A compact and efficient multi-mode antenna for parallel transmission of 7T magnetic resonance imaging

With the reduced radio frequency wavelength at Ultrahigh field magnetic resonance imaging (MRI) scanner, traditional volume-type RF hardware suffers from the standing wave effect and leads to RF artefacts, e.g. inhomogeneity in the magnetic field, and signal losses of MR images. Travelling wave excitation is proposed recently to utilize the waveguide effect of the magnet bore to achieve a homogeneous magnetic field (B
₁
field) distribution in large-size samples. However the current single patch antenna does not generate diverse B
₁
field patterns and therefore could not be utilize the latest parallel transmission (pTX) technology to accelerate imaging acquisition. In this work, a compact and efficient multi-mode antenna design is proposed to exploit the pTX technology. There are several advantages of the new design over the initially proposed dielectrically loaded waveguide: First, the high efficiency and directivity of the new design is able to achieve more power efficient B
₁
field. Second, the multi-mode nature of the new design allows diverse B
₁
field generation. Third, the compact nature of this design will provide more room and reduce claustrophobia for subjects being imaged.