Comparison of Dixon Sequences for Estimation of Percent Breast Fibroglandular Tissue.

Objectives: To evaluate sources of error in the Magnetic Resonance Imaging (MRI) measurement of percent fibroglandular tissue (%FGT) using two-point Dixon sequences for fat-water separation.

Methods: Ten female volunteers (median age: 31 yrs, range: 23-50 yrs) gave informed consent following Research Ethics Committee approval. Each volunteer was scanned twice following repositioning to enable an estimation of measurement repeatability from high-resolution gradient-echo (GRE) proton-density (PD)-weighted Dixon sequences.

Alternative screening for dense breasts: MRI.

OBJECTIVE. The purpose of this article is to review the use of MRI in breast density measurement and breast cancer risk estimation and to discuss the role of MRI as an alternative screening to mammography for screening women with dense breasts. CONCLUSION.

Investigating the influence of flip angle and k-space sampling on dynamic contrast-enhanced MRI breast examinations.

Rationale And Objectives: To retrospectively investigate the effect of flip angle (FA) and k-space sampling on the performance of dynamic contrast-enhanced (DCE-) magnetic resonance imaging (MRI) breast sequences.

Materials And Methods: Five DCE-MRI breast sequences were evaluated (10°, 14°, and 18° FAs; radial or linear k-space sampling), with 7-10 patients in each group (n = 45). All sequences were compliant with current technical breast screening guidelines.

Ruthenium-catalyzed meta sulfonation of 2-phenylpyridines.

A selective catalytic meta sulfonation of 2-phenylpyridines was found to occur in the presence of (arene)ruthenium(II) complexes upon reaction with sulfonyl chlorides. The 2-pyridyl group facilitates the formation of a stable Ru-C(aryl) σ bond that induces a strong para-directing effect. Electrophilic aromatic substitution proceeds with the sulfonyl chloride to furnish a sulfone at the position meta to the chelating group.

Ruthenium bidentate phosphine complexes for the coordination and catalytic dehydrogenation of amine- and phosphine-boranes.

Addition of the amine-boranes H(3)B⋅NH(2)tBu, H(3)B⋅NHMe(2) and H(3)B⋅NH(3) to the cationic ruthenium fragment [Ru(xantphos)(PPh(3))(OH(2))H][BAr(F)(4)] (2; xantphos=4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; BAr(F)(4)=[B{3,5-(CF(3))(2)C(6)H(3)}(4)](-)) affords the η(1)-B-H bound amine-borane complexes [Ru(xantphos)(PPh(3))(H(3)B⋅NH(2)tBu)H][BAr(F)(4)] (5), [Ru(xantphos)(PPh(3))(H(3) B⋅NHMe(2))H][BAr(F)(4)] (6) and [Ru(xantphos)(PPh(3))(H(3)B⋅NH(3))H][BAr(F)(4)] (7). The X-ray crystal structures of 5 and 7 have been determined with [BAr(F)(4)] and [BPh(4)] anions, respectively. Treatment of 2 with H(3)B⋅PHPh(2) resulted in quite different behaviour, with cleavage of the B-P interaction taking place to generate the structurally characterised bis-secondary phosphine complex [Ru(xantphos)(PHPh(2))(2)H][BPh(4)] (9).

Pincer phosphine complexes of ruthenium: formation of Ru(P-O-P)(PPh3)HCl (P-O-P = xantphos, DPEphos, (Ph2PCH2CH2)2O) and Ru(dppf)(PPh3)HCl and characterization of cationic dioxygen, dihydrogen, dinitrogen, and arene coordinated phosphine products.

Treatment of Ru(PPh(3))(3)HCl with the pincer phosphines 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene (xantphos), bis(2-diphenylphosphinophenyl)ether (DPEphos), or (Ph(2)PCH(2)CH(2))(2)O affords Ru(P-O-P)(PPh(3))HCl (xantphos, 1a; DPEphos, 1b; (Ph(2)PCH(2)CH(2))(2)O, 1c). The X-ray crystal structures of 1a-c show that all three P-O-P ligands coordinate in a tridentate manner through phosphorus and oxygen. Abstraction of the chloride ligand from 1a-c by NaBAr(4)(F) (BAr(4)(F) = B(3,5-C(6)H(3)(CF(3))(2))(4)) gives the cationic aqua complexes [Ru(P-O-P)(PPh(3))(H(2)O)H]BAr(4)(F) (3a-c).

[Ru(NHC)(xantphos)(CO)H(2)] complexes: intramolecular C-H activation and applications in C-C bond formation.

Treatment of [Ru(PPh3)(xantphos)(CO)H2] (1) with the N-heterocyclic carbenes (NHCs) IEt2Me2 (1,3-diethyl-4,5-dimethylimidazol-2-ylidene), IiPr2Me2 (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) and IMes (1,3-dimesitylimidazol-2-ylidene) at elevated temperature affords the C-H activated carbene complexes [Ru(NHC)(xantphos)(CO)H] (2-4). In contrast, ICy (1,3-dicyclohexylimidazol-2-ylidene) reacts with 1 to give the substitution product [Ru(ICy)(xantphos)(CO)H2] (6), which can be converted into the C-H activated species [Ru(ICy)(xantphos)(CO)H] (7) upon thermolysis in the presence of H2CCHSiMe3. Addition of H2 to 2 yields [Ru(IEt2Me2)(xantphos)(CO)H2] (5), while H2 reacts with 7 to reform 6.

Ruthenium xantphos complexes in hydrogen transfer processes: reactivity and mechanistic studies.

The in situ combination of [Ru(PPh3)3(CO)H2] with xantphos is catalytically active for the alkylation of alcohols with the ketonitrile (t)BuC(O)CH2CN in a model oxidation-Knoevenagel-reduction process. The precursor complex [Ru(xantphos)(PPh3)(CO)H2] was isolated and reacted with stoichiometric amounts of PhCH2OH and PhCHO. Under these conditions, the alcohol is decarbonylated to afford [Ru(xantphos)(CO)2H2] and finally [Ru(xantphos)(CO)3], both of which prove to be less active for catalysis than the starting complex.