Efficacy and safety of MR imaging with liver-specific contrast agent: U.S. multicenter phase III study

Hepatobiliary MR imaging with gadolinium-based contrast agents

The advent of gadolinium-based "hepatobiliary" contrast agents offers new opportunities for diagnostic magnetic resonance imaging (MRI) and has triggered great interest for innovative imaging approaches to the liver and bile ducts. In this review article we discuss the imaging properties of the two gadolinium-based hepatobiliary contrast agents currently available in the U.S., gadobenate dimeglumine and gadoxetic acid, as well as important pharmacokinetic differences that affect their diagnostic performance. We review potential applications, protocol optimization strategies, as well as diagnostic pitfalls. A variety of illustrative case examples will be used to demonstrate the role of these agents in detection and characterization of liver lesions as well as for imaging the biliary system. Changes in MR protocols geared toward optimizing workflow and imaging quality are also discussed. It is our aim that the information provided in this article will facilitate the optimal utilization of these agents and will stimulate the reader's pursuit of new applications for future benefit.

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.

Hepatocyte transporter expression in FNH and FNH-like nodule: correlation with signal intensity on gadoxetic acid enhanced magnetic resonance images

PURPOSE

Our aim was to evaluate the hepatocyte transporters in focal nodular hyperplasia (FNH) and FNH-like lesions and to correlate the grade of its expression with signal intensity on the hepatobiliary phase (HB phase) of gadoxetic-acid-enhanced magnetic resonance imaging (EOB-MRI).

MATERIALS AND METHODS

Thirteen histopathological confirmed cases including eight with EOB-MRI were studied. Immunohistochemical staining for transporter was performed and its grade semiquantitatively analyzed.

RESULTS

Histopathologically, ten cases showed almost equal organic anion transporter polypeptide (OATP) 8 expression relative to the surrounding liver; the remaining three showed stronger OATP8 expression. In eight cases with EOB-MRI, two demonstrated more hyperintensity on the HB phase, and their OATP8 expression was stronger compared with the surrounding liver. The remaining six cases showed isointensity on the HB phase and revealed almost equal OATP8 expression. The expression of export transporter multi-drug-resistant proteins (MRP) 1 and 2 were almost equal relative to the surrounding liver in most cases (11/12, 92 %; 11/12, 92 %, respectively), whereas MRP3 focally overexpressed in 75 % (9/12) of cases.

CONCLUSION

FNH and FNH-like nodules revealed equal or stronger OATP8 expression than background liver. OATP8 expression showed significant correlation with signal intensity on the HB phase.

Gadoxetic acid-enhanced T1-weighted MR cholangiography in primary sclerosing cholangitis

PURPOSE

To investigate the value of gadoxetic acid-enhanced three-dimensional T1-weighted MR cholangiography (T1w-MRC) in comparison to three-dimensional T2-weighted MR cholangiopancreaticography (T2w-MRCP) in patients with primary sclerosing cholangitis (PSC).

MATERIALS AND METHODS

Thirty-four MR exams in 29 patients (46.0 ± 16.1 years; 19 men, 10 women) scanned within a 14-month period were retrospectively included. Two abdominal radiologists independently evaluated image quality regarding image contrast, image quality degradation due to artifacts, and visualization quality of ducts. The order of biliary tree branches that were visualized and reader preference toward each method were recorded. Helpfulness of T1w-MRC was scored in consensus. Confirmatory endoscopic retrograde cholangiopancreaticography (ERCP) performed within 3 months of the MR examination was available in 8 patients.

RESULTS

Image quality of T1w-MRC and T2w-MRCP was graded good to excellent in all cases. There were advantages for both T1w-MRC (functional information, less degradation due to artifacts) and T2w-MRCP (higher order of visualized branches, better branch depiction). Both readers showed preference for T2w-MRCP; however, both readers found gadoxetic acid-enhanced T1w-MRC helpful in the majority of cases.

CONCLUSION

Gadoxetic acid-enhanced T1w-MRC is complementary to, but should not replace, T2w-MRCP. T1w-MRC is a useful adjunct to T2w-MRCP for morphologic evaluation and provides additional diagnostic information.

Contrast agent Gd-EOB-DTPA (EOB·Primovist®) for low-field magnetic resonance imaging of canine focal liver lesions

Contrast-enhanced magnetic resonance (MR) imaging with a new liver-specific contrast agent gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA; EOB·Primovist®) was studied in 14 normal beagles and 9 dogs with focal liver lesions. Gd-EOB-DTPA accumulates in normally functioning hepatocytes 20 min after injection. As with Gd-DTPA, it is also possible to perform a dynamic multiphasic examination of the liver with Gd-EOB-DTPA, including an arterial phase and a portal venous phase. First, a reliable protocol was developed and the appropriate timings for the dynamic study and the parenchymal phase in normal dogs using Gd-EOB-DTPA were determined. Second, the patterns of these images were evaluated in patient dogs with hepatic masses. The optimal time of arterial imaging was from 15 s after injection, and the optimal time for portal venous imaging was from 40 s after injection. Meanwhile, the optimal time to observe changes during the hepatobiliary phase was from 20 min after injection. In patient dogs, 11 lesions were diagnosed as malignant tumors; all were hypointense to the surrounding normal liver parenchyma during the hepatobiliary phase. Even with a low-field MR imaging unit, the sequences afforded images adequate to visualize the liver parenchyma and to detect tumors within an appropriate scan time. Contrast-enhanced MR imaging with Gd-EOB-DTPA provides good demarcation on low-field MR imaging for diagnosing canine focal liver lesions.

Possible utility of MRI using Gd-EOB-DTPA for estimating liver functional reserve

BACKGROUND

Preoperative estimation of the liver functional reserve is important in liver surgery. We evaluated the role of dynamic magnetic resonance (MR) imaging with gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA), i.e., EOB-MRI, for determining liver functional reserve.

METHODS

Fifty patients who underwent EOB-MRI to examine their liver tumors were included in this study. We first performed a pixel-by-pixel comparison of registered MR images and activity images with Tc-99m galactosyl human serum albumin (GSA) on each slice, and the correlation coefficient was calculated for 8 patients. We also determined the correlation coefficient between the relative signal intensity (SI) values of EOB-MRI and preoperative liver function, such as the GSA, indocyanine green dye retention at 15 min (ICGR15), and prothrombin time.

RESULTS

The mean of the correlation coefficients for 512 × 512 matrices between the EOB-MRI and the GSA was 0.83 ± 0.05 (ranging from 0.73 to 0.87). The correlation coefficient between the relative SI of the EOB-MRI and the receptor index (LHL15) of GSA was 0.56 (P < 0.01). Better correlation coefficients were observed between the relative SI and the liver function test, including ICGR15 (r = -0.67, P < 0.01) and prothrombin time (r = 0.59, P < 0.01). In a patient with hilar cholangiocarcinoma whose right hepatic duct was obstructed, the relative SI in the right lobe (2.4 ± 0.3) was significantly lower than that in the left lobe (3.1 ± 0.1).

CONCLUSION

EOB-MRI represents a practical and reliable imaging technique that may be used to estimate regional liver functional reserve in the clinical setting.

Comparison of Kupffer-phase Sonazoid-enhanced sonography and hepatobiliary-phase gadoxetic acid-enhanced magnetic resonance imaging of hepatocellular carcinoma and correlation with histologic grading

OBJECTIVES

To determine the relative wash-out of hepatocellular carcinomas and dysplastic nodules using Kupffer-phase sonography with Sonazoid (Daiichi-Sankyo, Tokyo, Japan) enhancement and hepatobiliary-phase gadoxetic acid-enhanced magnetic resonance imaging (MRI) in the evaluation of the histopathologic grades of individual nodules.

METHODS

This retrospective study included 66 consecutive patients with 78 histologically confirmed hepatocellular carcinomas and dysplastic nodules. In patients with carcinomas, 33 were well differentiated; 29 were moderately differentiated; and 11 were poorly differentiated; and there were 5 dysplastic nodules. All patients underwent both gadoxetic acid-enhanced MRI and Sonazoid-enhanced sonography. The interval between the two imaging examinations was less than 30 days. Six radiologists independently reviewed both images and rated the degree of relative wash-out between the tumorous and nontumorous areas on Kupffer- and hepatobiliary-phase images using a continuous rating scale. We compared these results with the histopathologic grade of each nodule, and the results were then analyzed with multireader multicase receiver operating characteristic analysis.

RESULTS

The average Kupffer-phase (P < .001) and hepatobiliary-phase (P = .004) rating scores increased as the carcinomas became less differentiated (Kruskal-Wallis test). The diagnostic accuracies of the average area under the receiver operating characteristic curve, which were estimated using the confidence levels of the relative wash-out of the Kupffer- and hepatobiliary-phase images, were 0.705 and 0.785 for dysplastic nodules versus well-, moderately, and poorly differentiated carcinomas (P = .517), 0.791 and 0.687 for dysplastic nodules and well-differentiated carcinomas versus moderately and poorly differentiated carcinomas (P = .093), and 0.871 and 0.716 for dysplastic nodules and well-and moderately differentiated carcinomas versus poorly differentiated carcinomas (P = .005), respectively.

CONCLUSIONS

Kupffer-phase Sonazoid-enhanced sonography and hepatobiliary-phase gadoxetic acid-enhanced MRI may be useful in estimating the histologic grade, although Kupffer-phase Sonazoid-enhanced sonography may be more accurate in distinguishing hepatocellular carcinomas, especially moderately and poorly differentiated types.

Appearance of hepatocellular adenomas on gadoxetic acid-enhanced MRI

OBJECTIVE

The purpose of this study was to evaluate enhancement characteristics of hepatocellular adenomas (HCAs) using gadoxetic acid as a hepatocyte-specific MR contrast agent.

METHODS

Twenty-four patients with histopathologically proven HCAs were retrospectively identified. MRI consisted of T1- and T2-weighted (w) sequences with and without fat saturation (fs), multiphase dynamic T1-w images, and fs T1-w images during the hepatobiliary phase. Standard of reference was surgical resection (n = 19) or biopsy (n = 5). Images were analysed for morphology and contrast behaviour including signal intensity (SI) measurement on T1-w images normalised to the pre-contrast base line.

RESULTS

In total 34 HCAs were evaluated. All HCAs showed enhancement in the arterial phase; 38 % of HCAs showed reduced contrast enhancement ("wash-out") in the venous phase. All HCAs showed enhancement (SI increase, 56 ± 53 %; P <0.001) in the hepatobiliary phase, although liver uptake was stronger (96 ± 58 %). Thus, 31 of all HCAs (91 %) appeared hypointense to the surrounding liver in the hepatobiliary phase, while 3 out of 34 lesions were iso-/hyperintense.

CONCLUSIONS

Gadoxetic acid accumulates in HCAs in the hepatobiliary phase, although significantly less than in surrounding liver. Thus, HCA appears in the vast majority of cases as a hypointense lesion on hepatobiliary phase images.

KEY POINTS

• Magnetic resonance-specific contrast agents are now available for hepatic imaging. • Hepatocellular adenomas enhance with gadoxetic acid as in previous CT/MRI experience. • Enhancement during the hepatobiliary phase is less in HCAs than in liver. • Typical HCAs appear as hypointense lesions on T1-w hepatobiliary phase images. • True hyperintense HCA enhancement can occasionally occur during the hepatobiliary phase.

CT and MR cholangiography: advantages and pitfalls in perioperative evaluation of biliary tree

Recent developments in imaging technology have enabled CT and MR cholangiopancreatography (MRCP) to provide minimally invasive alternatives to endoscopic retrograde cholangiopancreatography for the pre- and post-operative assessment of biliary disease. This article describes anatomical variants of the biliary tree with surgical significance, followed by comparison of CT and MR cholangiographies. Drip infusion cholangiography with CT (DIC-CT) enables high-resolution three-dimensional anatomical representation of very small bile ducts (e.g. aberrant branches, the caudate branch and the cystic duct), which are potential causes of surgical complications. The disadvantages of DIC-CT include the possibility of adverse reactions to biliary contrast media and insufficient depiction of bile ducts caused by liver dysfunction or obstructive jaundice. Conventional MRCP is a standard, non-invasive method for evaluating the biliary tree. MRCP provides useful information, especially regarding the extrahepatic bile ducts and dilated intrahepatic bile ducts. Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced MRCP may facilitate the evaluation of biliary structure and excretory function. Understanding the characteristics of each type of cholangiography is important to ensure sufficient perioperative evaluation of the biliary system.

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.

Characteristics and distinguishing features of hepatocellular adenoma and focal nodular hyperplasia on gadoxetate disodium-enhanced MRI

OBJECTIVE

The purpose of this study is to evaluate the performance of gadoxetate disodium-enhanced MRI in the characterization of focal nodular hyperplasia (FNH) and hepatocellular adenoma and to assess potential advantages of hepatocyte phase imaging in identifying features that distinguish FNH from hepatocellular adenoma.

MATERIALS AND METHODS

Gadoxetate disodium-enhanced MRI examinations of 12 patients with hepatocellular adenoma and 35 patients with FNH were retrospectively evaluated by three blinded readers. Diagnoses and confidence scores were recorded before and after disclosure of hepatocyte phase images. The data obtained were combined to create receiver operating characteristic curves, and the areas under the curves were compared. Imaging characteristics, including signal intensity, were recorded. Lesion-to-liver enhancement ratio was calculated for each contrast-enhanced phase.

RESULTS

The readers' average receiver operating characteristic area was significantly higher after disclosure of hepatocyte phase images (p=0.024). FNHs were correctly diagnosed in 74.3-97.1% of cases before and 97.1-100% of cases after the disclosure of hepatocyte phase images; hepatocellular adenoma was correctly diagnosed in 83-100% and 91.7-100% of cases (p>0.05). The presence of a central scar in FNH and fat on hepatocellular adenoma were the only morphologic features that were statistically significantly different (p<0.05). FNH had greater average contrast-enhanced signal intensity and enhancement ratio in all phases (p<0.001). A hepatocyte phase enhancement ratio of less than 0.7 was 100% specific and 91.6% sensitive for hepatocellular adenoma, with accuracy of 97.1% for these data.

CONCLUSION

Gadoxetate disodium-enhanced MRI had high accuracy in diagnosis of FNH and hepatocellular adenoma, and the hepatocyte phase improved their distinction. FNH enhances significantly more than hepatocellular adenoma. An enhancement ratio, particularly in the hepatocyte phase, can be potentially used as an additional distinguishing feature.

Clinical significance of the transitional phase at gadoxetate disodium-enhanced hepatic MRI for the diagnosis of hepatocellular carcinoma: preliminary results

OBJECTIVES

To investigate the clinical significance of the "transitional phase" at gadoxetate disodium (Gd-EOB)-enhanced magnetic resonance imaging for diagnosing hepatocellular carcinoma (HCC).

METHODS

We studied 54 patients with 70 histologically diagnosed HCC. Transitional- and hepatobiliary-phase (TP, HBP) images were acquired 3 and 20 minutes after Gd-EOB injection, respectively. Radiologists measured the size of the hepatic tumors on images and surgical specimens and qualitatively evaluated the signal intensity of the hepatic tumors during TP and HBP independently.

RESULTS

In 4 patients with portal tumor embolism who had undergone percutaneous transhepatic portal embolization and who manifested arterioportal (AP) shunts, the low-intensity area was larger during HBP than TP. Of the 70 HCCs, 4 were of high signal intensity during HBP and 2 were of slightly low intensity during TP.

CONCLUSION

Tumor extension seen during TP rather than HBP more accurately reflected histological findings in patients with HCC with portal tumor thrombi, percutaneous transhepatic portal embolization, or AP shunt.

Assessment of arterial hypervascularity of hepatocellular carcinoma: comparison of contrast-enhanced US and gadoxetate disodium-enhanced MR imaging

OBJECTIVE

To compare contrast-enhanced (CE) ultrasound with gadoxetate disodium-enhanced magnetic resonance (MR) imaging in the assessment of arterial hypervascularity of hepatocellular carcinoma (HCC) and dysplastic nodule (DN), with CT during hepatic arteriography (CTHA) as the reference standard.

METHODS

This study included 54 consecutively diagnosed patients, with 57 histologically confirmed HCCs and 3 DNs (high-grade). All patients underwent CE ultrasound, gadoxetate disodium-enhanced MR imaging and CTHA. Two trained diagnostic radiologists interpreted the CTHA images and rated the degree of intratumoral arterial vascularity by consensus using a five-point confidence scale as the reference standard. In the observer study, the degrees of vascularity on CE ultrasound and gadoxetate disodium-enhanced MR images were qualitatively analysed by four independent readers using a five-point confidence scale. Diagnostic accuracy was analysed by receiver-operating characteristic (ROC) analysis.

RESULTS

The diagnostic accuracies of the average area under the ROC curve (AUC) were significantly greater with CE ultrasound (average AUC: 0.94; 95% confidence interval [CI]: 0.88-1.00) than with gadoxetate disodium-enhanced MR imaging (average AUC 0.84, 95% CI 0.74-0.93, P = 0.0014).

CONCLUSION

Contrast-enhanced ultrasound yields a significantly higher AUC value than gadoxetate disodium-enhanced MR imaging in the assessment of arterial hypervascularity of HCC and DN.

KEY POINTS

• Arterial hypervascularity is an important feature determining treatment options in hepatocellular carcinoma. • It can be assessed by contrast-enhanced (CE) ultrasound or magnetic resonance (MR) imaging. • CE ultrasound was more accurate than Gd-EOB-DTPA MRI in assessing intratumoral vascularity. • Hypovascular hepatic nodules should be further investigated using CE ultrasound.

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.

Comparison of Gd-Bz-TTDA, Gd-EOB-DTPA, and Gd-BOPTA for dynamic MR imaging of the liver in rat models

To evaluate the competitive potential of a new lipophilic paramagnetic complex, Gd-Bz-TTDA [4-benzyl-3,6,10-tri (carboxymethyl)-3,6,10-triazado-decanedioic acid] compared with two other commercially available MR hepatobiliary contrast agents, gadobenate dimeglumine (Gd-BOPTA) and gadoxetic acid (Gd-EOB-DTPA), dynamic MR imaging studies were performed on normal and hepatocellular carcinoma (HCC) rat models using a 1.5-Tesla MR scanner. The results indicate that normal rats that were injected with 0.1 mmol/kg Gd-Bz-TTDA showed significantly more intense and persistent liver enhancement than those that were injected with the same dose of Gd-EOB-DTPA or Gd-BOPTA. All of these agents showed similar enhancement patterns in the implanted HCC. The liver-lesion contrast-to-noise ratios were higher and more persistent in rats that were injected with Gd-Bz-TTDA. These results indicate that Gd-Bz-TTDA is comparable with the commercially available hepatobiliary agents, Gd-EOB-DTPA and Gd-BOPTA, and can result in more intense and prolonged liver enhancement while still providing better liver-lesion discrimination. These results warrant further large-scale studies.

Gadoxetate disodium-enhanced magnetic resonance imaging versus contrast-enhanced 18F-fluorodeoxyglucose positron emission tomography/computed tomography for the detection of colorectal liver metastases

PURPOSE

: To compare the diagnostic accuracy of gadoxetate disodium-enhanced magnetic resonance imaging (EOB-MRI) on a 3-T system and integrated contrast-enhanced F-fluorodeoxyglucose positron emission tomography/computed tomography (CE-PET/CT) for the detection of hepatic metastases from colorectal cancers.

MATERIALS AND METHODS

: The approval from the institutional review board was obtained, and the requirement for informed consent was waived. We retrospectively evaluated 135 metastases in 68 patients (37 men, 31 women; mean age: 68 years; age range: 37-82 years) who underwent both EOB-MRI and CE-PET/CT. A total of 103 metastases were confirmed during surgery and 32 were confirmed by imaging findings during follow-up. The images were independently reviewed by 2 observers. The diagnostic accuracies of EOB-MRI and CE-PET/CT were determined by calculating the areas under each reader-specific receiver operating characteristic curve (Az). Patient-based lesion sensitivity and specificity were compared using the McNemar test.

RESULTS

: The mean area under the Az on EOB-MRI versus CE-PET/CT was 0.94 versus 0.81 for all lesions (P < 0.001), 0.92 versus 0.60 for lesions ≤1 cm in size (P < 0.001), and 0.88 versus 0.96 for lesions >1 cm (P = 0.098), respectively. The sensitivity, specificity, positive predictive values, and negative predictive value on a patient basis were 100%, 71%, 97%, and 100% for EOB-MRI and 93%, 71%, 97%, and 57% for CE-PET/CT, respectively.

CONCLUSIONS

: EOB-MRI using a 3-T system is more accurate than CE-PET/CT, especially for the detection of small (≤1.0 cm) lesions. Patient-based analysis revealed that EOB-MRI has a higher sensitivity and negative predictive value than CE-PET/CT.

Chronological evaluation of liver enhancement in patients with chronic liver disease at Gd-EOB-DTPA-enhanced 3-T MR imaging: does liver function correlate with enhancement?

PURPOSE

To investigate the chronological relationship between scan delay and liver enhancement for the hepatobiliary phase on Gd-EOB-DTPA-enhanced MRI and evaluate the effects of liver function on liver enhancement.

MATERIALS AND METHODS

Hepatobiliary-phase images were retrospectively evaluated in 125 patients with chronic liver disease. Hepatobiliary phase images were obtained at 5, 10, 15, and 20 min after injection. We calculated relative liver enhancement (RLE) at t min after injection by dividing the signal intensity (SI) of the liver at t min by precontrast SI. We compared RLE values at 5, 10, 15, and 20 min and evaluated the detectability of focal hepatic lesions. We analyzed the effect of liver function on RLE with the generalized linear model.

RESULTS

There was not significant difference in RLE and lesion detectability at 15 and 20 min. RLE in the Child-Pugh C group was significantly lower than in the Child-Pugh A and B groups. The serum albumin level and prothrombin time were significantly correlated with the liver enhancement.

CONCLUSION

A delay time of 15 min for the hepatobiliary phase was thought to be adequate in patients with mild liver dysfunction. The serum albumin level and prothrombin time would be predictive of liver enhancement in the hepatobiliary phase.

Detection of liver metastases using gadoxetic-enhanced dynamic and 10- and 20-minute delayed phase MR imaging

PURPOSE

To assess the incremental value of hepatobiliary phase images in gadoxetate disodium-enhanced magnetic resonance imaging (MRI), and to compare diagnostic accuracy and lesion conspicuity on 10- and 20-minute delayed images for preoperative detection of hepatic metastases with subgroup analysis according to size and history of chemotherapy.

MATERIALS AND METHODS

Forty-six patients with 107 metastases who underwent surgery after gadoxetate disodium-enhanced MRI were evaluated. Four observers independently interpreted three sets: dynamic set comprising precontrast T1-, T2-weighted, and dynamic images; 10-minute set comprising dynamic set and 10-minute delayed; 20-minute set comprising 10-minute set and 20-minute delayed. Diagnostic accuracy was compared with subgroup analysis. Liver-to-lesion signal ratio (SR) was calculated using the region of interest method and compared.

RESULTS

Mean A(z) and sensitivities were significantly higher for 10- (A(z) = 0.894, sensitivity = 95.6%) and 20-minute (0.910, 97.2%) than dynamic set (0.813, 79.9%) (P < 0.001), with no significant difference between 10- and 20-minute sets (P = 0.140). In patients with small (≤1 cm) metastases and a history of chemotherapy, sensitivities were significantly higher with 10- (88.2%) and 20-minute (91.6%) sets than dynamic set (48.6%) (P < 0.001). SR was significantly higher for 10- and 20-minute delayed than precontrast and dynamic, with significantly higher SR on 20- than 10-minute delayed.

CONCLUSION

Regardless of size or prior chemotherapy, detection of hepatic metastases was significantly improved by adding hepatobiliary phase images without significant differences between 10- and 20-minute delayed.

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.

Gadoxetic acid-enhanced MRI findings of early hepatocellular carcinoma as defined by new histologic criteria

PURPOSE

To describe the imaging features of early hepatocellular carcinoma (HCC) on gadoxetic acid-enhanced MRI (Gd-EOB-MRI) in comparison with multidetector computed tomography (MDCT) examinations.

MATERIALS AND METHODS

We analyzed imaging findings of 19 pathologically proven early HCC lesions in 15 patients who underwent both MDCT and Gd-EOB-MRI at 3.0 Tesla (T) units before surgery. MRI included in-phase and out-of-phase T1-weighted dual-echo gradient-recalled-echo sequences, dynamic T1-weighted images before and after bolus injection of gadoxetic acid disodium, fat-saturated T2-weighted fast spin-echo sequences, and T1-weighted hepatobiliary phase images 20 min after contrast injection. Two radiologists retrospectively evaluated the signal intensities and enhancement features on MRI and MDCT.

RESULTS

None of the lesions displayed arterial enhancement and washout on MDCT. On Gd-EOB-MRI, six (32%) lesions showed T2-hyperintensity, five (26%) lesions showed signal drop on opposed-phase. Three lesions (16%) showed arterial enhancement and washout. Twelve (63%), 13 (68%), and 15 (79%) lesions were hypointense on hepatic venous, equilibrium, and hepatobiliary phase, respectively.

CONCLUSION

Most early HCCs did not show arterial enhancement and washout pattern on both MDCT and Gd-EOB-MRI. Gd-EOB-MRI may provide several ancillary findings for diagnosis of early HCC such as decreased hepatobiliary uptake, T2 hyperintensity and signal drop in opposed phase.

Advances in pediatric body MRI

MRI offers an alternative to CT, and thus is central to an ALARA strategy. However, long exam times, limited magnet availability, and motion artifacts are barriers to expanded use of MRI. This article reviews developments in pediatric body MRI that might reduce these barriers: high field systems, acceleration, navigation and newer contrast agents.

Effect of lapatinib on hepatic parenchymal enhancement on gadoxetate disodium (EOB)-enhanced MRI scans

We present changes seen on hepatobiliary phase (HBP)-gadoxetate disodium (EOB)-enhanced magnetic resonance image of a woman with liver metastases who was treated with lapatinib. After treatment, the HBP images appeared like portal venous phase images. This suggests that lapatinib, an inhibitor of organic anion transporting polypeptide 1B1, one of the substrates of EOB, inhibits EOB uptake by hepatocytes. In patients treated with lapatinib, the ability to diagnose liver tumors on HBP images may be compromised.

Staging liver fibrosis by using liver-enhancement ratio of gadoxetic acid-enhanced MR imaging: comparison with aspartate aminotransferase-to-platelet ratio index

OBJECTIVE

To compare the diagnostic ability of gadoxetic acid-enhanced hepatocyte-phase MR images with aspartate aminotransferase-to-platelet ratio index (APRI) to predict liver fibrosis stage.

MATERIALS AND METHODS

Our study included 100 patients who underwent gadoxetic acid-enhanced MRI and either liver biopsy or liver surgery. Liver fibrosis stage was histologically determined according to the METAVIR system: F0 (n=16), F1 (n=17), F2 (n=10), F3 (n=21) and F4 (n=36). Four measures were used as imaging-based fibrosis markers: liver-spleen contrast ratio, liver-enhancement ratio, corrected liver-enhancement ratio and spleen index. APRI represented a blood test-based fibrosis marker. The diagnostic ability of those fibrosis markers were compared through receiver-operating characteristic analysis.

RESULTS

The area under the curve (AUC) for APRI prediction of severe fibrosis (≥F3 and F4) was significantly greater than that of corrected liver-enhancement ratio. However, corrected liver-enhancement ratio had a greater AUC for prediction of mild fibrosis (≥F1) than APRI, although the difference was insignificant.

CONCLUSION

Corrected liver-enhancement ratio with gadoxetic acid-enhanced MRI is correlated to the stage of liver fibrosis. APRI, however, has greater reliability for predicting severe fibrosis and cirrhosis than does the imaging-based fibrosis marker tested in this study.

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.

Estimation of liver function using T1 mapping on Gd-EOB-DTPA-enhanced magnetic resonance imaging

OBJECTIVES

To investigate the ability of T1 mapping of liver on gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging for the estimation of liver function.

MATERIALS AND METHODS

Local institutional review board approved this study. Ninety-one patients (64 men, 27 women; mean age, 67.4 years) were classified into 4 groups as follows: normal liver function (NLF), n = 16; chronic hepatitis (CH), n = 38; liver cirrhosis with Child-Pugh A (LCA), n = 20; and liver cirrhosis with Child-Pugh B (LCB), n = 17. Look-Locker sequences (single slice multiphase imaging using gradient-echo sequence with inversion recovery pulse) were obtained before and at 3, 8, 13, and 18 minutes after Gd-EOB-DTPA administration. T1 mapping of liver parenchyma was calculated from the Look-Locker sequence. T1 relaxation time of liver and reduction rate of T1 relaxation time between pre- and postcontrast enhancement were measured. The Bonferroni t test was used for comparisons between the 4 groups.

RESULTS

Precontrast T1 relaxation times were significantly longer for LCA and LCB than for NLF, and that of LCB was longer than that of chronic hepatitis (P < 0.05). Postcontrast T1 relaxation times were significantly longer for LCB than for other groups at all time points. Those of LCA were longer than those of NLF at all time points. Reduction rates were significantly lower for LCB than for the other groups at ≥8 minutes.

CONCLUSIONS

Evaluation of hepatic uptake of Gd-EOB-DTPA using T1 mapping of liver parenchyma can help estimate liver function.

Dynamic MR imaging of kidneys perfused with EOB-Gd-DTPA

Gandolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) is a hepatobiliary contrast agent for MRI. It was reported that Gd-EOB-DTPA is useful to detect liver tumors and differentially diagnose benign and malignant pathologies in the liver. Since Gd-EOB-DTPA partially accumulates in the hepatocytes and bile via various transporters after intravenous injection, signal intensity in the liver increases on T1-weighted images. The signal intensity of the liver after Gd-EOB-DTPA injection depends on the Gd-EOB-DTPA uptake by hepatocytes and bile excretion. It is known tha the Gd-EOB-DTPA accumulating in the kidney is excreted to the urine through glomerular filtration. Because Gd-DTPA is concentrated in the renal tubules after being filtered at the Bowman's capsule, and since it is neither secreted nor reabsorbed the concentrating and diluting function of the renal tubules can be studied by imaging techniques. since renal function can be evaluated with Gd-EOB-DTPA can also be used to evaluate renal function. Eith the development of MRI equipment and rapid imaging techniques, temporal resolution had improved greatly. However, no previous study has been carried out on renal function using Gd-EOB-DTPA dynamic MR study that was correlated with estimated glomerular filtration rate (eGFR) and stage of chronic kidney disease (CKD) in the Japan Association of chronic kidney disease initiative.

Hepatic hemangiomas: evaluation of enhancement patterns at dynamic MRI with gadoxetate disodium

OBJECTIVE

The aim of this retrospective study was to assess the enhancement patterns of hepatic hemangiomas on gadoxetate disodium.

MATERIALS AND METHODS

A total of 22 patients with 32 hepatic hemangiomas (23 typical type and nine high-flow type) in normal liver underwent gadoxetate disodium-enhanced MRI. Contrast-enhanced images were obtained before and after contrast injection, including arterial phase, portal phase, equilibrium phase, and three hepatobiliary phases (10, 15 and 20 minutes). Signal-to-phantom ratios of hemangiomas and the portal vein as well as lesion-to-liver contrast-to-phantom ratios were assessed.

RESULTS

Mean signal-to-phantom ratios of all 32 hemangiomas showed the highest value on the arterial phase and subsequently decreased over time (p = 0.029 to p < 0.001). Mean lesion-to-liver contrast-to-phantom ratios of all 32 hemangiomas showed a positive value during the arterial phase and increasingly negative values at later time points (p = 0.001 to p < 0.001). The enhancement pattern of hemangiomas was equal to that of the portal vein at all time points. There was no significant difference in signal-to-phantom ratio between typical hemangiomas and high-flow hemangiomas at any time point.

CONCLUSION

Most hepatic hemangiomas showed hypointensity relative to surrounding liver parenchyma during the equilibrium phase and the hepatobiliary phase. In addition, hepatic hemangiomas showed a signal intensity matching the portal vein at all phases, a finding we believe may be characteristic for hepatic hemangiomas on gadoxetate disodium-enhanced MR images.

Evaluation of possible drug-drug interaction between gadoxetic acid and erythromycin as an inhibitor of organic anion transporting peptides (OATP)

PURPOSE

To evaluate if erythromycin compromises liver-specific enhancement of gadoxetic acid; both compounds competing in organic anion transporting peptides (OATP) -mediated hepatocytic uptake.

MATERIALS AND METHODS

The study was approved by institutional review board. Twelve healthy subjects (nine men, three woman; mean age, 38.7 years) were examined twice by MR imaging with prior administration of NaCl solution (placebo) or 1000 mg of erythromycin following a randomized sequence. Gadoxetic acid (0.025 mmol/kg body weight) was administered 15 min after the end of infusions. Pre- and 20 min postcontrast two-dimensional gradient-recalled-echo sequences were acquired. Relative enhancements of liver parenchyma and ratio of means were calculated from signal intensity measurements. Plasma levels of gadoxetic acid and erythromycin were determined and given in geometric means and coefficients of variation (CV).

RESULTS

Concentration of erythromycin directly after end of infusion was 13.9 mg/L (CV 14.9%). Gadolinium plasma concentrations 5 min after gadoxetic acid administration were 138.7 μmol/L (CV 20.4%) after erythromycin infusion and 129.6 μmol/L (CV 22.8%) after placebo. Mean relative enhancements of liver parenchyma were 88.1 (SD 24.9%) after erythromycin infusion and 92.6 (SD 17.9%) after placebo. Ratio of relative enhancements was 0.951 (95% confidence interval, 0.833; 1.061; statistically not significant).

CONCLUSION

Coadministration of erythromycin has no effect on gadoxetic acid enhanced liver MR imaging.

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.

Staging hepatic fibrosis: comparison of gadoxetate disodium-enhanced and diffusion-weighted MR imaging--preliminary observations

PURPOSE

To evaluate the utility of hepatocyte-phase gadoxetate disodium-enhanced magnetic resonance (MR) imaging in staging hepatic fibrosis and to compare it with diffusion-weighted imaging.

MATERIALS AND METHODS

This retrospective study had institutional review board approval, and the requirement for informed consent was waived. Gadoxetate disodium-enhanced and diffusion-weighted MR images obtained in 114 consecutive patients (70 men, 44 women; age range, 37-91 years) were evaluated. Liver-to-muscle signal intensity (SI) ratio on hepatocyte-phase images (SI(post)), contrast enhancement index calculated as SI(post) /SI(pre), where SI(pre) is liver-to-muscle SI ratio on nonenhanced images, and apparent diffusion coefficient (ADC) of the liver were measured. Necroinflammatory activity grades and hepatic fibrosis stages were histopathologically determined in 99 patients. Multiple regressions of SI(post), contrast enhancement index, ADC, serum albumin concentration, serum total bilirubin level, prothrombin time, and Child-Pugh score were examined to determine correlation with hepatic necroinflammatory activity grades and fibrosis stages.

RESULTS

Among the MR, hematologic, and clinical parameters, contrast enhancement index was most strongly correlated with fibrosis stage (r = -0.79, P < .001). Multiple regression analysis showed that the contrast enhancement index, ADC, and prothrombin time were significantly correlated (r(2) = 0.66, P < .05) with fibrosis stage and that the contrast enhancement index and serum total bilirubin level were weakly correlated (r(2) = 0.24, P < .05) with the necroinflammatory activity grade.

CONCLUSION

Gadoxetate disodium-enhanced MR imaging is more reliable for staging hepatic fibrosis than are diffusion-weighted MR imaging, hematologic, and clinical parameters.

Assessment of adverse reaction rates during gadoteridol-enhanced MR imaging in 28,078 patients

PURPOSE

To determine adverse reaction rates in a tertiary care clinical setting after adoption of gadoteridol as the institutional routine magnetic resonance (MR) imaging contrast agent.

MATERIALS AND METHODS

With institutional review board approval, informed consent waiver, and HIPAA compliance, a prospective observational study of 28 078 patients who underwent intravenous gadoteridol-enhanced MR imaging from July 2007 to December 2009 was performed. Reactions were recorded by technologists who noted types of reactions, method of injection, and treatment. Reactions were classified as mild, moderate, or severe per American College of Radiology definitions. Comparisons of reaction rates with dose and method of injection were analyzed with the Fisher exact and χ(2) tests.

RESULTS

Overall reaction rate was 0.666% (187 patients), including 177 mild, six moderate, and four severe reactions. Treatment was given in 27 patients (14.4%). The most frequent reaction was nausea (and/or vomiting) in 149 patients (79.7% of patients with any adverse reaction, 0.530% of overall population). Method of injection did not affect reaction rate or severity. There was no difference in type or severity of reactions in comparison of patients receiving half the dose versus patients receiving the standard dose (P = .33-.75).

CONCLUSION

The observed adverse reaction rate to gadoteridol was lower than previously reported. Specifically, the rate of nausea (0.530%) was less than half the rate (1.4%) in clinical trials of 1251 patients, leading to FDA approval in 1992. Rates of adverse reactions for this macrocyclic contrast agent are comparable to those published for linear gadolinium-based contrast agents.

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.

Intraindividual comparison of gadoxetate disodium-enhanced MR imaging and 64-section multidetector CT in the Detection of hepatocellular carcinoma in patients with cirrhosis

PURPOSE

To prospectively compare gadoxetate disodium-enhanced magnetic resonance (MR) imaging with multiphasic 64-section multidetector computed tomography (CT) in the detection of hepatocellular carcinoma (HCC) in patients with cirrhosis.

MATERIALS AND METHODS

Institutional review board approval and informed patient consent were obtained for this prospective study. Fifty-eight patients (39 men, 19 women; mean age, 63 years; age range, 35-84 years) underwent gadoxetate disodium-enhanced MR imaging and multiphasic 64-section multidetector CT. The imaging examinations were performed within 30 days of each other. The two sets of images were qualitatively analyzed in random order by three independent readers in a blinded and retrospective fashion. Using strict diagnostic criteria for HCC, readers classified all detected lesions with use of a four-point confidence scale. The reference standard was a combination of pathologic proof, conclusive imaging findings, and substantial tumor growth at follow-up CT or MR imaging (range of follow-up, 90-370 days). The diagnostic accuracy, sensitivity, and positive predictive value were compared between the two image sets. Interreader variability was assessed. The accuracy of each imaging method was determined by using an adjusted modified chi(2) test.

RESULTS

Eighty-seven HCCs (mean size +/- standard deviation, 1.8 cm +/- 1.5; range, 0.3-7.0 cm) were confirmed in 42 of the 58 patients. Regardless of lesion size, the average diagnostic accuracy and sensitivity for all readers were significantly greater with gadoxetate disodium-enhanced MR imaging (average diagnostic accuracy: 0.88, 95% confidence interval [CI]: 0.80, 0.97; average sensitivity: 0.85, 95% CI: 0.74, 0.96) than with multidetector CT (average diagnostic accuracy: 0.74, 95% CI: 0.65, 0.82; average sensitivity: 0.69, 95% CI: 0.59, 0.79) (P < .001 for each). No significant difference in positive predictive value was observed between the two image sets for each reader. Interreader agreement was good to excellent.

CONCLUSION

Compared with multiphasic 64-section multidetector CT, gadoxetate disodium-enhanced MR imaging yields significantly higher diagnostic accuracy and sensitivity in the detection of HCC in patients with cirrhosis.

Detection and characterization of liver lesions using gadoxetic acid as a tissue-specific contrast agent

The value of cross-sectional liver imaging is evaluated by the accuracy, sensitivity, and specificity of the specific imaging technique. Magnetic resonance imaging (MRI) has become a key technique for the characterization and detection of focal and diffuse liver disease. More recently, gadoxetic acid, the hepatocyte-specific MR contrast agent, was clinically approved and introduced in many countries. Gadoxetic acid may be considered a "molecular imaging" probe because the compound is actively taken into hepatocytes via the ATP-dependent organic anion transport system in the plasma membrane for the hepatic uptake. The transport of gadoxetic acid from the cytoplasm to the bile is mainly determined by the capacity of the transport protein glutathione-S-transferase. Gadoxetic acid enhances hepatocyte-containing lesions and improves detection of lesions devoid of normal hepatocytes, such as metastases. Innovative rapid MR acquisition techniques with near isotropic 3D pulse sequences with fat saturation parallel the technical progress made by multidetector computed tomography combined with an impressive improvement in tumor-liver contrast when used for gadoxetic acid-enhanced MRI. The purpose of this review is to provide an overview of the development, clinical testing, and applications of this novel MR contrast agent.

Hepatocellular carcinoma: signal intensity at gadoxetic acid-enhanced MR Imaging--correlation with molecular transporters and histopathologic features

PURPOSE

To analyze the correlation between signal intensity in the hepatobiliary phase of gadoxetic acid-enhanced magnetic resonance (MR) imaging and the expression of hepatocyte transporters with histopathologic features in hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Institutional ethics committee approval and informed consent were obtained. Forty surgically resected HCCs were classified as hypointense (n = 32) or iso- or hyperintense (n = 8) on the basis of findings in the hepatobiliary phase of gadoxetic acid-enhanced MR imaging. The following were compared between hypointense and iso- or hyperintense HCCs: the time-signal intensity curves at gadoxetic acid-enhanced MR imaging, the expression levels of seven transporters (four organic anion-transporting polypeptides [OATPs] and three multidrug-resistant proteins [MRPs]) at polymerase chain reaction (PCR) (for 22 nodules), results of immunostaining of OATP8, and histologic features. Statistical analysis (unpaired t test, Mann-Whitney test, chi(2) test, and Fisher exact test) was performed for each result.

RESULTS

On the time-signal intensity curves, hypointense HCCs showed a decreasing pattern, whereas iso- or hyperintense HCCs showed an increasing pattern after the dynamic phase. PCR revealed that expression of OATP8 (an uptake transporter) in hypointense HCCs was lower and that in iso- or hyperintense HCCs was higher than in background liver (P < .001). The expression level of MRP3 (a sinusoidal export transporter) showed a similar trend to that of OATP8 (P < .001). Immunostaining revealed that OATP8 expression was weak in hypointense HCCs, whereas it was sustained in iso- or hyperintense HCCs (P < .001). At histologic examination, a pseudoglandular proliferation pattern with bile plugs was more commonly observed in iso- or hyperintense HCCs than in hypointense HCCs (P = .01 for proliferation patterns and P = .006 for bile plugs).

CONCLUSION

The enhancement ratio of HCCs in the hepatobiliary phase of gadoxetic acid-enhanced MR imaging positively correlated with expression levels of OATP8 and MRP3, indicating that gadoxetic acid is taken up by OATP8 and excreted by MRP3.

Outcome of small liver nodules detected by computed tomographic angiography in patients with hepatocellular carcinoma

PURPOSE

Hepatic lesions identified by computed tomography (CT) during arterial portography (CTAP) or CT hepatic arteriography (CTHA) in hepatocellular carcinoma (HCC) patients are sometimes too small to be diagnosed as HCC. We undertook this cohort study to assess whether these small lesions are actually HCC, and to clarify the effectiveness of these imaging examinations in a clinical setting.

METHODS

We assessed the characteristics of 74 tiny lesions detected by CTAP and/or CTHA, but not by CT in 67 patients.

RESULTS

Seven out of 10 nodules were histologically confirmed as HCC and 18 out of 64 lesions increased in size and showed typical findings of HCC during the follow-up period. Multivariate analysis revealed that the size of the main tumor (>30 mm in diameter) was associated with the presence of tiny additional HCC lesions (P = 0.002).

CONCLUSIONS

These findings indicate that CTAP and CTHA are recommended for determining the stage of HCC, especially when the HCC nodule is larger than 30 mm in diameter.

Imaging of the liver for hepatocellular cancer

BACKGROUND

Imaging of the liver is a key component in the detection, diagnosis, management, and follow-up of patients with hepatocellular carcinoma.

METHODS

The author uses his own experience as well as a review of pertinent literature to describe the capabilities and the limitations of the principal currently available imaging techniques for the liver.

RESULTS

Ultrasound is widely available, but sensitivity and specificity for small nodules are limited. Computed tomography effectively demonstrates extrahepatic lesions and can differentiate between cysts or hemangiomas and hepatocellular carcinomas. Magnetic resonance imaging better characterizes hepatic lesions, but positron emission tomography is of limited value.

CONCLUSIONS

Cross-sectional imaging with ultrasound, CT, or MRI is critical for nodule characterization in the cirrhotic liver, surgical planning of HCC, and treatment response evaluation.

Hepatocellular carcinoma: hepatocyte-selective enhancement at gadoxetic acid-enhanced MR imaging--correlation with expression of sinusoidal and canalicular transporters and bile accumulation

PURPOSE

To investigate the mechanism of enhancement of hepatocellular carcinoma (HCC) on gadoxetic acid-enhanced hepatobiliary phase magnetic resonance (MR) images and to characterize HCC thus enhanced.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board, and patient informed consent for research use of the resected specimen was obtained. MR images in 25 patients (20 men, five women; mean age, 68 years; range, 49-82 years) with 27 resected hypervascular HCCs (one well, 13 moderately, 13 poorly differentiated) that demonstrated hepatocyte-selective enhancement on gadoxetic acid-enhanced MR images, were quantitatively studied, and findings were correlated with results of immunohistochemical staining for a sinusoidal transporter, organic anion transporting polypeptide (OATP) 1B1 (OATP1B1) and/or OATP1B3 (OATP1B1 and/or -1B3), and a canalicular transporter, multidrug resistance-associated protein 2 (MRP2), and also with bile accumulation in tumors. Statistical analysis was performed with the Student t test and Scheffé post hoc test.

RESULTS

Combined with positive OATP1B1 and/or -1B3 expression (O+), two patterns of MRP2 expression contributed to high enhancement: decreased expression (M-, n = 3) and increased expression at the luminal membrane of pseudoglands (M+[P], n = 3). Nodules without OATP1B1 and/or -1B3 expression (O-, n = 13) and nodules with O+ associated with increased MRP2 expression only at the canaliculi (M+[C], n = 8) induced significantly lower enhancement than those with the two expression patterns described before (O+/M- group vs O- group, P = .002; O+/M- group vs O+/M+[C] group, P = .047; O+/M+[P] group vs O- group, P < .001; O+/M+[P] group vs O+/M+[C] group, P < .001). Nodules with bile pigment (n = 12) showed significantly higher enhancement (P = .004); all five nodules (one well differentiated HCC, four moderately differentiated HCCs), which were enhanced more than adjacent liver parenchyma, contained bile pigment.

CONCLUSION

High hepatocyte-selective enhancement is induced by expression patterns of transporters, which may result in accumulation of gadoxetic acid in cytoplasm of tumor cells or in lumina of pseudoglands. An HCC with gadoxetic acid enhancement is characterized by bile accumulation in tumors.