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Rotating frame spin-lattice relaxation, with the characteristic time constant T1ρ, provides a means to access motion-restricted (slow) spin dynamics in MRI. As a result of their restricted motion, these spins are sometimes characterized by a short transverse relaxation time constant T2 and thus can be difficult to detect directly with conventional image acquisition techniques. Here, we introduce an approach for three-dimensional adiabatic T1ρ mapping based on a magnetization-prepared sweep imaging with Fourier transformation (MP-SWIFT) sequence, which captures signal from almost all water spin populations, including the extremely fast relaxing pool. A semi-analytical procedure for T1ρ mapping is described. Experiments on phantoms and musculoskeletal tissue specimens (tendon, articular and epiphyseal cartilages) were performed at 9.4 T for both the MP-SWIFT and fast spin echo (FSE) read outs. In the phantom with liquids having fast molecular tumbling and a single-valued T1ρ time constant, the measured T1ρ values obtained with MP-SWIFT and FSE were similar. Conversely, in normal musculoskeletal tissues, T1ρ values measured with MP-SWIFT were much shorter than the values obtained with FSE. Studies of biological tissue specimens demonstrated that T1ρ-weighted SWIFT provides higher contrast between normal and diseased tissues relative to conventional acquisitions. Adiabatic T1ρ mapping with SWIFT readout captures contributions from the otherwise undetected fast relaxing spins, allowing more informative T1ρ measurements of normal and diseased states. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The objective of this study was to demonstrate the feasibility of simultaneous bilateral hip imaging at 7 Tesla. Hip joint MRI becomes clinically critical since recent advances have made hip arthroscopy an efficacious approach to treat a variety of early hip diseases. The success of these treatments requires a reliable and accurate diagnosis of intraarticular abnormalities at an early stage. Articular cartilage assessment is especially important to guide surgical decisions but is difficult to achieve with current MR methods. Because of gains in tissue contrast and spatial resolution reported at ultra high magnetic fields, there are strong expectations that imaging the hip joint at 7 Tesla will improve diagnostic accuracy. Furthermore, there is growing evidence that the majority of these hip abnormalities occur bilaterally, emphasizing the need for bilateral imaging. However, obtaining high quality images in the human torso, in particular of both hips simultaneously, must overcome a major challenge arising from the damped traveling wave behaviour of RF waves at 7 Tesla that leads to severe inhomogeneities in transmit B1 ( B1+) phase and magnitude, typically resulting in areas of low signal and contrast, and consequently impairing use for clinical applications. To overcome this problem, a 16-channel stripline transceiver RF coil was used, together with a B1 shimming algorithm aiming at maximizing B1+ in six regions of interest over the hips that were identified on axial scout images. Our successful results demonstrate that this approach effectively reduces inhomogeneities observed before B1 shimming and provides high joint tissue contrast in both hips while reducing the required RF power. Critical to this success was a fast small flip angle B1+ calibration scan that permitted the computation of subject-specific B1 shimming solutions, a necessary step to account for large spatial variations in B1+ phase observed in different subjects. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This synthetic and structural work describes a series of half-sandwich cyclopentadienylruthenium(II) complexes containing the diphosphazane ligands [(CH)P]N R ( R=H:H dppa, 1a; R=CH: dppma, 1b; R=CH: dppea, 1c; R=Li:Li dppa, 1d). Treatment of 1a, d with CpRuCl(PPh) (Cp=η-CH, Ph=CH, 2) in a molar ratio of 1:1 in boiling aromatic hydrocarbons affords the neutral complexes CpRuCl(H dppa) ( 3) and CpRu( dppa)PPh ( 6). The ionic complexes [CpRu(PhP-N R-(PPh)PPh)Cl ( R=CH: 4a; R=CH: 4b) are formed by the reaction of 1b, c with 2. One pot reactions of 1a-c with 2 in the presence of NHPF in boiling CHOH give only the ionic compounds [CpRu(PhP-NR-PPh)(PPh)]PF ( R=H, CH, CH; 5a-c). The sulfur dioxide and hydride complexes [CpRu(H dppa)η-SO]Cl ( 7) and CpRu(H)H dppa ( 8) are obtained by the interaction of 3 with SO or NaOCH. All compounds are characterized as far as possible by IR, Raman,P{H} NMR,H NMR,C{H} NMR, FD mass spectra, and their conductivity in CHCl solution. The X-ray crystal structures of 3 and 5a reveal that the P(1)-N(1)-P(2) angle of the coordinated ligand 1a in both complexes is reduced to about 100° in comparison to free uncoordinated 1a (119°). This small angle leads to a short P(1)-P(2) bond distance of 259.4 pm in 3 and 254.3 pm in 5a. The molecules of 3 are connected by intermolecular (NH...Cl) hydrogen bridging bonds forming chains along the z axis of the unit cell. The crystals of 5a contain two independent pairs of ions in the unit cell ( Z=8). In 5a no hydrogen bonds exist between the NH-groups and the PF anions. [ABSTRACT FROM AUTHOR]