Changes In Relaxation Times Research Articles

Longitudinal Changes in the Myocardial T1 Relaxation Time, Extracellular Volume Fraction, and Left Ventricular Function in Asymptomatic Men.

(1) Background: Longitudinal changes in myocardial T1 relaxation time are unknown. We aimed to assess the longitudinal changes in the left ventricular (LV) myocardial T1 relaxation time and LV function. (2) Methods: Fifty asymptomatic men (mean age, 52.0 years) who underwent 1.5 T cardiac magnetic resonance imaging twice at an interval of 54 ± 21 months were included in this study. The LV myocardial T1 times and extracellular volume fractions (ECVFs) were calculated using the MOLLI technique (before and 15 min after gadolinium contrast injection). The 10-year Atherosclerotic Cardiovascular Disease (ASCVD) risk score was calculated. (3) Results: No significant differences in the following parameters were noted between the initial and follow-up assessments: LV ejection fraction (65.0 ± 6.7% vs. 63.6 ± 6.3%, p = 0.12), LV mass/end-diastolic volume ratio (0.82 ± 0.12 vs. 0.80 ± 0.14, p = 0.16), native T1 relaxation time (982 ± 36 vs. 977 ± 37 ms, p = 0.46), and ECVF (24.97 ± 2.38% vs. 25.02 ± 2.41%, p = 0.89). The following parameters decreased significantly from the initial assessment to follow-up: stroke volume (87.2 ± 13.7 mL vs. 82.6 ± 15.3 mL, p = 0.01), cardiac output (5.79 ± 1.17 vs. 5.50 ± 1.04 L/min, p = 0.01), and LV mass index (110.16 ± 22.38 vs. 104.32 ± 18.26 g/m2, p = 0.01). The 10-year ASCVD risk score also remained unchanged between the two timepoints (4.71 ± 0.19% vs. 5.16 ± 0.24%, p = 0.14). (4) Conclusion: Myocardial T1 values and ECVFs were stable over time in the same middle-aged men.

Gestational age-related changes in relaxation times of neonatal brain by quantitative synthetic magnetic resonance imaging.

This study aimed to explore the correlation between T1 and T2 relaxation times of synthetic MRI (SyMRI) and gestational age (GA) in each hemisphere of preterm and term newborns at the initial 28 days of birth. Seventy preterm and full-term infants were prospectively included in this study. All subjects completed 3.0 T routine MRI and SyMRI (MAGiC) one-stop scanning within 28 days of birth (aged 34-42 W at examination). The SyMRI postprocessing software (v8.0.4) was used to measure the T1 and T2 relaxation values of each brain region. The linear regression equations of quantitative relaxation values with GA were established to compare the variation speed in each brain region. A significant linear and negative correlation was found between relaxation times and GA in the neonate cerebral cortex and subcortical gray and white matter regions (All p<.05). The relaxation time of the left centrum semiovale decreased with maximum variance with increasing GA among all white matter regions (T1: b = -51.45, β = -0.65, p < .0001; T2: b = -8.77, β = -0.71, p < .0001), whereas the right posterior limb of internal capsule showed minimal variance (T1: b = -27.94, β = -0.60, p < .0001; T2: b = -3.25, β = -0.68, p < .0001). Among all gray matter regions, the right globus pallidus and thalamus indicated the most significant decreasing degree of T1 and T2 relaxation values with GA (right globus pallidus T1: b = -33.14, β = -0.64, p < .0001; right thalamus T2: b = -3.94, β = -0.81, p < .0001), and the right and left occipital lobes indicated the least significant decreasing degree of T1 and T2 relaxation values with GA, respectively (right occipital lobes T1: b = -11.18, β = -0.26, p = .028; left occipital lobes T2: b = -1.22, β = -0.27, p = .024). SyMRI could quantitatively evaluate the linear changes of T1 and T2 relaxation values with GA in brain gray and white matter of preterm and term neonates.

Finding an effective MRI sequence to visualise the electroporated area in plant-based models by quantitative mapping

Plant-based models can reduce the number of animal studies for electroporation research in medical cancer treatment modalities like irreversible electroporation. Magnetic resonance imaging (MRI) provides volumetric visualisation of electroporated animal or plant tissues; however, contrast behaviour is complex, depending on tissue and sequence parameters. This study numerically analysed contrast between electroporated and non-electroporated tissue at 1.5 T in various MRI sequences (DWI, T1W, T2W, T2*W, PDW, FLAIR) performed 4 h after electroporation in apples (N = 4) and potatoes (N = 8). Sequence parameters (inversion time [TI], echo time [TE], b-value) for optimal contrast and electroporation-mediated changes in T1 and T2 relaxation times and apparent diffusion coefficient (ADC) were determined for potato (N = 4) using quantitative parameter mapping. FLAIR showed the electroporated zone in potatoes with best contrast, whereas no sequence yielded clear visibility in apples. After electroporation, T1 and T2 in potato decreased by 29% ([1245 ± 54 to 886 ± 119] ms) and 12% ([249 ± 17 to 217 ± 12] ms), respectively. ADC increased by 11% ([1303 ± 25 to 1449 ± 28] × 10–6 mm2/s). Optimal contrast was found for TI = 1000 ms, low TE and high b-value. T1 was most sensitive to EP-mediated tissue changes. Future research could use this methodology and findings to obtain high-contrast MR images of electroporated and non-electroporated biological tissues.

Dielectric spectroscopy of the low-losses sugar lyophilises: IV. Comparative study of four disaccharides at different moisture contents and temperatures

The purpose of this article is to study the effect of moisture content on the molecular dynamics of freeze-dried disaccharide excipients, in the context of understanding the instability of a pharmaceutical product. Four disaccharides were measured by broad band dielectric spectroscopy, over a wide temperature range (−140 to +80 °C) with increasing moisture content from 1 to 7.5%. The two observed sub-Tg relaxation processes (β and γ) were affected by the moisture content, with a dramatic change in relaxation time of the β-process, but only a moderate effect on the γ-process. A suggestion of the likely arrangement of dipoles, and intra-molecular mobility, was performed in the framework of the free-space theory and based primarily on the analysis of the relaxation times, activation energies and Frohlich parameters. This analysis allows for some speculation concerning the disaccharide moisture buffering in freeze-dried formulations.

Win-Win Cooperation: Magnetic relaxation switching biosensor for chloramphenicol detection based on the pipet platform and antigen-driven enzyme-free dual signal amplification strategy

Herein, we developed an enzyme-free dual signal amplification magnetic relaxation switching biosensor to detect the high hazard chloramphenicol based on the significant advantages of the pipet platform (low cost and easy operation). The competitive immunoassay was carried out by coating the polydopamine-modified pipets with the antibody, causing a content change of trigger DNA-chloramphenicol-antigen conjugate (the first signal amplification) in the supernatant. This triggered the aggregation of magnetic nanoparticles with three-dimensional DNA network structures (the second signal amplification) for chloramphenicol quantitative analysis by changes in transverse relaxation time (T2). The pipet platform can simplify the sample pretreatment process to eliminate the potential interference with magnetic probes. Its low-cost combined with the enzyme-free strategy greatly reduces the overall detection expenses. The antigen-driven dual signal amplification strategy not only has high sensitivity (1.37 pg/mL), but also provides an alternative path for the efficient combination of immunoassay and DNA signal amplification.

Loss of ganglioglomerular nerve input to the carotid body impacts the hypoxic ventilatory response in freely-moving rats.

The carotid bodies are the primary sensors of blood pH, pO2 and pCO2. The ganglioglomerular nerve (GGN) provides post-ganglionic sympathetic nerve input to the carotid bodies, however the physiological relevance of this innervation is still unclear. The main objective of this study was to determine how the absence of the GGN influences the hypoxic ventilatory response in juvenile rats. As such, we determined the ventilatory responses that occur during and following five successive episodes of hypoxic gas challenge (HXC, 10% O2, 90% N2), each separated by 15min of room-air, in juvenile (P25) sham-operated (SHAM) male Sprague Dawley rats and in those with bilateral transection of the ganglioglomerular nerves (GGNX). The key findings were that 1) resting ventilatory parameters were similar in SHAM and GGNX rats, 2) the initial changes in frequency of breathing, tidal volume, minute ventilation, inspiratory time, peak inspiratory and expiratory flows, and inspiratory and expiratory drives were markedly different in GGNX rats, 3) the initial changes in expiratory time, relaxation time, end inspiratory or expiratory pauses, apneic pause and non-eupneic breathing index (NEBI) were similar in SHAM and GGNX rats, 4) the plateau phases obtained during each HXC were similar in SHAM and GGNX rats, and 5) the ventilatory responses that occurred upon return to room-air were similar in SHAM and GGNX rats. Overall, these changes in ventilation during and following HXC in GGNX rats raises the possibility the loss of GGN input to the carotid bodies effects how primary glomus cells respond to hypoxia and the return to room-air.

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.

The mechanism of using NMR for cancer detection.

Today, a most powerful technique to detect cancer development in patient is the use of the MRI (Magnetic Resonance imaging) technology. Thus, it is important to understand how NMR measurements can differentiate normal cells from pre-neoplastic cells and cancer cells. In this talk, we will first review the history of the development of the NMR technique for cancer detection. Then, we will discuss the physical mechanism that allows the NMR measurement to distinguish the normal cells, the pre-cancer cells and cancer cells. One key point is that, the contrast of MRI image was found to be based on difference in nuclear relaxation times (T1 and T2) rather than based on the concentration difference of cellular water. At present, there is still an active interest to understand the mechanisms behind relaxation time changes of water protons during cancer development. In this talk, I will review several possible physical mechanisms that could explain the relaxation time changes between normal cells and cancer cells.

Time Course Changes of Synthetic Relaxation Time During Neoadjuvant Chemotherapy in Breast Cancer: The Optimal Parameter for Treatment Response Evaluation.

Synthetic MRI (syMRI) has enabled quantification of multiple relaxation parameters (T1/T2 relaxation time [T1/T2], proton density [PD]), and their longitudinal change during neoadjuvant chemotherapy (NAC) promises to be valuable parameters for treatment response evaluation in breast cancer. To investigate the time course changes of syMRI parameters during NAC and evaluate their value as predictors for pathological complete response (pCR) in breast cancer. Retrospective, longitudinal. A total of 129 women (median age, 50 years; range, 28-69 years) with locally advanced breast cancer who underwent NAC; all performed multiple conventional breast MRI examinations with added syMRI during NAC. A 3.0 T, T1-weighted dynamic contrast enhanced and syMRI acquired by a multiple-dynamic, multiple-echo sequence. Breast MRI was set at four time-points: baseline, after one cycle, after three or four cycles of NAC and preoperation. SyMRI parameters and tumor diameters were measured and their changes from baseline were calculated. All parameters were compared between pCR and non-pCR. Interaction between syMRI parameters and clinicopathological features was analyzed. Mann-Whitney U tests, random effects model of repeated measurement, receiver operating characteristic (ROC) analysis, interaction analysis. Median synthetic T1/T2/PD and tumor diameter generally decreased throughout NAC. Absolute T1 at early-NAC, T1, and PD at mid-NAC were significantly lower in the pCR group. After early-NAC, the T1 change was significantly higher in the pCR (median ± IQR, 18.17 ± 11.33) than the non-pCR group (median ± IQR, 10.90 ± 10.03), with the highest area under the ROC curves (AUC) of 0.769 (95% CI, 0.684-0.838). Interaction analysis showed that histological grade III patients had higher odds ratio (OR) (OR=1.206) compared to grade II patients (OR=1.067). Synthetic T1 changes after one cycle of NAC maybe useful for early evaluating NAC response in breast cancer during whole treatment cycles. However, its discriminative ability is significantly affected by histological grade. 4 TECHNICAL EFFICACY: Stage 2.

A novel molecular reporter for probing protein DNA recognition: An optical spectroscopic and molecular modeling study

A novel benzo[a]phenoxazine-based fluorescent dye LV2 has been employed as a molecular reporter to probe recognition of a linker histone protein H1 by calf-thymus DNA (DNA). Fluorescence lifetime of LV2 buried in the globular domain of H1 (∼2.1 ns) or in the minor groove of DNA (∼0.93 ns) increases significantly to 2.65 ns upon interaction of the cationic protein with DNA indicating formation of the H1-DNA complex. The rotational relaxation time of the fluorophore buried in the globular domain of H1 increases significantly from 2.2 ns to 8.54 ns in the presence of DNA manifesting the recognition of H1 by DNA leading to formation of the H1-DNA complex. Molecular docking and molecular dynamics (MD) simulations have shown that binding of LV2 is energetically most favourable in the interface of the H1-DNA complex than in the globular domain of H1 or in the minor groove of DNA. As a consequence, orientational relaxation of the LV2 is significantly hindered in the protein-DNA interface compared to H1 or DNA giving rise to a much longer rotational relaxation time (8.54 ns) in the H1-DNA complex relative to that in pure H1 (2.2 ns) or DNA (5.7 ns). Thus, via a significant change of fluorescence lifetime and rotational relaxation time, the benzo[a]phenoxazine-based fluorescent dye buried within the globular domain of the cationic protein, or within the minor groove of DNA, reports on recognition of H1 by DNA.

Usefulness of Voxel-Based Quantification (VBQ) Smoothing in Relaxation Time Mapping

Voxel-based quantification (VBQ) smoothing is a technique used to smooth quantitative parametric maps in the Montreal Neurological Institute standard space. Although VBQ smoothing could suppress changes in quantitative values at tissue boundaries, its effectiveness on relaxation time (T1 and T2 values and proton density PD) maps has not been investigated. The purpose of this study was to clarify the usefulness of VBQ smoothing in relaxation time mapping. T1 and T2 values and PD maps of the brains of 20 healthy participants were obtained using a two-dimensional multi-dynamic multi-echo sequence. VBQ and Gaussian smoothing were applied to the relaxation time maps by varying the kernel size by 1 mm from 1 to 6 mm. Changes in relaxation time before and after VBQ and Gaussian smoothing for the putamen, caudate nucleus, substantia nigra, and corpus callosum on the relaxation time maps were evaluated. The changes in relaxation time after VBQ smoothing application were smaller than those in that after Gaussian smoothing application. Although the differences in the relaxation time for all tissues before and after VBQ and Gaussian smoothing applications increased with increasing kernel size for all relaxation times for both methods, the changes in the relaxation time for VBQ smoothing were smaller than those in that for Gaussian smoothing. VBQ smoothing can suppress the change in the relaxation time on the boundary of the tissue and is thus a useful smoothing technique in relaxation time mapping.

A hundredfold enhancement of relaxation times among Er(iii) single-molecule magnets with comparable energy barriers

Three sandwich-type Er(iii) SMMs were reported. The relaxation times in the three SMMs are closely correlated with the number of TMS groups on the ligands, that one TMS group resulted in one-order of magnitude change of magnetic relaxation times.

Liver T1 Relaxation Quantification Using a 3-Dimensional Interleaved Look-Locker Acquisition With T2 Preparation Pulse Sequence (3D-QALAS): Comparison With Conventional 2-Dimensional MOLLI.

Changes in liver magnetic resonance imaging T1 relaxation times are associated with histologic inflammation and fibrosis. To compare liver T1 measurements obtained using a novel single-breath-hold 3-dimensional (3D) whole-liver T1 estimation method (3D-QALAS) to standard-of-care 2-dimensional (2D) modified Look-Locker (2D-MOLLI) measurements. With institutional review board approval, research magnetic resonance imaging examinations were performed in 19 participants at 1.5 T. T1 relaxometry of the liver was performed using a novel 3D whole-liver T1 estimation method (3D-QALAS) as well as a 2D modified Look-Locker (2D-MOLLI) method. The 3D method covered the entire liver in a single breath hold, whereas 2D imaging was performed at 4 anatomic levels in 4 consecutive breath holds. T1 measurements from parametric maps were obtained by a single operator, and region-of-interest area-weighted mean T1 values were calculated. Pearson correlation ( r ) was used to assess correlation between T1 estimation methods, and the paired t test and Bland-Altman analysis were used to compare agreement in T1 measurements. In 18 participants (1 participant was excluded from analysis because of respiratory motion artifacts on 3D-QALAS images), 2D-MOLLI and 3D-QALAS mean T1 measurements were strongly correlated ( r = 0.95, [95% CI: 0.87-0.98]; P < 0.0001). 2D-MOLLI T1 values were significantly longer than 3D-QALAS values (647.2 ± 87.3 milliseconds vs. 554.7 ± 75.8 milliseconds; P < 0.0001) with mean bias = 92.5 milliseconds (95% limits of agreement, 36.8, 148.2 milliseconds). Whole-liver T1 measurements obtained using a novel single-breath-hold 3D T1 estimation method correlate with a standard-of-care multiple consecutive-breath-hold 2D single-slice method but demonstrate systematic bias that should be considered or corrected when used in a clinical or research setting.

Photomechanical Solid Polymers: Model for Pressure and Strain Induced by Photoisomerization and Photo-Orientation

Photoactive polymers are important for fundamental studies and applications in several area of photonics such as data storage and holography and nonlinear optics and photomechanics. The latter is perhaps one of the most important applications of such materials, since they act as light to mechanical energy transducers and move under light action. For example, azo-polymers irradiated by inhomogeneous resonant ultra-violet or visible light undergo molecular and macroscopic motion, at sub-glass transition temperatures by photoisomerization of the azo dyes. Our recent research in this field highlighted the fundamentals of mobility enhancement by light, including light-induced viscosity change and acceleration of relaxation times, and photomechanics, encompassing motions in gradients of actinic light leading to surface structuring and actuation. In this paper, we present an original model which predicts the creation of mechanical pressure, i.e., motion, by a photo-induced change in the occupied volume and length of anisometric isomers, and we give simple analytical expressions describing the dynamics of volume as well as strain change upon polarized light irradiation of photomechanic samples.

Dose sensitivity of MAGIC-f polymer gel using different MRI sequences

This study aims to evaluate the dose sensitivity of MAGIC-f gel irradiated by high-energy photon beams, comparing quantification using different MRI sequences. Irradiation was performed using 6 MV photons with 600 cGy/min dose rate, field size of 20x20 cm², and 94 cm source-to-surface distance. Two gel batches were produced on different days and placed in vials. In the first batch, doses of 0, 2, 4, 6, 8, 10, 20, and 40 Gy were planned. The second batch was irradiated with doses of 0, 2, 4, 6, 10, 12, 14, and 16 Gy. MR images were acquired with Spin Echo (SE, TR=3 s) and Multi Spin Echo (MSE, TR = 3s or 10s, turbo factor 24) sequences. The dose is assessed via changes in the transverse relaxation time in the irradiated gel. In MSE, dose sensitivity in the first batch was 0.27 (TR=3 s) and 0.28 Gy-1s-1 (TR=10 s) and in the second batch, 0.31 and 0.31 Gy-1s-1 (TR = 3 s and TR = 10 s, respectively). In the SE sequence, dose sensitivity was 0.42 for the first batch and 0.43 Gy-1s-1 for the second batch. Linearity of dose-response was only obtained for doses below 10 Gy. Comparing the dose sensitivity extracted from MSE and SE sequences using TR= 3s, differences around 30% were found. Thus, although MSE-MRI offers a faster protocol of imaging acquisition it is less precise for quantification of relaxation times, as TE is not a well-defined quantity. The performance of the gel as a dosimeter is consequently sequence dependent.

One experiment makes a direct comparison of structural recovery with equilibrium relaxation.

For a molecular glass-former, propylene glycol, we directly compare the equilibrium fluctuations, measured as "structural" relaxation in the regime of linear response, with structural recovery, i.e., field induced physical aging in the limit of a small perturbation. The two distinct correlation functions are derived from a single experiment. Because the relaxation time changes only 2% during structural recovery, no aging model is needed to analyze the results. Although being conceptually different processes, dielectric relaxation and recovery dynamics are observed to be identical for propylene glycol, whereas single-particle dynamics as seen by photon correlation spectroscopy are significantly faster. This confirms the notion that structural recovery and aging are governed by all modes observed by dielectric spectroscopy, i.e., including cross correlations, not only by single-particle dynamics. A comparison with analogous results for other materials suggests that the relation between relaxation and recovery time scales may be material specific rather than universal.

An improved model assessing variation characteristics of pore structure of sandy soil thawing from extremely low temperature using NMR technique

During the construction of subway connecting passages in major cities in China, in last decades the artificial freezing method has gradually been becoming one of the most safe and effective methods in excavating saturated sandy soils. This work aims at exploring the changes of pore size and relaxation time induced by temperature change using NMR technology. Sandy soil samples were retrieved from a subway construction site in Beijing. In the laboratory experiments, these samples were loaded by different extremely low temperatures and natural convection thawing. The T2 (i.e., relaxation time) distribution curves and real-time temperature throughout the thawing process were recorded. It was observed that the variation of T2 distribution curves and pore structure changes with temperature may be divided into four stages, i.e., Stage I: spherical and cylindrical pores with radius r = 0.3 nm are formed at temperature lower than −28.0 °C; Stage II: the water adsorbed in pores melts and pore radius increases to the range of 0.3 nm < r < 32.0 nm as temperature increases in the range of −28.0 °C ∼ -0.2 °C; Stage III: capillary water in the pores with radius >32.0 nm melts rapidly as temperature increases in the range of −0.2 °C ∼ 0.7 °C; Stage IV: small amount of pores transform from small-sized absorptive pores and large-sized capillary pores to medium-sized absorptive pores as temperature increases to above 0.7 °C°. The specific threshold temperature and the threshold relaxation time are found as −0.2 °C and 5.17 ms respectively. By quantitatively analyzing the incremental change of T2 distribution curves and the rising temperature, an improved Gibbs-Thomson equation and a Two-Staged model of T2LM-Tmel (the geometric mean of relaxation time - the absolute value of temperature) and T2-Tmel (relaxation time - the absolute value of temperature), which are applicable to NMR technology, were proposed. Based on these results, a new pore structure evolution model of frozen sandy soil thawing from extremely-low temperature was proposed.

MRI of radiation chemistry: First images and investigation of potential mechanisms.

Paramagnetic species such as O2 and free radicals can enhance T1 and T2 relaxation times. If the change in relaxation time is sufficiently large, the contrast will be generated in magnetic resonance images. Since radiation is known to be capable of altering the concentration of O2 and free radicals during water radiolysis, it may be possible for radiation to induce MR signal change. We present the first reported instance of x-ray-induced MR signal changes in water phantoms and investigate potential paramagnetic relaxation enhancement mechanisms associated with radiation chemistry changes in oxygen and free radical concentrations. Images of water and 10 mM coumarin phantoms were acquired on a 0.35 T MR-linac before, during, and after a dose delivery of 80Gy using an inversion-recovery dual-echo sequence with water nullified. Radiation chemistry simulations of these conditions were performed to calculate changes in oxygen and free radical concentrations. Published relaxivity values were then applied to calculate the resulting T1 change, and analytical MR signal equations were used to calculate the associated signal change. Compared to pre-irradiation reference images, water phantom images taken during and after irradiation showed little to no change, while coumarin phantom images showed a small signal loss in the irradiated region with a contrast-to-noise ratio (CNR) of 1.0-2.5. Radiation chemistry simulations found oxygen depletion of -11µM in water and -31µM in coumarin, resulting in a T1 lengthening of 24ms and 68ms respectively, and a simulated CNR of 1.0 and 2.8 respectively. This change was consistent with observations in both direction and magnitude. Steady-state superoxide, hydroxyl, hydroperoxyl, and hydrogen radical concentrations were found to contribute less than 1ms of T1 change. Observed radiation-induced MR signal changes were dominated by an oxygen depletion mechanism. Free radicals were concluded to play a minor secondary role under steady-state conditions. Future applications may include in vivo FLASH treatment verification but would require an MR sequence with a better signal-to-noise ratio and higher temporal resolution than the one used in this study.

CMR Findings in COVID-19 Recovered Patients: A Review on Parametric Mapping, Feature-Tracking, and LGE.

On March 11, 2020, the World Health Organization raised the coronavirus disease 2019 (COVID-19) status to a pandemic level. The disease caused a global outbreak with devastating consequences, and a fair percentage of patients who have recovered from it continue experiencing persistent sequelae. Hence, identifying the medium and long-term effects of the COVID-19 disease is crucial for its future management. In particular, cardiac complications, from affected function to myocardial injuries, have been reported in these patients. Considering that cardiovascular magnetic resonance (CMR) imaging is the gold standard in diagnosing myocardial involvement and has more advantages than other medical imaging modalities, assessing the outcomes of patients who recovered from COVID-19 with CMR could prove beneficial. This review compiles common findings in CMR in patients from the general population who recovered from COVID-19. The CMR-based techniques comprised parametric mapping for analyzing myocardial composition, feature tracking for studying regional heart deformation, and late gadolinium enhancement for detecting compromised areas in the cardiac muscle. A total of 19 studies were included. The evidence suggests that it is more likely to find signs of myocardial injury in patients who recovered from COVID-19 than in healthy controls, including changes in T1 and T2 mapping relaxation times, affected strain, or the presence of late gadolinium enhancement (LGE) lesions. However, more than two years after the outbreak, there is still a lack of consensus about how these parameters may indicate cardiac involvement in patients who recovered from the disease, as limited and contradictory data is available.

Weight-bearing cross-country running influences on the knee articular cartilage -a study using T2 MRI and muscle monitoring

The purpose of this study was to develop a quantitative method to acquire and analyze the transverse relaxation time (T2 relaxation) of the magnetic resonance imaging of in-vivo knee joint articular cartilage. To reveal the practical significance of this research, participants who underwent weight-bearing cross-country running were assessed by MR T2 imaging and knee functional test. As a result, temporary changes in the cartilage relaxation time at regions of interest were observed shortly post the running (P &lt; 0.05), accompanying with EMG signal monitored in muscles around knee. This study shows the potentials of utilizing quantitative MRI T2 imaging technique as a non-invasive approach to detect the knee articular cartilage loading and stress, which is important for earlier prevention and intervention of cartilage lesions.