Impact of Magnetic Field Strength (1.5 T vs. 3.0 T) on the Prognostic Value of Quantitative ADC Indices in Patients After Out-of-Hospital Cardiac Arrest: A Prospective Multicenter Observational Study in Korea (The KORHN-PRO Registry)

Background/Objectives: Although 3.0-Tesla (3.0 T) MRI is widely used and affects quantitative imaging, its impact on predicting outcomes for cardiac arrest survivors remains unexplored. This study investigated how magnetic field strength affects voxel-based apparent diffusion coefficient (ADC) analysis in resuscitated cardiac arrest patients. Methods: Using multicenter data from the Korean Hypothermia Network, ADC images were extracted from patients who underwent diffusion-weighted imaging. For each patient, the mean ADC and the percentage of voxels (PV) below specific thresholds were calculated. Receiver operating characteristic (ROC) analysis evaluated predictive performance for poor outcomes and established cut-off values. All parameters were compared between 1.5 T and 3.0 T MRI groups. Results: In the poor outcome group, mean ADC and PV indices showed no significant differences between the two magnetic strengths. However, in the good outcome group, the 3.0 T group exhibited significantly higher PV indices than the 1.5 T group. For predicting poor outcomes, 3.0 T MRI showed numerically higher area under the curve (AUC) values (0.877–0.895) than 1.5 T MRI (0.821–0.831). Cut-off values for predicting poor outcomes were also generally higher in the 3.0 T group. Conclusions: Magnetic field strength may affect quantitative ADC values and prognostic performance in cardiac arrest patients. Although AUCs were numerically higher at 3.0 T for all evaluated indices, this difference reached statistical significance only for PV500. Field strength should therefore be considered when establishing quantitative ADC thresholds.