  Objective: To develop and evaluate a bore-integrated patch antenna array
designed for whole-body excitation in ultra-high-field (UHF) magnetic resonance
imaging (MRI) with improved transmit efficiency and address the limitations of
existing RF coil designs. Methods: The proposed patch antenna array utilizes
the MRI bore's RF shield as a functional component to enhance the RF magnetic
field ($B_1^+$) distribution. Numerical simulations were conducted to compare
the performance of the patch antenna array to bore-integrated stripline and
local dipole arrays. A decoupling structure was implemented to minimize
coupling between adjacent patch antennas. The performance of the patch array
was evaluated experimentally. Results: The proposed patch array provides 3.9
times higher averaged transmit (Tx) efficiency in the CP mode and 3.0 times
higher for the phase shimming regime versus the bore-integrated stripline
array. Conclusion: Compared to the stripline array, the bore-integrated patch
antenna array offers significant improvements in Tx efficiency for whole-body
UHF MRI. Significance: The findings support the feasibility of integrating
arrays into the RF shield of MRI scanners. This could broaden the clinical use
of UHF body MRI technology.
