title: Characterization of a dielectric phantom for high-field magnetic resonance imaging applications.
abstract: OBJECTIVE
  In this work, a generic recipe for an inexpensive and nontoxic phantom was developed within a range of biologically relevant dielectric properties from 150 MHz to 4.5 GHz.
  
  
  METHODS
  The recipe includes deionized water as the solvent, NaCl to primarily control conductivity, sucrose to primarily control permittivity, agar-agar to gel the solution and reduce heat diffusivity, and benzoic acid to preserve the gel. Two hundred and seventeen samples were prepared to cover the feasible range of NaCl and sucrose concentrations. Their dielectric properties were measured using a commercial dielectric probe and were fitted to a 3D polynomial to generate a recipe describing the properties as a function of NaCl concentration, sucrose concentration, and frequency.
  
  
  RESULTS
  Results indicated that the intuitive linear and independent relationships between NaCl and conductivity and between sucrose and permittivity are not valid. A generic polynomial recipe was developed to characterize the complex relationship between the solutes and the resulting dielectric values and has been made publicly available as a web application. In representative mixtures developed to mimic brain and muscle tissue, less than 2% difference was observed between the predicted and measured conductivity and permittivity values.
  
  
  CONCLUSIONS
  It is expected that the recipe will be useful for generating dielectric phantoms for general magnetic resonance imaging (MRI) coil development at high magnetic field strength, including coil safety evaluation as well as pulse sequence evaluation (including B₁(+) mapping, B₁(+) shimming, and selective excitation pulse design), and other non-MRI applications which require biologically equivalent dielectric properties.
authors.affiliation: Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Qi
authors.initials: Q
authors.lastname: Duan
authors.affiliation: Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Jeff H
authors.initials: JH
authors.lastname: Duyn
authors.affiliation: Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Natalia
authors.initials: N
authors.lastname: Gudino
authors.affiliation: Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Jacco A
authors.initials: JA
authors.lastname: de Zwart
authors.affiliation: Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Peter
authors.initials: P
authors.lastname: van Gelderen
authors.affiliation: The Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York 10016.
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Sodickson
authors.affiliation: The Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York 10016.
authors.forename: Ryan
authors.initials: R
authors.lastname: Brown
mesh_terms: D000362:Agar / Q000737:chemistry; D019817:Benzoic Acid / Q000737:chemistry; D001921:Brain; D004553:Electric Conductivity; D005240:Feasibility Studies; D020407:Internet; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008954:Models, Biological; D009132:Muscles / Q000737:chemistry; D019047:Phantoms, Imaging / Q000191:economics; D012965:Sodium Chloride / Q000737:chemistry; D013395:Sucrose / Q000737:chemistry; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D012965:Sodium Chloride; D013395:Sucrose; D019817:Benzoic Acid; D000362:Agar