Dielectric Phantom Recipe Generator

Dielectric phantoms are MRI phantoms that mimic the dielectric properties of human tissues.

Interest in dielectric phantoms has grown as whole-body devices have increased in static field strength from 1.5 T in the 1980s to 10.5 T today. Stronger magnets generate higher resonance frequencies associated with shorter wavelengths. Shorter wavelengths intensify interactions between an object and the electromagnetic field. These interactions cause constructive and destructive interference patterns that depend on the shape and dielectric properties of the object

Dielectric phantoms are useful in many MR applications such as RF coil development, thermometry, SAR estimation or electrical property mapping validation.

This tool can be used to determine the concentration of ingredients needed to obtain the desired relative permittivity and conductivity for a given resonance frequency (between 50 MHz and 4.5 GHz).

Our recipe comprises three ingredients:

  1. Distilled water as solvent
  2. NaCl (sodium chloride S9625: anhydrous, free-flowing, Redi-DriTM, ACS reagent, ≥ 99%, Sigma-Aldrich, St. Louis, MO) to control conductivity
  3. Polyvinylpyrrolidone (PVP-40: average molecular weight 40,000 g/mol, Sigma-Aldrich, St. Louis, MO) to control permittivity

PVP-based phantoms have several advantages, including straightforward fabrication, nontoxic character, and semitransparency that makes air bubbles easy to identify. Application of PVP-based phantoms is particularly valuable in MR thermometry due to their long T2* values and predominantly single spectral peak.

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The generator is a result of collaboration between CAI2R scientists and colleagues at the Advanced MRI Laboratory, part of the National Institutes of Health, and is hosted by the NIH.

With questions, comments, or suggestions about the dielectric phantom recipe generator, please get in touch with Ryan Brown, PhD.


Related publication:
Ianniello, C., de Zwart, J. A., Duan, Q., Deniz, C. M., Alon, L., Lee, J.-S., Lattanzi, R. and Brown, R. (2017), Synthesized tissue-equivalent dielectric phantoms using salt and polyvinylpyrrolidone solutions. Magn. Reson. Med. doi:10.1002/mrm.27005

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Philanthropic Support

We gratefully acknowledge generous support for radiology research at NYU Langone Medical Center from:
 
• The Big George Foundation
• Raymond and Beverly Sackler
• Bernard and Irene Schwartz

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