Phase-by-phase analysis of the effect of contrast dilution on multiple arterial phase image quality in gadoxetic acid-enhanced liver MRI

Background Gadoxetic acid-enhanced MRI is essential for detecting and characterizing focal liver lesions. However, transient severe motion artifacts in the arterial phase can degrade image quality. Gadoxetic acid dilution has been proposed to mitigate these artifacts, but its impact on multiple arterial phase acquisition remains unclear. Objective To evaluate the effect of gadoxetic acid dilution on image quality across multiple arterial phases in liver MRI, incorporating a phase-by-phase analysis. Methods This retrospective study included 81 patients (52 men, 29 women; mean age 70.1 years) who underwent serial gadoxetic acid-enhanced MRI with undiluted and diluted contrast (1:1 saline dilution). MRI was performed on 1.5-T and 3.0-T scanners with a standardized injection rate of 1.0 mL/s. Two radiologists independently rated anatomic conspicuity, respiratory motion artifacts, and overall image quality using a five-point Likert scale. A phase-by-phase analysis was conducted after a three-month washout period. Wilcoxon signed-rank tests were used for statistical comparisons, and inter-rater agreement was assessed with quadratic kappa coefficients. Results Inter-observer agreement was substantial (ƙ = 0.602–0.702). The diluted method showed higher but statistically non-significant improvements in anatomic conspicuity (3.73 vs. 3.59, p = 0.110), respiratory artifacts (3.54 vs. 3.41, p = 0.291), and overall image quality (3.67 vs. 3.51, p = 0.083). Phase-by-phase analysis revealed significant improvement in image quality for the first three arterial phases (p = 0.003, 0.005, 0.050), with a trend toward improvement in the last phase (p = 0.075). Conclusion Gadoxetic acid dilution improves image quality in early arterial phases of liver MRI, suggesting its potential to reduce motion artifacts.