Assessment of the Accuracy, Precision and Reproducibility of Apparent Diffusion Coefficient Measurements on a Clinical Magnetic Resonance Imaging System

Abstract

Purpose: The purpose of our work was to investigate delakis[1] quality control protocol for our MRI system on Tissue-equivalent diffusivity phantoms made of Nickel-doped agarose/sucrose gels.
Materials and Methods: we designed and manufactured a spherical phantom using these gels for T₁, T₂ and DW-MRI. Every compartments was filled with tissue equivalent relaxation and diffusivity gels. After that we assessed the quality control protocol for T₁, T₂ and DW-MRI on these gels and The magnetic resonance imaging of the phantom was performed on the 1.5 T clinical MRI system IMAM KHOMEINI hospital of TEHRAN (GE GENESIS SIGNA). Two parameters,Q and R, are used for the analysis of the quality control ADC values.
Results: T₂ gel values, 84.804, 80.773, 86.57, 77.774, 77 (ms), were respectively obtained for BT(body tissue), P2(tumur), P2 in air, P2 in oil, P1(ischemi). Also, their corresponding T₁ measurements were 1090.92, 1742.75, 1284.75, 1400, 1358.23 (ms) respectively. using this phantom DW- MRI experiments can be performed under very realistic conditions. The Q calculated for the p1 and p2 in different b-values (150, 400, 1000 mm s^-2 ) is smaller than the Q for BT. This observation is likely to indicate that for b values 150, 400, 1000 mm s^-2, the ADC measurement reproducibility is compromised by ADC deviations due to difference between effective and nominal b values over time. the R parameter used in our quality control protocol to quantitatively study the directional dependence is expected to be governed by the ADC fluctuation described by the equation of measurement of differences between nominal and effective b values.
Conclusion:. the quality control protocol presented in this study will be of value for monitoring the diffusion imaging performance of an MRI system in a clinically relevant way.