Hepatic arterial phase on gadoxetic acid-enhanced liver MR imaging: a randomized comparison of 0.5 mL/s and 1 mL/s injection rates

Reducing transient severe motion artifacts of gadoxetate disodium-enhanced MRI by oxygen inhalation: effective for pleural effusion but not ascites

OBJECTIVES

To evaluate the efficacy of low-flow oxygen inhalation in mitigating transient severe motion (TSM) artifacts associated with gadoxetate disodium-enhanced hepatic magnetic resonance imaging (MRI).

METHODS

Patients undergoing gadoxetate disodium-enhanced MRI were included. During the examination, the experimental group received oxygen at 2 L/min via nasal cannula, while the control group did not. Images and TSM scores were evaluated and compared across precontrast, arterial, venous, and hepatobiliary phases. Subgroup analyses were conducted based on the presence of pleural effusion or ascites.

RESULTS

A total of 325 patients were included. The motion scores were highest in the arterial phase and lowest in the hepatobiliary phase in both groups, but were significantly lower in the experimental group (p < 0.05). The incidence of TSM was significantly lower in the experimental group (3.29%) compared to the control group (13.29%, p = 0.01). While pleural effusion was associated with reduced image quality in both groups (p < 0.05), the image quality in the pleural effusion category was higher in the experimental group than in the control group. Oxygen inhalation showed limited efficacy in mitigating TSM related to ascites.

CONCLUSIONS

Low-flow oxygen inhalation can effectively reduce the occurrence of gadoxetate disodium-related TSM. Pleural effusion may impair respiratory function and contribute to TSM, which can be alleviated by oxygen supplementation. However, Oxygen inhalation is less effective under the condition of ascites.

Clinical impact and potential utility of non-enhanced computed tomography performed immediately after transarterial chemoembolization for hepatocellular carcinoma

Background

Intratumoral lipiodol deposition following transarterial chemoembolization (TACE) is associated with the prognosis of hepatocellular carcinoma (HCC) patients. However, there is insufficient evidence regarding the actual clinical significance of the imaging tests conducted to evaluate the lipiodol uptake after TACE. This study evaluates the clinical impact and potential utility of performing immediate post-TACE non-enhanced computed tomography (NECT) on the treatment of HCC.

Methods

This retrospective study at a tertiary referral center included patients undergoing their first session of conventional TACE for initial treatment of HCC from November 2021 to December 2022 with available immediate post-TACE NECT. Patients were categorized based on lipiodol uptake into Cohorts A (incomplete uptake with additional treatment before the first follow-up 1 month after TACE), B incomplete uptake without additional treatment before first follow-up), and C (complete uptake). Survival curves for the time to progression (TTP) were estimated using the Kaplan-Meier method and were compared by using the log-rank test.

Results

Out of 189 patients, 58 (29.6%) showed incomplete lipiodol uptake; 2 in Cohort A and 56 in Cohort B. Cohort C included 131 patients (69.3%). Cohort B had the highest rate of residual viable tumor (48.2%) 1 month after TACE, compared to the other cohorts (0% in Cohort A and 32.1% in Cohort C). The median TTP of Cohort B was 7.9 months [95% confidence interval (CI): 4.6-15.7 months], significantly shorter than the 15.4 months (95% CI: 10.9-20.9 months) for Cohort C (P=0.03). During follow-up, no progression occurred in Cohort A.

Conclusions

Assessment of lipiodol uptake by performing immediate post-TACE NECT can stratify HCC patients and facilitate early prediction of therapeutic response. Identifying suboptimal lipiodol uptake immediately after TACE can aid future treatment adjustments and potentially improving oncologic outcomes.

Multiarterial Phase Acquisition in Gadoxetic Acid-Enhanced Liver MRI for the Detection of Hypervascular Hepatocellular Carcinoma in High-Risk Patients: Comparison of Compressed Sensing Versus View Sharing Techniques

OBJECTIVES

The aim of this study was to compare compressed sensing (CS) and view sharing (VS) techniques for single breath-hold multiarterial phase imaging with respect to image quality and focal liver observation detectability during gadoxetic acid-enhanced magnetic resonance imaging in patients at high risk for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

A total of 385 patients who underwent gadoxetic acid-enhanced magnetic resonance imaging, including triple arterial phases using either CS (n = 224) or VS (n = 161) techniques, were retrospectively included. Among them, 117 patients had 171 focal liver observations (median diameter, 1.3 cm), which were classified according to Liver Imaging Reporting and Data System version 2018. The acquisition rate of optimally timed late arterial phase (LAP) was assessed, and image quality, including respiratory motion artifact and observation conspicuity, was rated on a 4-point scale by 3 radiologists. The Mann-Whitney U test and nonparametric test for repeated measures data were used for image quality and observation conspicuity analysis. The jackknife alternative free-response receiver operating characteristics method was used to compare the observation detectability between the 2 techniques.

RESULTS

The CS technique showed significantly higher acquisition rate of optimally timed LAP without transient severe motion (82.1% [184/224] vs 71.4% [115/161]; P = 0.013) than the VS technique. The CS technique also demonstrated significantly improved overall image quality (3.42 ± 0.70 vs 2.97 ± 0.61; P < 0.001) compared with the VS technique. Regarding the detection of hyperenhancing observations, there was no significant difference between the figure of merits of CS and VS techniques (0.660 vs 0.665; P = 0.890). However, the CS technique showed a higher detection rate in Liver Imaging Reporting and Data System M (LR-M, probably or definitely malignant but not HCC specific) observations than the VS technique (100.0% [9/9] vs 44.4% [8/18]; P = 0.009).

CONCLUSION

The CS technique tended to provide optimally timed LAP without transient severe motion and demonstrated greater detection rate of LR-M observations than the VS technique in patients at high risk of HCC.

Influence of dilution on arterial-phase artifacts and signal intensity on gadoxetic acid-enhanced liver MRI

OBJECTIVES

To investigate the effect of saline-diluted gadoxetic acid, done for arterial-phase (AP) artifact reduction, on signal intensity (SI), and hence focal lesion conspicuity on MR imaging.

METHODS

We retrospectively examined 112 patients who each had at least two serial gadoxetic acid-enhanced liver MRIs performed at 1 ml/s, first with non-diluted (ND), then with 1:1 saline-diluted (D) contrast. Two blinded readers independently analyzed the artifacts and graded dynamic images using a 5-point scale. The absolute SI of liver parenchyma, focal liver lesions (if present), aorta, and portal vein at the level of the celiac trunk and the SI of the paraspinal muscle were measured in all phases. The signal-to-norm (SI_Norm) of the vascular structures, hepatic parenchyma and focal lesions, and the contrast-to-norm (C_Norm) of focal liver lesions were calculated.

RESULTS

AP artifacts were significantly reduced with dilution. Mean absolute contrast-enhanced liver SI was significantly higher on the D exams compared to the ND exams. Likewise, SI_Norm of liver parenchyma was significantly higher in all contrast-enhanced phases except transitional phase on the D exams. SI_Norm values in the AP for the aorta and in the PVP for portal vein were significantly higher on the diluted exams. The C_Norm was not significantly different between ND and D exams for lesions in any imaging phase. The interclass correlation coefficient was excellent (0.89).

CONCLUSION

Gadoxetic acid dilution injected at 1ml/s produces images with significantly fewer AP artifacts but no significant loss in SI_Norm or C_Norm compared to standard non-diluted images.

KEY POINTS

• Diluted gadoxetic acid at slow injection (1 ml/s) yielded images with higher SI_Norm of the liver parenchyma and preserved C_Norm for focal liver lesions. • Gadoxetic acid-enhanced MRI injected at 1 ml/s is associated with arterial-phase (AP) artifacts in 31% of exams, which may degrade image quality and limits focal liver lesion detection. • Saline dilution of gadoxetic acid 1:1 combined with a slow injection rate of 1 ml/s significantly reduced AP artifacts from 31 to 9% and non-diagnostic AP artifacts from 16 to 1%.

Effect of Gadoxetic Acid Injection Duration on Tumor Enhancement in Arterial Phase Liver MRI

RATIONALE AND OBJECTIVES

Rapid injection of gadoxetic acid has been shown not to increase tumor enhancement in arterial phase liver MRI for unknown reasons. This study aimed to investigate the effect of injection durations on peak contrast concentration in tumors and to correlate it with signal enhancement in gadoxetic acid-enhanced arterial phase MRI.

MATERIALS AND METHODS

Gadoxetic acid-enhanced arterial phase MRI was obtained using a bolus-tracking technique with injection durations of 1, 3, and 6s in six rabbits with VX2 liver tumors. The peak concentration of gadoxetic acid in the aorta and tumor was estimated by iopromide-enhanced time-resolved CT using the same injection volume and durations with those for MRI. Signal enhancement on MRI and peak enhancement on CT were compared and correlated.

RESULTS

There was no significant difference in MR signal enhancement of tumors among the 3 injection durations (p = 0.87). In CT, shorter injection durations significantly increased peak contrast concentration in the aorta (p < 0.01) but produced equivalent peak contrast concentration in tumors (p = 0.24). The longer injections resulted in the stronger correlation between peak contrast concentration in CT and MR signal enhancement in tumors (r = 0.31, 0.43, and 0.86 with 1s-, 3s-, and 6s-injection, respectively) with a statistical significance only found with 6s-injection (p = 0.03).

CONCLUSION

Estimation of contrast concentration by CT demonstrated that shorter injections did not increase peak contrast concentration in tumors despite increased peak concentration in the aorta. Furthermore, tumor signal enhancement in gadoxetic acid-enhanced arterial phase MRI was less correlated with the peak contrast concentration with shorter injections.

Intra-individual comparison of gadolinium-enhanced MRI using pseudo-golden-angle radial acquisition with gadoxetic acid-enhanced MRI for diagnosis of HCCs using LI-RADS

OBJECTIVES

To determine the usefulness of extracellular contrast agent (ECA)-enhanced multiphasic liver magnetic resonance imaging (MRI) using a pseudo-golden-angle radial acquisition scheme by intra-individual comparison with gadoxetic acid-MRI (EOB-MRI) with regard to image quality and the diagnosis of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

This prospective study enrolled 15 patients with 18 HCCs who underwent EOB-MRI using a Cartesian approach and ECA-MRI using the pseudo-golden-angle radial acquisition scheme (free-breathing continuous data acquisition for 64 s following ECA injection, generating six images). Two reviewers evaluated the arterial and portal phases of each MRI for artifacts, organ sharpness, and conspicuity of intrahepatic vessels and the hepatic tumors. A Liver Imaging Reporting and Data System category was also assigned to each lesion.

RESULTS

There were no differences in the subjective image quality analysis between the arterial phases of two MRIs (p > 0.05). However, ghosting artifact was seen only in EOB-MRI (N = 3). Six HCCs showed different signal intensities in the arterial phase or portal phase between the two MRIs; five HCCs showed arterial hyperenhancement on ECA-MRI, but not on EOB-MRI. The capsule was observed in 15 HCCs on ECA-MRI and 6 HCCs on EOB-MRI. Five and one HCC were assigned as LR-5 and LR-4 with ECA-MRI and LR-4 and LR-3 with EOB-MRI, respectively.

CONCLUSION

Free-breathing ECA-enhanced multiphasic liver MRI using a pseudo-golden-angle radial acquisition was more sensitive in detecting arterial hyperenhancement of HCC than conventional EOB-MRI, and the image quality was acceptable.

KEY POINTS

• The pseudo-golden-angle radial acquisition scheme can be applied to perform free-breathing multiphasic dynamic liver MRI. • Adopting the pseudo-golden-angle radial acquisition scheme can improve the detection of arterial enhancement of HCC. • The pseudo-golden-angle radial acquisition scheme enables motion-free liver MRI.

Experimental studies on artifacts and tumor enhancement on gadoxetic acid-enhanced arterial phase liver MRI in a rabbit VX2 tumor model

Background Rapid injection of gadoxetic acid is reported to produce more frequent artifacts and lower vascular enhancement on arterial phase liver magnetic resonance imaging (MRI). However, its effect on tumor enhancement and the mechanism of the artifacts remain unclear. Purpose To evaluate the effect of rapid injection of gadoxetic acid on artifacts and tumor enhancement during arterial phase liver MRI, and on arterial blood gases (ABGs) which may explain the cause of the artifacts. Material and Methods ABG analysis was performed in 13 free-breathing rabbits after rapid injection (1 mL/s; injection time = 0.6-0.8 s) of gadoxetic acid (0.025 mmol/kg). Dynamic liver MRI was performed in six anesthetized rabbits with VX2 tumors under a ventilation stoppage after rapid and slow injection (0.25 mL/s; injection time = 2.4-3.2 s) of gadoxetic acid. Artifacts and signal enhancement on arterial phase imaging were compared with those obtained after rapid injection of gadopentetic acid (Gd-DTPA, 0.1 mmol/kg) using a Friedman test or Kruskal-Wallis test. Results ABG analysis did not find any significant changes. Artifacts were not related to injection protocols ( P = 0.95). Aortic enhancement with slow injection of gadoxetic acid was significantly higher than that with rapid injection ( P < 0.05), and was comparable to that with Gd-DTPA injection. Tumor enhancement obtained with gadoxetic acid was not significantly different between rapid and slow injection, and was significantly lower than that with Gd-DTPA injection ( P < 0.05). Conclusion Rapid injection of gadoxetic acid did not affect ABGs and may not be the cause of the artifacts. It lowered vascular enhancement but not arterial tumor enhancement.

Quantitative Measurement of Hepatic Fibrosis with Gadoxetic Acid-Enhanced Magnetic Resonance Imaging in Patients with Chronic Hepatitis B Infection: A Comparative Study on Aspartate Aminotransferase to Platelet Ratio Index and Fibrosis-4 Index

Objective

To quantitatively measure hepatic fibrosis on gadoxetic acid-enhanced magnetic resonance (MR) in chronic hepatitis B (CHB) patients and identify the correlations with aspartate aminotransferase-to-platelet ratio index (APRI) and fibrosis-4 index (FIB-4) values.

Materials and Methods

This study on gadoxetic acid-enhanced 3T MR imaging included 81 patients with CHB infection. To quantitatively measure hepatic fibrosis, MR images were analyzed with an aim to identify inhomogeneous signal intensities calculated from a coefficient of variation (CV) map in the liver parenchyma. We also carried out a comparative analysis between APRI and FIB-4 based on metaregression results. The diagnostic performance of the CV map was evaluated using a receiver-operating characteristic (ROC) curve.

Results

In the MR images, the mean CV values in control, groups I, II, and III based on APRI were 4.08 ± 0.92, 4.24 ± 0.80, 5.64 ± 1.11, and 5.73 ± 1.28, respectively (p < 0.001). In CHB patients grouped by FIB-4, the mean CV values of groups A, B, and C were 4.22 ± 0.95, 5.40 ± 1.19, and 5.71 ± 1.17, respectively (p < 0.001). The mean CV values correlated well with APRI (r = 0.392, p < 0.001) and FIB-4 (r = 0.294, p < 0.001). In significant fibrosis group, ROC curve analysis yielded an area under the curve of 0.875 using APRI and 0.831 using FIB-4 in HB, respectively.

Conclusion

Gadoxetic acid-enhanced MR imaging for calculating a CV map showed moderate correlation with APRI and FIB-4 values and could be employed to quantitatively measure hepatic fibrosis in patients with CHB.

Triple Arterial Phase MR Imaging with Gadoxetic Acid Using a Combination of Contrast Enhanced Time Robust Angiography, Keyhole, and Viewsharing Techniques and Two-Dimensional Parallel Imaging in Comparison with Conventional Single Arterial Phase

Objective

To determine whether triple arterial phase acquisition via a combination of Contrast Enhanced Time Robust Angiography, keyhole, temporal viewsharing and parallel imaging can improve arterial phase acquisition with higher spatial resolution than single arterial phase gadoxetic-acid enhanced magnetic resonance imaging (MRI).

Materials and Methods

Informed consent was waived for this retrospective study by our Institutional Review Board. In 752 consecutive patients who underwent gadoxetic acid-enhanced liver MRI, either single (n = 587) or triple (n = 165) arterial phases was obtained in a single breath-hold under MR fluoroscopy guidance. Arterial phase timing was assessed, and the degree of motion was rated on a four-point scale. The percentage of patients achieving the late arterial phase without significant motion was compared between the two methods using the χ² test.

Results

The late arterial phase was captured at least once in 96.4% (159/165) of the triple arterial phase group and in 84.2% (494/587) of the single arterial phase group (p < 0.001). Significant motion artifacts (score ≤ 2) were observed in 13.3% (22/165), 1.2% (2/165), 4.8% (8/165) on 1st, 2nd, and 3rd scans of triple arterial phase acquisitions and 6.0% (35/587) of single phase acquisitions. Thus, the late arterial phase without significant motion artifacts was captured in 96.4% (159/165) of the triple arterial phase group and in 79.9% (469/587) of the single arterial phase group (p < 0.001).

Conclusion

Triple arterial phase imaging may reliably provide adequate arterial phase imaging for gadoxetic acid-enhanced liver MRI.

Troubleshooting Arterial-Phase MR Images of Gadoxetate Disodium-Enhanced Liver

Gadoxetate disodium is a widely used magnetic resonance (MR) contrast agent for liver MR imaging, and it provides both dynamic and hepatobiliary phase images. However, acquiring optimal arterial phase images at liver MR using gadoxetate disodium is more challenging than using conventional extracellular MR contrast agent because of the small volume administered, the gadolinium content of the agent, and the common occurrence of transient severe motion. In this article, we identify the challenges in obtaining high-quality arterial-phase images of gadoxetate disodium-enhanced liver MR imaging and present strategies for optimizing arterial-phase imaging based on the thorough review of recent research in this field.