Over the years, contrast-enhanced 3D dynamic T1-weighted gradient-echo magnetic resonance (MR) imaging has played a critical role in detecting hepatocellular carcinoma (HCC). The introduction of gadoxetate disodium (GBCM_E) has promised the benefits of dynamic post-contrast imaging with the added availability of a hepatobiliary phase that may improve HCC detection and be acquired much more expeditiously than with gadobenate dimeglumine (GBCM_M). However, we found [1] recently that the arterial phase images with GBCM_E were more often contaminated with respiratory motion artifacts compared to GBCM_M, and concomitantly more patients reported acutely impaired breath-holding ability temporally related to contrast material administration. Similar observations have been reported by others [2-4]. In order to objectively quantify the effect on respiratory function, we have analyzed the respiratory waveforms recorded during dynamic scans in a prospective study. Here, we present the preliminary comparison results from two different contrast-enhanced liver dynamic MR studies on 104 subjects. All patients signed a consent form for this prospective IRB approved study. All measurements were performed on a 1.5T MR scanner (Philips Healthcare, Best, The Netherlands) equipped with multichannel phased-array coils. Subjects were instructed on breath-holding before acquiring the dynamic and 3 post-contrast phases (arterial, venous, and late dynamic) using a 3D spoiled-gradient echo pulse sequence. The respiratory waveforms for all dynamic phases were recorded. Linear partial Fourier k-space fillings were used for both phase encoding directions resulting in the time to k-space center to be equal to one third of the scan duration (< 20 sec). The outer loop in two phase encodings was set in the AP (anterior to posterior) direction. Both GBCM_E and GBCM_M were administrated intravenously following published protocols [1]. The choice of contrast agent was selected based on clinical need, with 67 and 37 subjects injected with GBCM_M and GBCM_E, respectively. The respiratory waveforms for each dynamic phase acquisition were extracted. Before calculating the discriminative metrics, those extracted waveforms were weighted by a Gaussian function whose highest point was matched to the time to k-space center. The root-mean-square (RMS) was derived from individual weighted respiratory waveforms, and two RMS differences were defined between pre-contrast and late dynamic (RMSD1) and between arterial phase and late dynamic (RMSD2). The mean (ave) and the standard-deviation (σ) of all RMSD1 were calculated to produce discriminative thresholds (ave ± 2σ), with which the relative change in RMSD2 (i.e. ΔRMSD = RMSD2 - RMSD1) was compared to determine the effect of contrast material injection on the respiratory waveform during the arterial phase. All data analysis and image visualization were done using home-grown software written in Matlab (Release 2014b, The MathWorks, Inc., Natick, MA.) and IDL (Release 8.5, Exelis Visual Information Solutions, Boulder, CO). For 93 out of 104 subjects, RMSD1 and RMSD2 were comparable within the discriminative thresholds (data not shown), indicating consistent breath-holding patterns during all phases dynamic scans. Figure 1 (b) shows ΔRMSD (filled circle and diamond) and the associated baseline RMSD1 (cross and plus) for those who received GBCM_E (in red) and GBCM_M (in blue), respectively. Discriminatory thresholds are represented by dashed green lines. If subjects held their breath well initially and had ΔRMSD values beyond the discriminatory thresholds, they are considered as having experienced unexpected contrast material-induced respiratory motion during the arterial phase. We found that GBCM_E was significantly more likely (9/37 vs. 1/67, p=0.0003) to cause adverse respiratory motion in the arterial phase compared with GBCM_M. Additionally, the percentages of subjects who could not hold their breath well during all phases dynamic scans (indicated by ‘+’ and ‘x’ beyond the dashed-lines) were similar (5/67 vs. 3/37) across contrast agents. An exemplary GBCM_E-enhanced case (indicated by a green arrow in Fig. 1 (b)) is presented in Figure 1 (a), which shows the compromised arterial phase image (lower-left panel) and the corresponding oscillated respiratory waveform (red line in upper-left panel). For comparison, an exemplary GBCM_M-enhanced case is presented in Figure 1 (c) showing consistent normal breath-holding and high-quality dynamic images. In summary, the indicative metrics derived from recorded respiratory waveforms objectively confirm prior reported observations that gadoxetate disodium (GBCM_E) has a significantly higher likelihood of inducing acute transient breath-holding difficulties that adversely affect arterial phase image quality.