High Spatial Resolution T1-Weighted MR Imaging of Liver and Biliary Tract During Uptake Phase of a Hepatocyte-Specific Contrast Medium:

Free-breathing liver fat and R 2 ∗ quantification using motion-corrected averaging based on a nonlocal means algorithm

PURPOSE

To propose a motion-robust chemical shift-encoded (CSE) method with high signal-to-noise (SNR) for accurate quantification of liver proton density fat fraction (PDFF) and R 2 ∗ .

METHODS

A free-breathing multi-repetition 2D CSE acquisition with motion-corrected averaging using nonlocal means (NLM) was proposed. PDFF and R 2 ∗ quantified with 2D CSE-NLM were compared to two alternative 2D techniques: direct averaging and single acquisition (2D 1ave) in a digital phantom. Further, 2D NLM was compared in patients to 3D techniques (standard breath-hold, free-breathing and navigated), and the alternative 2D techniques. A reader study and quantitative analysis (Bland-Altman, correlation analysis, paired Student's t-test) were performed to evaluate the image quality and assess PDFF and R 2 ∗ measurements in regions of interest.

RESULTS

In simulations, 2D NLM resulted in lower standard deviations (STDs) of PDFF (2.7%) and R 2 ∗ (8.2  s - 1 ) compared to direct averaging (PDFF: 3.1%, R 2 ∗ : 13.6  s - 1 ) and 2D 1ave (PDFF: 8.7%, R 2 ∗ : 33.2  s - 1 ). In patients, 2D NLM resulted in fewer motion artifacts than 3D free-breathing and 3D navigated, less signal loss than 2D direct averaging, and higher SNR than 2D 1ave. Quantitatively, the STDs of PDFF and R 2 ∗ of 2D NLM were comparable to those of 2D direct averaging (p>0.05). 2D NLM reduced bias, particularly in R 2 ∗ (-5.73 to -0.36  s - 1 ) that arises in direct averaging (-3.96 to 11.22  s - 1 ) in the presence of motion.

CONCLUSIONS

2D CSE-NLM enables accurate mapping of PDFF and R 2 ∗ in the liver during free-breathing.

Usefulness of breath-hold inversion recovery-prepared T1-weighted two-dimensional gradient echo sequence for detection of hepatocellular carcinoma in Gd-EOB-DTPA-enhanced MR imaging

The aim is to evaluate the diagnostic performance and the added value of breath-hold inversion recovery-prepared T1-weighted two-dimensional gradient echo (IR-2D-GRE) sequence for detection of hepatocellular carcinoma (HCC) in patients with insufficient liver parenchymal enhancement during the hepatobiliary phase (HBP) of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI). Seventeen patients with a quantitative liver-to-spleen contrast ratio of ≤1.5 on HBP images and 36 HCCs were included. Liver-to-lesion contrast ratios on HBP images obtained with IR-2D-GRE sequence were significantly higher than those with three-dimensional gradient echo sequence. The addition of IR-2D-GRE sequence during HBP of Gd-EOB-DTPA-enhanced MRI yielded higher diagnostic accuracy and improved sensitivity.

The Impact of Gd-Eob-Dtpa-Enhanced MR Cholangiography in Biliary Diseases: Comparison with T2-Weighted MR Cholangiopancreatography

BACKGROUND

Contrast enhanced magnetic resonance cholangiography is a novel technique and promising method in demonstrating biliary tree anatomy and evaluating biliary disorders. However, to date, there are a limited number of studies that have focused on the impact of this technique.

AIMS

We aimed to evaluate the additional role of contrast enhanced MR cholangiography (MRC) and compare contrast enhanced MRC with T2-weighted (w) magnetic resonance cholangiopancreatography (MRCP) in the diagnosis of biliary disorders.

STUDY DESIGN

Diagnostic accuracy study.

METHODS

The T2w-MRCP and contrast enhanced MRC sequences of 31 patients whose gold standard test results were available were scored visually for the existence of pathological findings with regard to any of the biliary diseases. Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) was used as the contrast agent. The correlation values were determined according to the statistical analysis made from those scores and the sensitivity, specificity and accuracy values of each sequence were detected as well.

RESULTS

We detected that the correlation values with gold standard methods of contrast enhanced MRC sequences were significantly higher than the ones of T2w-MRCP sequences. The correlation ratios of T2w-MRCP sequences were between 26 and 34%, while those for contrast enhanced MRC sequences were between 81 and 83% for the first reader and the correlation ratios of T2w-MRCP sequences were between 10 and 61%, whereas those of contrast enhanced MRC were between 79 and 81% for the second reader The mean sensitivity, specificity and accuracy values of T2w-MRCP sequences were 14.3-42.5%, 85-89.2% and 59.3-72.5%, respectively, while the mean sensitivity, specificity and accuracy values of contrast enhanced MRC sequences were 100%, 86.7% and 93.2-93.3%, respectively.

CONCLUSION

We suggest that obtaining of contrast enhanced MRC sequences in addition to the T2w-MRCP can be useful in the diagnosis of many diseases in relation with biliary tree.

Single-breath-hold thin-slice gadoxetic acid-enhanced hepatobiliary MR imaging using a newly developed three-dimensional fast spoiled gradient-echo sequence

PURPOSE

To prospectively evaluate the efficacy of a new three-dimensional gradient-echo sequence (Turbo LAVA) that uses undersampled k-space acquisition combined with a two-dimensional parallel imaging technique for hepatobiliary MRI.

MATERIALS AND METHODS

Sixty patients underwent T1-weighted gadoxetic acid-enhanced hepatobiliary axial MRI during a single breath-hold using both Turbo LAVA (thickness/interval=1.6/0.8mm) and conventional three-dimensional gradient-echo (4/2mm; LAVA) sequences at 3T. Axial 4-mm-thick reformation was performed from Turbo LAVA images. Portal vein-to-liver contrast (PLC), bile duct-to-liver contrast (BLC), and lesion-to-liver contrast (LLC) were compared. Two radiologists independently assessed image quality using a five-point scale. Sagittal 4-mm-thick multiplanar reconstructions (MPR) were performed from both sequences and assessed together with directly obtained 4-mm-thick sagittal LAVA images in terms of sharpness. The paired t-test was used to compare PLC, BLC, and LLC. The Wilcoxon signed rank test was used to compare five-point scales.

RESULTS

The mean PLC (P<0.001), BLC (P<0.001), and LLC (P<0.005) were significantly higher for Turbo LAVA than for LAVA; the scores for image noise and sharpness were inferior (P=0.000 and 0.005) and superior (0.005 and 0.157) for Turbo LAVA. There were no significant differences in the scores for bile duct visualization, artifacts, fat suppression quality, overall quality, and focal lesion conspicuity. For sagittal images, MPR Turbo LAVA showed significantly better sharpness than MPR LAVA but showed significantly worse sharpness compared with directly obtained LAVA.

CONCLUSION

High-spatial-resolution single-breath-hold hepatobiliary MRI using Turbo LAVA was feasible. Diagnostic-quality MPR images can be obtained using this sequence.

Navigated three-dimensional T1-weighted gradient-echo sequence for gadoxetic acid liver magnetic resonance imaging in patients with limited breath-holding capacity

PURPOSE

To determine whether a navigator-gated three-dimensional T1-weighted gradient-echo sequence (T1W-GRE, navigated LAVA) can improve diagnostic performance for the detection of focal liver lesions (FLLs) compared to standard breath-hold (BH) T1W-GRE breath-hold LAVA (BH-LAVA) during the hepatobiliary phase (HBP) of gadoxetic acid liver magnetic resonance imaging (MRI) in patients with limited breath-holding capacity.

MATERIALS AND METHODS

This retrospective study was approved by our institutional review board and the requirement for informed consent was waived. We included 372 patients who underwent liver MRI including both navigated LAVA and BH-LAVA sequences. Overall image quality of the two HBP image sets was compared. In patients with limited breath-holding capacity, diagnostic performances in detecting FLLs on the two HBP images were compared using jackknife-alternative free-response receiver-operating characteristic (JAFROC) analysis by two reviewers.

RESULTS

There were 13 cases (13/372; 3.5%) of image acquisition failure using the navigated LAVA sequence due to severe irregular breathing, and 50 of 359 patients had limited breath-holding capacity. In these patients, overall image quality of navigated LAVA (2.78 ± 0.95) was significantly better than that of BH-LAVA (2.42 ± 0.81, P < 0.005), and both readers showed significantly higher JAFROC figure-of-merit values with navigated LAVA compared to BH-LAVA (0.94 and 0.86 in reviewer 1, respectively; 0.89 and 0.83 in reviewer 2, respectively, P < 0.005). Overall image quality of navigated LAVA was also better than that of BH-LAVA in patients with sufficient breath-holding capacity (n = 309, 3.96 ± 0.88, 3.81 ± 0.66, respectively, P < 0.001).

CONCLUSION

The navigated LAVA sequence could provide better image quality and diagnostic performance in detecting FLLs than BH-LAVA in patients with limited breath-holding capacity during HBP of gadoxetic acid MRI.

Quantification of liver fat with respiratory-gated quantitative chemical shift encoded MRI

PURPOSE

To evaluate free-breathing chemical shift-encoded (CSE) magnetic resonance imaging (MRI) for quantification of hepatic proton density fat-fraction (PDFF). A secondary purpose was to evaluate hepatic R2* values measured using free-breathing quantitative CSE-MRI.

MATERIALS AND METHODS

Fifty patients (mean age, 56 years) were prospectively recruited and underwent the following four acquisitions to measure PDFF and R2*; 1) conventional breath-hold CSE-MRI (BH-CSE); 2) respiratory-gated CSE-MRI using respiratory bellows (BL-CSE); 3) respiratory-gated CSE-MRI using navigator echoes (NV-CSE); and 4) single voxel MR spectroscopy (MRS) as the reference standard for PDFF. Image quality was evaluated by two radiologists. MRI-PDFF measured from the three CSE-MRI methods were compared with MRS-PDFF using linear regression. The PDFF and R2* values were compared using two one-sided t-test to evaluate statistical equivalence.

RESULTS

There was no significant difference in the image quality scores among the three CSE-MRI methods for either PDFF (P = 1.000) or R2* maps (P = 0.359-1.000). Correlation coefficients (95% confidence interval [CI]) for the PDFF comparisons were 0.98 (0.96-0.99) for BH-, 0.99 (0.97-0.99) for BL-, and 0.99 (0.98-0.99) for NV-CSE. The statistical equivalence test revealed that the mean difference in PDFF and R2* between any two of the three CSE-MRI methods was less than ±1 percentage point (pp) and ±5 s(-1) , respectively (P < 0.046).

CONCLUSION

Respiratory-gated CSE-MRI with respiratory bellows or navigator echo are feasible methods to quantify liver PDFF and R2* and are as valid as the standard breath-hold technique.

An increased flip angle in late phase Gd-EOB-DTPA MRI shows improved performance in bile duct visualization compared to T2w-MRCP

OBJECTIVES

To estimate the additional value of an increased flip angle of 35° in late phase Gd-EOB-DTPA-enhanced magnetic resonance cholangiography, as compared to T2w-MRCP.

METHODS

40 adult patients underwent Gd-EOB-DTPA enhanced MRI of the liver including a T2-weighted 3D TSE MRCP (T2w-MRCP) as well as a late phase T1-weighted THRIVE sequences applying a flip angle of 35° (fa35). Two experienced observers evaluated the images regarding the delineation of the different biliary regions using a three-point grading system. A five-point scale was applied to determine the readers' confidence in identifying anatomical variations of the biliary tree. ROI analysis was performed to compare the signal-to-noise (SNR) and contrast-to-noise (CNR) ratios.

RESULTS

The quality for visualizing the biliary tree differed between T2w-MRCP and fa35 (p=<0.001). Late phase EOB-MRC was rated as good for delineating the entire biliary system, whereas T2w-MRCP received an overall poor rating. Especially the depiction of the intrahepatic bile ducts was estimated as problematic in T2w-MRCP. T2w-MRCP and fa35 revealed a discordant assessment of anatomical variations in 12.5% of the cases, comprising a generally higher confidence level for fa35 (4.0 ± 1.1 vs. 2.2 ± 1.2, p=<0.001). SNR proofed to be significantly higher in fa35 (p=<0.001), whereas T2w-MRCP revealed a significantly higher CNR (<0.001).

CONCLUSIONS

Gd-EOB-DTPA enhanced magnetic resonance cholangiography acquired with a flip angle of 35° revealed a better diagnostic performance compared to T2w-MRCP and might be a valuable adjunct in assessing functional bile duct abnormalities.

MRI assessment of biliary ductal obstruction: is there added value of T1-weighted gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced MR cholangiography?

OBJECTIVE

The goal of the present study was to determine the added value of gadolium-ethoxybenzyl-diethylenetriamine pentaacetic acid (gadoxetate disodium)-enhanced magnetic resonance cholangiography (MRC) to standard liver MRI including T2-weighted MRCP in assessment of biliary ductal obstruction.

MATERIALS AND METHODS

Thirty-eight patients (mean age, 48.1 ± 16.7 years) (40 total examinations) who underwent liver MRI (including T2-weighted MRCP and gadoxetate disodium-enhanced MRC) for suspicion of biliary disease were included in this institutional review board-approved, HIPAA-compliant retrospective study. Three blinded radiologists first evaluated MR images without gadoxetate disodium-enhanced MRC for presence and significance of biliary obstruction, underlying cause for obstruction, and confidence in final diagnosis. After inclusion of gadoxetate disodium-enhanced MRC, readers again determined presence and significance of biliary obstruction and confidence in final diagnosis. Reference standard was established using MRI along with ERCP, percutaneous transhepatic cholangiography, intraoperative cholangiography, or a combination thereof.

RESULTS

Overall sensitivity across all readers in diagnosing significance of obstruction was 60% without gadoxetate disodium-enhanced MRC and 91% with gadoxetate disodium- enhanced MRC (p < 0.001). Across all readers, assessment of significance of obstruction was changed when adding gadoxetate disodium-enhanced MRC in 40 of 120 cases (33%); significance of obstruction was correctly changed in 35 of 40 cases (87.5%). Biliary obstruction was graded of unknown significance in 27 of 120 cases (22.5%) across all readers when gadoxetate disodium-enhanced MRC was not reviewed. Significance of biliary obstruction was classified correctly after adding gadoxetate disodium-enhanced MRC in 25 of these 27 cases (93%). Confidence in final diagnosis was significantly higher with addition of gadoxetate di-sodium-enhanced MRC for two of three readers (p < 0.003).

CONCLUSION

Addition of gadoxetate disodium-enhanced MRC to liver MRI significantly improves sensitivity in assessing significance of biliary obstruction and can improve reader confidence in establishing a final diagnosis. This added information could have a substantial impact in the determination of the most appropriate therapeutic options.

Comparison of high spatial resolution respiratory triggered inversion recovery-prepared spoiled gradient echo sequence with standard breathhold T1 sequence MRI of the liver using gadoxetic acid

PURPOSE

To assess if a high resolution respiratory triggered inversion recovery prepared GRE sequence (RT) improved image quality and detection of lesions compared with breathhold GRE T1 weighted MR sequence (BH) in the hepatobiliary uptake phase of MR of the liver using gadoxetic acid (Gd-EOB-DTPA).

MATERIALS AND METHODS

Thirty-eight consecutive patients from July 2009 to September 2010 who had undergone Gd-EOB-DTPA enhanced liver exams were retrospectively identified. Qualitative assessment performed on reference lesions and background liver by two independent readers. Quantitative assessment performed by one reader.

RESULTS

Liver parenchyma signal-to-noise ratio for BH was 90.3 ± 23.9 (mean ± SD) and RT, 106.1 ± 40.4 (P = 0.119). For BH, 320 lesions were detected compared with 257 for RT. Lesion to liver contrast was significantly better on RT sequences (0.26 ± 0.24; mean ± SD) compared with BH sequence (0.21 ± 0.20; P = 0.044). Fifty-seven reference lesions assessed. Both reviewers rated BH better for lesion margin and hepatic vessel sharpness. BH was rated with less artifact (P < 0.05). Lesion to liver contrast on BH was significantly better for one reviewer.

CONCLUSION

BH sequence had better overall image quality than RT in several quantitative and qualitative factors including number of lesions detected and level of artifact.

Flip angle modulations in late phase Gd-EOB-DTPA MRI improve the identification of the biliary system

OBJECTIVES

To assess the improvement of bile duct visualization in Gd-EOB-DTPA enhanced MR-cholangiography (EOB-MRC) by using an increased flip angle.

METHODS

35 patients underwent Gd-EOB-DTPA enhanced MRI of the liver including T2-weighted MRCP and hepatobiliary phase EOB-MRC using a flip angle of 10° (FA10) and of 35° (FA35), respectively. Images were evaluated regarding the delineation of biliary ducts, the order of branching and anatomic visualization of the biliary tree. ROI analysis was performed to estimate the signal-to-noise (SNR) and contrast-to-noise (CNR) ratios.

RESULTS

Applying the FA35 resulted in a significantly better SNR and CNR as compared to FA10. The overall image quality was rated as good for both, FA10 and FA35. The overall rating for regional delineation of the biliary system was rated significantly better for FA35 than for FA10 (p=0.02). Classification of bile duct anatomy variations, however, was equivalent in both techniques.

CONCLUSIONS

Increasing the flip angle of a T1-weighted 3D-sequence from 10° to 35° during the hepatobiliary phase of Gd-EOB enhanced MRI visually and quantitatively improved the visualization of the biliary ducts.

Diagnostic accuracy and sensitivity of diffusion-weighted and of gadoxetic acid-enhanced 3-T MR imaging alone or in combination in the detection of small liver metastasis (≤ 1.5 cm in diameter)

PURPOSE

To compare the diagnostic accuracy and sensitivity of combined gadoxetic acid-enhanced magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) with each imaging approach alone for detecting small hepatic metastases (≤ 1.5 cm).

MATERIALS AND METHODS

Institutional review board approved this retrospective study and waived informed patient consent. Eighty-six patients with 179 liver metastases underwent liver MRI including unenhanced and gadoxetic acid-enhanced imaging and DWI at 3.0 T. Three image sets including unenhanced images-gadoxetic acid set (early dynamic and hepatocyte phase), DWI set, and the combined set-were analyzed independently and in consensus by 2 observers for detecting liver metastases using receiver operating characteristic analysis.

RESULTS

There was a tendency toward an increased diagnostic accuracy for the combined set (mean, 0.965) compared with that for each image set alone (mean, 0.911 for gadoxetic acid set; 0.926 for DWI set). The combined set showed better sensitivity (mean, 97.47%/95.0%: values on per-lesion/per-patient basis) than each imaging set alone (mean, 90.7%/83.7% for gadoxetic acid set; 91.6%/83.0% for DWI set) (P < 0.05) on both per-lesion basis and per-patient basis. All image sets showed similar positive predictive values.

CONCLUSIONS

The combination of gadoxetic acid-enhanced MRI and DWI yielded better diagnostic accuracy and sensitivity in the detection of small liver metastasis than each magnetic resonance scan sequence alone.

High resolution navigated three-dimensional T₁-weighted hepatobiliary MRI using gadoxetic acid optimized for 1.5 Tesla

PURPOSE

To determine optimal delay times and flip angles for T1-weighted hepatobiliary imaging at 1.5 Tesla (T) with gadoxetic acid and to demonstrate the feasibility of using a high-resolution navigated optimized T1-weighted pulse sequence to evaluate biliary disease.

MATERIALS AND METHODS

Eight healthy volunteers were scanned at 1.5T using a T1-weighted three-dimensional (3D)-SPGR pulse sequence following the administration of 0.05 mmol/kg of gadoxetic acid. Navigator-gating enabled acquisition of high spatial resolution (1.2 × 1.4 × 1.8 mm(3) , interpolated to 0.7 × 0.7 × 0.9 mm(3) ) images in approximately 5 min of free-breathing. Multiple breath-held acquisitions were performed at flip angles between 15° and 45° to optimize T1 weighting. To evaluate the performance of this optimized sequence in the setting of biliary disease, the image quality and biliary excretion of 51 consecutive clinical scans performed to assess primary sclerosing cholangitis (PSC) were evaluated.

RESULTS

Optimal hepatobiliary imaging occurs at 15-25 min, using a 40° flip angle. The image quality and visualization of biliary excretion in the PSC scans were excellent, despite the decreased liver function in some patients. Visualization of reduced excretion often provided diagnostic information that was unavailable by conventional magnetic resonance cholangiopancreatography (MRCP).

CONCLUSION

High-resolution navigated 3D-SPGR hepatobiliary imaging using gadoxetic acid and optimized scan parameters is technically feasible and can be clinically useful, even in patients with decreased hepatobiliary function.

Correlation of liver parenchymal gadolinium-ethoxybenzyl diethylenetriaminepentaacetic acid enhancement and liver function in humans with hepatocellular carcinoma

Animal studies have demonstrated that liver function parameters affect the degree of liver enhancement by gadolinium-ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA). The present study prospectively investigated whether liver function parameters and liver damage scores similarly correlate with the degree of liver enhancement by Gd-EOB-DTPA in humans with hepatocellular carcinoma (HCC). A total of 41 patients (32 males, 9 females; mean age, 71.9 years; range, 38-86 years) with suspected HCC provided written, informed consent to undergo a Gd-EOB-DTPA (30 μmol/kg of body weight)-enhanced T1-gradient-echo (GRE) magnetic resonance imaging (MRI) study. The signal intensity of the liver parenchyma was quantified at various time points following injection of Gd-EOB-DTPA. We investigated the correlations between maximal relative enhancement (RE) values and liver function parameters, and liver damage scores. Correlations between parameters and maximum RE values were determined using the Student's t-test and univariate regression analyses. The effect of potential confounding factors was controlled by multiple stepwise regression analysis. Two-tailed values of p<0.05 were considered to indicate a statistically significant difference. The RE values were maximal in 8 and 33 patients at 20 and 30 min, respectively, following Gd-EOB-DTPA injection and did not significantly differ between respective liver damage scores. Univariate analyses revealed that maximal RE values were associated with serum aspartate aminotransferase, total bilirubin, albumin and 15-min indocyanine green retention rates. Multiple stepwise regression analyses revealed that serum albumin and total bilirubin remained independently significant. The degree of liver parenchyma enhancement by Gd-EOB-DTPA depends on liver function parameters in humans, as in animals. The results from this study suggest that Gd-EOB-DTPA has potential for use as a liver function test, and for providing a short examination time for liver MRI results in patients with normal liver function.

A simple way to acquire T(1)-weighted MR images of rat liver with respiratory triggering

To acquire high-resolution T(1)-weighted images of the liver in rats, for which breath-holding cannot be ensured, respiratory triggering is essential. At the respiratory rate of 30-60 times/min in rats, however, T(1)-weighted images cannot be obtained with simple triggering. As a simple solution to this, we applied multiple repeated acquisitions with one trigger signal. With this technique, sufficient T(1) contrast could be easily achieved in rat liver enhanced by gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid infusion.

Contrast-enhanced MR cholangiography (MRCP) with GD-EOB-DTPA in evaluating biliary complications after surgery

PURPOSE

We assessed the usefulness of contrast-enhanced magnetic resonance cholangiography (CE-MRC) with liver-specific contrast agent in evaluating the biliary tree after hepatic surgery.

MATERIALS AND METHODS

A total of 142 patients with suspected biliary complications after liver surgery underwent hepatobiliary MR before and after administration of gadolinium ethoxy benzylic diethylenetriamine pentaacetic acid (Gd-EOB-DTPA). Unenhanced MR cholangiopancreatography (MRCP) and postcontrast MRC were obtained in all patients. Blinded image evaluation and semiquantitative analysis comparing MRCP and CE-MRC were performed by two experienced radiologists.

RESULTS

In all cases, optimal postcontrast visualisation of the biliary tract was obtained. In 22 patients, a postsurgical biliary complication was confirmed. MRCP detected 64% of lesions, but in 36% of cases, an alteration was only suspected but not clearly defined. CE-MRC allowed definite diagnosis in 100% of cases.

CONCLUSIONS

Hepatobiliary-specific contrast agents allow for accurate and extensive study of biliary tract alterations, especially in assessing postsurgical complications.

Gd-EOB-DTPA as a functional MR cholangiography contrast agent: imaging gallbladder filling in patients with and without hepatobiliary dysfunction

OBJECTIVE

To evaluate cystic duct patency on hepatobiliary-phase magnetic resonance (MR) images after intravenous gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) administration.

METHODS

A radiology information system search identified patients with gallbladders that had MR imaging after intravenous Gd-EOB-DTPA injection. No patients had acute cholecystitis. Magnetic resonance image findings were correlated with clinical notes, other imaging studies, time of contrast injection, and serum laboratory tests.

RESULTS

Contrast accumulated in the gallbladder in 80% of patients (n = 100) with hepatobiliary-phase MR imaging at a median of 22 minutes (range, 15-83 minutes). Absence of contrast accumulation in the gallbladder (n = 20) was associated with hepatobiliary imaging less than 30 minutes after contrast administration, gallbladder contraction, cholelithiasis, elevated liver function tests, elevated bilirubin, and cirrhosis.

CONCLUSIONS

Functional assessment of cystic duct patency by Gd-EOB-DTPA-enhanced liver MR is best conducted when hepatobiliary-phase T1-weighted imaging is delayed by more than 30 minutes after contrast injection. Hepatobiliary dysfunction is associated with nonfilling of the gallbladder.

Detection of small hepatocellular carcinoma: intraindividual comparison of gadoxetic acid-enhanced MRI at 3.0 and 1.5 T

PURPOSE

To investigate the diagnostic efficacy of gadoxetic acid-enhanced magnetic resonance imaging (MRI) at 3.0 T for the detection of hepatocellular carcinomas (HCC) and compare with that at 1.5 T.

MATERIALS

Forty patients with 54 HCCs (size range: 0.6-2.0 cm) underwent gadoxetic acid-enhanced MRIs at both 1.5 and 3.0 T with 3 to 8 days interval. The MRIs were compared quantitatively by measuring tumor-liver contrast-to-noise ratio, and qualitatively by evaluating tumor-liver contrast using matched pairs analysis. Diagnostic accuracy and sensitivity were also evaluated by the consensus readings of 2 reviewers using the alternative-free response receiver operator characteristic (ROC) method.

RESULTS

Although the tumor-liver contrast-to-noise ratio for the arterial phase was significantly higher at 3.0 T than at 1.5 T (30.2 ± 21.4 vs. 35.2 ± 22.9; P = 0.04), we found similar values for the hepatocyte phase (38.2 ± 24.6 vs. 38.4 ± 25.3; P = 0.762). Matched pairs analysis indicated that the relative tumor-liver contrast was better in 7 and 9 lesions in the arterial phase and hepatocyte phase at 3.0 T, respectively, than those at 1.5 T. The diagnostic accuracy and sensitivity of 3.0-T imaging [Az, 0.988; 92.6% (n = 50)] were slightly higher than those of 1.5-T imaging [Az, 0.981; 88.9% (n = 48)], but the difference was not statistically significant (P = 0.487).

CONCLUSIONS

Gadoxetic acid-enhanced MRIs at 1.5 and 3.0 T showed similar diagnostic performances for detecting small HCCs. However, there was a tendency toward increased reader confidence for the arterial phase and hepatocyte phase with 3.0 T compared with 1.5 T.

Optimized high-resolution contrast-enhanced hepatobiliary imaging at 3 tesla: a cross-over comparison of gadobenate dimeglumine and gadoxetic acid

PURPOSE

To evaluate the signal to noise ratio (SNR) and contrast to noise ratio (CNR) performance of 0.05 mmol/kg gadoxetic acid and 0.1 mmol/kg gadobenate dimeglumine for dynamic and hepatobiliary phase imaging. In addition, flip angles (FA) that maximize relative contrast-to-noise performance for hepatobiliary phase imaging were determined.

MATERIALS AND METHODS

A cross-over study in 10 volunteers was performed using each agent. Imaging was performed at 3 Tesla (T) with a 32-channel phased-array coil using breathheld 3D spoiled gradient echo sequences for SNR and CNR analysis, and for FA optimization of hepatobiliary phase imaging.

RESULTS

Gadobenate dimeglumine (0.1 mmol/kg) had superior SNR performance during the dynamic phase, statistically significant for portal vein and hepatic vein in the portal venous and venous phase (for all, P < 0.05) despite twice the approved dose of gadoxetic acid (0.05 mmol/kg), while gadoxetic acid had superior SNR performance during the hepatobiliary phase. Optimal FAs for hepatobiliary phase imaging using gadoxetic acid and gadobenate dimeglumine were 25-30° and 20-30° for relative contrast liver versus muscle (surrogate for nonhepatocellular tissues), and 45° and 20° (relative contrast liver versus biliary structures), respectively.

CONCLUSION

Gadobenate dimeglumine may be preferable for applications that require dynamic phase imaging only, while gadoxetic acid may be preferable when the hepatobiliary phase is clinically important. Hepatobiliary phase imaging with both agents benefits from flip angle optimization.

Detection of liver malignancy with gadoxetic acid-enhanced MRI: is addition of diffusion-weighted MRI beneficial?

AIM

To determine the additive value of diffusion-weighted MRI (DWI) to gadoxetic acid-enhanced MRI for the detection of hepatic metastases and hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Thirty-five patients with 38 liver metastases and 18 HCCs were included in this study. Ten patients also had hemangiomas (n = 3) or cysts (n = 8). Liver MRI consisted of pre-contrast and gadoxetic acid-enhanced 3D T1-weighted MRIs (arterial, portal, 2-min delay, 20 min hepatocyte-selective phases), a post-contrast T2-weighted image, and post-contrast DWI (b values: 0, 50, 600 s/mm²). Two observers independently analyzed the gadoxetic acid-enhanced MRI with and without DWI. The diagnostic accuracy and sensitivity for the detection of liver lesions were evaluated using receiver operating characteristic analysis.

RESULTS

Although there were no significant differences in diagnostic accuracy for detecting metastases and HCCs between the gadoxetic acid set alone and the combined DWI and gadoxetic acid set for both observers (mean Az, 0.974 vs 0.987), we found the sensitivity for detecting metastases to be significantly higher with the combined images (97.4%) than with the gadoxetic acid set alone (89.5%) for observer 1 (p = 0.008). Three and two metastases for each observer were clearly verified by adding DWI to gadoxetic acid-enhanced MRI. However, sensitivities for both image sets were equivalent in detecting HCCs.

CONCLUSION

The addition of DWI to gadoxetic acid-enhanced MRI has the potential to increase sensitivity for the detection of liver metastases. However, for detecting HCC, we found no additive value of DWI to gadoxetic acid-enhanced MRI.

Gadoxetate disodium-enhanced MRI of the liver: part 1, protocol optimization and lesion appearance in the noncirrhotic liver

OBJECTIVE

The purpose of this article is to review the pharmacokinetic and pharmacodynamic properties of gadoxetate disodium (Gd-EOB-DTPA), to describe a workflow-optimized pulse sequence protocol, and to illustrate the imaging appearance of focal lesions in the noncirrhotic liver.

CONCLUSION

Gd-EOB-DTPA allows a comprehensive evaluation of the liver with the acquisition of both dynamic and hepatocyte phase images. This provides potential additional information, especially for the detection and characterization of small liver lesions. However, protocol optimization is necessary for improved image quality and workflow.

MR imaging of the biliary tract with Gd-EOB-DTPA: effect of liver function on signal intensity

OBJECTIVE

To quantitatively evaluate the signal intensity of the biliary tract in gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) imaging and to investigate the effect of liver function on the signal intensity of the biliary tract.

MATERIALS AND METHODS

A total of 32 patients with and without chronic liver disease (normal liver group, n = 15; chronic liver disease group, n = 17) were included in this study. All patients were prospectively enrolled for evaluation of known or suspected focal liver lesions. In the chronic liver disease group, the etiologies were chronic hepatitis C virus infection (n = 12) and chronic hepatitis B virus infection (n = 5). The median Child-Pugh score was 5 (range, 5-7). Each patient received the standard dose of Gd-EOB-DTPA (0.025 mmol/kg of body weight). Post-contrast T1-weighted MR images were obtained at 5, 10, 15, 20, 25, and 30 min after administration of Gd-EOB-DTPA. Maximum signal intensities (SIs) of the right and left hepatic ducts, common hepatic duct, and common bile duct were measured. Relative signal intensity was calculated as follows: relative SI = maximum SI(bileduct)/mean SI(muscle). Serum albumin level, serum total bilirubin level, prothrombin time, indocyanine green retention rate at 15 min (ICG-R15), and estimated glomerular filtration rate were entered into regression analysis.

RESULTS

The signal intensity of the bile duct reached a peak 30 min after administration of Gd-EOB-DTPA. The mean relative signal intensity of the right and left hepatic ducts at the peak time point was not significantly different between the two groups, while increase in signal intensity was delayed in the chronic liver disease group. The mean relative signal intensity of the common hepatic duct and that of the common bile duct at the peak time point were significantly different between the two groups (Wilcoxon rank-sum test, P = 0.03, respectively). Stepwise regression analysis revealed that ICG-R15 was a significant predictor of the signal intensity of the bile duct (right and left hepatic ducts, P = 0.04; common hepatic duct, P = 0.008; common bile duct, P = 0.003).

CONCLUSIONS

The results of our study demonstrate that the presence of chronic liver disease significantly affects the signal intensity of the bile duct in Gd-EOB-DTPA-enhanced MR imaging. ICG-R15 was only a significant predictor of the signal intensity of the bile duct. The signal intensity of the bile duct may reflect underlying liver function.