T2 Relaxation Times Research Articles

Histological Findings and T2 Relaxation Time in Canine Menisci of Elderly Dogs—An Ex Vivo Study in Stifle Joints

Osteoarthritis is a chronic disease that often affects the canine stifle joint. Due to their biomechanical function, the menisci in the canine stifle play an important role in osteoarthritis. They compensate for the incongruence in the joint and distribute and minimize compressive loads, protecting the hyaline articular cartilage from damage. Meniscal degeneration favors the development and progression of stifle joint osteoarthritis. Qualitative magnetic resonance imaging (MRI) is the current golden standard for detecting meniscal changes, but it has limitations in detecting early signs of meniscal degeneration. A quantitative MRI offers new options for detecting early structural changes. T2 mapping can especially visualize structural changes such as altered collagen structures and water content, as well as deviations in proteoglycan content. This study evaluated T2 mapping and performed a histological scoring of menisci in elderly dogs that had no or only low radiographic osteoarthritis grades. A total of 16 stifles from 8 older dogs of different sex and breed underwent ex vivo magnet resonance imaging, including a T2 mapping pulse sequence with multiple echoes. A histological analysis of corresponding menisci was performed using a modified scoring system. The mean T2 relaxation time was 18.2 ms and the mean histological score was 4.25. Descriptive statistics did not reveal a correlation between T2 relaxation time and histological score. Ex vivo T2 mapping of canine menisci did not demonstrate histological changes, suggesting that early meniscal degeneration can be present in the absence of radiological signs of osteoarthritis, including no significant changes in T2 relaxation time.

Arthroscopic surgery for symptomatic discoid lateral meniscus improves meniscal status assessed by magnetic resonance imaging T2 mapping.

Discoid lateral meniscus (DLM) is an anatomic knee variant associated with increased tears and degeneration. This study aimed to quantify meniscal status with magnetic resonance imaging (MRI) T2 mapping before and after arthroscopic reshaping surgery for DLM. We retrospectively reviewed the records of patients undergoing arthroscopic reshaping surgery for symptomatic DLM with ≥ 2-year follow-up. MRI T2 mapping was performed preoperatively and at 12 and 24months postoperatively. T2 relaxation times of the anterior and posterior horns of both menisci and of the adjacent cartilage were assessed. Thirty-six knees from 32 patients were included. The mean age at surgery was 13.7years (range 7-24), and the mean follow-up duration was 31.0months. Saucerization alone was performed on five knees and saucerization with repair on 31 knees. Preoperatively, the T2 relaxation time of the anterior horn of the lateral meniscus was significantly longer than that of the medial meniscus (P < 0.01). T2 relaxation time significantly decreased at 12 and 24months postoperatively (P < 0.01). Assessments of the posterior horn were comparable. The T2 relaxation time was significantly longer in the tear versus non-tear side at each time point (P < 0.01). There were significant correlations between the T2 relaxation time of the meniscus and that of the corresponding area of the lateral femoral condyle cartilage (anterior horn: r = 0.504, P = 0.002; posterior horn: r = 0.365, P = 0.029). The T2 relaxation time of symptomatic DLM was significantly longer than that of the medial meniscus preoperatively, and it decreased 24months after arthroscopic reshaping surgery. The meniscal T2 relaxation time of the tear side was significantly longer than that of the non-tear side. There were significant correlations between the cartilage and meniscal T2 relaxation times at 24months after surgery.

Silicone-based materials with tailored MR relaxation characteristics for use in reduced coil visibility and in tissue-mimicking phantom design.

The development of materials with tailored signal intensity in MR imaging is critically important both for the reduction of signal from non-tissue hardware, as well as for the construction of tissue-mimicking phantoms. Silicone-based phantoms are becoming more popular due to their structural stability, stretchability, longer shelf life, and ease of handling, as well as for their application in dynamic imaging of physiology in motion. Moreover, silicone can be also used for the design of stretchable receive radio-frequency (RF) coils. Fabrication of materials with tailored signal intensity for MRI requires knowledge of precise T1 and T2 relaxation times of the materials used. In order to increase the range of possible relaxation times, silicone materials can be doped with gadolinium (Gd). In this work, we aim to systematically evaluate relaxation properties of Gd-doped silicone material at a broad range of Gd concentrations and at three clinically relevant magnetic field strengths (1.5 T, 3 T, and 7 T). We apply the findings for rendering silicone substrates of stretchable receive RF coils less visible in MRI. Moreover, we demonstrate early stage proof-of-concept applicability in tissue-mimicking phantom development. Ten samples of pure and Gd-doped Ecoflex silicone polymer samples were prepared with various Gd volume ratios ranging from 1:5000 to 1:10, and studied using 1.5T and 3T clinical and 7T preclinical scanners. T1 and T2 relaxation times of each sample were derived by fitting the data to Bloch signal intensity equations. A receive coil made from Gd-doped Ecoflex silicone polymer was fabricated and evaluated in vitro at 3T. With the addition of a Gd-based contrast agent, it is possible to significantly change T2 relaxation times of Ecoflex silicone polymer (from 213ms to 20ms at 1.5T; from 135ms to 17ms at 3T; and from 111.4ms to 17.2ms at 7T). T1 relaxation time is less affected by the introduction of the contrast agent (changes from 608ms to 579ms; from 802.5ms to 713ms at 3T; from 1276ms to 979ms at 7T). First results also indicate that liver, pancreas, and white matter tissues can potentially be closely mimicked using this phantom preparation technique. Gd-doping reduces the appearance of the silicone-based coil substrate during the MR scan by up to 81%. Gd-based contrast agents can be effectively used to create Ecoflex silicone polymer-based phantoms with tailored T2 relaxation properties. The relative low cost, ease of preparation, stretchability, mechanical stability, and long shelf life of Ecoflex silicone polymer all make it a good candidate for "MR invisible" coil development and bears promise for tissue-mimicking phantom development applicability.

Application of Multiparameter Quantitative Magnetic Resonance Imaging in the Evaluation of Graves' Ophthalmopathy.

Assessment of the activity of Graves' ophthalmopathy (GO) is difficult. Existing methods need improvement. Investigate the application of multiparametric magnetic resonance imaging (MRI) in GO. Retrospective. A total of 235 GO patients (age: 38.8± 13.4 years; 90 male; 96 active patients). Short-tau inversion recovery (STIR) fast spin echo, multiecho spin echo T2 mapping and 3D T1-weighted fast field echo sequences at 3.0 T. Two physicians assessed the mean and maximum signal intensity ratio of extraocular muscles to white matter (SIR), T2 relaxation time (T2RT), extraocular muscle area (EMA), fat fraction (FF), retrobulbar fat volume (RFV), and extraocular muscle volume (EMV). Clinical activity score (CAS)≧3 was in active stage. The optimal cut-off point of diagnostic efficacy was selected using receiver operating characteristic (ROC) curve analysis and evaluated using area under the curve (AUC), compared using Student's t test, analysis of variance or Kruskal-Wallis H test. The correlation used Pearson correlation analysis. The discriminant equation used a binary logistic regression analysis. P < 0.05 was considered statistically significant. The SIRmean, SIRmax, T2RTmean, T2RTmax, EMA, and EMV in active GO patients were significantly higher than those in inactive and were positively correlated with CAS (r=0.276, 0.228, 0.438, 0.388, 0.502, and 0333, respectively). The FFmax of active patients was significantly lower than that of inactive patients and was negatively correlated with CAS (r=-0.44). Logistic regression analysis indicated that T2RTmean was independently associated with GO active periods and had good diagnostic performance (area under ROC curve=0.736, sensitivity 70.7%, specificity 69.3%). T2RTmean≧74.295 could be a diagnostic cut-off for judging GO activity (sensitivity 55.3%). SIR, T2RT, EMV, and FF can quantitatively assess the activity and severity of GO and can potentially provide a basis for clinical judgment and selection of treatment options. 4. Stage 2.

Diffusion of surfactant from a micellar solution to a bare interface. 1. Absorbing boundary

We analyze dynamic adsorption of surfactant from a micellar solution to a rapidly created surface that acts as an absorbing boundary for surfactant monomers (single molecules), along which the monomer concentration vanishes, with no direct micelle adsorption. This somewhat idealized situation is analyzed as a prototype for situations in which strong suppression of monomer concentration accelerates micelle dissociation, and will be used as a starting point for analysis of more realistic boundary conditions in subsequent work. We present scaling arguments and approximate models for particular time and parameter regimes and compare the resulting predictions to numerical simulations of the reaction–diffusion equations for a polydisperse system containing surfactant monomers and clusters of arbitrary aggregation number. The model considered here exhibits an initial period of rapid shrinkage and ultimate dissociation of micelles within a narrow region near the interface. This opens a micelle-free region near the interface after some time τe, the width of which increases as t1/2 at times t≫τe. In systems that exhibit disparate fast and slow bulk relaxation times τ1 and τ2 in response to small perturbations, τe is usually comparable to or greater than τ1 but much less than τ2. Such systems exhibit a wide intermediate time regime τe<t<τ2 in which the remaining micellar region reaches a state of partial local equilibrium, followed by a final stage t≫τ2 in which full local equilibrium is established.

Effects of Citrus Fiber on the Gel Properties of Mutton Myofibrillar Protein

This work investigated the effects of different additions of water-soluble citrus fiber (SCF) and water-insoluble citrus fiber (ICF) on the gel properties of the mutton myofibrillar protein (MP). The key parameters of water-holding capacity (WHC), rheological properties, and microstructure were evaluated. The addition of 2.5-10% of SCF and ICF significantly improved (p < 0.05) the WHC and gel strength of mutton MP gel. The rheological results showed that the viscoelasticity of MP with 5% SCF was the best, and the T2 relaxation time of the gel was significantly shortened. SEM results showed SCF reduced the number of pores in the MP gel, forming a more compact network structure. ICF stabilized the MP gel network structure as a filler after water absorption and expansion. However, the gel lost moisture under the action of strong external force (freeze-drying), which left large pores. These data confirmed that SCF and ICF could effectively improve the gel properties of meat products.

Creating Solid Solutions of Metallocenes: Migration of Nickelocene into the Ferrocene Crystal Lattice in the Absence of a Solvent

Ferrocene and nickelocene do not react with each other in solution; however, the large impact of the paramagnetic component on the ferrocene 1H NMR signal linewidth and relaxation times has been quantified. Co-crystallization of ferrocene and nickelocene at any ratio from a solvent can be explained with both pure substances crystallizing in the same space group P21/n. As a new phenomenon, when a ferrocene single crystal is exposed to polycrystalline nickelocene in the absence of a solvent, the nickelocene migrates into the ferrocene crystal lattice and a mixed crystal is formed that retains its macroscopic shape. This process has been proven visually by cutting the single crystal. Mixing polycrystalline ferrocene with polycrystalline nickelocene at different molar ratios with a mortar and pestle leads to crystalline solid solutions with the corresponding molar ratios of both components. This migration of one organometallic component into an existing crystal lattice of another at ambient temperature in the absence of a solvent has not been described previously. Paramagnetic 1H solid-state NMR spectroscopy of static and rotating samples of dry ferrocene/nickelocene mixtures at varying ratios is used to prove and quantify the mixing of both metallocenes at the molecular level. A single-crystal X-ray structure of a 50/50 mixed crystal corroborates the NMR results that nickelocene and ferrocene are randomly distributed in the lattice and that the space group P21/n is retained. All ferrocene molecules in the mixed crystal lattice show a broadening of their 1H wideline signals and residual magic-angle spinning (MAS) lines at ambient temperature. The broadening of the ferrocene signals correlates with the nickelocene content. 1H T1 relaxation time measurements for the signals of ferrocene in samples with different amounts of nickelocene corroborate the assumption that the signal broadening is due to paramagnetic dipole–dipole relaxation of ferrocene molecules in the vicinity of nickelocene. Spatially separated ferrocene and nickelocene powders in one rotor show the solid-state NMR characteristics of the individual polycrystalline metallocenes. The described formation of solid solutions of metallocenes in the absence of a solvent will open new pathways to homogeneously mixed nanoparticles with desired metal ratios and dual-atom catalysts.

Experimental study on the effects of an electric field on the pore characterization in anode, middle and cathode regions of tight sandstone samples

Electric field stimulation is more favour for the enhancement of oil recovery from tight sandstones compared to conventional resources, since electroosmotic flow of fluids in smaller pores is stronger. However, the question concerning the character of electric field on the pore structure of tight sandstones (PSTS) remains open, especially the effects in three treated regions: the anode (A), middle (M), and cathode (C) regions. Therefore, in this study, for the first time, several techniques including nuclear magnetic resonance (NMR), high-pressure mercury intrusion (HPMI), and low-temperature nitrogen adsorption (LNA), were combined to explore this topic. First, the T2 relaxation time distribution was converted to the pore size distribution (PSD) through a power-law relation. After that, the changes in the PSTS before and after applying an electric field in the three treated regions were analyzed. The differences in the anode and cathode regions occur in the changes in pore types and pore volume. The reason for this difference is attributed to the effect of electrophoresis and the motion of polar water molecules. Apart from the effect of the dissolution of clay minerals due to the presence of hydrogen ions, the negatively charged particles move to the anode region to fill the pore space, consequently decreasing the number of micropores there. However, the escape of polar water molecules from the anode region increases the number of nanopores in the anode region. This study offers useful information concerning the application of electric fields, which could help electric field-related technologies greatly improve the oil recovery of unconventional resources.

Estimating the asymptotic characteristic time scales for diffusion-controlled drug release systems using partially sampled data

Drug release experiments and numerical simulations only give access to partial release data (i.e., within a finite time range t∈[0,tf]). In this article, we propose fitting-based procedures to estimate the asymptotic time scales of the release process, namely the global relaxation time τ∗ and the longest (or terminal) relaxation time τ0, from partially sampled data of diffusion-controlled drug release systems. We test these procedures on both synthetic and experimental data using, as an example, the well-known Weibull function. Our results show that the Weibull function must be used with great care because the values of the fitting parameters can vary significantly depending on the ratio tf/τ0. Beyond their practical simplicity, the usefulness of our procedures is evidenced by the fact that: (1) the initial loading profile does not need to be known and (2) the chosen fitting function does not require any physical basis. These two advantages allow us to determine the diffusion coefficient of the molecules directly from the characteristic time τ0.

Developing a medical device-grade T2 phantom optimized for myocardial T2 mapping by cardiovascular magnetic resonance

IntroductionA long T2 relaxation time can reflect oedema, and myocardial inflammation when combined with increased plasma troponin levels. Cardiovascular magnetic resonance (CMR) T2 mapping therefore has potential to provide a key diagnostic and prognostic biomarkers. However, T2 varies by scanner, software, and sequence, highlighting the need for standardization and for a quality assurance system for T2 mapping in CMR. AimTo fabricate and assess a phantom dedicated to the quality assurance of T2 mapping in CMR. MethodA T2 mapping phantom was manufactured to contain 9 T1 and T2 (T1|T2) tubes to mimic clinically relevant native and post-contrast T2 in myocardium across the health to inflammation spectrum (i.e., 43–74 ms) and across both field strengths (1.5 and 3 T). We evaluated the phantom's structural integrity, B0 and B1 uniformity using field maps, and temperature dependence. Baseline reference T1|T2 were measured using inversion recovery gradient echo and single-echo spin echo (SE) sequences respectively, both with long repetition times (10 s). Long-term reproducibility of T1|T2 was determined by repeated T1|T2 mapping of the phantom at baseline and at 12 months. ResultsThe phantom embodies 9 internal agarose-containing T1|T2 tubes doped with nickel di-chloride (NiCl2) as the paramagnetic relaxation modifier to cover the clinically relevant spectrum of myocardial T2. The tubes are surrounded by an agarose-gel matrix which is doped with NiCl2 and packed with high-density polyethylene (HDPE) beads. All tubes at both field strengths, showed measurement errors up to ≤ 7.2 ms [< 14.7%] for estimated T2 by balanced steady-state free precession T2 mapping compared to reference SE T2 with the exception of the post-contrast tube of ultra-low T1 where the deviance was up to 16 ms [40.0%]. At 12 months, the phantom remained free of air bubbles, susceptibility, and off-resonance artifacts. The inclusion of HDPE beads effectively flattened the B0 and B1 magnetic fields in the imaged slice. Independent temperature dependency experiments over the 13–38 °C range confirmed the greater stability of shorter vs longer T1|T2 tubes. Excellent long-term (12-month) reproducibility of measured T1|T2 was demonstrated across both field strengths (all coefficients of variation < 1.38%). ConclusionThe T2 mapping phantom demonstrates excellent structural integrity, B0 and B1 uniformity, and reproducibility of its internal tube T1|T2 out to 1 year. This device may now be mass-produced to support the quality assurance of T2 mapping in CMR.

Reference ranges of myocardial T1 and T2 mapping in healthy Chinese adults: a multicenter 3T cardiovascular magnetic resonance study

BackgroundAlthough reference ranges of T1 and T2 mapping are well established for cardiovascular magnetic resonance (CMR) at 1.5T, data for 3T are still lacking. The objective of this study is to establish reference ranges of myocardial T1 and T2 based on a large multicenter cohort of healthy Chinese adults at 3T CMR. MethodsA total of 1015 healthy Chinese adults (515 men, age range: 19–87 years) from 11 medical centers who underwent CMR using 3T Siemens scanners were prospectively enrolled. T1 mapping was performed with a motion-corrected modified Look–Locker inversion recovery sequence using a 5(3)3 scheme. T2 mapping images were acquired using T2-prepared fast low-angle shot sequence. T1 and T2 relaxation times were quantified for each slice and each myocardial segment. The T1 mapping and extracellular volume standardization (T1MES) phantom was used for quality assurance at each center prior to subject scanning. ResultsThe phantom analysis showed strong consistency of spin echo, T1 mapping, and T2 mapping among centers. In the entire cohort, global T1 and T2 reference values were 1193 ± 34 ms and 36 ± 2.5 ms. Global T1 and T2 values were higher in females than in males (T1: 1211 ± 29 ms vs. 1176 ± 30 ms, p < 0.001; T2: 37 ± 2.3 ms vs. 35 ± 2.5 ms, p < 0.001). There were statistical differences in global T2 across age groups (p < 0.001), but not in global T1. Linear regression showed no correlation between age and global T1 or T2 values. In males, positive correlation was found between heart rate and global T1 (r = 0.479, p < 0.001). ConclusionsUsing phantom-validated imaging sequences, we provide reference ranges for myocardial T1 and T2 values on 3T scanners in healthy Chinese adults, which can be applied across participating sites.Trial registration URL: http://www.chictr.org.cn/index.aspx. Unique identifier: ChiCTR1900025518. Registration name: 3T magnetic resonance myocardial quantitative imaging standardization and reference value study: a multi-center clinical study.

Effect of Organic Acids on CO2 Trapping in Carbonate Geological Formations: Pore-Scale Observations Using NMR

Stearic acid is an example of a carboxylic compound naturally present in geological formations (deep saline aquifers and depleted hydrocarbon reservoirs), which renders the rock hydrophobic (CO2-wet) over a geological time scale. Such hydrophobic surfaces are detrimental to residual CO2 trapping. There is, however, a lack of comprehensive dataset about how traces of these organic molecules affect the rock′s CO2 wettability and residual CO2 trapping. We, thus, used in situ NMR T1–T2 2D images to visualize fluid configurations in the pore network and used T1/T2 ratios to assess the microscopic wettability of the rock to pore space fluids subsequent to each process step. The T2 relaxation time was measured to demonstrate displacement processes and evaluate the trapping behavior at the pore scale, which is closely correlated to reservoir-scale flow functions. The trapping in the CO2-wet sample (14%) was significantly lower than that of the analogous water-wet sample (18%). This reduction in CO2 trapping is due to surface macroscopic flow layers acting as conduits allowing slow desaturation of CO2. Importantly, in the CO2-wet sample, trapping predominately occurred in meso- and micropores, whereas trapping in the analogous water-wet rock primarily occurred in macropores. This work thus provides a comprehensive dataset on the impact of organic acids on residual trapping at the pore scale, which ultimately helps to advance industrial-scale implementation of CGS and EOR project schemes in carbonate reservoirs.

Fast calibration of magnetic field coils in miniaturized NMRGs from Rabi oscillation of nuclear spins

We propose a fast and accurate method for the in situ calibration of the transverse coils in miniaturized nuclear magnetic resonance gyroscopes based on the Rabi oscillation of hyperpolarized gaseous 129Xe nuclear spins. In contrast to the conventional method based on the free induction decay initial amplitude of different pulse durations, this method circumvents the error introduced by the frequency detuning of the transverse driving field. We experimentally confirm that the accuracy of the calibration is influenced by the longitudinal relaxation time T1, the transverse relaxation time T2, and the magnitude of the transverse driving field B1. Through the numerical simulation of Bloch equations, we show that the behavior of My′ and Mz can be completely specified by two dimensionless quantities a and b, and we provide a ready-to-use selection criterion of b ≥ 24 for choosing the proper B1. By switching the embedded magnetometer into the longitudinal mode, we demonstrate the effectiveness and efficiency of our new calibration method. Finally, we examine the effectiveness of the selection criterion with our new calibration method. This method is expected to improve the authenticity of coil calibration and relaxation measurement in a more efficient way.

Cardiac MRI-based right-to-left ventricular blood pool T2 relaxation times ratio correlates with exercise capacity in patients with chronic heart failure

BackgroundMRI T2 mapping has been proven to be sensitive to the level of blood oxygenation. We hypothesized that impaired exercise capacity in chronic heart failure is associated with a greater difference between right (RV) to left ventricular (LV) blood pool T2 relaxation times due to a higher level of peripheral blood desaturation, compared to patients with preserved exercise capacity and to healthy controls. MethodsPatients with chronic heart failure (n = 70) who had undergone both cardiac MRI (CMR) and a 6-min walk test (6MWT) were retrospectively identified. Propensity score matched healthy individuals (n = 35) served as control group. CMR analyses included cine acquisitions and T2 mapping to obtain blood pool T2 relaxation times of the RV and LV. Following common practice, age- and gender-adjusted nominal distances and respective percentiles were calculated for the 6MWT. The relationship between the RV/LV T2 blood pool ratio and the results from 6MWT were evaluated by Spearman's correlation coefficients and regression analyses. Inter-group differences were assessed by independent t-tests and univariate analysis of variance. ResultsThe RV/LV T2 ratio moderately correlated with the percentiles of nominal distances in the 6MWT (r = 0.66) while ejection fraction, end-diastolic and end-systolic volumes showed no correlation (r = 0.09, 0.07 and − 0.01, respectively). In addition, there were significant differences in the RV/LV T2 ratio between patients with and without significant post-exercise dyspnea (p = 0.001). Regression analyses showed that RV/LV T2 ratio was an independent predictor of the distance walked and the presence of post-exercise dyspnea (p < 0.001). ConclusionThe proposed RV/LV T2 ratio, obtained by two simple measurements on a routinely acquired four-chamber T2 map, was superior to established parameters of cardiac function to predict exercise capacity and the presence of post-exercise dyspnea in patients with chronic heart failure.

Cardiac reverse remodeling in primary mitral regurgitation: mitral valve replacement vs. mitral valve repair

BackgroundWhen feasible, guidelines recommend mitral valve repair (MVr) over mitral valve replacement (MVR) to treat primary mitral regurgitation (MR), based upon historic outcome studies and transthoracic echocardiography (TTE) reverse remodeling studies. Cardiovascular magnetic resonance (CMR) offers reference standard biventricular assessment with superior MR quantification compared to TTE. Using serial CMR in primary MR patients, we aimed to investigate cardiac reverse remodeling and residual MR post-MVr vs MVR with chordal preservation. Methods83 patients with ≥ moderate-severe MR on TTE were prospectively recruited. 6-min walk tests (6MWT) and CMR imaging including cine imaging, aortic/pulmonary through-plane phase contrast imaging, T1 maps and late-gadolinium-enhanced (LGE) imaging were performed at baseline and 6 months after mitral surgery or watchful waiting (control group). Results72 patients completed follow-up (Controls = 20, MVr = 30 and MVR = 22). Surgical groups demonstrated comparable baseline cardiac indices and co-morbidities. At 6-months, MVr and MVR groups demonstrated comparable improvements in 6MWT distances (+ 57 ± 54 m vs + 64 ± 76 m respectively, p = 1), reduced indexed left ventricular end-diastolic volumes (LVEDVi; − 29 ± 21 ml/m2 vs − 37 ± 22 ml/m2 respectively, p = 0.584) and left atrial volumes (− 23 ± 30 ml/m2 and − 39 ± 26 ml/m2 respectively, p = 0.545). At 6-months, compared with controls, right ventricular ejection fraction was poorer post-MVr (47 ± 6.1% vs 53 ± 8.0% respectively, p = 0.01) compared to post-MVR (50 ± 5.7% vs 53 ± 8.0% respectively, p = 0.698). MVR resulted in lower residual MR-regurgitant fraction (RF) than MVr (12 ± 8.0% vs 21 ± 11% respectively, p = 0.022). Baseline and follow-up indices of diffuse and focal myocardial fibrosis (Native T1 relaxation times, extra-cellular volume and quantified LGE respectively) were comparable between groups. Stepwise multiple linear regression of indexed variables in the surgical groups demonstrated baseline indexed mitral regurgitant volume as the sole multivariate predictor of left ventricular (LV) end-diastolic reverse remodelling, baseline LVEDVi as the most significant independent multivariate predictor of follow-up LVEDVi, baseline indexed LV end-systolic volume as the sole multivariate predictor of follow-up LV ejection fraction and undergoing MVR (vs MVr) as the most significant (p < 0.001) baseline multivariate predictor of lower residual MR. ConclusionIn primary MR, MVR with chordal preservation may offer comparable cardiac reverse remodeling and functional benefits at 6-months when compared to MVr. Larger, multicenter CMR studies are required, which if the findings are confirmed could impact future surgical practice.

Lymphatic insufficiency leads to distinct myocardial infarct content assessed by magnetic resonance TRAFFn, T1ρ and T2 relaxation times

The role of cardiac lymphatics in the pathogenesis of myocardial infarction (MI) is unclear. Lymphatic system regulates cardiac physiological processes such as edema and tissue fluid balance, which affect MI pathogenesis. Recently, MI and fibrosis have been assessed using endogenous contrast in magnetic resonance imaging (MRI) based on the relaxation along a fictitious field with rank n (RAFFn). We extended the RAFFn applications to evaluate the effects of lymphatic insufficiency on MI with comparison to longitudinal rotating frame (T1ρ) and T2 relaxation times. MI was induced in transgenic (TG) mice expressing soluble decoy VEGF receptor 3 that reduces lymphatic vessel formation and their wild-type (WT) control littermates for comparison. The RAFFn relaxation times with rank 2 (TRAFF2), and rank 4 (TRAFF4), T1ρ and T2 were acquired at time points 0, 3, 7, 21 and 42 days after the MI at 9.4 T. Infarct sizes were determined based on TRAFF2, TRAFF4, T1ρ and T2 relaxation time maps. The area of differences (AOD) was calculated based on the MI areas determined on T2 and TRAFF2, TRAFF4 or T1ρ relaxation time maps. Hematoxylin–eosin and Sirius red stained histology sections were prepared to confirm MI locations and sizes. MI was detected as increased TRAFF2, TRAFF4, T1ρ and T2 relaxation times. Infarct sizes were similar on all relaxation time maps during the experimental period. Significantly larger AOD values were found together with increased AOD values in the TG group compared to the WT group. Histology confirmed these findings. The lymphatic deficiency was found to increase cardiac edema in MI. The combination of TRAFF2 (or TRAFF4) and T2 characterizes MI and edema in the myocardium in both lymphatic insufficiency and normal mice without any contrast agents.

Valeramide and Halo-phenol in a Non-polar Liquid: DFT Based Characterization and Reactivity, Non-covalent Interaction, and Dielectric Relaxation Studies

Valeramide and halogenated phenol in solvent benzene have been studied using DFT. Dielectric relaxation studies have also been undertaken. The wave functional characteristics like reduced density gradient (RDG), electron localization function (ELF), localized orbital locator (LOL) are also evaluated. It has been found that the computed FMO energies accurately depict the characteristics of electron excitation which provide an explanation for the charge transfer. MEP analysis is done to identify electrophilic and nucleophilic sites. The theoretical analysis of the UV-Visible spectrum using the TD-DFT method in solution and the computational investigation of spectroscopic wavenumbers was also carried out (IR, Raman). Thermodynamic properties of title compound at different temperatures was carried out. Various dielectric parameters, like the dielectric constant the dielectric loss at microwave frequency, the static dielectric constant ε0 and the dielectric constant ε∞ at optical frequency, were measured across five distinct molar ratios (i.e. 1:3, 1:2, 1:1, 2:1 and 3:1). While the relaxation time τ2 for group rotation is utilized to identify the steric interaction of the proton donor, Higasi’s single-frequency equation is proven to measure multiple relaxation time τ1 to determine the intensity of hydrogen bonding. At a 1:1 (molar ratio) , the values of relaxation time were found to be high. Molecular docking was done in a supplementary effort to support intermolecular interactions.

Hyperpolarized 129Xe MRI at low field: Current status and future directions

Magnetic Resonance Imaging (MRI) is dictated by the magnetization of the sample, and is thus a low-sensitivity imaging method. Inhalation of hyperpolarized (HP) noble gases, such as helium–3 and xenon-129, is a non-invasive, radiation-risk free imaging technique permitting high resolution imaging of the lungs and pulmonary functions, such as the lung microstructure, diffusion, perfusion, gas exchange, and dynamic ventilation. Instead of increasing the magnetic field strength, the higher spin polarization achievable from this method results in significantly higher net MR signal independent of tissue/water concentration. Moreover, the significantly longer apparent transverse relaxation time T2* of these HP gases at low magnetic field strengths results in fewer necessary radiofrequency (RF) pulses, permitting larger flip angles; this allows for high-sensitivity imaging of in vivo animal and human lungs at conventionally low (<0.5 T) field strengths and suggests that the low field regime is optimal for pulmonary MRI using hyperpolarized gases.In this review, theory on the common spin-exchange optical-pumping method of hyperpolarization and the field dependence of the MR signal of HP gases are presented, in the context of human lung imaging. The current state-of-the-art is explored, with emphasis on both MRI hardware (low field scanners, RF coils, and polarizers) and image acquisition techniques (pulse sequences) advancements. Common challenges surrounding imaging of HP gases and possible solutions are discussed, and the future of low field hyperpolarized gas MRI is posed as being a clinically-accessible and versatile imaging method, circumventing the siting restrictions of conventional high field scanners and bringing point-of-care pulmonary imaging to global facilities.

Enhancing the coherence of superconducting quantum bits with electric fields

In the endeavor to make quantum computers a reality, integrated superconducting circuits have become a promising architecture. A major challenge of this approach is decoherence originating from spurious atomic tunneling defects at the interfaces of qubit electrodes, which may resonantly absorb energy from the qubit’s oscillating electric field and reduce the qubit’s energy relaxation time T1. Here, we show that qubit coherence can be improved by tuning dominating defects away from the qubit resonance using an applied DC-electric field. We demonstrate a method that optimizes the applied field bias and enhances the average qubit T1 time by 23%. We also discuss how local gate electrodes can be implemented in superconducting quantum processors to enable simultaneous in situ coherence optimization of individual qubits.

Effect of Nanoconfinement on NMR Relaxation of Heptane in Kerogen from Molecular Simulations and Measurements

Kerogen-rich shale reservoirs will play a key role during the energy transition, yet the effects of nanoconfinement on the NMR relaxation of hydrocarbons in kerogen are poorly understood. We use atomistic MD simulations to investigate the effects of nanoconfinement on the 1H NMR relaxation times T1 and T2 of heptane in kerogen. In the case of T1, we discover the important role of confinement in reducing T1 by ∼3 orders of magnitude from that of bulk heptane, in agreement with measurements of heptane dissolved in kerogen from the Kimmeridge Shale, without any models or free parameters. In the case of T2, we discover that confinement breaks spatial isotropy and gives rise to residual dipolar coupling which reduces T2 by ∼5 orders of magnitude from the value for bulk heptane. We use the simulated T2 to calibrate the surface relaxivity and thence predict the pore-size distribution of the organic nanopores in kerogen, without additional experimental data.