Fast Chemical-Shift T₁ Imaging in Toroid Cavities for the Structural Analysis of Gels and Emulsions


Fast chemical-shift T1 imaging in toroid cavity cells (TCCs) is introduced and applications to diagnostic ultrasound gel and skin-care ointment are presented. TCCs are an advancement over previously used toroid cavity detectors because they combine resonator and sample container into one part. Additionally, they are removable from the top of the probe and facilitate convenient probe and sample handling. Radially resolved T1 relaxation times in TCCs are obtained through combination of SR (saturation recovery) experiments with the RIPT (rapid imaging with a pulse train) technique. Because of the strong radial B1 gradient in TCCs, only pulse-burst saturation was found satisfactory to generate the most even starting condition for SR experiments. Because RIPT does not resolve chemical-shift information, magnetization and T1 profiles of individual components in mixed samples are monitored by double-transient experiments with selective on-resonance saturation, which is achieved by converging trains of sinc pulses. The new techniques were applied to cellulose hydrogel and oil-in-water emulsion both exposed to significant shear stress deformation during the charging of the TCC. In both cases, T1 profiles as a function of time reveal structural recovery (thixotropy) that slowly progresses from one or more sample interfaces into the bulk.



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© 2002 Springer Verlag, All rights reserved.

Publication Date

01 Jun 2002