Synthesized tissue-equivalent dielectric phantoms using salt and polyvinylpyrrolidone solutions : Synthesized Tissue-Equivalent Dielectric Properties Using a Water-Soluble Polymer

Abstract

<div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d8604119e179">Purpose</h5> <p id="P1">To explore the use of polyvinylpyrrolidone (PVP) for simulated materials with tissue-equivalent dielectric properties. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d8604119e184">Methods</h5> <p id="P2">PVP and salt were used to control, respectively, relative permittivity and electrical conductivity in a collection of 63 samples with a range of solute concentrations. Their dielectric properties were measured with a commercial probe and fitted to a 3D polynomial in order to establish an empirical recipe. The material’s thermal properties and MR spectra were measured. </p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d8604119e189">Results</h5> <p id="P3">The empirical polynomial recipe (available at <a data-untrusted="" href="http://www.amri.ninds.nih.gov/phantomrecipe.html" id="d8604119e193" target="xrefwindow">http://www.amri.ninds.nih.gov/phantomrecipe.html</a>) provides the PVP and salt concentrations required for dielectric materials with permittivity and electrical conductivity values between ~ 45 and 78, and 0.1 to 2 S/m, respectively, from 50 MHz to 4.5 GHz. The second (solute concentrations) and seventh (frequency) order polynomial recipe provided less than 2.5% relative error between the measured and target properties. PVP’s side peaks in the spectra were negligible and unaffected by temperature changes. </p> </div><div class="section"> <a class="named-anchor" id="S4"> <!-- named anchor --> </a> <h5 class="section-title" id="d8604119e197">Conclusion</h5> <p id="P4">PVP-based phantoms are easy to prepare, non-toxic, and their semi-transparency makes air bubbles easy to identify. The polymer can be used to create simulated material with a range of dielectric properties, negligible spectral side peaks and long T ₂ relaxation time, which are favorable in many MR applications. </p> </div>