Reducing Artifacts during Arterial Phase of Gadoxetate Disodium-enhanced MR Imaging: Dilution Method versus Reduced Injection Rate

Purpose: To compare two contrast material-administration protocols (dilution vs slow injection) in terms of their effectiveness in arterial phase artifact reduction at gadoxetic acid-enhanced magnetic resonance (MR) imaging. Materials and Methods: This HIPAA-compliant retrospective case-controlled cohort study was approved by the institutional review board, with a waiver of informed patient consent. A total of 318 consecutive patients undergoing gadoxetic acid-enhanced MR imaging were placed into one of two subcohorts of 159 consecutive patients each: the dilution subcohort (gadoxetic acid was diluted 1: 1 with saline and injected at a rate of 2.0 mL/sec) and the slow injection subcohort (gadoxetic acid was not diluted and was injected at a rate of 1.0 mL/sec). Eighty-nine patients in the dilution subcohort also underwent follow-up MR imaging with the slow injection method, and 34 patients in the slow injection subcohort underwent follow-up MR imaging with the dilution method. Both patient-and image-based analyses, as well as intraindividual analysis, were used to compare two parameters-mean artifact score rated by two observers using a five-point scale and frequency of severe artifact-between the dilution and slow injection subcohorts with the Wilcoxon Mann-Whitney test, chi(2) test, and generalized estimating equation. Results: In both patient-and image-based analyses, the mean artifact score and frequency of severe artifact were lower in the dilution subcohort (mean, 1.46% and 3.8% [six of 159]) than in the slow injection subcohort (mean, 1.95% and 15.1% [24 of 159]) (P <=.001 and P<.001, respectively). In intraindividual analysis, both variables were also decreased in the dilution subcohort (P=.007 and P=.001, respectively). We found the two variables to be significantly increased in the slow injection subcohort when compared with that in the dilution subcohort for three different MR platforms (P<.05). Conclusion: In comparison with slow injection of undiluted contrast material at a rate of 1.0 mL/sec, gadoxetic acid diluted to 50% and injected at a rate of 2 mL/sec had a significantly less severe ghosting artifact in the arterial phase of gadoxetic acid-enhanced MR imaging.