München 2009 – scientific programme

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ST: Fachverband Strahlen- und Medizinphysik

ST 8: Poster-Session FV Radiation and Medical Physics

ST 8.5: Poster

Wednesday, March 11, 2009, 17:00–17:30, Dekanatsgang

Ultrasound Frequency Doubling for MRI Detection — •Christian Höhl, Nouri Elmiladi, and Karl Maier — Helmholtz- Institut für Strahlen und Kernphysik (HISKP), Rheinische Friedrich-Wilhelms-Universität, Bonn, Germany

In combination with MRI, ultrasound (US) at Larmor frequency is of interest. But damping of high frequency US (18 MHz) in tissue is significant and prevents its penetration beyond some surface depth. In addition, the high frequency amplifier produces electromagnetic crosstalk at US frequency which influences MRI electronics.

The nonlinear answer of tissue to compressional waves at moderate US amplitudes, exploit already in modern US diagnostics, offers a possibility to solve both challenges. Generating low frequency US waves avoids resonant coupling to the MRI device and allows reasonable penetration depth in tissue. Focusing these waves increases the US amplitude locally and produces high frequency US components which can be utilized for MRI experiments.

A sample application for resonant US in MRI in combination with asymmetric magnetic nanoparticles is going to be presented.