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Zusammenfassung:
This manuscript aims to create new kinds of volume radiofrequency coils for UHF MRI (B0 ≥ 7 T) derived from the well-known birdcage coil. Their designs are inspired from metamaterials. Based on transmission line analysis, the radiofrequency B1 field and coil’s geometry can be shaped almost as will in order to obtain coils with unique features. At first, we propose a volume coil that eases access to its inner volume. This “opencage” coil does not only improve the comfort during MRI examinations, especially for patients suffering from claustrophobia but it can also be useful for some specific applications of MRI such as motion correction. A small-animal and a head-size prototypes working at 7 T have been built and tested. Then we propose to apply this metamaterial approach to develop dualband birdcages that are sensitive simultaneously to two nuclei. Finally, we introduce a new method of passive B1 shimming based on phase conjugation technique. We theoretically investigate this method for developing a head coil for 7 T imaging, whereas later we build a prototype for imaging of rodents in a 17.2 T scanner.
