Measuring temperature in polyvinylpyrrolidone (PVP) solutions using MR spectroscopy.

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Materials Science

Background:

• Polyvinylpyrrolidone (PVP) water solutions are valuable for validating diffusion measurements across sites and vendors.
• Accurate temperature determination is crucial as water diffusivity is temperature-dependent.

Purpose of the Study:

• Investigate the use of MR spectroscopy (MRS) for absolute temperature measurements in PVP solutions.
• Assess the reproducibility and repeatability of temperature measurements across three different MRI scanner vendors.

Main Methods:

• Utilized a 40% PVP w/w solution in a spherical container.
• Employed a Point Resolved Spectroscopy (PRESS) sequence with water suppression on 3T scanners (GE, Siemens, Philips).
• Mapped the frequency shift of a specific PVP methylene proton peak against temperatures measured by a fiber optic probe.

Main Results:

• Identified stable proton peaks in PVP solutions, with the water peak shifting by ~-0.01 ppm/°C relative to a methylene peak.
• Demonstrated excellent repeatability (std range: 0.00-0.14°C) and reproducibility (mean difference: 0.1-0.4°C) across scanners.
• MRS-derived temperatures showed good agreement with probe measurements for in-house phantoms, with variations for commercial phantoms.

Conclusions:

• PVP solutions possess stable proton peaks suitable for temperature assessment via MR proton spectroscopy.
• MRS-based temperature measurements are fast, feasible with standard sequences, and essential for calibrating diffusion MRI.
• This technique provides fundamental data for cross-vendor validation of diffusion measurements.