Reduction of wave phenomena in high-field MRI experiments using absorbing layers.
Wave behavior, such as constructive and destructive interference, can decrease RF field homogeneity. As the static magnetic field strengths increase, these effects become more significant, resulting in image inhomogeneities. For a surface coil, wave interference is due to reflections at boundaries separating regions with largely different dielectric constants. An approach is presented to eliminate wave reflections through the use of absorbing layers. A one-dimensional plane wave model and a three-dimensional finite difference time domain numerical model at 470 MHz are presented validating the theoretical effectiveness of the approach. The findings are verified experimentally with 1 H MRI on phantoms at 11.1 T, demonstrating greatly reduced interference patterns in the images.
Caserta
Jim
J
Analog Devices, 1208 Crabtree Dr., Winston Salem, NC 27127, USA. jim.caserta@triad.rr.com
Beck
Barbara L
BL
Fitzsimmons
Jeffrey R
JR
D000042:Absorption; D003198:Computer Simulation; D006801:Humans; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D008962:Models, Theoretical; D019047:Phantoms, Imaging