Transverzální relaxivit nanočásticových kontrastních látek pro MRI

Podrobnosti jsou k dispozici pouze v anglickém jazyce.

Four types of magnetic nanoparticles were synthesized, namely the LaSrsub>0.35MnO₃ and La_0.80Na_0.20MnO₃ perovskite manganites and the Mn_0.61Zn_0.42Fe_1.97O₃ and Co_0.44Zn_0.70Fe_1.86O₄ spinel ferrites. Subsequent coating with silica provided typical core-shell particles with the mean shell thickness of 14–19 nm and the mean size of cores of 49–52 nm in case of manganites and 26–33 nm in case of ferrites. Moreover, two other surface modifications were employed for Mn-Zn ferrite nanoparticles, specifically coating with titania, leading to larger clusters with more complex morphology, and the stabilization by citrate anions. The products were characterized by powder X-ray diffraction and transmission electron microscopy, and their magnetic properties were probed by SQUID magnetometry. The main attention was devoted to the relaxometry on aqueous suspensions of particles in magnetic field of 0.5 T. For distinct types of the prepared core-shell nanoparticles, the temperature dependence of transverse relaxivity was measured and the role of different relaxation regimes was analyzed.

Popis

Analysis of the temperature dependence of the transverse relaxivity, r2, for (a) silica-coated Co0.44Zn0.70Fe1.86O4 nanoparticles, (b) Mn0.61Zn0.42Fe1.97O3 nanoparticles with different coatings, and (c) two different types of silica-coated manganite nanoparticles. The transverse relaxivity is compared with the inverse value of the self-diffusion coefficient of water, 1/DH2O, the magnetization of bare nanoparticles, M, in magnetic field of B = 0.5 T, and the expression M2/DH2O, that models the motional averaging regime. All the quantities are normalized using their values at the temperature of t = 6 °C.