Adaptive radiofrequency shimming in MRI using reconfigurable dielectric materials
Paulina Šiurytė (TU Delft - ImPhys/Weingärtner group)
Robert van de Velde (Student TU Delft)
Jasper van Leeuwen (Student TU Delft)
Kadir Berat Yildirim (Student TU Delft)
Ömer Can Akgün (Nikhef)
Wyger Brink (University of Twente)
Sebastian Weingärtner (TU Delft - ImPhys/Weingärtner group)
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Abstract
Inhomogeneity of the transmitted radiofrequency field () is a major factor hindering the image quality in Magnetic Resonance Imaging (MRI) at high field strengths. Here, a novel approach is presented, to locally modulate the utilizing an array of high permittivity materials with switchable connections. A 33 array of barium titanate suspension elements was constructed, with two PIN diode-based switchable connectors per element. Electromagnetic simulations were performed to determine configurations that produce strong modulation. Remote field switching was tested in a disk- and a torso-shaped phantom at 3T by applying different bias voltages to the PIN diodes. The attained modulation was assessed at various switching pattern positions and various depths within the phantoms. The configuration with the strongest effect size has produced up to 11 modulation in simulations at 15 mm depth, with excellent translation properties. The effects were successfully replicated in phantoms, with a 5 V bias voltage producing up to 11.6±0.2 modulation. At the relative depth of the human heart, up to 6 of modulation was observed in the torso phantom. The presented method may provide a promising direction for cost-effective, and adaptive shimming without changes to the scanner hardware.
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