Novel quantification of the regional strain distribution in the anterior cruciate ligament in response to simulated loading using micro-CT imaging

Purpose A large percentage of anterior cruciate ligament (ACL) surgical reconstructions experience sub-optimal outcomes within 2 years. A potential factor contributing to poor outcomes is an incomplete understanding of micro-level, regional ACL biomechanics. This research aimed to demonstrate a minimally invasive method that uses micro-CT imaging to quantify regional ACL strains under clinically relevant joint loading. Methods A pattern of 0.8 mm diameter zirconium dioxide beads were arthroscopically inserted into four regions of the ACL of four cadaveric knee specimens (mean [SD] age = 59 [9] years). A custom micro-CT compatible joint motion simulator then applied clinically relevant joint loading conditions, while an image was acquired at each condition. From the resulting images, strains within each region were calculated using the centroid coordinates of each tissue-embedded bead. Strain repeatability was assessed using the mean intra-specimen standard deviation across repeated load applications. A one-way repeated measures ANOVA (α = 0.05) was used to determine regional strain variations. Results The mean intra-specimen standard deviation across repeated load application was ±0.003 strain for all specimens. No statistically significant differences were found between tissue regions, although medium and large effect sizes (0.095–0.450) suggest that these differences may be clinically relevant. Conclusions The method presented here demonstrates a minimally invasive measurement of regional ACL strain under clinically relevant joint loads using micro-CT imaging. The strain measurements demonstrated excellent reliability across the five repeated load applications and suggest a non-homogenous distribution of strain through the ACL.

FluidRock Interactions in a Paleo-Geothermal Reservoir (Noble Hills Granite, California, USA). Part 2: The Influence of Fracturing on Granite Alteration Processes and Fluid Circulation at Low to Moderate Regional Strain

Fracture connectivity within fractured granitic basement geothermal reservoirs is an important factor controlling their permeability. This study aims to improve the understanding of fluid–rock interaction processes at low to moderate regional strain. The Noble Hills range (Death Valley, CA, USA) was chosen as a naturally exhumed paleo geothermal reservoir. A series of petrographic, petrophysical, and geochemical investigations, combined with a fracture distribution analysis, were carried out on samples collected across fracture zones. Our results indicate that several generations of fluids have percolated through the reservoir. An increase of (1) the alteration degree; (2) the porosity values; and (3) the calcite content was observed when approaching fracture zones. No correlation was identified among the alteration degree, the porosity, or the calcite content. At a local scale, samples showed that the degree of alteration does not necessarily depend on the fracture density or on the amount of the strain. It is concluded that the combined influence of strain and coeval fluid–rock interaction processes drastically influence the petrophysical properties of fracture zones, which in turn impact geothermal production potential.

Speckle-Tracking Global Longitudinal and Regional Strain Analysis in Neonates with Coarctation of Aorta: A Case-Control Study

Our objectives are to compare speckle-tracking peak global longitudinal (pGLS) and regional strain values in neonates with coarctation of aorta (CoA) and control groups. Echocardiographic parameters measured by speckle-tracking were studied in a retrospective single-center study. A comparison of pGLS and segmental deformation between neonates with CoA and control group was performed using a three-way mixed ANOVA model. There was a significant difference in the means of segmental strain values between CoA and control group at the apical (p = 0.018) and basal segments (p = 0.031) of the interventricular septum and at the apical segment (p = 0.026) of the left ventricle (LV). After correcting for multiple comparisons, the results had a tendency toward statistical significance (adjusted-p < 0.10). There was significant difference in the mean values of pGLS [F(1, 39) = 7.61, p = 0.009, adjusted p = 0.018] between the studied groups. The results of ROC analysis showed that a cut-off value of −16.60% for pGLS provided an estimated sensitivity of 92.31% (95% CI: [63.97, 99.81]) and 71.43% specificity (95% CI: [51.33, 86.78]) for the diagnosis of CoA in neonates (AUC = 0.794, 95% CI: [0.66, 0.93]). pGLS can be regarded as a feasible and reproducible parameter reflecting LV dysfunction in newborns with CoA when compared to newborns with a false-positive diagnosis.

Two Mechanisms of Earthquake-Induced Hydrochemical Variations in an Observation Well

Due to frequent large earthquakes in the Lanping-Simao fault basin—located in China’s Yunnan Province—the Simao observation well has observed groundwater discharge, as well as Ca2+, Mg2+, and HCO3− concentrations every day between 2001–2018. Over 18 years of observations, M ≥ 5.6 earthquakes within a radius of 380 km from the well were seen to cause hydrochemical variations. In this study, we investigated CO2 release and groundwater mixing as possible causes of regional earthquake precursors, which were caused by the characteristics of the regional structure, lithology, water-rock reactions, and a GPS velocity field. Precursory signals due to CO2 injection are normally short-term changes that take two months. However, groundwater mixing linked to earthquakes was found to take, at the earliest, 15 months. The proportion of shallow water that contributes to mixing was found to significantly increase gradually with the stronger regional strain. These finding delineate the two mechanisms of earthquake-induced hydrochemical variations in an observation well, and would contribute to a better understanding of chemical changes before events in the Simao basin.

Dynamic relative regional strain visualized by electrical impedance tomography in patients suffering from COVID-19

Respiratory failure due to SARS-CoV-2 may progress rapidly. During the course of COVID-19, patients develop an increased respiratory drive, which may induce high mechanical strain a known risk factor for Patient Self-Inflicted Lung Injury (P-SILI). We developed a novel Electrical Impedance Tomography-based approach to visualize the Dynamic Relative Regional Strain (DRRS) in SARS-CoV-2 positive patients and compared these findings with measurements in lung healthy volunteers. DRRS was defined as the ratio of tidal impedance changes and end-expiratory lung impedance within each pixel of the lung region. DRRS values of the ten patients were considerably higher than those of the ten healthy volunteers. On repeated examination, patterns, magnitude and frequency distribution of DRRS were reproducible and in line with the clinical course of the patients. Lung ultrasound scores correlated with the number of pixels showing DRRS values above the derived threshold. Using Electrical Impedance Tomography we were able to generate, for the first time, images of DRRS which might indicate P-SILI in patients suffering from COVID-19.Trial Registration This observational study was registered 06.04.2020 in German Clinical Trials Register (DRKS00021276).

Post-COVID-19 syndrome: morpho-functional abnormalities of the heart and arrhythmias

Aim. To study the myocardial morpho-functional abnormalities, the incidence and nature of cardiac arrhythmias in patients 3 months after the coronavirus disease 2019 (COVID-19).Material and methods. The study included 77 patients (mean age, 35,9 years) treated for coronavirus infection, which underwent echocardiography and 24-hour Holter monitoring 3 months after COVID-19. The patients were divided into 3 groups: group 1 — 31 patients with upper respiratory tract involvement; group 2 — 27 patients with bilateral pneumonia (CT grade 1, 2), 3 — 19 patients with severe pneumonia (CT grade 3, 4). Statistical processing was carried out using Statistica 10.0.Results. According to echocardiography, the peak tricuspid late diastolic velocity and isovolumetric contraction time in all groups increased (P<0,001). The tricuspid and mitral Em/Am ratio decreased depending on the disease severity. In group 3, the right ventricular and atrial size increased (P<0,001). The pulmonary artery systolic pressure, left atrial volume in patients of the 2nd and 3rd groups was higher than in the control one (P<0,001). In group 1 and 2 patients, the regional strain in basal and basal/middle segments decreased, respectively, while, in group 3, not only regional but also global left ventricular (LV) strain decreased (P<0,001). In all groups, cardiac arrhythmias and pericardial effusion were found. The relationship was established between coronavirus activity and the structural and functional myocardial parameters (P<0,001).Conclusion. Cardiovascular injury 3 months after COVID-19 was found in 71%, 93%, and 95% of patients with mild, moderate and severe course. In mild course patients, a decrease in regional myocardial strain in LV basal segments, signs of past pericarditis, and various cardiac arrhythmias were noted. In patients of moderate severity, these changes were more pronounced and were accompanied by an additional decrease in regional strain in LV middle segments, impaired right ventricular diastole and increased pulmonary artery pressure. In severe patients, in addition to the above changes, dilatation of the right heart and inferior vena cava was recorded, as well as LV diastolic and global systolic function decreased.

Algorithmic Approaches in Diagnostic Decision Support for Combined Use of Speckle-Tracking Echocardiography and Coronary Angiography in Patients with Coronary Artery Disease

Background. Improving methods of coronary artery disease (CAD) diagnosis involves determining the most informative and less expensive methods. Speckle tracking echocardiography (STE) is now widely used for early myocardial ischemia diagnosis, allowing better verification of ambivalent results of coronary angiography (CAG). The aim. To develop algorithmic approaches to early CAD diagnosis through the combined use of STE and CAG in order to increase accuracy and reduce the cost of diagnosis and treatment of CAD. Methods. We examined 568 patients (425 [74.8%] men and 143 [25.2%] women) aged 62.3±8.9 years admitted to our center for diagnosis verification and establishing indications for coronary interventions. All the patients underwent CAG directly before or after STE. Results. Through both methods no pathology was detected in 5.2% of men and 16.8% of women. In 2.6% of men and 4.2% of women, STE found no regional strain disorders in the absence of significant alterations in coronary arteries (CA) according to CAG. Such false-positive STE results may witness of: 1) insignificant myocardial ischemia due to congenital distal coronary branches tortuosity or intramural (I/M) CA course, as well as myocardial ischemia due to microcirculation disorders not diagnosed by CAG; 2) non-coronary myocardial dysfunction. In 1.2% of men and 4.2% of women, CAG found significant or insignificant (up to 50–70%) atherosclerotic stenotic lesions in the absence of data suggestive of myocardial ischemia by longitudinal strain “drop” during STE. Such false-negative STE results may witness of high coronary reserve due to advanced collateral circulation in viable myocardium in ischemic coronary area. Myocardial ischemia according to both coronary beds visualization through CAG, as well as according to characteristic regional strain decrease revealed by STE, was found in 91.1% men and 74.8% women, witnessing of high correlation of the results obtained through both methods. Such results show coincidence of signs of hemodynamically significant CA stenoses according to both methods, including I/M CA segments course. Conclusions. Combination of CAG and STE in patients with CAD allows better determination of CA lesions hemodynamic significance, including I/M CA segments course, and to use STE as a non-invasive imaging technique in CAD, including pharmacological stress test. Combined CAG and STE use with integrated analysis thereof allows identification of coronary circulatory disorders that could not be detected separately, helping to increase diagnostic accuracy and to improve cost-effectiveness of diagnosis and treatment.

Tidal Calibration of Multicomponent Borehole Strainmeters and Validation of the Method Using Surface Waves

We conducted in-situ calibration of fifteen multicomponent borehole strainmeters deployed in and around the expected focal zones of the Nankai megathrust earthquake. The in-situ calibration method compares tidal strain observed by the borehole strainmeters with predicted tidal strains from the solid Earth’s tide and oceanic tidal loading. Then we obtained a calibration matrix to transfer observed strain data to the regional strain field. We estimated the oceanic tidal loading accurately using a Green’s function, which takes the depth of deployment into consideration. We calculated four sets of calibration matrices using combinations of any three of a group of four gauges as well as a calibration matrix using all four gauges. The estimated calibration matrix was validated by comparing observed seismic strain waves after applying the calibration matrix with theoretical seismic strain waves excited by the 2010 Chile earthquake (Mw 8.8). The in-situ calibration was found to be appropriate for all eleven Ishii-type borehole strainmeters and for one of the four Gladwin Tensor Strainmeters (GTSMs). It was also effective with respect to two shear strains for two of the other three GTSMs.

Multivendor comparison of global and regional 2D cardiovascular magnetic resonance feature tracking strains vs tissue tagging at 3T

Background Cardiovascular magnetic resonance (CMR) 2D feature tracking (FT) left ventricular (LV) myocardial strain has seen widespread use to characterize myocardial deformation. Yet, validation of CMR FT measurements remains scarce, particularly for regional strain. Therefore, we aimed to perform intervendor comparison of 3 different FT software against tagging. Methods In 61 subjects (18 healthy subjects, 18 patients with chronic myocardial infarction, 15 with dilated cardiomyopathy, and 10 with LV hypertrophy due to hypertrophic cardiomyopathy or aortic stenosis) were prospectively compared global (G) and regional transmural peak-systolic Lagrangian longitudinal (LS), circumferential (CS) and radial strains (RS) by 3 FT software (cvi42, Segment, and Tomtec) among each other and with tagging at 3T. We also evaluated the ability of regional LS, CS, and RS by different FT software vs tagging to identify late gadolinium enhancement (LGE) in the 18 infarct patients. Results GLS and GCS by all 3 software had an excellent agreement among each other (ICC = 0.94–0.98 for GLS and ICC = 0.96–0.98 for GCS respectively) and against tagging (ICC = 0.92–0.94 for GLS and ICC = 0.88–0.91 for GCS respectively), while GRS showed inconsistent agreement between vendors (ICC 0.10–0.81). For regional LS, the agreement was good (ICC = 0.68) between 2 vendors but less vs the 3rd (ICC 0.50–0.59) and moderate to poor (ICC 0.44–0.47) between all three FT software and tagging. Also, for regional CS agreement between 2 software was higher (ICC = 0.80) than against the 3rd (ICC = 0.58–0.60), and both better agreed with tagging (ICC = 0.70–0.72) than the 3rd (ICC = 0.57). Regional RS had more variation in the agreement between methods ranging from good (ICC = 0.75) to poor (ICC = 0.05). Finally, the accuracy of scar detection by regional strains differed among the 3 FT software. While the accuracy of regional LS was similar, CS by one software was less accurate (AUC 0.68) than tagging (AUC 0.80, p < 0.006) and RS less accurate (AUC 0.578) than the other two (AUC 0.76 and 0.73, p < 0.02) to discriminate segments with LGE. Conclusions We confirm good agreement of CMR FT and little intervendor difference for GLS and GCS evaluation, with variable agreement for GRS. For regional strain evaluation, intervendor difference was larger, especially for RS, and the diagnostic performance varied more substantially among different vendors for regional strain analysis.