Analysis of a Monopole and Dipole Hybrid Antenna Compared With Monopole and Dipole Antennas
- Author:
Jun Moo KWAK
1
;
Yu Bin LEE
;
Myung Kyun WOO
Author Information
- Publication Type:Original Article
- From:Investigative Magnetic Resonance Imaging 2026;30(1):47-55
- CountryRepublic of Korea
- Language:English
-
Abstract:
Purpose:To characterize the electromagnetic (EM) behavior of a monopole and dipole hybrid (MDH) antenna and evaluate its performance relative to monopole and dipole antennas for 10.5 tesla (T) magnetic resonance imaging (MRI) applications.
Materials and Methods:Full-wave EM simulations were performed to model an inductor-shortened 20-cm dipole and an MDH antenna with asymmetric 9-cm and 12-cm poles. Single elements and 16-channel arrays were arranged on cylindrical formers (inner diameter 25 cm) around a tissue-mimicking phantom (εr = 49, σ = 0.6 S/m, diameter = 18 cm, height = 30 cm) with ~4 cm inter-element spacing and no additional decoupling circuitry. The eight-channel monopole antenna and MDH arrays were further modeled and analyzed with and without coaxial feed cables to assess cable-induced effects on magnetic (B) field distribution. Relative individual transmit field maps of the 8-channel monopole antenna and MDH arrays were acquired on a 10.5 T MRI system using a gradient echo (GRE) sequence (repetition time [TR] = 4000 ms, echo time [TE] = 3.0 ms, acquisition time [TA] = 7:48 ms, flip angle = 60°, field of view [FOV] = 354 × 354 mm3 , resolution = 3.0 × 1.5 × 3.0 mm3 ).
Results:The MDH antenna demonstrated enhanced longitudinal B-field concentration and improved directivity compared with the dipole antenna element. Across the 8- and 16-channel arrays, the MDH structures consistently exhibited lower coupling, reducing S 21 by up to 10 dB relative to the monopole and dipole antenna arrays. Cable attachment significantly altered the MDH field patterns, reflecting dipole-like sensitivity to commonmode currents; however, appropriate cable management preserved field stability.
Conclusion:The MDH antenna provides intrinsic decoupling advantages and robust multichannel behavior without requiring additional decoupling circuitry. These characteristics make the MDH architecture a strong candidate for next-generation high-density arrays for ultra-high field MRI.
