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Fast field-cycling (FFC) nuclear magnetic resonance relaxometry is a well-established method to determine the relaxation rates as a function of magnetic field strength. This so-called nuclear magnetic relaxation dispersion gives insight into the underlying molecular dynamics of a wide range of complex systems and has gained interest especially in the characterisation of biological tissues and diseases. The combination of FFC techniques with magnetic resonance imaging (MRI) offers a high potential for new types of image contrast more specific to pathological molecular dynamics. This article reviews the progress in FFC-MRI over the last decade and gives an overview of the hardware systems currently in operation. We discuss limitations and error correction strategies specific to FFC-MRI such as field stability and homogeneity, signal-to-noise ratio, eddy currents and acquisition time. We also report potential applications with impact in biology and medicine. Finally, we discuss the challenges and future applications in transferring the underlying molecular dynamics into novel types of image contrast by exploiting the dispersive properties of biological tissue or MRI contrast agents. [ABSTRACT FROM AUTHOR]

The MR aspect of articular cartilage, that reflects the interactions between protons and macromolecular constituents, is affected by the intrinsic tissue structure (water content, the content of matrix constituents, collagen network organization), imager characteristics, and acquisition parameters. On the T 1-weighted sequences, the bovine articular cartilage appears as an homogeneous tissue in high signal intensity, whatever the age of animals considered, whereas on the T2-weighted sequences, the articular bovine cartilage presents variations of its imaging pattern (laminar appearance) well correlated to the variations of its histological and biochemical structure. The T2 relaxation time measurement (T2 mapping), which reflects quantitatively the signal intensity variations observed on T2 weighted sequences, is a way to evaluate more precisely the modifications of cartilage structure during the aging and maturation processes (rat's study). This technique so far confined to experimental micro-imagers is now developed on clinical imagers. Consequently, it may permit to depict the early stages of osteoarthritic disease (OA) or to evaluate the chondroprotective effect of drugs. [ABSTRACT FROM AUTHOR]

The Multi-turn Transmission Line Resonator (MTLR) design allows for developing very small and highly sensitive radiofrequency (RF) coils for magnetic resonance imaging. However the monolithic feature and the small size of the developed coils, imposes to employ dedicated contact-free tuning techniques. In this work, we investigated two contact-free tuning principles for small monolithic RF coils: a dielectric tuning principle based on the interception of the electric field lines by a dielectric layer, and an inductive tuning principle based on the interception of magnetic field lines by a closed conducting ring. For both tuning principles, we used experimental measurements co-supported by electromagnetic simulation and analytical modelling to determine the accessible tuning range as a function of both the tuning element's characteristics and its distance to the RF coil. A maximal tuning range about 9% and 24% was achieved using the dielectric tuning principle and the inductive tuning principle, respectively. Contrarily to the dielectric tuning principle, the inductive tuning principle was found to strongly limit the quality factor of the coil. To implement the two investigated tuning principles, we have developed an automated system based on piezoelectric actuators that achieves microscopic displacements of the tuning elements. The automated system was also used to perform inductive impedance matching of the coil. For purposes of both tuning and matching, when starting from a strongly un-tuned or un-matched configuration, the automated system reaches convergence within a few tens of seconds. First MRI experiments were performed to evaluate the MRI compatibility of the automated system. [ABSTRACT FROM AUTHOR]

Objectives: To compare fatigue in a large multinational systemic sclerosis (SSc) cohort to general population data and identify associated sociodemographic, lifestyle and SSc disease factors., Methods: Scleroderma Patient-centered Intervention Network Cohort participants completed the Patient-Reported Outcomes Measurement Information System-29 v2.0 fatigue domain. T-scores were compared with the USA general population (mean = 50; SD = 10). Multivariable linear regression was used to assess associations with sociodemographic, lifestyle, and disease-related variables., Results: Among 2,385 participants (mean age 54.9 (SD = 12.6) years, 87% female, 38% diffuse SSc), mean fatigue T-score was 54.6 (SD = 11.0); 438 (18%) reported mild fatigue, 641 (27%) moderate, and 180 (8%) severe fatigue. Fatigue was independently associated with sociodemographic factors age (-0.10 points per year, [95% CI -0.14;-0.07]), male sex (-1.67 points, [-2.96;-0.37]), non-married status (0.97 points [0.04; 1.89]), and country (reference USA; France -2.35 points [-3.48;-1.21] and UK 2.38 points [0.80; 3.97]), and lifestyle factors smoking (4.16 points [2.52; 5.80]), alcohol consumption (-0.18 points per drink per week [-0.28;-0.07]), and body-mass index (0.34 points per unit [0.27; 0.42]). Fatigue was associated with disease-related factors gastrointestinal involvement (4.21 points [2.99; 5.43]), digital ulcers (1.51 points, [0.25; 2.77]), moderate small joints contractures (1.41 points [0.13; 2.69]), rheumatoid arthritis (4.34 points [2.37-6.31]) and Sjögren's syndrome (1.89 points [0.23; 3.55]). When pain was included in the model, its association was large (2.19 points [2.03; 2.34]) and interstitial lung disease was also associated (1.21 points [0.42; 2.00])., Conclusions: In people with SSc, fatigue scores were substantially higher than the general population and associated with multiple disease factors including gastrointestinal involvement, several painful disease manifestations, and lung involvement., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Society for Rheumatology.)

Objective: To evaluate the degree that the Cochin Hand Function Scale (CHFS) generates scores that are comparable across language, sex, and disease subtype., Methods: We included participants enrolled in the Scleroderma Patient-centered Intervention Network (SPIN) Cohort who completed the CHFS at their baseline assessment between April 2014 and September 2020. Confirmatory factor analysis (CFA) was used to test unidimensionality, and multiple indicator multiple cause (MIMIC) models were used for differential item functioning (DIF) analysis based on language, sex, and disease subtype. Both intraclass correlation coefficient (ICC) and Pearson's correlation were calculated using factor scores obtained from unadjusted and DIF-adjusted MIMIC models to evaluate agreement and correlation between scores., Results: A total of 2,155 participants were included. CFA with covarying error terms supported a good fit of the model (χ 2 [127] = 1,754.671; P < 0.001; Tucker-Lewis index = 0.985; comparative fit index = 0.987; root mean square error of approximation = 0.077). Nine items displayed statistically significant DIF for language of administration, 10 items for sex, and 10 items for disease subtype. However, the overall impact of DIF was negligible when comparing factor scores that did and did not account for DIF (ICC = 0.999; r = 0.999)., Conclusion: The CHFS has score comparability in systemic sclerosis regardless of participants' language, sex, and disease subtype., (© 2023 American College of Rheumatology.)