Characterization and reduction of gradient-induced eddy currents in the RF shield of a TEM resonator.
Radiofrequency (RF) shields that surround MRI transmit/receive coils should provide effective RF screening, without introducing unwanted eddy currents induced by gradient switching. Results are presented from a detailed examination of an effective RF shield design for a prototype transverse electromagnetic (TEM) resonator suitable for use at 3 Tesla. It was found that effective RF shielding and low eddy current sensitivity could be achieved by axial segmentation (gap width = 2.4 mm) of a relatively thick (35 microm) copper shield, etched on a kapton polyimide substrate. This design has two main advantages: first, it makes the TEM less sensitive to the external environment and RF interference; and second, it makes the RF shield mechanically robust and easy to handle and assemble.
Alecci
Marcello
M
Center for Functional Magnetic Resonance Imaging of the Brain, Department of Clinical Neurology, John Radcliffe Hospital, University of Oxford, UK.
Jezzard
Peter
P
D055590:Electromagnetic Phenomena; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D011846:Radio Waves