A preparatory study for the setting up of a QC protocol for the use of the sensitometry vials of an MR Magphan phantom

Abstract

Background: Quantitative MRI (qMRI) enables detailed tissue characterization via T1 and T2 relaxation times but lacks standardized validation protocols, hence limiting clinical adoption. In Malta, the absence of quality control (QC) procedures for relaxometry on clinical MRI systems creates further uncertainty around the reproducibility and validity of qMRI results, ultimately affecting the reliability of patient diagnosis and monitoring. Objectives: To establish a QC framework for the Magphan SMR100 phantom’s sensitometry vials by introducing a standard operating procedure (SOP) for phantombased relaxometry assessment. This included the development of a tissue-equivalent phantom, optimized imaging protocols, and accurate post-processing techniques for relaxometry analysis. Research Methodology: A set of gel-based phantom solutions with varying agarose and nickel chloride concentrations were prepared to simulate clinically relevant relaxation values. Imaging was conducted over three sessions using established pulse sequences on a 3T scanner. Relaxometry values for each solution and sequence were estimated and compared using two- and three-parameter fitting models. Accuracy was evaluated against an established benchmark, while consistency was monitored over three months. Additionally, the impact of temperature on relaxation times was examined. Finally, a SOP was developed. Results: The three-parameter fitting model provided more accurate and stable T1 estimates with improved R² values. T1 and T2 measurements demonstrated high reproducibility, with coefficients of variation below 3%. Deviation analysis showed that T1 values remained within ±9% of target values, while T2 deviations were within ±18%. Both relaxation times decreased with cooling, with T2 showing greater sensitivity. T1 mapping sequences showed strong agreement, validating the use of accelerated protocols for QC. Conclusions and Recommendations: The study laid the groundwork for a qMRI QC framework by developing a tissue-mimicking phantom, accurate relaxometry protocols, and formulating a SOP. This framework can be applied directly to routine phantom-based measurements or serve as a validation reference for future qMRI techniques.