geographic distance between two pairs of brain regions, whether the two regions are symmetrically opposite (homotopic), and whether the two regions are members of the same functional network. Additionally, a covariate for each brain region can be included, to account for the possibility that some regions have consistently higher or lower connectivity. This style of analysis allows us to characterize the fraction of variation explained by each type of covariate. Additionally, comparisons across subjects can then be made using the fitted connectivity regression models, offering a more parsimonious alternative to edge-at-a-time approaches.

Results

We apply our approach to Human Connectome Project data on 268 regions of interest (ROIs), grouped into eight functional networks. We find that a high proportion of variation is explained by region covariates and network membership covariates, while geographic distance and homotopy have high relative importance after adjusting for the number of predictors. We also find that the degree of data repeatability using our connectivity regression model-which uses only partial location information about pairs of ROI's-is comparably as high as the repeatability obtained using full location information.

Discussion

While our analysis uses data that have been transformed into a common template-space, we also envision the method being useful in multi-atlas registration settings, where subject data remains in its own geometry and templates are warped instead. These results suggest the tantalizing possibility that fMRI connectivity analysis can be performed in subject-space, using less aggressive registration, such as simple affine transformations, multi-atlas subject-space registration, or perhaps even no registration whatsoever.

Repeatability of computed tomography liver radiomic features in a nonhuman primate model of diet-induced steatosis

Purpose

We describe a method to identify repeatable liver computed tomography (CT) radiomic features, suitable for detection of steatosis, in nonhuman primates. Criteria used for feature selection exclude nonrepeatable features and may be useful to improve the performance and robustness of radiomics-based predictive models.

Approach

Six crab-eating macaques were equally assigned to two experimental groups, fed regular chow or an atherogenic diet. High-resolution CT images were acquired over several days for each macaque. First-order and second-order radiomic features were extracted from six regions in the liver parenchyma, either with or without liver-to-spleen intensity normalization from images reconstructed using either a standard (B-filter) or a bone-enhanced (D-filter) kernel. Intrasubject repeatability of each feature was assessed using a paired t -test for all scans and the minimum p -value was identified for each macaque. Repeatable features were defined as having a minimum p -value among all macaques above the significance level after Bonferroni's correction. Features showing a significant difference with respect to diet group were identified using a two-sample t -test.

Results

A list of repeatable features was generated for each type of image. The largest number of repeatable features was achieved from spleen-normalized D-filtered images, which also produced the largest number of second-order radiomic features that were repeatable and different between diet groups.

Conclusions

Repeatability depends on reconstruction kernel and normalization. Features were quantified and ranked based on their repeatability. Features to be excluded for more robust models were identified. Features that were repeatable but different between diet groups were also identified.

Repeatability and heritability of inhibitory control performance in wild toutouwai (Petroica longipes)

Despite increasing interest in the evolution of inhibitory control, few studies have examined the validity of widespread testing paradigms, the long-term repeatability and the heritability of this cognitive ability in the wild. We investigated these aspects in the inhibitory control performance of wild toutouwai (North Island robin; Petroica longipes), using detour and reversal learning tasks. We assessed convergent validity by testing whether individual performance correlated across detour and reversal learning tasks. We then further evaluated task validity by examining whether individual performance was confounded by non-cognitive factors. We tested a subset of subjects twice in each task to estimate the repeatability of performance across a 1-year period. Finally, we used a population pedigree to estimate the heritability of task performance. Individual performance was unrelated across detour and reversal learning tasks, indicating that these measured different cognitive abilities. Task performance was not influenced by body condition, boldness or prior experience, and showed moderate between-year repeatability. Yet despite this individual consistency, we found no evidence that task performance was heritable. Our findings suggest that detour and reversal learning tasks measure consistent individual differences in distinct forms of inhibitory control in toutouwai, but this variation may be environmentally determined rather than genetic.

Time-specific convergence and divergence in individual differences in behavior: Theory, protocols and analyzes

Over the years, theoreticians and empiricists working in a wide range of disciplines, including physiology, ethology, psychology, and behavioral ecology, have suggested a variety of reasons why individual differences in behavior might change over time, such that different individuals become more similar (convergence) or less similar (divergence) to one another. Virtually none of these investigators have suggested that convergence or divergence will continue forever, instead proposing that these patterns will be restricted to particular periods over the course of a longer study. However, to date, few empiricists have documented time-specific convergence or divergence, in part because the experimental designs and statistical methods suitable for describing these patterns are not widely known. Here, we begin by reviewing an array of influential hypotheses that predict convergence or divergence in individual differences over timescales ranging from minutes to years, and that suggest how and why such patterns are likely to change over time (e.g., divergence followed by maintenance). Then, we describe experimental designs and statistical methods that can be used to determine if (and when) individual differences converged, diverged, or were maintained at the same level at specific periods during a longitudinal study. Finally, we describe why the concepts described herein help explain the discrepancy between what theoreticians and empiricists mean when they describe the "emergence" of individual differences or personality, how they might be used to study situations in which convergence and divergence patterns alternate over time, and how they might be used to study time-specific changes in other attributes of behavior, including individual differences in intraindividual variability (predictability), or genotypic differences in behavior.

Genetic aspects of Wood's lactation curve parameters in Jersey crossbred cattle using Bayesian approach

The study was undertaken to estimate the genetic parameters of lactation curve parameters of Wood's function in Jersey crossbred cattle using the Bayesian approach. Data on 33,906 fortnightly test day milk yields of 1,718 lactation records of Jersey crossbred cows, maintained at the ICAR-National Dairy Research Institute in West Bengal, were collected over a period of 40 years. The lactation curve parameters including 'a' (initial milk yield after calving), 'b' (ascending slope up to peak yield) and 'c' (descending slope after peak yield) and lactation curve traits, peak yield (ymax), time of peak yield (tmax) and persistency of milk yield (P) of individual cow for each lactation were estimated using the incomplete gamma function (Wood's model) by fitting the Gauss-Newton algorithm as an iteration method using PROC NLIN procedure of SAS 9.3. Variance components and genetic parameters of lactation curve parameters/traits were estimated by a repeatability animal model using the Bayesian approach. Estimates of heritabilities were found to be 0.18 ± 0.05, 0.09 ± 0.03 and 0.11 ± 0.04 for parameters 'a', 'b' and 'c', respectively and 0.24 ± 0.05, 0.12 ± 0.04, and 0.15 ± 0.05 for ymax, tmax and P, respectively. Repeatability estimates were 0.31 ± 0.03, 0.21 ± 0.04 and 0.30 ± 0.04 for parameters 'a', 'b' and 'c' respectively and 0.39 ± 0.03, 0.24 ± 0.03 and 0.37 ± 0.03 for ymax, tmax and p, respectively. Genetic correlations among lactation curve parameters/traits ranged from -0.75 to 0.95. Existence of genetic correlations among lactation curve parameters/traits indicated substantial genetic and physiological relationships among lactation curve parameters/traits of Jersey crossbred cattle.

Development of "personality" in the domestic cat: A longitudinal study

Although individual differences in the behavior of animals, sometimes referred to as personality, have recently received considerable attention, the development of such differences remains understudied. We previously found consistent individual differences in behavior in four tests simulating everyday contexts in 74 preweaning age kittens from 16 litters of the domestic cat. To study the development of consistent among-individual differences in four behavioral traits in cats, we followed a subset of these same individuals and repeated the same tests at 6 and 12 months of age. Some individual differences in behavior became increasingly repeatable with age due to a combination of decreased individual-level variance (canalization) and increased among-individual variance; these changes in variance and repeatability continued into adulthood (12 months). We did not observe behavioral syndromes at any age, in contrast to our previous reports in a different population of adult cats. The mechanisms that underlie increased repeatability with age and the possibility of personality structure differing between populations in this species remain to be studied.

Repeatability of Quantitative Knee Cartilage T1 , T2 , and T1ρ Mapping With 3D-MRI Fingerprinting

BACKGROUND

Three-dimensional MR fingerprinting (3D-MRF) techniques have been recently described for simultaneous multiparametric mapping of knee cartilage. However, investigation of repeatability remains limited.

PURPOSE

To assess the intra-day and inter-day repeatabilities of knee cartilage T1 , T2 , and T1ρ maps using a 3D-MRF sequence for simultaneous measurement.

STUDY TYPE

Prospective.

SUBJECTS

Fourteen healthy subjects (35.4 ± 9.3 years, eight males), scanned on Day 1 and Day 7.

FIELD STRENGTH/SEQUENCE

3 T/3D-MRF, T1 , T2 , and T1ρ maps.

ASSESSMENT

The acquisition of 3D-MRF cartilage (simultaneous acquisition of T1 , T2 , and T1ρ maps) were acquired using a dictionary pattern-matching approach. Conventional cartilage T1 , T2 , and T1ρ maps were acquired using variable flip angles and a modified 3D-Turbo-Flash sequence with different echo and spin-lock times, respectively, and were fitted using mono-exponential models. Each sequence was acquired on Day 1 and Day 7 with two scans on each day.

STATISTICAL TESTS

The mean and SD for cartilage T1 , T2 , and T1ρ were calculated in five manually segmented regions of interest (ROIs), including lateral femur, lateral tibia, medial femur, medial tibia, and patella cartilages. Intra-subject and inter-subject repeatabilities were assessed using coefficient of variation (CV) and intra-class correlation coefficient (ICC), respectively, on the same day and among different days. Regression and Bland-Altman analysis were performed to compare maps between the conventional and 3D-MRF sequences.

RESULTS

The CV in all ROIs was lower than 7.4%, 8.4%, and 7.5% and the ICC was higher than 0.56, 0.51, and 0.52 for cartilage T1 , T2 , and T1ρ , respectively. The MRF results had a good agreement with the conventional methods with a linear regression slope >0.61 and R2  > 0.59.

CONCLUSION

The 3D-MRF sequence had high intra-subject and inter-subject repeatabilities for simultaneously measuring knee cartilage T1 , T2 , and T1ρ with good agreement with conventional sequences.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 1.

The effect of gel pads on the measurement of breast superficial lesions by shear wave elastography

OBJECTIVE

This study aimed to compare the repeatability and diagnostic efficiency of shear wave elastography (SWE) while using coupling gel and gel pads in the diagnosis of superficial breast lesions.

METHODS

Two experienced sonographers, trained in SWE, used different methods to perform the maximum Young's modulus (Emax) measurement of the lesion while using coupling gel SWE and gel pad SWE at different time points. All 80 lesions were in the superficial layer of the breast. The interclass correlation coefficient (ICC) was calculated to evaluate the intraobserver and interobserver repeatability. Meanwhile, the receiver operating characteristic curve (ROC curve) was used to calculate the sensitivity, specificity and area under the curve of the two methods.

RESULTS

In the 80 breast lesions, the intraobserver and interobserver reproducibility of SWE measurements using coupling gel were considered good, and the ICCs were 0.728 (95% CI: 0.509-0.813) and 0.702 (95% CI: 0.492-0.795), respectively. The intraobserver and interobserver reproducibility of the SWE measured by the gel pad were also considered good, and the ICCs were 0.745 (95% CI: 0.501-0.801) and 0.713 (95% CI: 0.498-0.802), respectively. The sensitivity, specificity and area under the curve were 0.711 and 0.737, 0.929 and 0.905, and 0.873 and 0.878, respectively.

CONCLUSIONS

In the SWE measurement of superficial breast lesions, the use of a gel pad does not affect the repeatability and diagnostic efficiency of the measurement.

The Reliability of a Single-Trial Measurement of Maximal Accumulated Oxygen Deficit Determined via Perceptually-Regulated Exercise

Purpose: The aim of this study was to evaluate the reliability of a single-trial determination of maximal accumulated oxygen deficit (MAOD) achieved via the aid of perceptually-regulated incremental exercise. Methods: 14 trained male cyclists (age: 45 ± 8 yrs; height: 1.82 ± 0.06 m; mass: 79.7 ± 6.7 kg; V ˙ O 2 m a x : 4.09 ± 0.57 L·min-1) performed three trials of a submaximal incremental cycling test followed by a test to exhaustion at 116% of predicted V ˙ O 2 m a x . The intensity for each stage of the incremental test was regulated by participants to elicit perceived exertion levels of 9-15 on the Borg (6-20) scale. Linear regression was used to estimate V ˙ O 2 m a x at a perceived exertion level of 19. MAOD was calculated from the difference between predicted and actual oxygen demand in the test to exhaustion, reported in oxygen equivalents (O2 eq). A separate incremental test was used to measure V ˙ O 2 m a x directly. Results: Correlation coefficients between perceived exertion and V ˙ O 2 across trials were strong (r ≥0.99), and there were no between-trial differences in predicted V ˙ O 2 m a x (4.03 ± 1.04, 3.76 ± 0.53, and 3.69 ± 0.64 L·min-1, respectively; p = .142) or MAOD (2.75 ± 2.28, 2.50 ± 1.53, and 2.93 ± 1.40 L O2 eq, respectively; p = .633). Nevertheless, the coefficients of variation for predicted V ˙ O 2 m a x (14.2%) and MAOD (142.8%) were poor. Conclusions: The prediction of V ˙ O 2 m a x from perceptually-regulated exercise displays a level of test-retest reliability which prevents its use as a means of evaluating MAOD reliably in a single-trial.

Test-retest repeatability in macular retinal oximetry

CLINICAL RELEVANCE

Evaluation of retinal macular oxygen saturation in healthy controls can aid in understanding the pathological changes seen in similar locations of those with vascular diseases like diabetes.

BACKGROUND

The aim of this study was to determine the test-retest repeatability of localised retinal oximetry measurements in the macula on the Zilia Oximeter within healthy subjects of different races, 18-40 years old. Oxygen saturation was measured between three time points within the same locations of the right eye.

METHODS

Twenty seven subjects were included (aged 26.3 ± 3.6 years). All were confirmed to have healthy retinas and at least 6/9 vision. Oximetry measurements were taken using the Zilia to acquire local oxygen saturation measurements (300 µm diameter) at four points 3.1 degrees from the fovea in the superior/temporal, superior/nasal, inferior/temporal, and inferior/nasal locations. Oximetry measurements were taken twice on the same day 20 minutes apart and then again 1-2 weeks later. Oximetry data was analysed with intraclass correlation between visits. To assess intrasubject repeatability, the Bland-Altman repeatability coefficient and coefficient of variation were calculated.

RESULTS

Average Intraclass correlation for the three acquisition times of the right eye was 0.78. The averaged intrasubject repeatability coefficient for the three acquisition times was 8.4. The averaged coefficient of variation was 5.4%.

CONCLUSION

The Zilia oximeter has good macular test-retest repeatability; however, multiple measurements may be needed to ensure accuracy.

Sex-specific life-history strategies among immature jumping spiders: Differences in body parameters and behavior

Selection forces often generate sex-specific differences in various traits closely related to fitness. While in adult spiders (Araneae), sexes often differ in coloration, body size, antipredator, or foraging behavior, such sex-related differences are less pronounced among immatures. However, sex-specific life-history strategies may also be adaptive for immatures. Thus, we hypothesized that among spiders, immature individuals show different life-history strategies that are expressed as sex-specific differences in body parameters and behavioral features, and also in their relationships. We used immature individuals of a protandrous jumping spider, Carrhotus xanthogramma, and examined sex-related differences. The results showed that males have higher mass and larger prosoma than females. Males were more active and more risk tolerant than females. Male activity increased with time, and larger males tended to capture the prey faster than small ones, while females showed no such patterns. However, females reacted to the threatening abiotic stimuli more with the increasing number of test sessions. In both males and females, individuals with better body conditions tended to be more risk averse. Spiders showed no sex-specific differences in interindividual behavioral consistency and in intraindividual behavioral variation in the measured behavioral traits. Finally, we also found evidence for behavioral syndromes (i.e., correlation between different behaviors), where in males, only the activity correlated with the risk-taking behavior, but in females, all the measured behavioral traits were involved. The present study demonstrates that C. xanthogramma sexes follow different life-history strategies even before attaining maturity.

Robust quantification of CT-ventilation biomarker techniques and repeatability in a porcine model

BACKGROUND

Biomarkers estimating local lung ventilation have been derived from computed tomography (CT) imaging using various image acquisition and post-processing techniques. CT-ventilation biomarkers have potential clinical use in functional avoidance radiation therapy (RT), in which RT treatment plans are optimized to reduce dose delivered to highly ventilated lung. Widespread clinical implementation of CT-ventilation biomarkers necessitates understanding of biomarker repeatability. Performing imaging within a highly controlled experimental design enables quantification of error associated with remaining variables.

PURPOSE

To characterize CT-ventilation biomarker repeatability and dependence on image acquisition and post-processing methodology in anesthetized and mechanically ventilated pigs.

METHODS

Five mechanically ventilated Wisconsin Miniature Swine (WMS) received multiple consecutive four-dimensional CT (4DCT) and maximum inhale and exhale breath-hold CT (BH-CT) scans on five dates to generate CT-ventilation biomarkers. Breathing maneuvers were controlled with an average tidal volume difference <200 cc. As surrogates for ventilation, multiple local expansion ratios (LERs) were calculated from the acquired CT scans using Jacobian-based post-processing techniques.L E R 2 $LER_2$ measured local expansion between an image pair using either inhale and exhale BH-CT images or two 4DCT breathing phase images.L E R N $LER_N$ measured the maximum local expansion across the 4DCT breathing phase images. Breathing maneuver consistency, intra- and interday biomarker repeatability, image acquisition and post-processing technique dependence were quantitatively analyzed.

RESULTS

Biomarkers showed strong agreement with voxel-wise Spearman correlationρ > 0.9 $\rho > 0.9$ for intraday repeatability andρ > 0.8 $\rho > 0.8$ for all other comparisons, including between image acquisition techniques. Intra- and interday repeatability were significantly different (p < 0.01). LER2 and LERN post-processing did not significantly affect intraday repeatability.

CONCLUSIONS

4DCT and BH-CT ventilation biomarkers derived from consecutive scans show strong agreement in controlled experiments with nonhuman subjects.

Similarity in milk microbiota in replicates

Receiving the same results from repeated analysis of the same sample is a basic principle in science. The inability to reproduce previously published results has led to discussions of a reproducibility crisis within science. For studies of microbial communities, the problem of reproducibility is more pronounced and has, in some fields, led to a discussion on the very existence of a constantly present microbiota. In this study, DNA from 44 bovine milk samples were extracted twice and the V3-V4 region of the 16S rRNA gene was sequenced in two separate runs. The FASTQ files from the two data sets were run through the same bioinformatics pipeline using the same settings and results from the two data sets were compared. Milk samples collected maximally 2 h apart were used as replicates and permitted comparisons to be made within the same run. Results show a significant difference in species richness between the two sequencing runs although Shannon and Simpson's diversity was the same. Multivariate analyses of all samples demonstrate that the sequencing run was a driver for variation. Direct comparison of similarity between samples and sequencing run showed an average similarity of 42%-45% depending on whether binary or abundance-based similarity indices were used. Within-run comparisons of milk samples collected maximally 2 h apart showed an average similarity of 39%-47% depending on the similarity index used and that similarity differed significantly between runs. We conclude that repeated DNA extraction and sequencing significantly can affect the results of a low microbial biomass microbiota study.

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

Background

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.

Methods

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.

Results

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).

Conclusions

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.

Intrasexual aggression reduces mating success in field crickets

Aggressive behaviour is thought to have significant consequences for fitness, sexual selection and the evolution of social interactions, but studies measuring its expression across successive encounters-both intra- and intersexual-are limited. We used the field cricket Teleogryllus oceanicus to evaluate factors affecting repeatability of male aggression and its association with mating success. We quantified focal male aggression expressed towards partners and received from partners in three successive, paired trials, each involving a different male partner. We then measured a proxy of focal male fitness in mating trials with females. The likelihood and extent of aggressive behaviour varied across trials, but repeatability was negligible, and we found no evidence that patterns of focal aggression resulted from interacting partner identity or prior experience. Males who consistently experienced aggression in previous trials showed decreased male mating 'efficiency'-determined by the number of females a male encountered before successfully mating, but the effect was weak and we found no other evidence that intrasexual aggression was associated with later mating success. During mating trials, however, we observed unexpected male aggression towards females, and this was associated with markedly decreased male mating efficiency and success. Our findings suggest that nonadaptive aggressive spillover in intersexual mating contexts could be an important but underappreciated factor influencing the evolution of intrasexual aggression.

Magnetic Resonance Elastography-Based Technique to Assess the Biomechanics of the Skull-Brain Interface: Repeatability and Age-Sex Characteristics

Increasing concerns have been raised about the long-term negative effects of subconcussive repeated head impact (RHI). To elucidate RHI injury mechanisms, many efforts have studied how head impacts affect the skull-brain biomechanics and have found that mechanical interactions at the skull-brain interface dampen and isolate brain motions by decoupling the brain from the skull. Despite intense interest, in vivo quantification of the functional state of the skull-brain interface remains difficult. This study developed a magnetic resonance elastography (MRE) based technique to non-invasively assess skull-brain mechanical interactions (i.e., motion transmission and isolation function) under dynamic loading. The full MRE displacement data were separated into rigid body motion and wave motion. The rigid body motion was used to calculate the brain-to-skull rotational motion transmission ratio (Rtr) to quantify skull-brain motion transmissibility, and the wave motion was used to calculate the cortical normalized octahedral shear strain (NOSS) (calculated based on a partial derivative computing neural network) to evaluate the isolation capability of the skull-brain interface. Forty-seven healthy volunteers were recruited to investigate the effects of age/sex on Rtr and cortical NOSS, and 17 of 47 volunteers received multiple scans to test the repeatability of the proposed techniques under different strain conditions. The results showed that both Rtr and NOSS were robust to MRE driver variations and had good repeatability, with intraclass correlation coefficient (ICC) values between 0.68 and 0.97 (fair to excellent). No age or sex dependence were observed with Rtr, whereas a significant positive correlation between age and NOSS was found in the cerebrum, frontal, temporal, and parietal lobes (all p < 0.05), but not in the occipital lobe (p = 0.99). The greatest change in NOSS with age was found in the frontal lobe, one of the most frequent locations of traumatic brain injury (TBI). Except for the temporal lobe (p = 0.0087), there was no significant difference in NOSS between men and women. This work provides motivation for utilizing MRE as a non-invasive tool for quantifying the biomechanics of the skull-brain interface. It evaluated the age and sex dependence and may lead to a better understanding of the protective role and mechanisms of the skull-brain interface in RHI and TBI, as well as improve the accuracy of computational models in simulating the skull-brain interface.

Intraspecific variation in feeding and locomotor kinematics during prey capture in redbreast sunfish (Lepomis auritus)

Biomechanics research often revolves around understanding traits impacting suction feeding performance in fishes, using freshwater ray-finned sunfishes (Family Centrarchidae) as models. However, simultaneous feeding and locomotion kinematics during prey capture are not recorded for many species and there is less information on how these kinematics vary within a species and within individuals. To (1) add to existing data on the prey capture kinematics of centrarchids, (2) assess variation in a species both within and across individuals, and (3) compare morphology and prey capture kinematics of well-sampled centrarchids, we filmed five redbreast sunfish (Lepomis auritus) at 500 fps-1 approaching and striking non-evasive prey. Redbreast approach prey at ~30 cm s-1 and use approximately 70% of their maximum gape size. Traits related to feeding are more repeatable than traits related to locomotion. However, the Accuracy Index (AI) was consistent across individuals (AI = 0.76 ± 0.07). Functionally, redbreast sunfish are more similar to bluegill sunfish but morphologically they fall in the intermediate morphospace alongside green sunfish when compared with other centrarchids. These data show that whole organism outcomes (AI) are similar despite variation present both within and across individuals and demonstrate the importance of considering both interspecific and intraspecific differences in the functional diversity of ecologically and evolutionarily important behaviors such as prey capture.

Enhancing Genetic Gains in Grain Yield and Efficiency of Testing Sites of Early-Maturing Maize Hybrids under Contrasting Environments

The major challenges of maize production and productivity in Sub-Saharan Africa (SSA) include Striga hermonthica infestation, recurrent drought, and low soil nitrogen (low N). This study assessed the following: (i) accelerated genetic advancements in grain yield and other measured traits of early-maturing maize hybrids, (ii) ideal test environments for selecting early-maturing multiple-stress tolerant hybrids, and (iii) high-yielding and stable hybrids across multiple-stress and non-stress environments. Fifty-four hybrids developed during three periods of genetic enhancement (2008-2010, 2011-2013, and 2014-2016) were evaluated in Nigeria, The Republic of Benin, and Ghana under multiple stressors (Striga infestation, managed drought, and Low N) and non-stress environments from 2017 to 2019. Under multiple-stress and non-stress environments, annual genetic gains from selection in grain yield of 84.72 kg ha-1 (4.05%) and 61 kg ha-1 (1.56%), respectively, were recorded. Three mega-environments were identified across 14 stress environments. Abuja was identified as an ideal test environment for selecting superior hybrids. The hybrid TZdEI 352 × TZEI 355 developed during period 3 was the most outstanding under multiple-stress and non-stress environments. On-farm testing of this hybrid is required to verify its superior performance for commercialization in SSA. Considerable progress has been made in the genetic improvement of early-maturing maize hybrids for tolerance of multiple stressors and high yield. The identified core testing sites of this study could be used to enhance the testing and selection of promising hybrids.

Analytical Validation of an Immunohistochemical 7-Biomarker Prognostic Assay (immunoprint®) for Early-Stage Cutaneous Melanoma in Archival Tissue of Patients with AJCC v8 T2-T3 Disease

Selected patients with early-stage melanoma have a "hidden high risk" of poor oncologic outcomes. They might benefit from clinical trials, and ultimately, if warranted by trial results, judicious everyday use of adjuvant therapy. A promising tool to identify these individuals is the immunoprint® assay. This immunohistochemical 7-biomarker prognostic test was clinically validated in three independent cohorts (N = 762) to classify early-stage patients as high-risk or low-risk regarding melanoma recurrence and mortality. Using College of American Pathologists (CAP) recommendations, we analytically validated this assay in primary melanoma specimens (N = 20 patients). We assessed assay precision by determining consistency of risk classification under repeated identical conditions (repeatability) or across varying conditions (reproducibility), involving separate assay runs, operators (laboratory scientists), and/or observers (e.g., dermatopathologists). Reference classification was followed by five analytical validation phases: intra-run/intra-operator, intra-observer, inter-run, inter-operator, and inter-observer. Concordance of classifications in each phase was assessed via Fleiss' kappa (primary endpoint) and percent agreement (secondary endpoint). Seven-marker signature classification demonstrated high consistency across validation categories (Fleiss' kappa 0.864-1.000; overall percent agreement 95-100%), in 9/10 cases, exceeding, and in 1/10 cases, closely approaching, CAP's recommended 0.9 level. The 7-marker assay has now been verified to provide excellent repeatability, reproducibility, and precision, besides having been clinically validated.

Differences in Donor Animal Production Stage Affect Repeatability of In Vitro Rumen Fermentation Kinetics

In vitro gas production techniques (IVGPT) are widely used to screen feeds and feed additives to reduce the number of animals needed for experiments, which in turn, reduces costs and increases animal welfare. However, information about repeatability is scarce. The objective of this study was to evaluate the variation from in vitro gas production fermentations in the same laboratory using the same feed substrate. The source of rumen fluid used in the fermentations was from two different farms with either cannulated lactating dairy cows or cannulated fasting heifers, representing two distinct stages of production (donor types). Seventeen 24 h fermentations, undertaken during a year, were used to evaluate the variation between the following parameters: gas curve parameters, baseline-corrected total gas production (TGP (mL at Standard Temperature and Pressure (STP))/g incubated dry matter (DM)), methane concentration (%) and yield (mL gas at STP/g DM), pH and degraded dry matter (dDM). Significant differences between donor types were found for the pH of the rumen fluid from individual animals and pH of fermented fluid. However, no significant differences were observed within donor type. The means for methane concentration and yield, after 24 h of fermentation, were not significantly different between or within donor types. Rate of early gas production was significantly different between donor types, but baseline-corrected TGP was not significantly different at 24 h. No dDM differences after 24 h of fermentation between or within donor types were detected. Gas production curves were different between donor types, being either a monophasic version of the sigmoidal model or an exponential curve for the heifers and the production animals, respectively. No differences were observed within type. Repeatability of rumen fluid (CVRF), calculated as the coefficient of variation, and the associated parameters, which were investigated, was best for methane yield (CVRFALL = 0.3%) and least for TGP at 3 h (CVRFALL = 3%). Repeatability was dependent on donor type.

The utility of the reperfusion rate of tissue oxygen saturation as a measure of vascular endothelial function in adolescents: reliability, validity and sensitivity

Introduction: The near-infrared spectroscopy (NIRS)-derived reperfusion rate of tissue oxygen saturation (slope 2 StO2) may provide a surrogate measure of vascular function, however, this has yet to be examined in a paediatric population. This study investigated in adolescents: 1) the between-day reliability of NIRS-derived measurements; 2) the relationship between slope 2 StO2 and macro- (flow-mediated dilation, FMD) and microvascular (peak reactive hyperaemia, PRH) function; and 3) the effect of high-intensity interval exercise (HIIE) on slope 2 StO2, FMD, and PRH. Methods: Nineteen boys (13.3 ± 0.5 y) visited the laboratory on two occasions, separated by ∼ 1 week. On visit 1, participants underwent simultaneous assessment of brachial artery FMD and slope 2 StO2 and PRH on the internal face of the forearm. On visit 2, participants completed a bout of HIIE with slope 2 StO2, FMD and PRH measured pre-, immediately post- and 1.5 h post-exercise. Results: Slope 2 StO2 showed no mean bias (p = 0.18) and an intraclass correlation coefficient of 0.67 (p = 0.003) between visits. No significant correlation between slope 2 StO2 and FMD or PRH was observed on visit 1 (r = -0.04, p = 0.89 and r = -0.30, p = 0.23, respectively) or visit 2 pre-exercise (r = -0.28, p = 0.25 and r = -0.31, p = 0.20, respectively). Compared to pre-exercise, FMD decreased immediately post-exercise (p < 0.001) and then increased 1.5 h post-exercise (p < 0.001). No significant change was detected for slope 2 StO2 (p = 0.30) or PRH (p = 0.55) following HIIE. Conclusion: In adolescents, slope 2 StO2 can be measured reliably, however, it is not correlated with FMD or PRH and does not follow the acute time course of changes in FMD post-exercise. Hence, the use of slope 2 StO2 as a surrogate measure of vascular function in youth must be refuted.

Multisite MRI Intravoxel Incoherent Motion Repeatability and Reproducibility across 3 T Scanners in a Breast Diffusion Phantom: A BReast Intravoxel Incoherent Motion Multisite (BRIMM) Study

BACKGROUND

Monoexponential apparent diffusion coefficient (ADC) and biexponential intravoxel incoherent motion (IVIM) analysis of diffusion-weighted imaging is helpful in the characterization of breast tumors. However, repeatability/reproducibility studies across scanners and across sites are scarce.

PURPOSE

To evaluate the repeatability and reproducibility of ADC and IVIM parameters (tissue diffusivity (Dt ), perfusion fraction (Fp ) and pseudo-diffusion (Dp )) within and across sites employing MRI scanners from different vendors utilizing 16-channel breast array coils in a breast diffusion phantom.

STUDY TYPE

Phantom repeatability.

PHANTOM

A breast phantom containing tubes of different polyvinylpyrrolidone (PVP) concentrations, water, fat, and sponge flow chambers, together with an MR-compatible liquid crystal (LC) thermometer.

FIELD STRENGTH/SEQUENCE

Bipolar gradient twice-refocused spin echo sequence and monopolar gradient single spin echo sequence at 3 T.

ASSESSMENT

Studies were performed twice in each of two scanners, located at different sites, on each of 2 days, resulting in four studies per scanner. ADCs of the PVP and water were normalized to the vendor-provided calibrated values at the temperature indicated by the LC thermometer for repeatability/reproducibility comparisons.

STATISTICAL TESTS

ADC and IVIM repeatability and reproducibility within and across sites were estimated via the within-system coefficient of variation (wCV). Pearson correlation coefficient (r) was also computed between IVIM metrics and flow speed. A P value <0.05 was considered statistically significant.

RESULTS

ADC and Dt demonstrated excellent repeatability (<2%; <3%, respectively) and reproducibility (both <5%) at the two sites. Fp and Dp exhibited good repeatability (mean of two sites 3.67% and 5.59%, respectively) and moderate reproducibility (mean of two sites 15.96% and 13.3%, respectively). The mean intersite reproducibility (%) of Fp /Dp /Dt was 50.96/13.68/5.59, respectively. Fp and Dt demonstrated high correlations with flow speed while Dp showed lower correlations. Fp correlations with flow speed were significant at both sites.

DATA CONCLUSION

IVIM reproducibility results were promising and similar to ADC, particularly for Dt . The results were reproducible within both sites, and a progressive trend toward reproducibility across sites except for Fp .

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 1.

A Graphene-Coated Silicon Wafer Plate Improves the Sensitivity and Reproducibility of MALDI-TOF MS Analysis of Proteins

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used to analyze small and large molecules. However, proteins are difficult to analyze with MALDI-TOF MS in clinical applications because of their low ionization efficiency and heterogeneous crystallization with the matrix on the sample spots. Here, we investigate the potential of a customized graphene-coated silicon wafer (G/SiO2) plate for MALDI-TOF MS analysis of a clinically important protein, KPC-2, in comparison with a conventional stainless steel (SUS) plate. Our results demonstrate that the G/SiO2 plate outperforms the SUS plate in terms of sensitivity, reproducibility, and mass accuracy/precision across a wide range of molecular weights, even with highly complex samples. Furthermore, a five-day robustness test confirms the practical applicability of the G/SiO2 plate for the reliable identification of target protein(s) in MALDI-TOF MS analysis. Overall, our findings suggest that the use of the G/SiO2 plate holds great potential for improving the sensitivity and reproducibility of MALDI-TOF MS analysis for the identification of proteins, making it a promising tool for clinical applications.

Handedness and individual roll-angle specialism when plunge diving in the northern gannet

Many vertebrates show lateralized behaviour, or handedness, where an individual preferentially uses one side of the body more than the other. This is generally thought to be caused by brain lateralization and allows functional specializations such as sight, locomotion, and decision-making among other things. We deployed accelerometers on 51 northern gannets, Morus bassanus, to test for behavioural lateralization during plunge dives. When plunge diving, gannets 'roll' to one side, and standard indices indicated that 51% of individuals were left-sided, 43% right-sided, and 6% 'non-lateralized'. Lateralization indices provide no measure of error and do not account for environmental covariance, so we conducted two repeatability analyses on individuals' dive roll direction and angle. Dive side lateralization was highly repeatable among individuals over time at the population level (R = 0.878, p < 0.001). Furthermore, roll angle was also highly repeatable in individuals (R = 0.751, p < 0.001) even after controlling for lateralized state. Gannets show individual specializations in two different parts of the plunge diving process when attempting to catch prey. This is the first demonstration of lateralization during prey capture in a foraging seabird. It is also one of the few demonstrations of behavioural lateralization in a mixed model approach, providing a structure for further exploring behavioural lateralization.

Repeatability and reproducibility of comparison decisions by firearms examiners

In a comprehensive study to assess various aspects of the performance of qualified forensic firearms examiners, volunteer examiners compared both bullets and cartridge cases fired from three different types of firearms. They rendered opinions on each comparison according to the Association of Firearm & Tool Mark Examiners (AFTE) Range of Conclusions, as Identification, Inconclusive (A, B, or C), Elimination, or Unsuitable. In this part of the study, comparison sets used previously to characterize the overall accuracy of examiners were blindly resubmitted to examiners to assess the repeatability (105 examiners; 5700 comparisons of bullets and cartridge cases) and reproducibility (191 examiners of bullets, 193 of cartridge cases; 5790 comparisons) of firearms examinations. Data gathered using the prevailing AFTE Range were also recategorized into two hypothetical scoring systems. Consistently positive differences between observed agreement and expected agreement indicate that the repeatability and reproducibility of examiners exceed chance agreement. When averaged over bullets and cartridge cases, the repeatability of comparison decisions (involving all five levels of the AFTE Range) was 78.3% for known matches and 64.5% for known nonmatches. Similarly averaged reproducibility was 67.3%% for known matches and 36.5% for known nonmatches. For both repeatability and reproducibility, many of the observed disagreements were between a definitive and inconclusive category. Examiner decisions are reliable and trustworthy in the sense that identifications are unlikely when examiners are comparing non-matching items, and eliminations are unlikely when they are comparing matching items.