Airflow through the supraglottis during inspiration

Exercise-induced laryngeal obstruction is a paradoxical laryngeal closure during inspiration at high-intensity exercise, with supraglottic closure being most common. This study develops a model based on the computational fluid dynamics to investigate airflow velocity and pressure and the air-induced loads on the supraglottis at various inspiratory flow rates. It is found that at high flow rates, positive wall pressure is formed in the hypopharynx localise towards its lower region, while posterior supraglottic wall pressures shift from positive to negative. These findings suggest that high inspiratory flow rates may increase supraglottic pressure differentials, ultimately contributing in the collapse.

Design of an adaptive randomized clinical trial of intravenous citrulline for sickle cell pain crisis in the emergency department

Background

Vaso-occlusive pain crisis (VOC) is the most frequent cause for Emergency Department (ED) visits and hospital admissions for patients with sickle cell disease (SCD). Nitric oxide plays a critical role in the pathogenesis of vaso-occlusion. The amino acid, citrulline, is the main endothelial nitric oxide booster that offers the potential to ameliorate vaso-occlusion and decrease the risk of hospitalization.

Objective

In this two-part study, the goal of the first part is to determine the pharmacokinetic profile of intravenous (IV) l-citrulline and optimal dose for the second part of the study, which is to determine the efficacy and tolerability of the intervention in patients with SCD.

Design

A phase I/IIA open-label dose-finding study with subsequent double-blind, placebo-controlled, randomized Study of l-citrulline in children and adolescents with SCD presenting to the ED in VOC.

Methods

Part 1: Subjects experiencing VOC are enrolled in an open-label, ascending dose of IV l-citrulline to identify the optimum dose with endpoints of pharmacokinetic parameters, pain scores, reduction of opioid use, quality of life, proportion admitted to the hospital for treatment of pain, readmission rates, and assessment of adverse events. Part 2 of the trial is a double-blind, placebo-controlled adaptive "pick-the-winner" design to evaluate the efficacy and tolerability of IV l-citrulline in patients with SCD while receiving standard of care therapy for VOC.

Summary

This ED based sickle cell adaptive trial will determine the optimal dose for IV citrulline and whether the intervention improves outcome as a potential novel therapy for VOC in SCD.

Evaluation of 2 Novel Ratio-Based Metrics for Lumbar Spinal Stenosis

BACKGROUND AND PURPOSE

Quantitative metrics of the dural sac such as the cross-sectional area are commonly used to evaluate central canal stenosis. The aim of this study was to analyze 2 new metrics to measure spinal stenosis on the basis of the ratio between the dural sac and disc cross-sectional areas (DDRCA) and the dural sac and disc anterior-posterior diameters (DDRDIA) and compare them with established quantitative metrics of the dural sac.

MATERIALS AND METHODS

T2-weighted axial MR images (n = 260 patients) were retrospectively evaluated, graded for central canal stenosis as normal (no stenosis), mild, moderate, or severe from L1/L2 through L5/S1 with 1 grade per spinal level and annotated to measure the DDRCA and DDRDIA. Thresholds were obtained using a decision tree classifier on a subset of patients (n = 130) and evaluated on the remaining patients (n = 130) for accuracy and consistency across demographics, anatomic variation, and clinical outcomes.

RESULTS

DDRCA and DDRDIA had areas under the receiver operating characteristic curve of 98.6 (97.4-99.3) and 98.0 (96.7-98.9) compared with dural sac cross-sectional area at 96.5 (95.0-97.7) for binary classification. DDRDIA and DDRCA had κ scores of 0.75 (0.71-0.79) and 0.80 (0.75-0.83) compared with dural sac cross-sectional area at 0.62 (0.57-0.66) for multigrade classification. No significant differences (P > .1) in the area under the receiver operating characteristic curve were observed for the DDRDIA across variations in the body mass index. The DDRDIA also had the highest area under the receiver operating characteristic curve among symptomatic patients (visual analog scale ≥ 7) or patients who underwent surgery.

CONCLUSIONS

Ratio-based metrics (DDRDIA and DDRCA) are accurate and robust to anatomic and demographic variability compared with quantitative metrics of the dural sac and better correlated with symptomatology and surgical outcomes.

Structural correlation to ferroelectric order, non-Griffiths like phase and magnetocaloric effect in YbCrO4

We report a ferroelectric order around ∼99 K (T_FE), which is considerably above the long range ferrimagnetic order at 25 K (T_N). The value of saturation electric polarization is considerable as ∼570μC m^-2for a poling field of 5 kV cm^-1. The ferroelectric order is associated with a significant magnetoelectric coupling below ∼90 K. A weak signature ofT_FEis observed in the dielectric constant, which is associated with a linear magnetodielectric response at 18 K(<TN). A transition to a polar structure has been correlated with the occurrence of ferroelectric order. A non-Griffiths like phase is observed around ∼48 K, which is also linked with the structural distortion. A reasonable value of the magnetic entropy change of 5.07 J Kg^-1 K^-1is noted atT_Nfor a change in field of 50 kOe, which involves a strong magnetoelastic coupling. The results indicate considerable structural instabilities, which is linked with the observed multifunctional properties of YbCrO₄.

Amelioration of immune and digestive system through weed supplemented feed against Aeromonas hydrophila in Clarias gariepinus

Aquaculture is one of the important globally growing industries. It serves as an important food source of protein for human beings. With the expanding demand for the fish and their products it has become extremely important to improve the aquaculture practices. Aquaculture in India has witnessed huge mortalities caused by bacteria, viruses, fungi, nematodes etc. Aquatic weeds plants are harmful for aquaculture in many ways. Present study is aimed to overcome the disease caused by Aeromonas hydrophila (fish pathogenic bacteria) through feed supplementation of two aquatic weed plants (Azolla pinnata and Ceratophyllum demersum). The fish were divided into 6 groups: experimental groups (fish fed on supplementary feed at 5% and 2.5% concentration for individual plant and challenged with bacteria), positive control (fish fed on non-supplemented feed and challenged with bacteria) and negative control (fish fed on non-supplementary feed and not challenged with bacteria). It was observed that supplemented feed enhanced both cell mediated and humoral immunity in fish. Therefore, we advocate that feed formulated with incorporation of Azolla pinnata and Ceratophyllum demersum leaf powder at 5% and 2.5% could be used to prevent disease caused by A. hydrophila or can be used to enhance fish health by boosting its immune system. The results of this study also showed an improved digestibility in fish fed on supplemented feed.

Significant magneto-elastic coupling at Griffiths-like phase boundaries in low dimensional oxides,ASb2O6(ANi and Mn)

The compounds, NiSb₂O₆(NSO) and MnSb₂O₆(MSO) attract the community for the quasi one-dimensional and layered structure composed of Ni²⁺and Mn²⁺, which orders antiferromagnetically atT_N= 6.7 and 12 K, respectively. Here, we report the Griffiths-like phase much aboveT_Nin the range of 37-85 K and 25-80 K for NSO and MSO, respectively. The dc magnetization results indicate the Griffiths-like phase, following the modified Curie-Weiss law. The magneto-capacitive responses for both the compounds show anomalies at the onset of the Griffiths-like phase. Intriguingly, the low temperature synchrotron diffraction results are conclusive for determining the singularities for both the compounds. Interplay between the low-dimensionality, magnetic frustration, and magneto-elastic coupling correlates the observed short range ordered state, which is suggested as a Griffiths-like phase, aboveT_Nfor both the compounds.

Prevalence of early hip OA features on MRI in high-impact athletes. The femoroacetabular impingement and hip osteoarthritis cohort (FORCe) study

OBJECTIVE

To compare early hip osteoarthritis (OA) features on magnetic resonance imaging (MRI) in high-impact athletes with and without hip and/or groin pain, and to evaluate associations between early hip OA features, the International Hip Outcome Tool (iHOT33) and Copenhagen Hip and Groin Outcome Score (HAGOS).

DESIGN

This case-control study evaluated data of the femoroacetabular impingement and hip osteoarthritis cohort (FORCe). One hundred and eighty-two symptomatic (hip and/or groin pain >6 months and positive flexion-adduction-internal-rotation (FADIR) test) and 55 pain-free high-impact athletes (soccer or Australian football (AF)) without definite radiographic hip OA underwent hip MRI. The Scoring Hip Osteoarthritis with MRI (SHOMRI) method quantified and graded the severity of OA features. Each participant completed the iHOT33 and HAGOS.

RESULTS

Hip and/or groin pain was associated with higher total SHOMRI (0-96) (mean difference 1.4, 95% CI: 0.7-2.2), labral score (adjusted incidence rate ratio (aIRR) 1.33, 95% CI: 1.1-1.6). Differences in prevalence of cartilage defects, labral tears and paralabral cysts between symptomatic and pain-free participants were inconclusive. There was a lower prevalence of effusion-synovitis in symptomatic participants when compared to pain-free participants (adjusted odds ratio (aOR) 0.46 (95% CI: 0.3-0.8). Early hip OA features were not associated with iHOT33 or HAGOS.

CONCLUSIONS

A complex and poorly understood relationship exists between hip and/or groin pain and early hip OA features present on MRI in high-impact athletes without radiographic OA. Hip and/or groin pain was associated with higher SHOMRI and labral scores.

Preparation and Characterization of Nb-1Zr-0.1C Alloy Suitable for Liquid Metal Coolant Channels of High Temperature Reactors

A novel process comprising of aluminothermic coreduction of mixed oxides followed by arc and electron beam melt refining was developed for preparation of Nb-1Zr-0.1C alloy. The parameters of the process were optimized by considering the thermodynamic (heat) and mass balance phenomenon. The ingots of the homogenized alloy produced after electron beam melt consolidation were further extruded into tubes. The alloy was vacuum annealed at 1350–1800 °C to study the stability of Nb2C and Nb(Zr)C carbide precipitates in the microstructure. Compression creep tests conducted at 900 and 1000 °C revealed a stress exponent value of 2 and activation energy of 508 kJ/mol. NbSi2-based coatings were developed on the Nb-1Zr-0.1C alloy tubes using pack siliconizing process. The coated alloy was tested for oxidation at 1250 °C, and corrosion in liquid lead-bismuth eutectic (LBE) alloy at 875 °C for prolonged duration. The silicide-coated alloy showed superior oxidation and LBE corrosion resistance at high temperatures. The alloy was found to be a promising material for coolant channels of high temperature reactors.

Interplay between positive magnetoresistance and thermoelectric properties by tuning carrier concentration in Sb2-xSnxTe3(x⩽ 0.05) crystals

We report transport properties of Sb2-xSnxTe3(x⩽ 0.05) single crystals, where the tuning of the charge carrier densities via Sn doping significantly improves the magnetoresistance (MR) and the thermoelectric (TE) properties. The MR increases significantly at 2 K forx= 0.01, which reduces considerably with further Sn doping atx= 0.05. The MR results below 90 K forx= 0.01 satisfy the semi-classical two-band approach of Kohler's rule, which does not satisfy the MR results forx= 0.05. At 300 K, the Seebeck coefficient (S) is positive and small forx= 0.01 and it changes the sign with the further increase in Sn doping atx= 0.05 at 300 K. The value of |S| is considerable with an enhancement of the thermoelectric power factor compared to the value forx= 0.01 at 300 K. Analysis of the Hall conductivity indicates the interplay between carrier mobilities and densities, leading to the tuning of MR and TE properties with Sn doping. These results demonstrate that the p-type Sb2Te3becomes n-type with a suitable doping engineering.

Quantitative earthquake-like statistical properties of the flow of soft materials below yield stress

The flow behavior of soft materials below the yield stress can be rich and is not fully understood. Here, we report shear-stress-induced reorganization of three-dimensional solid-like soft materials formed by closely packed nematic domains of surfactant micelles and a repulsive Wigner glass formed by anisotropic clay nano-discs having ionic interactions. The creep response of both the systems below the yield stress results in angular velocity fluctuations of the shearing plate showing large temporal burst-like events that resemble seismic foreshocks-aftershocks data measuring the ground motion during earthquake avalanches. We find that the statistical properties of the quake events inside such a burst map on to the scaling relations for magnitude and frequency distribution of earthquakes, given by Gutenberg-Richter and Omori laws, and follow a power-law distribution of the inter-occurrence waiting time. In situ polarized optical microscopy reveals that during these events the system self-organizes to a much stronger solid-like state.

Diagnosing osteoarthritis from T2 maps using deep learning: an analysis of the entire Osteoarthritis Initiative baseline cohort

OBJECTIVE

We aim to study to what extent conventional and deep-learning-based T2 relaxometry patterns are able to distinguish between knees with and without radiographic osteoarthritis (OA).

METHODS

T2 relaxation time maps were analyzed for 4,384 subjects from the baseline Osteoarthritis Initiative (OAI) Dataset. Voxel Based Relaxometry (VBR) was used for automatic quantification and voxel-based analysis of the differences in T2 between subjects with and without radiographic OA. A Densely Connected Convolutional Neural Network (DenseNet) was trained to diagnose OA from T2 data. For comparison, more classical feature extraction techniques and shallow classifiers were used to benchmark the performance of our algorithm's results. Deep and shallow models were evaluated with and without the inclusion of risk factors. Sensitivity and Specificity values and McNemar test were used to compare the performance of the different classifiers.

RESULTS

The best shallow model was obtained when the first ten Principal Components, demographics and pain score were included as features (AUC = 77.77%, Sensitivity = 67.01%, Specificity = 71.79%). In comparison, DenseNet trained on raw T2 data obtained AUC = 83.44%, Sensitivity = 76.99%, Specificity = 77.94%. McNemar test on two misclassified proportions form the shallow and deep model showed that the boost in performance was statistically significant (McNemar's chi-squared = 10.33, degree of freedom (DF) = 1, P-value = 0.0013).

CONCLUSION

In this study, we presented a Magnetic Resonance Imaging (MRI)-based data-driven platform using T2 measurements to characterize radiographic OA. Our results showed that feature learning from T2 maps has potential in uncovering information that can potentially better diagnose OA than simple averages or linear patterns decomposition.

Towards prevention of post-traumatic osteoarthritis: report from an international expert working group on considerations for the design and conduct of interventional studies following acute knee injury

OBJECTIVE

There are few guidelines for clinical trials of interventions for prevention of post-traumatic osteoarthritis (PTOA), reflecting challenges in this area. An international multi-disciplinary expert group including patients was convened to generate points to consider for the design and conduct of interventional studies following acute knee injury.

DESIGN

An evidence review on acute knee injury interventional studies to prevent PTOA was presented to the group, alongside overviews of challenges in this area, including potential targets, biomarkers and imaging. Working groups considered pre-identified key areas: eligibility criteria and outcomes, biomarkers, injury definition and intervention timing including multi-modality interventions. Consensus agreement within the group on points to consider was generated and is reported here after iterative review by all contributors.

RESULTS

The evidence review identified 37 studies. Study duration and outcomes varied widely and 70% examined surgical interventions. Considerations were grouped into three areas: justification of inclusion criteria including the classification of injury and participant age (as people over 35 may have pre-existing OA); careful consideration in the selection and timing of outcomes or biomarkers; definition of the intervention(s)/comparator(s) and the appropriate time-window for intervention (considerations may be particular to intervention type). Areas for further research included demonstrating the utility of patient-reported outcomes, biomarkers and imaging outcomes from ancillary/cohort studies in this area, and development of surrogate clinical trial endpoints that shorten the duration of clinical trials and are acceptable to regulatory agencies.

CONCLUSIONS

These considerations represent the first international consensus on the conduct of interventional studies following acute knee joint trauma.

Metamagnetic transition and observation of spin-fluctuations in the antiferromagnetic Heusler compound Pd2MnIn

We report detailed investigations on the structural, magnetic, magneto-transport and calorimetric aspects of a partially ordered Heusler compound Pd₂MnIn. The sample shows antiferomagnetic (AFM) state below around 120 K, though positive paramagnetic Curie temperature signifies a complex magnetic ground state with the presence of both ferromagnetic (FM) and AFM correlations. A clear spin-flop type metamagnetic transition is observed as evident from the magnetization and resistivity data. However, non-saturation of magnetization even at 145 kOe of applied field implies that the high field state may be a spin canted state, originating from the enhanced FM correlations by field induced conduction electron spin polarization. The sample shows a profound quadratic temperature dependence of resistivity below about 20-25 K indicating a spin-fluctuation dominated low temperature region. Previous electronic structure calculations show the existence of a subtle balance between superexchange mediated AFM state and an RKKY (Ruderman-Kittel-Kasuya-Yoshida) interaction mediated FM state in Pd₂MnIn. Such competing AFM-FM correlations can be accounted for the observed spin fluctuations.

Mathematical structural descriptors and mutagenicity assessment: a study with congeneric and diverse datasets$

Quantitative bioactivity and toxicity assessment of chemical compounds plays a central role in drug discovery as it saves a substantial amount of resources. To this end, high-performance computing has enabled researchers and practitioners to leverage hundreds, or even thousands, of computed molecular descriptors for the activity prediction of candidate compounds. In this paper, we evaluate the utility of two large groups of chemical descriptors by such predictive modelling, as well as chemical structure discovery, through empirical analysis. We use a suite of commercially available and in-house software to calculate molecular descriptors for two sets of chemical mutagens - a homogeneous set of 95 amines, and a diverse set of 508 chemicals. Using calculated descriptors, we model the mutagenic activity of these compounds using a number of methods from the statistics and machine-learning literature, and use robust principal component analysis to investigate the low-dimensional subspaces that characterize these chemicals. Our results suggest that combining different sets of descriptors is likely to result in a better predictive model - but that depends on the compounds being modelled and the modelling technique being used.

Coexisting exchange bias effect and ferroelectricity in geometrically frustrated ZnCr2O4

Concomitant occurrence of exchange bias effect and ferroelectric order is revealed in antiferromagnetic spinel ZnCr₂O₄. The exchange bias effect is observed below antiferromagnetic Neél temperature (T _N) with a reasonable value of exchange bias field ([Formula: see text] Oe at 2 K). Intriguingly, the [Formula: see text] ratio is found unusually high as  ∼2.2, where H _C is the coercivity. This indicates that large H _C is not always primary for obtaining large exchange bias effect. Ferroelectric order is observed at T _N, where non-centrosymmetric magnetic structure with [Formula: see text] space group associated with the magnetoelectric coupling correlates the ferroelectric order, proposing that, ZnCr₂O₄ is an improper multiferroic material. Rare occurrence of exchange bias effect and ferroelectric order in ZnCr₂O₄ attracts the community for fundamental interest and draws special attention in designing new materials for possible electric field control of exchange bias effect.

Effect of dietary manipulation and vaccination of turkey breeder hens on immunoglobulin levels of yolk, yolk sac and neonate poults

Two hundred turkey breeder hens and 24 viable toms of 30-35 weeks age of small white variety were distributed into two treatment groups having four replicates of 25 hens and three toms in each treatment. First four replicates were offered a turkey breeder diet (Diet A) (Nutrient requirements of poultry, 1994, National Academic Press, Washington, DC) and the rest four replicates were maintained on a higher plane of nutrition (Diet B) for 8-week duration. After 6 weeks of experimental feeding, two replicates from each treatment groups were vaccinated with ND (R₂ B) vaccine. Yolk sac of embryo from birds fed Diet B had a significantly higher (p < .05) IgG, IgM level and HI titre (log 2) than those fed Diet A. HI titre values of embryonic yolk sac from the vaccinated birds fed Diet B were significantly higher (p < .05) than that of the control groups. In addition, HI titre values were significantly higher (p < .05) in the day-old poults of the birds fed Diet B than that of those fed Diet A. There was significantly (p < .01) positive correlation between serum IgG and IgM of the breeder birds and day-old chicks. Similarly, there was significantly (p < .05) positive correlation between yolk IgG and IgM after 1-month experimental feeding and yolk sac IgG and IgM. Positive correlation (p < .05) also existed between yolk sac IgM and day-old chick serum IgM. Furthermore, the HI titres of breeder birds' serum at 14 days post-vaccination were positively correlated with their egg yolk after 10 and 15 days post-vaccination, yolk sac and day-old chicks. Thus, the study envisaged that a higher immunity in neonate poults from turkey breeders maintained on a higher plane of nutrition may be elicited as there was maternal transfer of antibodies from the serum of breeder birds to their offsprings through their yolk sac.

Glassy magnetic ground state and Kondo-like behaviour in Mn10FeGe8 alloy

We report a detailed investigation of the ground-state magnetic properties of newly synthesized [Formula: see text] [Formula: see text] alloy. The sample can be thought of being derived by substituting one Mn atom by Fe of the parent compound [Formula: see text] [Formula: see text]. Fe-substitution leads to a drastic change in the magnetic ground state as well as to the magneto-transport properties of the parent alloy. On cooling below 250 K, [Formula: see text] [Formula: see text] undergoes a transition from paramagnetic phase to a state having significant ferromagnetic correlations. The ground state is found to be canonical spin glass (CSG) type in nature as evident from the dc magnetization and ac susceptibility measurements. Interestingly, the resistivity data shows an upturn at low temperature below about 30 K, mimicking Kondo-like behaviour. [Formula: see text] [Formula: see text] turns out to be a rare example among 3d transition metal alloys, where a Kondo-like state coexists within a CSG phase.

Mechanisms of photoinduced magnetization in Pr0.6Ca0.4MnO3 studied above and below charge-ordering transition temperature

We report the effect of photonic field on the electronic and magnetic structure of a low bandwidth manganite [Formula: see text] [Formula: see text]MnO₃ (PCMO) thin film. In particular, the present study confirmed a mechanism that was recently proposed to explain how optical excitation can bias or directly activate the metamagnetic transition associated with the colossal magnetoresistance (CMR) effect of PCMO. The transition is characterized by a shift in the dynamic equilibrium between ferromagnetic (FM) and antiferromagnetic clusters, explaining how it can be suddenly triggered by a sufficient external magnetic field. The film was always found to support some population of FM-clusters, the proportional size of which could be adjusted by the magnetic field and, especially in the vicinity of a thermomagnetic irreversibility, by optical excitation. The double exchange mechanism couples the magnetic degrees of freedom of manganites to their electronic structure, which is further coupled to the ion lattice via the Jahn-Teller mechanism. In accordance, it was found that producing optical phonons into the lattice could lower the free energy of the FM phase enough to significantly bias the CMR effect.

Thymic Atrophy: Experimental Studies and Therapeutic Interventions

The thymus is essential for T cell development and maturation. It is extremely sensitive to atrophy, wherein loss in cellularity of the thymus and/or disruption of the thymic architecture occur. This may lead to lower naïve T cell output and limited TCR diversity. Thymic atrophy is often associated with ageing. What is less appreciated is that proper functioning of the thymus is critical for reduction in morbidity and mortality associated with various clinical conditions including infections and transplantation. Therefore, therapeutic interventions which possess thymopoietic potential and lower thymic atrophy are required. These treatments enhance thymic output, which is a vital factor in generating favourable outcomes in clinical conditions. In this review, experimental studies on thymic atrophy in rodents and clinical cases where the thymus atrophies are discussed. In addition, mechanisms leading to thymic atrophy during ageing as well as during various stress conditions are reviewed. Therapies such as zinc supplementation, IL7 administration, leptin treatment, keratinocyte growth factor administration and sex steroid ablation during thymic atrophy involving experiments in animals and various clinical scenarios are reviewed. Interventions that have been used across different scenarios to reduce the extent of thymic atrophy and enhance its output are discussed. This review aims to speculate on the roles of combination therapies, which by acting additively or synergistically may further alleviate thymic atrophy and boost its function, thereby strengthening cellular T cell responses.

[18F]-Sodium Fluoride PET MR-Based Localization and Quantification of Bone Turnover as a Biomarker for Facet Joint-Induced Disability

Our aim was to prospectively evaluate the relationship between low back pain-related disability and quantitative measures from [¹⁸F]-sodium fluoride ([¹⁸F]-NaF) MR imaging. Six patients with facetogenic low back pain underwent dynamic [¹⁸F]-NaF PET/MR imaging. PET metrics were correlated with clinical measures and MR imaging grading of lumbar facet arthropathy. A significant positive correlation was observed between maximum facet joint uptake rate and clinical disability (P < .05). These data suggest that dynamic [¹⁸F]-NaF PET may serve as a useful biomarker for facetogenic disability.

The comparability of HR-pQCT bone measurements is improved by scanning anatomically standardized regions

We investigated the sensitivity of distal bone density, structure, and strength measurements by high-resolution peripheral quantitative computed tomography (HR-pQCT) to variability in limb length. Our results demonstrate that HR-pQCT should be performed at a standard %-of-total-limb-length to avoid substantial measurement bias in population study comparisons and the evaluation of individual skeletal status in a clinical context.

INTRODUCTION

High-resolution peripheral quantitative computed tomography (HR-pQCT) measures of bone do not account for anatomic variability in bone length: a 1-cm volume is acquired at a fixed offset from an anatomic landmark. Our goal was to evaluate HR-pQCT measurement variability introduced by imaging fixed vs. proportional volumes and to propose a standard protocol for relative anatomic positioning.

METHODS

Double-length (2-cm) scans were acquired in 30 adults. We compared measurements from 1-cm sub-volumes located at the default fixed offset, and the average %-of-length offset. The average position corresponded to 4.0% ± 1.1 mm for radius, and 7.2% ± 2.2 mm for tibia. We calculated the RMS difference in bone parameters and T-scores to determine the measurement variability related to differences in limb length. We used anthropometric ratios to estimate the mean limb length for published HR-pQCT reference data, and then calculated mean %-of-length offsets.

RESULTS

Variability between fixed vs. relative scan positions was highest in the radius, and for cortical bone in general (RMS difference Ct.Th = 19.5%), while individuals had T-score differentials as high as +3.0 SD (radius Ct.BMD). We estimated that average scan position for published HR-pQCT reference data corresponded to 4.0% at the radius, and 7.3% at tibia.

CONCLUSION

Variability in limb length introduces significant bias to HR-pQCT measures, confounding cross-sectional analyses and limiting the clinical application for individual assessment of skeletal status. We propose to standardize scan positioning using 4.0 and 7.3% of total bone length for the distal radius and tibia, respectively.

Cross-sectional and longitudinal study of the impact of posterior meniscus horn lesions on adjacent cartilage composition, patient-reported outcomes and gait biomechanics in subjects without radiographic osteoarthritis

OBJECTIVE

The aim of this study was to assess cross-sectional and longitudinal effects of meniscal lesions on adjacent cartilage T_1ρ and T₂ relaxation times, patient-reported outcomes and gait biomechanics.

DESIGN

Thirty patients with no cartilage morphological defects reported by Whole Organ MRI Score (WORMS) magnetic resonance imaging (MRI) grading and no radiographic osteoarthritis (OA) (Kellgren--Lawrence (KL) ≤ 1) were selected, 15 with posterior meniscus horn lesions and 15 matched controls without meniscal lesions. All were imaged on a 3T MR scanner for three consecutive years, except those who dropped from the study. Sagittal and frontal plane kinematic gait data were acquired at baseline. The Knee Injury and Osteoarthritis Outcome Score (KOOS) survey was taken each time. All images were automatically segmented and registered to an atlas for voxel-by-voxel cross-sectional and longitudinal analyses.

RESULTS

Relaxation time comparisons between groups showed elevated T_1ρ of the lateral tibia (LP) and elevated T₂ of the medial tibia (MT) and LT at 1 and 2 years in the lesion group. Longitudinal comparisons within each group revealed greater relaxation time elevations over one and 2 years in the group with lesions. KOOS Quality of Life (QOL) was significantly different between the groups at all time points (P < 0.05), as were other KOOS subcategories. No significant differences in the frontal or sagittal biomechanics were observed between the groups at baseline.

CONCLUSIONS

Individuals with healthy cartilage and posterior meniscal horn lesions have increased relaxation times when compared to matched controls, increased relaxation time changes over 2 years, and consistently report a lower KOOS QOL, yet show no difference in gait biomechanics.

Observation of ultrasharp metamagnetic jumps in polycrystalline Er2Cu2O5

The observation of ultrasharp metamagnetic jumps in the field variation of magnetization (M versus H) data for the highly insulating metal oxide Er₂Cu₂O₅ is investigated. The compound orders antiferromagnetically below about T _N1  =  28 K and shows conventional 'not-so-sharp' metamagnetism around 13 kOe on the field-increasing leg in the polycrystalline sample. The uniqueness of the ultrasharp jumps in Er₂Cu₂O₅ resides in the fact that they are only observed in the field-decreasing segment of the magnetization curve. We observe that the jumps are affected by the sweep rate of the magnetic field, similarly to several other systems that show such ultrasharp jumps. Er₂Cu₂O₅ shows a considerable amount of thermo-remanent magnetization when it is cooled in a field that is higher than the critical field of 13 kOe. Our analysis indicates that above 13 kOe the system remains phase separated, with the coexistence of antiferromagnetic and field-induced ferromagnetic-like phases. The jumps in the return leg occur because of the shear-dominated martensitic-like phase transition of the ferromagnetic-like phase to an antiferromagnetic phase, and interfacial strain plays a major role in the observed jumps.

Operator variability in scan positioning is a major component of HR-pQCT precision error and is reduced by standardized training

In this study, we determined that operator positioning precision contributes significant measurement error in high-resolution peripheral quantitative computed tomography (HR-pQCT). Moreover, we developed software to quantify intra- and inter-operator variability and demonstrated that standard positioning training (now available as a web-based application) can significantly reduce inter-operator variability.

INTRODUCTION

HR-pQCT is increasingly used to assess bone quality, fracture risk, and anti-fracture interventions. The contribution of the operator has not been adequately accounted in measurement precision. Operators acquire a 2D projection ("scout view image") and define the region to be scanned by positioning a "reference line" on a standard anatomical landmark. In this study, we (i) evaluated the contribution of positioning variability to in vivo measurement precision, (ii) measured intra- and inter-operator positioning variability, and (iii) tested if custom training software led to superior reproducibility in new operators compared to experienced operators.

METHODS

To evaluate the operator in vivo measurement precision, we compared precision errors calculated in 64 co-registered and non-co-registered scan-rescan images. To quantify operator variability, we developed software that simulates the positioning process of the scanner's software. Eight experienced operators positioned reference lines on scout view images designed to test intra- and inter-operator reproducibility. Finally, we developed modules for training and evaluation of reference line positioning. We enrolled six new operators to participate in a common training, followed by the same reproducibility experiments performed by the experienced group.

RESULTS

In vivo precision errors were up to threefold greater (Tt.BMD and Ct.Th) when variability in scan positioning was included. The inter-operator precision errors were significantly greater than the short-term intra-operator precision (p < 0.001). New trained operators achieved comparable intra-operator reproducibility to experienced operators and lower inter-operator reproducibility (p < 0.001). Precision errors were significantly greater for the radius than for the tibia.

CONCLUSION

Operator reference line positioning contributes significantly to in vivo measurement precision and is significantly greater for multi-operator datasets. Inter-operator variability can be significantly reduced using a systematic training platform, now available online ( http://webapps.radiology.ucsf.edu/refline/ ).

Associations between patellofemoral joint cartilage T1ρ and T2 and knee flexion moment and impulse during gait in individuals with and without patellofemoral joint osteoarthritis

OBJECTIVE

This study aimed to investigate the associations between patellofemoral cartilage T1ρ and T2 relaxation times and knee flexion moment (KFM) and KFM impulse during gait.

METHOD

Knee magnetic resonance (MR) images were obtained from 99 subjects with and without patellofemoral joint (PFJ) osteoarthritis (OA), using fast spin-echo, T1ρ and T2 relaxation time sequences. Patellar and trochlear cartilage relaxation times were computed for the whole cartilage, and superficial and deep layers (laminar analysis). Subjects also underwent three-dimensional (3D) gait analysis. Peak KFM and KFM impulse were calculated during the stance phase. Linear regressions were used to examine whether cartilage relaxation times were associated with knee kinetics during walking while adjusting age, sex, body mass index (BMI) and walking speed.

RESULTS

Higher peak KFM and KFM impulse were significantly related to higher T1ρ and T2 relaxation times of the trochlear and patellar cartilage, with standardized regression coefficients ranging from 0.21 to 0.28. Laminar analysis showed that overall the superficial layer of patellofemoral cartilage showed stronger associations with knee kinetics. Subgroup analysis revealed that in subjects with PFJ OA, every standard deviation change in knee kinetics was related to greater increases in PFJ cartilage T1ρ and T2 (standardized coefficients: 0.29 to 0.41). Conversely, in subjects without OA, weaker relationships were observed between knee kinetics and PFJ cartilage T1ρ and T2.

CONCLUSIONS

Our findings suggest that increased peak KFM and KFM impulse were related to worse cartilage health at the PFJ. This association is more prominent in superficial layer cartilage and cartilage with morphological lesions.