Reducing respiratory artifacts in gadoxetic acid-enhanced magnetic resonance imaging via a patient-adapted...

In gadoxetic acid-enhanced liver magnetic resonance imaging (MRI), an inadequate breath-holding strategy is an independent risk factor for image quality degradation in single-phase arterial acquisition. Therefore, optimizing breath-holding training protocols is critical. This study aimed to assess the effectiveness of a nongradual breath training protocol combined with contrast dilution for reducing arterial phase (AP) respiratory artifacts in upper abdomen gadoxetic acid-enhanced MRI.

In this retrospective study, we enrolled 126 patients (91 males; mean age 52.65±11.07 years) who underwent gadoxetic acid-enhanced upper abdomen MRI for the first and only time from May 2019 to February 2020. All patients were divided into four groups according to different breath-holding training strategies and contrast injection patterns (group 1: gradual strategy + diluted injection; group 2: nongradual strategy + diluted injection; group 3: gradual strategy + undiluted injection; group 4: nongradual strategy + undiluted injection). Two radiologists evaluated AP images in a blinded manner using a 5-point scale. Semiquantitative scores, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) of the hepatic artery and portal vein to the liver parenchyma, and CNR of the hepatic artery to the portal vein were compared between the four groups via Mann-Whitney and Kruskal-Wallis tests. The differences in transient severe motion (TSM) incidence rates and respiratory artifact scores between the gradual and nongradual groups were calculated via the adjusted the Chi-squared test and the Mann-Whitney, respectively.

The results of the 5-point scale evaluation showed that respiratory artifacts significantly differed between groups (group 1: 2.56±1.16; group 2: 1.53±0.62; group 3: 2.12±1.08; group 4: 1.79±0.89; P=0.002): groups 2 and 4 had smaller artifacts, and group 2 had the fewest number of artifacts. However, no statistically significant differences were observed in the scores for the hepatic artery (P=0.177), portal vein (P=0.214), abdominal aorta (P=0.599), and liver parenchyma (P=0.243) or for the total score (P=0.235). The groups significantly differed terms of portal vein SNR (P<0.001), liver parenchyma SNR (P=0.035), and the CNR of the portal vein to the liver parenchyma (P=0.008). These parameters were optimal in group 2. The incidence of TSM and the respiratory artifact score were significantly higher in the gradual group (groups 1 and 3) compared to the nongradual group (groups 2 and 4).

The nongradual breath-holding training strategy combined with an injection rate of 2 mL/s with 50% diluted gadoxetic acid could significantly reduce respiratory artifacts and improve AP image quality.