Early exploration of MRI-compatible diagnostic ultrasound transducers

Ultrasonic echography and magnetic resonance imaging (MRI) are widely used medical diagnostic tools. The interest of combining them is based on the fact that the images are created in different ways and show different features of human tissue. Ultrasound creates images based on mechanical properties whereas MRI creates images based ultimately on chemical composition. MRI-guided focused ultrasound surgery (MRgFUS) requires operation of ultrasound transducers within the MRI system. In this case, the ultrasound intensities and corresponding electrical excitation signals are large and careful engineering can realize MRI-compatible hardware. Ultrasound imaging within MRI is more complicated, since the electrical signals in ultrasound receive mode are very much smaller. The preliminary work reported here aimed to show that it is possible to combine ultrasound and MRI technologies for imaging, with little or no degradation in signal and image quality, even though the MRI environment is hostile to other passive and electrically-active devices. The particular innovation that is reported is the use of 0-3 connectivity Cu - epoxy composites providing both electromagnetic shielding and ultrasonic matching.