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

To use the apparent diffusion coefficient (D-app) as a quantitative imaging parameter, wellsuited 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 degrees C, D-app ranged from 1.594 (95% CI: 1.593, 1.595) mu m(2)/ms to 0.3326 (95% CI: 0. 3304, 0.3348) mu m(2)/ms for PVP-concentrations ranging from 10% (w/w) to 50% (w/w) using K30 polymer lengths. The temperature dependence of Dapp was found to be so strong that a negligence seems not advisable. The temperature dependence is descriptively modelled by an exponential function exp(c(2) (T-20 degrees C)) and the determined c(2) 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.