Consensus report of the 2nd International Forum for Liver MRI

Early hepatocellular carcinomas showing isointensity or hyperintensity in gadoxetic acid-enhanced, hepatocyte-phase magnetic resonance images

Hypointensity in the hepatocyte phase is believed to be a key feature of hypovascular early hepatocellular carcinoma, which indicates malignancy. The 3 cases we present suggest that the converse is not true. Three small hepatocellular lesions showed isointensity/hyperintensity on gadoxetic acid-enhanced, hepatocyte-phase magnetic resonance images and were pathologically confirmed as early hepatocellular carcinomas. We conclude that isointensity or hyperintensity in the hepatocyte phase does not always represent benignity of hepatocellular lesions in the cirrhotic liver.

Newly developed hypervascular hepatocellular carcinoma during follow-up periods in patients with chronic liver disease: observation in serial gadoxetic acid-enhanced MRI

OBJECTIVE

The purpose of our study was to evaluate the process and frequency of newly developed hypervascular hepatocellular carcinoma (HCC) in serial gadoxetic acid-enhanced MRI examinations in patients with chronic liver disease during clinical follow-up periods.

MATERIALS AND METHODS

After review of 341 MRI examinations in 100 patients with chronic liver diseases who underwent gadoxetic acid-enhanced MRI at least twice during the observation period, 32 newly developed hypervascular HCCs in 14 patients were retrospectively evaluated. Serial MRI examinations before detecting hypervascular HCC were evaluated to determine whether hypervascular HCC showed the presence of a hypointense nodule on the hepatobiliary phase and hypovascularity (high-risk nodule) before hyper-vascularization. The size of newly developed hypervascular HCCs and the duration of hyper-vascularization from initial detection of a high-risk nodule were compared between HCCs with and without the presence of a high-risk nodule.

RESULTS

Eleven (34.4%) of 32 newly developed hypervascular HCCs had the presence of high-risk nodule before hypervascularization. The size of newly developed hypervascular HCCs was significantly smaller in HCC with high-risk nodule presence (mean, 9.5 mm) than in HCC without the presence of high-risk nodule (mean, 16.4 mm) (p = 0.004). In hypervascular HCCs with high-risk nodule presence, the mean duration of hypervascularization from initial high-risk nodule was 330.7 days, with mean size change from 5.4 mm of high-risk nodules to 9.5 mm of hypervascular HCCs.

CONCLUSION

Approximately one third of newly developed hypervascular HCCs had the presence of high-risk nodule before hypervascularization in the serial gadoxetic acid-enhanced MRI examinations. High-risk nodule tended to develop into hypervascular HCC after having almost doubled in size during 1 year of high-risk nodule presence.

Gadoxetic acid-enhanced fat suppressed three-dimensional T1-weighted MRI using a multiecho dixon technique at 3 tesla: emphasis on image quality and hepatocellular carcinoma detection

PURPOSE

To compare the image quality between T1 high-resolution isotropic volume examination using the multi-echo Dixon technique (mDixon-eTHRIVE) and that using spectrally adiabatic inversion recovery (SPAIR-eTHRIVE) in gadoxetic acid-enhanced liver MRI, and to evaluate the detectability of hepatocellular carcinoma (HCC) on mDixon-eTHRIVE.

MATERIALS AND METHODS

Seventy patients with 117 HCCs underwent gadoxetic acid-enhanced liver MRI using mDixon-eTHRIVE. All patients also underwent gadoxetic acid-enhanced MRI using SPAIR-eTHRIVE (mean interval of 96 days). Two radiologists performed a consensus review of MRIs for image quality, homogeneity of fat suppression, artifact, and anatomic sharpness using a four-point scale. The detectability for HCC with mDixon-eTHRIVE was assessed using alternative-free response receiver operating characteristic.

RESULTS

All mDixon-eTHRIVE images received higher scores for homogeneity of fat suppression and image quality (P < 0.05) compared with those for SPAIR-eTHRIVE. With respect to artifact and anatomic sharpness, there was no significant difference between two MRIs (P > 0.05). Diagnostic accuracy (Az) and sensitivity for detecting HCCs with mDixon-eTHRIVE images were mean 0.954 and 93.2%, respectively.

CONCLUSION

For gadoxetic acid-enhanced liver MRI, mDixon-eTHRIVE showed improved homogeneity of fat suppression and overall image quality compared with SPAIR-eTHRIVE.

Hypovascular hepatic nodules showing hypointense on the hepatobiliary-phase image of Gd-EOB-DTPA-enhanced MRI to develop a hypervascular hepatocellular carcinoma: a nationwide retrospective study on their natural course and risk factors

OBJECTIVE

We aimed to investigate the natural outcome of nonhypervascular lesions detected in the hepatobiliary phase of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI by performing a longitudinal study retrospectively enrolled in a nationwide manner.

METHODS

Between February 2008 and March 2011, 224 patients with 504 nodules that were diagnosed as nonhypervascular by imaging were recruited from institutions that participated in the present study. We examined the natural outcome of nonhypervascular lesions and evaluated the risk factors.

RESULTS

Of the 504 nodules, 173 (34.3%) showed hypervascular transformation. The overall cumulative incidence of hypervascular transformation was 14.9% at 12 months and 45.8% at 24 months. Multivariate analysis using the Cox regression model revealed previous treatment history for hepatocellular carcinoma (HCC; relative risk = 1.498; p = 0.036, 95% CI 1.03-2.19) and hyperintensity on T2-weighted images (relative risk = 1.724; p = 0.015, 95% CI 1.11-2.67) were identified as independent factors for hypervascular transformation.

CONCLUSIONS

Patients who have a previous treatment history for HCC and with hypointense nodules showing hyperintensity on T2-weighted images need careful follow-up because of the high incidence of hypervascular transformation.

Accuracy and confidence of Gd-EOB-DTPA enhanced MRI and diffusion-weighted imaging alone and in combination for the diagnosis of liver metastases

PURPOSE

To evaluate the accuracy and confidence in diagnosing liver metastases using combined gadolinium-EOB-DTPA (Gd-EOB-DTPA) enhanced magnetic resonance imaging (MRI)/diffusion-weighted imaging (DWI) in comparison to Gd-EOB-DTPA enhanced MRI and DWI alone.

MATERIALS AND METHODS

Forty-three patients (age, 58 ± 13 years) with 89 liver lesions (28 benign, 61 malignant) underwent liver MRI for suspected liver metastases. Three image sets (DWI, Gd-EOB-DTPA and combined Gd-EOB-DTPA/DWI) in combination with unenhanced T1- and T2-weighted images were reviewed by three readers. Detection rates of focal liver lesions were assessed and diagnostic accuracy was evaluated by calculating the areas under the receiver-operating-characteristics curve (AUC). Confidence in diagnosis was evaluated on a 3-point scale. Histopathology and imaging follow-up served as the standard of reference.

RESULTS

Detection of liver lesions and confidence in final diagnosis for all readers were significantly higher for the combined Gd-EOB-DTPA/DWI dataset than for DWI. The combination of DWI and Gd-EOB-DTPA rendered a significantly higher confidence in final diagnosis (2.44 vs. 2.50) than Gd-EOB-DTPA alone for one reader. For two readers, accuracy in diagnosis of liver metastases was significantly higher for Gd-EOB-DTPA/DWI (AUCs of 0.84 and 0.83) than for DWI datasets (AUCs of 0.73 and 0.72). Adding DWI to Gd-EOB-DTPA did not significantly increase diagnostic accuracy as compared to Gd-EOB-DTPA imaging alone.

CONCLUSION

Addition of DWI sequences to Gd-EOB-DTPA enhanced MRI did not significantly increase diagnostic accuracy as compared to Gd-EOB-DTPA enhanced MRI alone in the diagnosis of liver metastases. However, the increase in diagnostic confidence might justify acquisition of DWI sequences in a dedicated MRI protocol.

Time-intensity curve in the abdominal aorta on dynamic contrast-enhanced MRI with high temporal and spatial resolution: Gd-EOB-DTPA versus Gd-DTPA in vivo

PURPOSE

To evaluate the difference in the time-intensity curves (TICs) of the abdominal aorta on dynamic contrast-enhanced MRI (DCE-MRI) between Gd-DTPA and Gd-EOB-DTPA.

MATERIALS AND METHODS

Ten healthy volunteers underwent DCE-MRI three times with the following protocol: group A, Gd-DTPA at an injection rate of 3 ml/s; group B, Gd-EOB-DTPA, 3 ml/s; group C, Gd-EOB-DTPA, 1.5 ml/s. Signal intensities (SIs) of the abdominal aorta were measured, and the contrast enhancement ratio (CER) was calculated. Time-to-CER curves were compared among the three groups. The differences in maximum CER (CERmax) and time-to-peak of CER were analyzed.

RESULTS

The time-to-CER curve showed a double peak pattern in group A and single-peak pattern in groups B and C. The mean time between the first and the second peak was 6.2 s. The mean CERmax of each group was 4.50, 4.52 and 4.27, respectively. In group A, B and C, the mean time-to-peak was 14.6, 10.6 and 12.6 s, respectively. There was a significant difference between group A and B (P < 0.01).

CONCLUSION

To set up the optimal protocol for abdominal DCE-MRI, it should be noted that TIC in the Gd-DTPA and Gd-EOB-DTPA group showed different patterns, and a slower injection rate showed a less abrupt SI change in the Gd-EOB-DTPA group than in the Gd-DTPA group.

Intrahepatic periportal high intensity on hepatobiliary phase images of Gd-EOB-DTPA-enhanced MRI: imaging findings and prevalence in various hepatobiliary diseases

PURPOSE

To reveal the incidence and degree of intrahepatic periportal high intensity (PHI) on hepatobiliary phase images of Gd-EOB-DTPA-enhanced MRI (EOB-MRI) in patients with or without various hepatobiliary diseases.

MATERIALS AND METHODS

Patients with normal liver (N = 256) and those with hepatic disorder (N = 857) who underwent EOB-MRI were the subjects in this study. Incidence of PHI was evaluated among the patients with normal liver and those with hepatic disorder. Degree of PHI was categorized into four grades and compared among the various hepatic diseases. Enhancement ratios (ER) of the PHI area, background liver with PHI, and background liver in control cases without PHI were evaluated.

RESULTS

PHI was observed in 2.7 % of the patients with hepatic disorder. No PHI was observed in the patients with normal liver. The incidence rates of PHI among various hepatobiliary diseases were as follows; liver cirrhosis 3.1 %, chronic hepatitis 1.0 %, primary biliary cirrhosis 12.5 %, idiopathic portal hypertension 33.3 %. The ER of the PHI area and background liver were 3.92 and 2.48 (p = 0.0002). There were no significant differences between the ER of the PHI area and the ER of background liver in the noncirrhotic control without PHI.

CONCLUSION

In 2.7 % of the patients with a hepatic disorder, the periportal area was saved from decrease of EOB uptake and it showed PHI.

Early phase detection of bile leak after hepatobiliary surgery: value of Gd-EOB-DTPA-enhanced MR cholangiography

PURPOSE

To assess the value of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MR cholangiography for the detection of bile leaks after hepatobiliary surgery.

METHODS

Twenty-three patients with symptoms suggestive of bile leak underwent conventional fat-suppressed T1- and T2-weighted MR cholangiography followed by Gd-EOB-DTPA-enhanced MR cholangiography using gradient-echo (GRE) T2-weighted sequences and fat-suppressed T1-weighted 3D gradient-echo sequences 20 min after an intravenous bolus of Gd-EOB-DTPA. The results of Gd-EOB-DTPA-enhanced MR cholangiography correlated with clinical findings, surgical repair, and the results of endoscopic retrograde cholangiopancreatography and percutaneous transhepatic cholangiography.

RESULTS

The results of Gd-EOB-DTPA-enhanced MR cholangiography were negative in 13 patients (cholecystectomy 5, liver transplantation 2, liver resection for focal lesions 2, cholangiocarcinoma 1, and partial hepatectomy after liver injury 1). In 10 patients in whom bile leaks were detected, this complication occurred after liver resection for focal lesions in 3, cholecystectomy in 4, liver transplantation in 2, and liver resection for intrahepatic cholangiocarcinoma in 1. The diagnostic accuracy of Gd-EOB-DTPA-enhanced MR for the detection or exclusion of bile leaks was 100%.

CONCLUSIONS

Gd-EOB-DTPA-enhanced MR cholangiography is a highly reliable technique for the detection of bile leaks after hepatobiliary surgery and may avoid the use of other, potentially risky invasive diagnostic techniques.

Hypovascular hypointense nodules on hepatobiliary phase gadoxetic acid-enhanced MR images in patients with cirrhosis: potential of DW imaging in predicting progression to hypervascular HCC

PURPOSE

To investigate the imaging features of hypovascular hypointense nodules on hepatobiliary phase gadoxetic acid-enhanced magnetic resonance (MR) images in patients with cirrhosis that may be associated with progression to hypervascular hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

The institutional review board approved this retrospective study and waived informed patient consent. This study included 135 patients with a diagnosis of hepatitis B-induced liver cirrhosis and 214 hypovascular hypointense nodules on hepatobiliary phase gadoxetic acid-enhanced MR images. MR images were analyzed with respect to nodule size, degree of hypointensity at hepatobiliary phase (four grades), presence of fat, and signal intensity on T1- and T2-weighted and diffusion-weighted (DW) images. Univariate and multivariate Cox regression analyses were used to identify variables that are associated with developing hypervascular HCC.

RESULTS

On follow-up MR images, 139 nodules (65.0%) had no evidence of HCC (mean follow-up, 522 days) (group 1), but 75 (35.0%) became hypervascular HCC (mean follow-up, 388 days) (group 2). Univariable Cox analysis revealed that the degree of hypointensity on hepatobiliary phase images (P=.044 and .001) and hyperintensity on T2-weighted and DW images (P=.001 and .0001) was significantly related to the development of hypervascular HCC. According to the multivariable Cox analysis, no other variable significantly adjusted the model once hyperintensity at initial DW imaging was already included as an associated variable, (hazard ratio, 7.44; 95% confidence interval: 4.28, 12.94; P=.0001).

CONCLUSION

Hyperintensity on DW images in hypovascular hypointense nodules on hepatobiliary phase gadoxetic acid-enhanced MR images in patients with cirrhosis is strongly associated with progression to hypervascular HCC.

Liver stiffness measured by magnetic resonance elastography as a risk factor for hepatocellular carcinoma: a preliminary case-control study

OBJECTIVE

To examine if liver stiffness measured by magnetic resonance elastography (MRE) is a risk factor for hepatocellular carcinoma (HCC) in patients with chronic liver disease.

METHODS

By reviewing the records of magnetic resonance (MR) examinations performed at our institution, we selected 301 patients with chronic liver disease who did not have a previous medical history of HCC. All patients underwent MRE and gadoxetic acid-enhanced MR imaging. HCC was identified on MR images in 66 of the 301 patients, who were matched to controls from the remaining patients without HCC according to age. MRE images were obtained by visualising elastic waves generated in the liver by pneumatic vibration transferred via a cylindrical passive driver. Risk factors of HCC development were determined by the odds ratio with logistic regression analysis; gender and liver stiffness by MRE and serum levels of aspartate transferase, alanine transferase, alpha-fetoprotein, and protein induced by vitamin K absence-II.

RESULTS

Multivariate analysis revealed that only liver stiffness by MRE was a significant risk factor for HCC with an odds ratio (95 % confidence interval) of 1.38 (1.05-1.84).

CONCLUSION

Liver stiffness measured by MRE is an independent risk factor for HCC in patients with chronic liver disease.

Intrahepatic mass-forming cholangiocarcinoma: enhancement patterns on gadoxetic acid-enhanced MR images

PURPOSE

To evaluate the enhancement patterns of intrahepatic mass-forming cholangiocarcinomas (IMCCs) with emphasis on the hepatobiliary phase (HBP) of gadoxetic acid-enhanced magnetic resonance (MR) imaging.

MATERIALS AND METHODS

This retrospective study was institutional review board approved, and the requirement for informed consent was waived. Fifty patients (41 men, nine women; mean age, 62.3 years; range, 44-76 years) with IMCC underwent unenhanced and gadoxetic acid-enhanced T1- and T2-weighted MR imaging including dynamic phase and hepatobiliary phase imaging between May 2008 and December 2010. Signal intensity and enhancement patterns of lesions were compared with those of the liver parenchyma in each phase. Conspicuity and margin sharpness of lesions on dynamic phase and HBP images were rated on a 4- or 5-point scale and compared by using the Wilcoxon signed-rank test. Percentage of relative enhancement was compared among pathologic subgroups by using the unpaired Student t test.

RESULTS

On dynamic phase images, 29 of 48 (60%) lesions showed a thin peripheral rim with centripetal or gradual progression. On HBP images, 48 of 50 (96%) IMCCs were hypointense, and two of 50 (4%) were hyperintense. Subjective ratings of conspicuity and margin sharpness were significantly higher on HBP (median scores, 5 and 4, respectively) (P < .001) than on the dynamic phase (median scores, 4 and 3, respectively) images (P < .001). Additional daughter nodules were found in five patients and intrahepatic metastasis was found in one. Percentage of relative enhancement on HBP images was significantly higher in moderately differentiated (66.4% ± 42.1) than in poorly differentiated (36.84% ± 21.5) tumors (P = .039) and in patients without (59.7% ± 28.8) than in those with (24.9% ± 14.7) (P = .036) lymph node metastasis.

CONCLUSION

The most prevalent enhancement pattern on gadoxetic acid-enhanced MR images of IMCCs was a thin peripheral rim with internal heterogeneous enhancement during the dynamic phase. HBP images showed increased lesion conspicuity and better delineation of daughter nodules and intrahepatic metastasis, which may aid in the diagnosis of IMCC.

Visualization of hepatic uptake transporter function in healthy subjects by using gadoxetic acid-enhanced MR imaging

PURPOSE

To determine if genetic polymorphisms of liver-specific human organic anion transporting polypeptide (OATP) 1B1 and OATP1B3 influence cellular uptake of gadoxetic acid in vitro and if functionally relevant polymorphisms are confounders for liver enhancement by gadoxetic acid in healthy subjects.

MATERIALS AND METHODS

This study received ethics approval, and all subjects provided written informed consent. Cellular uptake of gadoxetic acid by OATP1B1 and OATP1B3 and their frequent genetic variants was measured by using stable transfected embryonic kidney HEK293 cells. Liver signal intensity at gadoxetic acid-enhanced MR imaging and pharmacokinetics of gadoxetic acid were evaluated in 36 healthy carriers of SLCO1B1/1B3 wild-type alleles (n = 10), SLCO1B1*1b/*1b (n = 8), SLCO1B1*15/*15 (n = 7), SLCO1B1*5/*15 (n = 1), SLCO1B1*1a/*5 (n = 6), and SLCO1B3*4/*4 (n = 4) by using T1-weighted MR imaging and liquid chromatography tandem mass spectrometry.

RESULTS

Transport activity for gadoxetic acid was increased in cells transfected with SLCO1B1c.388A>G (12.8 pmol/[mg·min]6 3.53, P = .001) but decreased in cells with SLCO1B1c.388A>G/521T>C (3.11 pmol/[mg·min] ± 0.918, P = .004) compared with cells with nonvariant transporter (6.32 pmol/[mg·min] ± 2.73). Compared with activity of cells transfected with the nonvariant SLCO1B3 (7.43 pmol/[mg·min] ± 2.43), SLCO1B3c.699G>A was a gain-of-function variant (15.1 pmol/[mg·min] ± 5.52, P = .002), whereas SLCO1B3c.334T>G (0.364 pmol/[mg·min] ± 0.125, P = .0001) and SLCO1B3c.1564G>T (0.295 pmol/[mg·min] ± 0.247, P = .0001) were variants with lower function. Liver enhancement with gadoxetic acid was reduced in subjects with OATP1B1*1a/*5 compared with wild-type subjects and those with OATP1B1*1b/*1b (area under enhancement curve, 3-480 minutes in arbitrary units [au]; 20.7 au ± 6.85 vs 36.5 au ± 8.08 [P = .006] vs 34.6 au ± 8.92 [P = .026]). The OATP1B3*4 polymorphism was not of functional relevance. No pharmacokinetic characteristics of gadoxetic acid were influenced by genetic polymorphisms of OATP1B1 and OATP1B3.

CONCLUSION

Liver-specific OATP1B1 and OATP1B3 are uptake carriers for gadoxetic acid in subjects. Genetic polymorphisms of OATP1B1 are signal confounders in gadoxetic acid-enhanced liver MR imaging.

MR liver imaging with Gd-EOB-DTPA: a delay time of 10 minutes is sufficient for lesion characterisation

OBJECTIVES

To assess whether, in patients with normal liver function, a hepatobiliary delay time of 10 min after Gd-EOB-DTPA injection is sufficient for lesion characterisation.

METHODS

In 42 consecutive patients with suspected focal liver lesions, dynamic MRI was performed after intravenous Gd-EOB-DTPA, followed by hepatobiliary phases at 5, 10 and 20 min. The following items were assessed at each hepatobiliary phase: parenchymal enhancement, contrast agent excretion in bile ducts, lesion enhancement characteristics (hypo-, iso-, or hyperintensity, rim enhancement, central non-enhancement), and contrast- and signal-to-noise ratios, separately for hypo- and hyperintense lesions.

RESULTS

Following enhancement, parenchymal signal intensity increased significantly up to 10 min (86.3%, P < 0.001), and subsequently stabilised (86.5% after 20 min, P = 0.223). Biliary contrast agent excretion was first observed in 2, 32 and 5 patients after 5, 10 and 20 min respectively. Hepatobiliary lesion enhancement characteristics observed after 5 min persisted during later hepatobiliary phases. CNR and SNR ratios increased significantly (P < 0.05) up to 10 min after enhancement without further increase at 20 min, in hypo- and hyperintense lesions.

CONCLUSIONS

If lesion characterisation is the primary reason for performing MRI, a hepatobiliary delay time of 10 min after Gd-EOB-DTPA injection is sufficient in patients with normal liver function.

KEY POINTS

• Magnetic resonance imaging is now a first line of investigation of the liver. • Optimal CNR and SNR are achieved 10 min after Gd-EOB-DTPA injection. • Typical enhancement characteristics are observed early and do not change. • Ten-minute hepatobiliary delay is sufficient for characterisation of focal liver lesions.

Gadoxetate acid-enhanced MRI of hepatocellular carcinoma in a c-myc/TGFα transgenic mouse model including signal intensity and fat content: initial experience

Genetically engineered mouse models, such as double transgenic c-myc/TGFα mice, with specific pathway abnormalities might be more successful at predicting the clinical response of hepatocellular carcinoma (HCC) treatment. But a major drawback of the tumour models is the difficulty of visualizing endogenously formed tumours. The optimal imaging procedure should be brief and minimally invasive. Magnetic resonance imaging (MRI) satisfies these criteria and gadoxetate acid-enhanced MRI improves the detection of HCC. Fat content is stated to be an additional tool to help assess tumour responses, for example, in cases of radiofrequency ablation. Therefore the aim of this study was to investigate if gadoxetate acid-enhanced MRI could be used to detect HCC in c-myc/TGFα transgenic mice by determining the relation between the signal intensity of HCC and normal liver parenchyma and the corresponding fat content as a diagnostic marker of HCC. In our study, 20 HCC in c-myc/TGFα transgenic male mice aged 20–34 weeks were analyzed. On gadoxetate acid-enhanced MRI, the signal intensity was 752.4 for liver parenchyma and 924.5 for HCC. The contrast to noise ratio was 20.4, the percentage enhancement was 267.1% for normal liver parenchyma and 353.9% for HCC. The fat content was 11.2% for liver parenchyma and 16.2% for HCC. There was a correlation between fat content and signal intensity with r = 0.7791. All parameters were statistically significant with P < 0.05. Our data indicate that gadoxetate acid contrast enhancement allows sensitive detection of HCC in c-myc/TGFα transgenic mice and determination of the fat content seems to be an additional useful parameter for HCC.

Using low tube voltage (80kVp) quadruple phase liver CT for the detection of hepatocellular carcinoma: two-year experience and comparison with Gd-EOB-DTPA enhanced liver MRI

PURPOSE

To validate the diagnostic performance of quadruple phase low tube voltage liver CT through the comparison with Gd-EOB-DTPA enhanced liver MRI for the detection of HCC.

MATERIALS AND METHODS

Non-obese patients (38 men, eight women) with 68 HCCs underwent quadruple-phase CT at 16 MDCT (using low tube voltage, 80kVp; moderately high tube current, 280mAs) and Gd-EOB-DTPA-enhanced 3T MRI. Three observers independently and randomly reviewed the CT and MR images on a tumor-by-tumor basis. The diagnostic accuracy of these techniques for detecting HCC was assessed using alternative free-response receiver operating characteristic analysis. Sensitivity and positive predictive values were evaluated. The mean effective doses for the low dose CT were also evaluated.

RESULTS

The areas under the ROC curves were 0.963, 0.959, and 0.941 for low dose CT and 0.981, 0.982, and 0.976 for MRI. Differences in Az of the two techniques for each observer were not statistically significant (P>.05). Differences in sensitivity and positive predictive values between the two techniques for each observer were not also statistically significant: sensitivity (86.8%, 82.4%, 85.3% for CT and 95.6%, 94.1%, 91.2% for MRI) and positive predictive values (92.2%, 90.3%, 89.2% for CT and 92.9%, 92.8%, 92.5% for MRI). Six HCCs (8.8%) in five patients were observed only on hepatobiliary phase of MRI, and all were smaller than 1.5cm. The mean effective dose for CT was approximately 10.2mSv.

CONCLUSIONS

Quadruple-phase low-dose liver CT (80kVp, 280mAs) had relatively good diagnostic performance for detecting HCC in non-obese patients. Because no significant difference was observed between low-dose CT and MRI, the use of low-dose liver CT can be justified based on its reduced radiation effects.

Fate of hypointense lesions on Gd-EOB-DTPA-enhanced magnetic resonance imaging

PURPOSE

To investigate the natural outcome and clinical implication of hypointense lesions in the hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI.

MATERIALS AND METHODS

Forty patients underwent Gd-EOB-DTPA-enhanced MRI for preoperative evaluation of HCC. Hypointense lesions in the hepatobiliary phase that were hypovascular 5mm of more were extracted for follow-up. We performed a longitudinal study retrospectively for these lesions regardless of whether classical HCC developed or emerged in a different area from that of the lesions being followed.

RESULTS

Thirty one patients displayed 130 hypointense lesions on MRI and only nine showed no hypointense lesions. In total, 17 (13.1%) of 130 hypointense lesions on MRI developed into classical HCC. The cumulative rates for these lesions to develop into classical HCC were 3.2% at 1 year, 11.1% at 2 years and 15.9% at 3 years. The total occurrence rates of classical HCC (25.8% at 1 year, 52.6% at 2 years and 76.4% at 3 years) were higher compared to those regarding only occurrence of classical HCC from hypointense lesions on MRI (10.0% at 1 year, 35.6% at 2 years and 44.6% at 3 years), although no significant difference was observed (p=0.073).

CONCLUSIONS

Hypointense lesions that are detected in the hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI have some malignant potential, although treating these lesions aggressively in patients who already have HCC may be too severe.

Different signal intensity at Gd-EOB-DTPA compared with Gd-DTPA-enhanced MRI in hepatocellular carcinoma transgenic mouse model in delayed phase hepatobiliary imaging

PURPOSE

To evaluate hyperintense Gd-DTPA- compared with hyper- and hypointense Gd-EOB-DTPA-enhanced magnet resonance imaging (MRI) in c-myc/TGFα transgenic mice for detecting hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Twenty HCC-bearing transgenic mice with overexpression of the protooncogene c-myc and transforming growth factor-alpha (TGF-α) were analyzed. MRI was performed using a 3-T MRI scanner and an MRI coil. The imaging protocol included Gd-DTPA- and Gd-EOB-DTPA-enhanced T1-weighted images. The statistically evaluated parameters are signal intensity (SI), signal intensity ratio (SIR), contrast-to-noise ratio (CNR), percentage enhancement (PE), and signal-to-noise ratio (SNR).

RESULTS

On Gd-DTPA-enhanced MRI compared with Gd-EOB-DTPA-enhanced MRI, the SI of liver was 265.02 to 573.02 and of HCC 350.84 to either hyperintense with 757.1 or hypointense with 372.55 enhancement. Evaluated parameters were SNR of HCC 50.1 to 56.5/111.5 and SNR of liver parenchyma 37.8 to 85.8, SIR 1.32 to 1.31/0.64, CNR 12.2 to 26.1/-30.08 and PE 42.08% to 80.5/-98.2%, (P < 0.05).

CONCLUSION

Gd-EOB-DTPA is superior to Gd-DTPA for detecting HCC in contrast agent-enhanced MRI in the c-myc/TGFα transgenic mouse model and there was no difference between the hyperintense or hypointense appearance of HCC. Either way, HCCs can easily be distinguished from liver parenchyma in mice.

Differentiating focal eosinophilic liver disease from hepatic metastases using unenhanced and gadoxetic acid-enhanced MRI

PURPOSE

To examine the differential features of focal eosinophilic liver disease (FELD) from liver metastases on gadoxetic acid-enhanced MRI.

MATERIALS

Twenty patients with 41 FELD and 20 patients with 55 metastases were enrolled in this study. Liver MRI consisted of precontrast 2D T1-weighted image (T1WI) and gadoxetic acid-enhanced 3D T1WI (arterial, portal, 20 min hepatocyte-selective phases), and a postcontrast T2WI. Images were analyzed for the margin and shape of the lesions; lesion conspicuity on T1- and T2WI; signal intensity of the lesions on 3D T1WI; presence of rim enhancement and misty signs; and presence of significant smaller lesions on the unenhanced T1WI (<50%) compared to hepatocyte phase image.

RESULTS

Univariate analysis revealed the following significant parameters to favor FELD: a fuzzy margin, irregular shape, subtle signal intensity changes on T1- and T2WI, absence of target signs on the hepatocyte phase image, presence of misty signs, and size discrepancies on T1WI and hepatocyte phase images. Multivariate analysis revealed only a significantly smaller lesion size on T1WI compared to hepatocyte phase images to be predictive of FELD.

CONCLUSION

A significantly smaller lesion size on T1WI relative to hepatocyte phase image is the best predictor for identifying FELD on gadoxetic acid-enhanced MRI.

Hypervascular hepatocellular carcinomas: detection with gadoxetate disodium-enhanced MR imaging and multiphasic multidetector CT

OBJECTIVES

To retrospectively compare the accuracy of detection of hypervascular hepatocellular carcinoma (HCC) by multiphasic multidetector CT and by gadoxetate disodium-enhanced MR imaging.

METHODS

After ethical approval, we analysed a total of 73 hypervascular HCC lesions from 31 patients suspected of having HCC, who underwent both gadoxetate disodium-enhanced MR imaging and multiphasic multidetector CT. Five blinded observers independently reviewed CT images, as well as dynamic MR images alone and combined with hepatobiliary phase MR images. Diagnostic accuracy (Az values), sensitivities and positive predictive values were compared by using the Scheffe post hoc test.

RESULTS

The mean Az value for dynamic and hepatobiliary phase MR combined (0.81) or dynamic MR images alone (0.78) was significantly higher than that for CT images (0.67, P < 0.001, 0.005, respectively). The mean sensitivity of the combined MR images (0.67) was significantly higher than that of dynamic MR alone (0.52, P < 0.05) or CT images (0.44, P < 0.05). The mean positive predictive values were 0.96, 0.95 and 0.94, for CT, dynamic MR alone and combined MR images, respectively.

CONCLUSIONS

Compared with multiphasic multidetector CT, gadoxetate disodium-enhanced MR imaging combining dynamic and hepatobiliary phase images results in significantly improved sensitivity and diagnostic accuracy for detection of hypervascular HCC.

KEY POINTS

Gadoxetate disodium is a new liver-specific MR imaging contrast agent. Gadoxetate disodium-enhanced MRI helps the assessment of patients with liver disease. It showed high diagnostic accuracy for the detection of hepatocellular carcinoma.

Effects of gadoxetic acid on liver elasticity measurement by using magnetic resonance elastography

The purpose of this study was to evaluate the effect of gadoxetic acid (Gd-EOB-DTPA) on measurements of liver stiffness by using magnetic resonance elastography (MRE). In this study, 104 consecutive patients (mean age, 67.7±9.4 years) underwent MRE using a 1.5-T MR scanner equipped with a cylindrical passive driver that was placed across the right chest wall for delivering vibrations. Axial gradient-echo images, which were automatically converted to elastograms that represented stiffness (kPa), were acquired using a continuous sinusoidal vibration of 60 Hz. Two raters independently placed a region of interest on the right lobe of the liver on the elastograms obtained before and after Gd-EOB-DTPA was administered. Liver stiffness was measured using these two elastograms and compared using a paired t test and correlation analysis. No significant difference was observed in liver stiffness before and after Gd-EOB-DTPA was administered (Rater 1, P=.1200; Rater 2, P=.3585). The correlation coefficients were 0.986 (Rater 1) and 0.984 (Rater 2), indicating excellent correlation between the stiffness values before and after Gd-EOB-DTPA was administered. Liver stiffness measured by MRE did not differ before and after Gd-EOB-DTPA was administered.

Hepatocellular carcinoma in patients with chronic liver disease: a comparison of gadoxetic acid-enhanced MRI and multiphasic MDCT

AIM

To compare the diagnostic performances of gadoxetic acid-enhanced magnetic resonance imaging (MRI) and multiphasic multidetector computed tomography (MDCT) in the detection of hepatocellular carcinoma (HCC) in patients with chronic liver disease.

MATERIALS AND METHODS

Institutional review board approval was obtained for this study and informed consent was obtained from all patients. Fifty-one patients (43 men, eight women; age range 32-80 years) with 73 HCCs underwent gadoxetic acid-enhanced MRI and multiphasic MDCT. Two readers independently analysed each image in three separate reading sessions. The alternative free-response receiver operating characteristic (AFROC) method was used to analyse the diagnostic accuracy. Positive and negative predictive values and sensitivity were evaluated.

RESULTS

A total of 73 HCCs were detected in 51 patients. Although not significant (p>0.05), the areas under the receiver operating characteristic curves were 0.877 and 0.850 for MDCT, 0.918 and 0.911 for dynamic MRI, and 0.905 and 0.918 for combined interpretation of dynamic and hepatobiliary phase MR images. Differences in sensitivity, specificity, and positive and negative predictive values between the readers were not statistically significant (p>0.05). Combined interpretation of dynamic and hepatobiliary phase MRI images was more useful than MDCT in the detection of HCC lesions ≤1cm in diameter for one reader (p=0.043).

CONCLUSION

Gadoxetic acid-enhanced MRI and MDCT show similar diagnostic performances for the detection of HCC in patients with chronic liver disease. However, the combined interpretation of dynamic and hepatobiliary phase MRI images may improve diagnostic accuracy in the detection of HCC lesions ≤1cm in diameter.

Dynamic contrast-enhanced magnetic resonance imaging with Gd-EOB-DTPA for the evaluation of liver fibrosis in chronic hepatitis patients

OBJECTIVES

To develop a non-invasive MRI method for evaluation of liver fibrosis, with histological analysis as the reference standard.

METHODS

The study protocol was approved by the Institutional Review Board for Human Studies of our hospital, and written informed consent was obtained from all subjects. Seventy-nine subjects who received dynamic contrast-enhanced MRI (DCE-MRI) with Gd-EOB-DTPA were divided into three subgroups according to Metavir score: no fibrosis (n = 30), mild fibrosis (n = 34), and advanced fibrosis (n = 15). The DCE-MRI parameters were measured using two models: (1) dual-input single-compartment model for arterial blood flow (F (a)), portal venous blood flow, total liver blood flow, arterial fraction (ART), distribution volume, and mean transit time; and (2) curve analysis model for Peak, Slope, and AUC. Statistical analysis was performed with Student's t-test and the nonparametric Kruskal-Wallis test.

RESULTS

Slope and AUC were two best perfusion parameters to predict the severity of liver fibrosis (>F2 vs. ≦F2). Four significantly different variables were found between non-fibrotic versus mild-fibrotic subgroups: F (a), ART, Slope, and AUC; the best predictor for mild fibrosis was F (a) (AUROC:0.701).

CONCLUSIONS

DCE-MRI with Gd-EOB-DTPA is a noninvasive imaging, by which multiple perfusion parameters can be measured to evaluate the severity of liver fibrosis.

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.

Outcome of hypovascular hepatic nodules revealing no gadoxetic acid uptake in patients with chronic liver disease

PURPOSE

To elucidate the natural history of hypovascular nodules that appear hypointense on hepatocyte-phase gadoxetic acid-enhanced MR images by focusing on hypervascularization over time.

MATERIALS AND METHODS

In this study, 135 hypovascular nodules revealing no gadoxetic acid uptake in 53 patients were examined. All nodules were retrospectively examined using serial follow-up computed tomography (CT) and MRI examinations until hypervascularity was observed on arterial-phase dynamic CT or gadoxetic acid-enhanced MR images, or on CT during hepatic arteriography. Logistic regression analysis was used to investigate the association between hypervascularization and MR findings including a presence of fat assessed by a signal drop on opposed-phase T1-weighted images.

RESULTS

Of the 135 nodules, 16 underwent hypervascularization. The size of the nodules and the presence of fat in the nodules were independent indicators of hypervascularization. The 1-year cumulative risk of hypervascularization was 15.6%. This risk was significantly increased in the case of nodules >10 mm (37.6%, P < 0.01) and fat-containing nodules (26.5%, P < 0.01).

CONCLUSION

Hypovascular nodules that appear hypointense on hepatocyte-phase gadoxetic acid-enhanced MR images may progress to conventional hypervascular hepatocellular carcinoma. Nodules more than 10 mm in diameter and containing fat are at high risk for developing hypervascularization.

Focal liver lesion detection and characterization with GD-EOB-DTPA

Superior soft-tissue contrast affords magnetic resonance imaging (MRI) some advantages compared to computed tomography (CT) in both detection and characterization of focal liver lesions. Because of its relatively recently introduction into clinical practice, a growing number of articles in the literature have demonstrated the usefulness of the hepatobiliary-specific MRI contrast agent gadoxetic acid disodium (Gd-EOB-DTPA) in liver imaging. The purpose of this review is to demonstrate the typical enhancement patterns of the most common liver lesions using Gd-EOB-DTPA in daily clinical scenarios and briefly describe its mechanism of action. Radiologists interpreting liver MRI studies with this agent must be familiar with the appearance of focal lesions in the hepatocyte phase to avoid misinterpretation.

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 Acid-Enhanced MR Imaging for HCC: A Review for Clinicians

Hepatocellular carcinoma (HCC) is increasingly being detected at an earlier stage, owing to the screening programs and regular imaging follow-up in high-risk populations. Small HCCs still pose diagnostic challenges on imaging due to decreased sensitivity and increased frequency of atypical features. Differentiating early HCC from premalignant or benign nodules is important as management differs and has implications on both the quality of life and the overall survival for the patients. Gadoxetate acid (Gd-EOB-DTPA, Primovist(®), Bayer Schering Pharma) is a relatively new, safe and well-tolerated liver-specific contrast agent for magnetic resonance (MR) imaging of the liver that has combined perfusion- and hepatocyte-specific properties, allowing for the acquisition of both dynamic and hepatobiliary phase images. Its high biliary uptake and excretion improves lesion detection and characterization by increasing liver-to-lesion conspicuity in the added hepatobiliary phase imaging. To date, gadoxetate acid-enhanced MRI has been mostly shown to be superior to unenhanced MRI, computed tomography, and other types of contrast agents in the detection and characterization of liver lesions. This review article focuses on the evolving role of gadoxetate acid in the characterization of HCC, differentiating it from other mimickers of HCC.

Magnetic resonance imaging: Review of imaging techniques and overview of liver imaging

Magnetic resonance imaging (MRI) of the liver is slowly transitioning from a problem solving imaging modality to a first line imaging modality for many diseases of the liver. The well established advantages of MRI over other cross sectional imaging modalities may be the basis for this transition. Technological advancements in MRI that focus on producing high quality images and fast imaging, increasing diagnostic accuracy and developing newer function-specific contrast agents are essential in ensuring that MRI succeeds as a first line imaging modality. Newer imaging techniques, such as parallel imaging, are widely utilized to shorten scanning time. Diffusion weighted echo planar imaging, an adaptation from neuroimaging, is fast becoming a routine part of the MRI liver protocol to improve lesion detection and characterization of focal liver lesions. Contrast enhanced dynamic T1 weighted imaging is crucial in complete evaluation of diseases and the merit of this dynamic imaging relies heavily on the appropriate timing of the contrast injection. Newer techniques that include fluoro-triggered contrast enhanced MRI, an adaptation from 3D MRA imaging, are utilized to achieve good bolus timing that will allow for optimum scanning. For accurate interpretation of liver diseases, good understanding of the newer imaging techniques and familiarity with typical imaging features of liver diseases are essential. In this review, MR sequences for a time efficient liver MRI protocol utilizing newer imaging techniques are discussed and an overview of imaging features of selected common focal and diffuse liver diseases are presented.

Detection of hepatocellular carcinoma by Gd-EOB-DTPA-enhanced liver MRI: comparison with triple phase 64 detector row helical CT

PURPOSE

To compare the diagnostic performance of Gd-EOB-DTPA-enhanced MRI with that of triple phase 64-MDCT in the detection of hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Thirty-four patients with 52 surgically proven lesions underwent Gd-EOB-DTPA-enhanced MRI and triple phase 64-MDCT. Two observers independently evaluated MR and CT imaging on a lesion-by-lesion basis. Sensitivity, positive and negative predictive values and reproducibility were evaluated. The diagnostic accuracy of each modality was assessed with alternative-free response receiver operating characteristic (ROC) analysis.

RESULTS

Both observers showed higher sensitivity in detecting lesions with MRI compared to CT, however, only the difference between the two imaging techniques for observer 2 was significant (P=0.034). For lesions 1cm or smaller, MRI and CT showed equal sensitivity (both 62.5%) with one observer, and MRI proved superior to CT with the other observer (MRI 75% vs. CT 56.3%), but the latter difference was not significant (P=0.083). The difference in positive and negative predictive value between the two imaging techniques for each observer was not significant (P>0.05). The areas under the ROC curve for each observer were 0.843 and 0.861 for MRI vs. 0.800 and 0.833 for CT and the differences were not significant. Reproducibility was higher using MRI for both observers, but the result was not significant (MRI 32/33 vs. CT 29/33, P=0.083).

CONCLUSION

Gd-EOB-DTPA-enhanced MRI tended to show higher diagnostic accuracy, sensitivity and reproducibility compared to triple phase 64-MDCT in the detection of hepatocellular carcinoma, however statistical significance was not achieved.

Cirrhotic rat liver: reference to transporter activity and morphologic changes in bile canaliculi--gadoxetic acid-enhanced MR imaging

PURPOSE

To analyze the difference in signal intensity on gadoxetic acid-enhanced magnetic resonance (MR) images between normal and cirrhotic livers in rats as correlated with the expressions of the transporters of gadoxetic acid and the morphopathologic change in bile canaliculi.

MATERIALS AND METHODS

Institutional animal review board approval was received prior to the commencement of all studies. Fifteen rats received thioacetamide (TAA) in their drinking water for 12 weeks to induce liver cirrhosis. As a control, 15 rats were given normal water. After 12 weeks, seven rats in the TAA group and seven rats in the control group underwent gadoxetic acid-enhanced MR imaging (0.025 mmol gadolinium per kilogram of body weight). Five rats in each group were used for comparison of transporter (organic anion-transporting polypeptide 1 [oatp1] and multidrug resistance-associated protein 2 [mrp2]) activities. Three rats in each group were used for morphologic examination. The Wilcoxon rank sum test was used for statistical analysis.

RESULTS

Signal enhancement of the liver in the TAA group significantly decreased in comparison with that in the control group, although the signal enhancement of the kidney in both groups was almost identical. The oatp1 and mrp2 activities were as follows: 2.17 +/- 0.71 (standard deviation) for oatp1 in the TAA group, 2.58 +/- 0.35 for oatp1 in the control group, 3.37 +/- 1.04 for mrp2 in the TAA group, and 0.93 +/- 0.34 for mrp2 in the control group (P = .175 for oatp1, P = .009 for mrp2). At morphologic examination, enlargement of bile canaliculi and hyperplasia or elongation of microvilli were observed in the TAA group.

CONCLUSION

Findings showed that liver cirrhosis promotes the elimination of gadoxetic acid mediated by mrp2; therefore, mrp2 up-regulation may explain the significant signal intensity loss noted on gadoxetic acid-enhanced MR images in the rat. In addition, the up-regulation of mrp2 may be accompanied by morphologic changes in bile canaliculi and microvilli.