authors 
Pereira, GA; Norek, M; Peters, JA; Ananias, D; Rocha, J; Geraldes, CFGC 
nationality 
International 
journal 
DALTON TRANSACTIONS 
keywords 
MRI CONTRAST AGENTS; MAGNETICSUSCEPTIBILITY SHIFTS; OXIDE NANOPARTICLES; RELAXATION; RESONANCE; EXCHANGE; TISSUES; SPHERES; MODEL 
abstract 
A series of zeolitetype silicates containing stoichiometric amounts of Ln(3+) ions in the framework (LnAV9 materials), with composition (Na4K2)(Ln(2)Si(16)O(38)) center dot 10H(2)O (Ln = Nd, Sm, Eu, Tb, Gd, Dy) has recently been synthesized and characterized. They form paramagnetic microparticles, which as aqueous suspensions have negligible water H1 longitudinal relaxivities (r(1)) for all Ln(3+) ions studied and quite large transverse relaxivities (r(2)). In this work we further analysed the size distribution of the LnAV9 particles and their r(2)* and r(2) relaxivities. The r(2)* relaxivity effects are explained by the static dephasing regime (SDR) theory. The r(2) relaxivities appear to be strongly dependent on the interval between two consecutive refocusing pulses (tau(CP)) in the train of 180 degrees pulses applied. For long tau(CP) values, the r(2) of the systems saturates at a value, which is always an order of magnitude smaller than r(2)*. These features are explained by a crude model, which takes into account the residual diffusion effect in the static dephasing regime. The large microparticles, although not efficient in T1 relaxation, are quite effective in enhancing T2 relaxation, particularly at high magnetic fields. The r(2)* values and the saturation values for r(2) were found to increase linearly with B0 and mu(2)(0). The largest transversal relaxation rate enhancements were observed for DyAV9 with a saturation value of r2 of 60 s(1) mM(1) and a r(2)* value of 566 s(1) mM(1) at 9.4 T and 298 K. 
publisher 
ROYAL SOC CHEMISTRY 
issn 
14779226 
year published 
2008 
issue 
17 
beginning page 
2241 
ending page 
2247 
digital object identifier (doi) 
10.1039/b718438g 
web of science category 
Chemistry, Inorganic & Nuclear 
subject category 
Chemistry 
unique article identifier 
WOS:000254999200006

ciceco authors
impact metrics
journal analysis (jcr 2019):

journal impact factor 
4.174 
5 year journal impact factor 
3.812 
category normalized journal impact factor percentile 
90 
dimensions (citation analysis):


altmetrics (social interaction):


