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, 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) μm(2)/ms to 0.3326 (95% CI: 0. 3304, 0.3348) μm(2)/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(c(2) (T − 20°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.