Transient respiratory motion artifacts in multiple arterial phases on abdominal dynamic magnetic resonance imaging: a comparison using gadoxetate disodium and gadobutrol

Breath-hold High-resolution T1-weighted Gradient Echo Liver MR Imaging with Compressed Sensing Obtained during the Gadoxetic Acid-enhanced Hepatobiliary Phase: Image Quality and Lesion Visibility Compared with a Standard T1-weighted Sequence

PURPOSE

To evaluate the feasibility of breath-hold (BH) high-resolution (HR) T1-weighted gradient echo hepatobiliary phase (HBP) imaging using compressed sensing (CS) in gadoxetic acid-enhanced liver MRI in comparison with standard HBP imaging using parallel imaging (PI).

METHODS

The study included 122 patients with liver tumors with hypointensity in the HBP who underwent both HR HBP imaging with CS and standard HBP imaging with PI. Two radiologists evaluated the liver edge sharpness, hepatic vessel conspicuity, bile duct conspicuity, image noise, and overall image quality, as well as the lesion conspicuity on HR and standard HBP imaging and the contrast-enhanced (CE) MR cholangiography (MRC) image quality reconstructed from HBP images. As a quantitative analysis, the SNR of the liver and the liver to lesion signal intensity ratio (LLSIR) were also determined.

RESULTS

The liver edge sharpness, hepatic vessel conspicuity, bile duct conspicuity, and overall image quality as well as the lesion conspicuity and the LLSIR on HR HBP imaging with CS were significantly higher than those on standard HBP imaging (all of P < 0.001). The image quality of CE-MRC reconstructed from HR HBP imaging with CS was also significantly higher than that from standard HBP imaging (P < 0.001). Conversely, the SNR of liver in standard HBP was significantly higher than that in HR HBP with CS (P < 0.001).

CONCLUSION

BH HR HBP imaging with CS provided an improved overall image quality, lesion conspicuity, and CE-MRC visualization when compared with standard HBP imaging without extending the acquisition time.

An Intra-individual Comparison between Free-breathing Dynamic MR Imaging of the Liver Using Stack-of-stars Acquisition and the Breath-holding Method Using Cartesian Sampling or View-sharing

PURPOSE

To compare the quality of dynamic imaging between stack-of-stars acquisition without breath-holding (DISCO-Star) and the breath-holding method (Cartesian LAVA and DISCO).

METHODS

This retrospective study was conducted between October 2019 and February 2020. Two radiologists performed visual assessments of respiratory motion or pulsation artifacts, streak artifacts, liver edge sharpness, and overall image quality using a 5-point scale for two datasets: Dataset 1 (n = 107), patients with Cartesian LAVA and DISCO-Star; Dataset 2 (n = 41), patients with DISCO and DISCO-Star at different time points. Diagnosable image quality was defined as ≥ 3 points in overall image quality. Whether the scan timing of the arterial phase (AP) was appropriate was evaluated, and results between the pulse sequences were compared. In cases of inappropriate scan timing in the DISCO-Star group, retrospective reconstruction with a high frame rate (80 phases, 3 s/phase) was added.

RESULTS

The overall image quality of Cartesian LAVA was better than that of DISCO-Star in AP. However, noninferiority was shown in the ratio of diagnosable images between Cartesian LAVA and DISCO-Star in AP. There was no significant difference in the ratio of appropriate scan timing between DISCO-Star and Cartesian LAVA; however, the ratio of appropriate scan timing in DISCO-Star with high frame rate reconstruction was significantly higher than that in Cartesian LAVA in both readers. Overall image quality scores between DISCO and DISCO-Star were not significantly different in AP. There was no significant difference in the ratio of appropriate scan timing between DISCO-Star with high frame rate reconstruction and DISCO in both readers.

CONCLUSION

The use of DISCO-Star with high frame rate reconstruction is a good solution to obtain appropriate AP scan timing compared with Cartesian LAVA. DISCO-Star showed equivalent image quality in all phases and in the ratio of appropriate AP scan timing compared with DISCO.

Assessment of the relationship between the hepatic contrast enhancement effect in the hepatobiliary phase and hepatic signal changes in free-breathing continuous multiphasic dynamic EOB-MRI

PURPOSE

To investigate the relationship between the hepatic contrast enhancement effect in the hepatobiliary phase (HBP) and the contrast enhancement parameters based on the data of continuous signal changes in free-breathing multiphasic dynamic EOB-MR imaging using a compressed sensing (CS) and the self-gating technique, and to clarify which contrast enhancement parameters are useful for estimating the hepatic enhancement effect in the HPB.

METHOD

This study included 96 patients. The contrast enhancement ratio (CER) of the liver parenchyma from phase x to phase y was calculated as follows: CER_y-x: (SI_y -SI_x)/SI_x. The gradient of the regression line (GRL) was also calculated. Patients can be divided into two groups with sufficient or insufficient liver enhancement in the HBP, then each parameter was compared between these two groups.

RESULTS

In the analysis of the arterioportal phases, CER_7-pre in the sufficient HBP enhancement group was significantly higher than that in the insufficient HBP enhancement group (0.50 vs 0.44, p < 0.001). Regarding 5 min early hepatocyte phase (phases 1-28) analysis, significant differences were observed in CER_28-pre, CER_28-7 and Gradient_28-7 between the two groups (0.64 vs 0.47, 0.10 vs 0.03, 1.27 vs 0.27, all p < 0.001). For the strength of correlation, CER_7-pre, CER_28-pre, CER_28-7, and GRL_28-7 had higher correlation coefficients, compared with the blood sampling data.

CONCLUSION

CER in the arterio-portal phase and 5 min early hepatocyte phase had significant correlation with hepatic contrast enhancement effects in the 20 min HBP, suggesting that sufficient 20 min HBP enhancement may be estimated by the CER in the portal phase and 5 min early hepatocyte phase.