Temperature and concentration calibration of aqueous polyvinylpyrrolidone (PVP) solutions for isotropic diffusion MRI phantoms

by Friedrich Wagner, Frederik B. Laun, Tristan A. Kuder, Anna Mlynarska, Florian Maier, Jonas Faust, Kerstin Demberg, Linus Lindemann, Boris Rivkin, Armin M. Nagel, Mark E. Ladd, Klaus Maier-Hein, Sebastian Bickelhaupt, Michael Bach

To use the "apparent diffusion coefficient" (D_app) as a quantitative imaging parameter, well-suited test fluids are essential. In this study, the previously proposed aqueous solutions of polyvinylpyrrolidone (PVP) were examined and temperature calibrations were obtained. For example, at a temperature of 20°C, D_app ranged from 1.594 (95% CI: 1.593, 1.595) μm²/ms to 0.3326 (95% CI: 0. 3304, 0.3348) μm²/ms for PVP-concentrations ranging from 10% (w/w) to 50% (w/w) using K30 polymer lengths. The temperature dependence of D_app was found to be so strong that a negligence seems not advisable. The temperature dependence is descriptively modelled by an exponential function exp(c₂ (T − 20°C)) and the determined c₂ values are reported, which can be used for temperature calibration. For example, we find the value 0.02952 K^-1 for 30% (w/w) PVP-concentration and K30 polymer length. In general, aqueous PVP solutions were found to be suitable to produce easily applicable and reliable D_app-phantoms.

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