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A simple head‐sized phantom for realistic static and radiofrequency characterization at high fields
Author(s) -
Brink Wyger M.,
Wu Zhiyi,
Webb Andrew G.
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.27153
Subject(s) - imaging phantom , materials science , head (geology) , biomedical engineering , human head , nuclear magnetic resonance , characterization (materials science) , optics , physics , nanotechnology , coupling (piping) , medicine , geomorphology , metallurgy , geology
Purpose To demonstrate a simple head‐sized phantom for realistic static and RF field characterization in high field systems. Methods The head‐sized phantom was composed of an ellipsoidal compartment and a spherical cavity to mimic the nasal cavity. The phantom was filled with an aqueous solution of polyvinylpyrrolidone (PVP), to mimic the average dielectric properties of brain tissue. The static and RF field distributions were characterized on a 7T MRI system and compared to in vivo measurements and simulations. MR thermometry was performed, and the results were compared to thermal simulations for RF validation purposes. Results Accurate reproduction of both static and RF fields patterns observed in vivo was confirmed experimentally and was shown to be strongly affected by the inclusion of the spherical cavity. MR thermometry and transmit efficiency ( B 1 + ) measurements were obtained in close agreement with simulations (peak values agreeing within 0.3 °C and 0.02 μT/√W) as well as fiber optic thermal probes (RMSE < 0.18 °C). Conclusions A simple head‐sized phantom has been presented that produces B 0 andB 1 +nonuniformities similar to those encountered in the human head and allows for accurate MR thermometry measurements, making this a suitable reference phantom for RF validation and methodological development in high field MRI.