München 2009 – scientific programme
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ST: Fachverband Strahlen- und Medizinphysik
ST 9: Magnetic Resonance and PET Imaging
ST 9.1: Talk
Thursday, March 12, 2009, 09:00–09:15, A021
Enhanced MRI Contrast Agents with Resonant Ultrasound — •Nouri Elmiladi, Christian Höhl, and Karl Maier — Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, 53115 Bonn
We have developed a method involving the application of ultrasound (US) in magnetic resonance imaging (MRI) in the presence of antibody coated magnetic nanoparticles to generate contrast. Similar magnetic nanoparticles are already used as contrast agents. It is interesting to control their effect by additional parameters, which can be switched on and off externally, and depend on the properties of the surrounding tissue. In performing proton nuclear magnetic resonance spectroscopy, US is applied to an aqueous sample containing magnetic nanoparticles coated with antibodies from one side only. Therefore, while the asymmetric magnetic nanoparticles in the sample are subjected to an US wave, a torque is initiated along the vibrational motion and will cause the particles to tilt periodically. The asymmetric magnetic nanoparticles will act as an US driven radio frequency antenna, leading to an increase in the spectral density function at the US frequency. If the US frequency matches the Larmor frequency, protons in the near field region of the particle are stimulated to lose energy, and the T1 of the aqueous solution decreases. A significant increase of the longitudinal proton relaxation rate is experimentally observed when using a colloidal aqueous solution of asymmetric magnetic nanoparticles.