TU‐C‐12A‐08: Thermally‐Stabilized Isotropic Diffusion Phantom for Multisite Assessment of Apparent Diffusion Coefficient Reproducibilty

Abstract

Purpose:To construct an appropriate phantom for quality control use in diffusion‐weighted imaging (DWI), to establish ground truth for measurement of apparent diffusion coefficient (ADC) and to characterize measurement linearity across a relevant physiological range of ADC.Methods:Aqueous solutions containing the polymer polyvinylpyrrolidone (PVP) were mixed at concentrations of 0, 10, 20, 30, 40 and 50% by mass PVP. These solutions were placed in 20 mL vials, arranged in concentric inner and outer circles, with a central water vial, and were fixed in a spherical phantom with a diameter of 194 mm, designed to fit into commercially‐available MRI head coils. Two prototype phantoms were constructed, and underwent inter‐site comparison in the US and EU. The phantoms were filled with an ice‐water bath to ensure stable temperature; 0 °C temperature was verified by use of a thermocouple before and after scans. The phantoms were scanned using b‐values of 0, 500 and 900 s/mm2 at several sites, using coronal and/or axial orientations and scan planes.Results:ADC values ranged from 0.12 to 1.12 × 10‐3 mm2/s, and exhibited a high degree of reproducibility across different scanners and imaging sites (coefficient of variations (CoV) ranged from 1.1 to 2.2% for 0 to 40% PVP, with 50% PVP at 11.3%). Little difference in ADCs was seen between inner and outer ring vials of the same PVP concentration (average CoV< 5% across vials, 10.3% for 50% PVP).Conclusion:The range of ADCs covers a relevant physiological range, most notably in brain white matter. The ADCs of water vials were in excellent agreement with literature values of the diffusion coefficient of water at 0 °C (1.1 × 10‐3 mm2/s). The phantom provides a much needed quality control tool for DWI, and provides ground truth with the diffusion coefficient of water at 0 °C.