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

Histogram analysis of gadoxetic acid-enhanced MRI for quantitative hepatic fibrosis measurement

PURPOSE

The diagnosis and monitoring of liver fibrosis is an important clinical issue; however, this is usually achieved by invasive methods such as biopsy. We aimed to determine whether histogram analysis of hepatobiliary phase images of gadoxetic acid-enhanced magnetic resonance imaging (MRI) can provide non-invasive quantitative measurement of liver fibrosis.

METHODS

This retrospective study was approved by the institutional ethics committee, and a waiver of informed consent was obtained. Hepatobiliary phase images of preoperative gadoxetic acid-enhanced MRI studies of 105 patients (69 males, 36 females; age 56.1±12.2) with pathologically documented liver fibrosis grades were analyzed. Fibrosis staging was F0/F1/F2/F3/F4 (METAVIR system) for 11/20/13/15/46 patients, respectively. Four regions-of-interest (ROI, each about 2 cm2) were placed on predetermined locations of representative images. The measured signal intensity of pixels in each ROI was used to calculate corrected coefficient of variation (cCV), skewness, and kurtosis. An average value of each parameter was calculated for comparison. Statistical analysis was performed by ANOVA, receiver operating characteristic (ROC) curve analysis, and linear regression.

RESULTS

The cCV showed statistically significant differences among pathological fibrosis grades (P<0.001) whereas skewness and kurtosis did not. Univariable linear regression analysis suggested cCV to be a meaningful parameter in predicting the fibrosis grade (P<0.001, β = 0.40 and standard error  = 0.06). For discriminating F0-3 from F4, the area under ROC score was 0.857, standard deviation 0.036, 95% confidence interval 0.785-0.928.

CONCLUSION

Histogram analysis of hepatobiliary phase images of gadoxetic acid-enhanced MRI can provide non-invasive quantitative measurements of hepatic fibrosis.

CT and MR imaging diagnosis and staging of hepatocellular carcinoma: part I. Development, growth, and spread: key pathologic and imaging aspects

Computed tomography (CT) and magnetic resonance (MR) imaging play critical roles in the diagnosis and staging of hepatocellular carcinoma (HCC). The first article of this two-part review discusses key concepts of HCC development, growth, and spread, emphasizing those features with imaging correlates and hence most relevant to radiologists; state-of-the-art CT and MR imaging technique with extracellular and hepatobiliary contrast agents; and the imaging appearance of precursor nodules that eventually may transform into overt HCC.

Quantitative evaluation of enhancement patterns in focal solid liver lesions with Gd-EOB-DTPA-enhanced MRI

Purpose

The objective was to investigate the dynamic enhancement patterns in focal solid liver lesions after the administration of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) by means of dynamic magnetic resonance imaging (MRI) including hepatobiliary phase (HP) images 20 min after Gd-EOB-DTPA administration.

Materials and Methods

Non-enhanced T1/T2-weighted as well as dynamic magnetic resonance (MR) images during the arterial phase (AP), the portal venous phase (PVP), the late phase (LP), and the HP (20 min) were obtained from 83 patients (54 male, 29 female, mean age 62.01 years) with focal solid liver lesions. MRI was conducted by means of a 1.5-T system for 63 patients with malignant liver lesions (HCCs: n = 34, metastases: n = 29) and for 20 patients with benign liver lesions (FNH lesions: n = 14, hemangiomas: n = 3, adenomas: n = 3). For quantitative analysis, signal-to-noise ratios (SNR), contrast enhancement ratios (CER), lesion-to-liver contrast ratios (LLC), and signal intensity (SI) ratios were measured.

Results

The SNR of liver parenchyma significantly increased in each dynamic phase after Gd-EOB-DTPA administration compared to the SNR of non-enhanced images (p<0.001). The CER of HCCs and metastases significantly decreased between LP and HP images (p = 0.0011, p<0.0001). However, FNH lesions did not show any significant difference, whereas an increased CER was found in hemangiomas. The mean LLCs of FNH lesions were significantly higher than those of HCCs and metastases. The LLC values of hemangiomas remained negative during the entire time course, whereas the LLC of adenomas indicated hyperintensity from the AP to the LP. Furthermore, adenomas showed hypointensity in HP images.

Conclusion

Gd-EOB-DTPA-enhanced MRI may help diagnose focal solid liver lesions by evaluating their enhancement patterns.

Noninvasive differentiation of simple steatosis and steatohepatitis by using gadoxetic acid-enhanced MR imaging in patients with nonalcoholic fatty liver disease: a proof-of-concept study

PURPOSE

To determine whether gadoxetic acid-enhanced magnetic resonance (MR) imaging can be used to distinguish between simple steatosis and nonalcoholic steatohepatitis (NASH) in patients with nonalcoholic fatty liver disease (NAFLD), defined according to the steatosis activity and fibrosis (SAF) scoring system, which is based on the semiquantitative scoring of steatosis activity and liver fibrosis.

MATERIALS AND METHODS

The local institutional review committee approved this study and waived written informed consent. This was a retrospective study of gadoxetic acid-enhanced 3-T MR imaging performed in 81 patients with NAFLD (45 men [56%]; mean age, 56 years; range, 25-78 years). The MR images were analyzed by using the relative enhancement (the ratio of signal intensities of the liver parenchyma before and 20 minutes after intravenous administration of gadoxetic acid). Univariate and multiple regression analyses were applied to identify variables associated with relative enhancement measurements. The ability of relative enhancement to allow differentiation between simple steatosis and NASH was assessed by using area under the receiver operating characteristic (ROC) curve analysis.

RESULTS

Relative enhancement negatively correlated with the degree of lobular inflammation (r = -0.59, P < .0001), ballooning (r = -0.44, P < .0001), and fibrosis (r = -0.59, P ≤ .0001), but not with steatosis (r = -0.16, P = .15). Patients with NASH had a significantly lower relative liver enhancement (0.82 ± 0.22) than those with simple steatosis (1.39 ± 0.52) (P < .001). Relative enhancement measurements performed well in the differentiation between simple steatosis and NASH, with an area under the ROC curve of 0.85 (95% confidence interval: 0.75, 0.91) (cutoff = 1.24, sensitivity = 97%, specificity = 63%).

CONCLUSION

Gadoxetic acid relative enhancement was significantly lower in patients with NASH than in patients with simple steatosis, but further prospective studies are warranted.

Assessing liver function by liver enhancement during the hepatobiliary phase with Gd-EOB-DTPA-enhanced MRI at 3 Tesla

OBJECTIVES

The purpose of this study was to evaluate the usefulness of Gd-EOB-DTPA-enhanced 3-T MRI to determine the hepatic functional reserve expressed by the model for end-stage liver disease (MELD) score.

METHODS

A total of 121 patients with normal liver function (NLF; MELD score ≤ 10) and 29 patients with impaired liver function (ILF; MELD score > 10) underwent contrast-enhanced MRI with a hepatocyte-specific contrast agent at 3T. T1-weighted volume interpolated breath-hold examination (VIBE) sequences with fat suppression were acquired before and 20 min after contrast injection. Relative enhancement (RE) between plain signal intensity and contrast-enhanced signal intensity was calculated and was used to determine Gd-EOB-DTPA uptake into the liver parenchyma for patients with different MELD scores.

RESULTS

RE differed significantly (p ≤ 0.001) between patients with NLF (87.2 ± 29.5 %) and patients with ILF (45.4 ± 26.5 %). The optimal cut-off value for RE to differentiate NLF from ILF was 47.7 % (AUC 0.87). This cut-off value showed a sensitivity of 82.8 % and a specificity of 92.7 % for the differentiation of the analysed groups.

CONCLUSION

Gd-EOB-DTPA uptake in hepatocytes is strongly affected by liver function. Gd-EOB-DTPA-enhanced MRI and assessment of RE during the hepatobiliary phase (HBP) may serve as a useful image-based test in liver imaging for determining regional and global liver function.

KEY POINTS

Hepatic uptake of Gd-EOB-DTPA is strongly affected by liver function. Relative enhancement during HBP in GD-EOB-DTPA MRI correlates with the MELD score. Assessment of relative enhancement may help improve treatment in routine clinical practice.

Curcumin prevents bile canalicular alterations in the liver of hamsters infected with Opisthorchis viverrini

Opisthorchis viverrini infection causes inflammation and liver injury leading to periductal fibrosis. Little is known about the pathological alterations in bile canaliculi in opisthorchiasis. This study aimed to investigate bile canalicular alterations in O. viverrini-infected hamsters and to examine the chemopreventive effects of curcumin on such changes. Hamsters were infected with O. viverrini and one group of animals was fed with 1% dietary curcumin supplement. Animals were examined during the acute infection phase, days 21 and 30 post-infection (PI) and chronic infection phase (day 90 PI). Scanning electron microscopy revealed that in the infected group fed with a normal diet, bile canaliculi became slightly tortuous by 30 day PI and more tortuous at day 90 PI. Transmission electron microscopy showed a reduction in microvilli density of canaliculi starting at day 30 PI, with a marked loss of microvilli at day 90 PI. These ultrastructral changes were slightly seen at day 21 PI, which was similar to that found in infected animals fed with 1% curcumin-supplemented diet. Notably, curcumin treatment prevented the reduction of microvilli density, reduced the dilation of bile canaliculi, and decreased the tortuosity of the bile canaliculi relative to non-infected animals on a normal diet at days 30 and 90 PI. These results suggest that curcumin reduces alteration of bile canaliculi and may be a promising agent to prevent the onset of bile duct abnormalities induced by O. viverrini infection.

Assessment of clinical signs of liver cirrhosis using T1 mapping on Gd-EOB-DTPA-enhanced 3T MRI

OBJECTIVES

To assess the differences between normal and cirrhotic livers by means of T1 mapping of liver parenchyma on gadoxetic acid (Gd-EOB-DTPA)-enhanced 3 Tesla (3T) MR imaging (MRI).

METHODS

162 patients with normal (n = 96) and cirrhotic livers (n = 66; Child-Pugh class A, n = 30; B, n = 28; C, n = 8) underwent Gd-EOB-DTPA-enhanced 3T MRI. To obtain T1 maps, two TurboFLASH sequences (TI = 400 ms and 1000 ms) before and 20 min after Gd-EOB-DTPA administration were acquired. T1 relaxation times of the liver and the reduction rate between pre- and post-contrast enhancement images were measured.

RESULTS

The T1 relaxation times for Gd-EOB-DTPA-enhanced MRI showed significant differences between patients with normal liver function and patients with Child-Pugh class A, B, and C (p < 0.001). The T1 relaxation times showed a constant significant increase from Child-Pugh class A up to class C (Child-Pugh class A, 335 ms ± 80 ms; B, 431 ms ± 75 ms; C, 557 ms ± 99 ms; Child-Pugh A to B, p < 0.001; Child-Pugh A to C, p < 0.001; Child-Pugh B to C, p < 0.001) and a constant decrease of the reduction rate of T1 relaxation times (Child-Pugh class A, 57.1% ± 8.8%; B, 44.3% ± 10.2%, C, 29.9% ± 6.9%; Child-Pugh A to B, p < 0.001; Child-Pugh A to C,p < 0.001; Child-Pugh B to C, p < 0.001).

CONCLUSION

Gd-EOB-DTPA-enhanced T1 mapping of the liver parenchyma may present a useful method for determining severity of liver cirrhosis.

Consensus report from the 6th International forum for liver MRI using gadoxetic acid

As the utility of liver-specific magnetic resonance imaging (MRI) increases, it is pertinent to optimize and expand protocols to improve accuracy and foster evolution of techniques; in turn, positive impacts should be seen in patient management. This article reports on the latest expert thinking and current evidence in the field of liver-specific MRI, as discussed at the 6(th) International Forum for Liver MRI, which was held in Vancouver, Canada in September 2012. Topics discussed at this forum described the use of gadoxetic acid-enhanced MRI for the assessment of liver function at the segmental level; to increase accuracy in the diagnosis of liver metastases; to overcome current challenges in patients with cirrhosis, including management of arterial hypo-/isovascular, hepatobiliary phase hypointense nodules; and the data which would be required in order to recommend the use of this modality in hepatocellular carcinoma management guidelines. Growing evidence suggests that gadoxetic acid-enhanced MRI can help to improve the management of patients with a number of different liver disorders; however, more data are needed in some areas, and there may be a case for developing an interpretation guideline for gadoxetic acid-enhanced MRI findings to aid standardization.

Biologic factors affecting HCC conspicuity in hepatobiliary phase imaging with liver-specific contrast agents

OBJECTIVE

The purpose of this study was to evaluate factors influencing hepatic enhancement and the conspicuity of hepatocellular carcinoma (HCC) on gadobenate dimeglu-mine- and gadoxetate disodium-enhanced hepatobiliary phase MR images.

MATERIALS AND METHODS

Patients with chronic liver disease who underwent liver MRI with gadobenate dimeglumine (n = 93) or gadoxetate disodium (n = 92) were included in this study. The degree of hepatic enhancement on 1-hour and 3-hour delayed phase gadobenate dimeglumine-enhanced and 20-minute delayed phase gadoxetate disodium-enhanced hepatobiliary phase images were evaluated with quantitative and visual indexes. The conspicuity of 40 HCCs in the gadobenate dimeglumine group and 38 HCCs in the gadoxetate disodium group were graded on a 5-point scale. Correlation between hepatic enhancement indexes and clinical factors (age, body weight, serum bilirubin concentration, model for end-stage liver disease score, Child-Pugh class, and renal function stage) and association between the conspicuity of HCCs and clinical factors, lesion diameter, and hepatic enhancement indexes were evaluated.

RESULTS

In the gadobenate dimeglumine group, the visual index of hepatic enhancement independently correlated with Child-Pugh class on both 1- and 3-hour delayed images (p < 0.001) and with renal function stage only on 3-hour delayed images (p ≤ 0.031). In the gadoxetate disodium group, both quantitative and visual indexes of hepatic enhancement independently correlated with Child-Pugh class (p ≤ 0.019). The conspicuity of HCCs independently correlated with Child-Pugh class and lesion diameter on 3-hour delayed gadobenate dimeglumine-enhanced images (p ≤ 0.031) and on gadoxetate disodium-enhanced images (p = 0.033) and significantly correlated with the visual index of hepatic enhancement on both gadobenate dimeglumine- and gadoxetate disodium-enhanced images (p ≤ 0.001).

CONCLUSION

Liver enhancement and conspicuity of HCC are significantly affected by Child-Pugh class on both gadobenate dimeglumine- and gadoxetate disodium-enhanced hepatobiliary phase MR images.

Liver fibrosis: histopathologic and biochemical influences on diagnostic efficacy of hepatobiliary contrast-enhanced MR imaging in staging

PURPOSE

To evaluate the diagnostic performance of gadoxetic acid-enhanced magnetic resonance (MR) imaging in the staging of liver fibrosis in patients with diffuse chronic liver diseases (CLDs) and to investigate the factors that may influence the results.

MATERIALS AND METHODS

With the approval of the Hospital Ethics Committee and waiver of the informed consent requirement, data in 102 patients with histologically proven liver fibrosis (classified according to the METAVIR system) of various underlying causes were retrospectively analyzed. Patients underwent 3.0-T MR imaging with gadoxetic acid. The signal intensity of the liver was defined by using region of interest measurements before contrast material injection and in the hepatobiliary phase (20 minutes after contrast material administration), and relative enhancement was calculated. Univariate and multivariate regression analyses were applied to identify variables associated with relative enhancement measurements, and the performance of relative enhancement measurements in the staging of liver fibrosis was assessed by using area under the receiver operating characteristic curve (AUC) analysis.

RESULTS

At analysis of the relationship between enhancement measurements and histologic parameters, the relative enhancement values correlated strongly with liver fibrosis stage (r = -0.65, P < .0001) and moderately with necroinflammatory activity grades (r = -0.41, P = .002) and the presence of iron load (r = -0.21, P = .05). In multivariate analysis, only liver fibrosis stage independently influenced relative enhancement values (P < .001). The measurements performed well in the staging of liver fibrosis, with an AUC of 0.81 for stages of F1 or greater, 0.82 for stages of F2 or greater, 0.85 for stages of F3 or greater, and 0.83 for stage F4. Increased aspartate aminotransferase, gammaglutamyl transpeptidase, and alkaline phosphatase levels were independent predictors of false-negative results.

CONCLUSION

The presence of hepatic fibrosis can be assessed with good discrimination by using gadoxetic acid-enhanced MR imaging, but assessment can be confounded in the setting of abnormal aspartate aminotransferase, gammaglutamyl transpeptidase, and alkaline phosphatase levels.

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

PURPOSE

The purpose of this study was to investigate the effect of lapatinib treatment on hepatic parenchymal enhancement on Gd-EOB-MRI scans in rat.

MATERIALS AND METHODS

Institutional animal review board approval was received prior to the commencement of all studies. Five rats received a single oral dose of 100 mg/kg/day lapatinib for 7 consecutive days. The controls (n = 5) were given 0.5 % (w/v) aqueous hydroxypropyl methyl cellulose containing 0.1 % (v/v) Tween 80 for 7 days. After the acquisition of gadoxetate disodium-enhanced MR images using 0.025 mmol gadolinium/kg, their livers were subjected to pathologic study to determine the expression level of organic anion-transporting polypeptide 1 (oatp1) and multi-drug resistance-associated protein 2 (mrp2).

RESULTS

Relative enhancement of the liver was similar in both groups. At the hepatobiliary phase, which in rats occurs 3 min after the injection of Gd-EOB, it was 0.90 ± 0.06 in lapatinib-treated rats and 0.84 ± 0.08 in the controls (p = 0.30). There was also no difference in the expression level of oatp1 and mrp2.

CONCLUSION

In rats, the administration of lapatinib for 7 days had no effect on hepatic parenchymal enhancement on Gd-EOB-MRI scans.

Relationship between severity of liver dysfunction and the relative ratio of liver to aortic enhancement (RE) on MRI using hepatocyte-specific contrast

PURPOSE

To evaluate differences in liver enhancement among patients with low and high morbidity risks and to determine the relationship between severity of liver dysfunction and the relative ratio of liver to aortic enhancement (RE) on MRI using hepatocyte-specific contrast.

MATERIALS AND METHODS

A total of 126 patients underwent magnetic resonance imaging (MRI) and blood serum testing including serology, bilirubin, international normalized ratio, and creatinine tests. Radiologists analyzed a region of interest in the liver and aorta on precontrast and 10- and 20-minute delayed hepatobiliary phase MR images. Liver enhancement after 10 (LE10min ) and 20 minutes (LE20min ) were compared between the low- and high-risk groups by independent t-test. Regression analysis was used to assess the relationship between the Model for Endstage Liver Disease (MELD) score and RE.

RESULTS

All 126 patients were classified into either the low-risk group (MELD <8; n = 85) or high-risk group (MELD ≥8; n = 41). The mean LE10min and LE20min were significantly higher in the low-risk group (471.61; 95% confidence interval [CI]: 449.79-493.43 and 510.69; 95% CI: 486.51-534.87, respectively) than in the high-risk group (401.6776; 95% CI: 364.75-438.61 and 413.81; 95% CI: 370.91-456.70). There was a moderate inverse correlation between MELD score and the relative ratio of liver enhancement (RLE) (r = -0.5442; 95% CI: -0.6480 to -0.4207; P<0.01), but a high positive correlation between MELD score and RE (r = 0.7470; 95% CI: 0.6665-0.8102; P < 0.01).

CONCLUSION

Although liver enhancement was significantly greater in low-risk patients compared to high-risk patients, RE may be a better predictor of liver function than RLE.

Hyperintense lesions on gadoxetate disodium-enhanced hepatobiliary phase imaging

OBJECTIVE

The purpose of this article is to illustrate various focal hepatic lesions that may show hyperintensity on hepatobiliary phase images on gadoxetate disodium-enhanced MRI.

CONCLUSION

Hyperintense lesions on gadoxetate disodium-enhanced MRI include focal nodular hyperplasia (FNH) or FNH-like nodules, hepatocellular adenoma, dysplastic nodules, and hepatocellular carcinoma. Understanding the contrast enhancement patterns on hepatobiliary phase images and other imaging findings is important to ensure correct diagnosis.

Disodium gadoxetate uptake in progressive familial intrahepatic cholestasis type I: Enhancing our understanding of the cholestatic disease

Hepatocyte-specific magnetic resonance imaging (MRI) contrast agents are commonly used to depict anatomic hepatobiliary lesions and are also useful in characterizing the kinetics of hepatocyte uptake and excretion. We report a case of a 13-year old female with progressive familial intrahepatic cholestasis (PFIC) type 1 who demonstrated decreased uptake and excretion of gadoxetate disodium contrast material. This case illustrates the challenge of imaging children with cholestasis using hepatobiliary-specific contrast agents; we propose an alternative explanation for the delayed excretion that may be related to the underlying genetic defect of this child.

Usefulness of Gd-EOB-DTPA-enhanced MR imaging in the evaluation of simple steatosis and nonalcoholic steatohepatitis

PURPOSE

To evaluate the usefulness of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced MR imaging (EOB-MRI) in differentiating between simple steatosis and nonalcoholic steatohepatitis (NASH), as compared with MR in-phase/out-of-phase imaging. The correlations between the MR features and histological characteristics were preliminarily investigated.

MATERIALS AND METHODS

From April 2008 to October 2011, 25 patients (13 simple steatosis and 12 NASH) who underwent both EOB-MRI and in-phase/out-of-phase imaging were analyzed. The hepatobiliary-phase enhancement ratio and signal intensity loss on opposed-phase T1-weighted images (fat fraction) were compared between the simple steatosis and NASH groups. In the simple steatosis and NASH groups, the correlations between enhancement ratio and histological grade/stage were explored. In the NASH group, fat fraction was correlated with the steatosis score.

RESULTS

The enhancement ratio in NASH was significantly lower than that in simple steatosis (P = 0.03). In the simple steatosis and NASH groups, the enhancement ratio was significantly correlated with the fibrosis stage (r = -0.469, P = 0.018). Fat fraction in NASH was strongly correlated with the steatosis score (r = 0.728, P = 0.007).

CONCLUSION

In simple steatosis and NASH, the hepatobiliary-phase enhancement ratio of EOB-MRI showed significant association with fibrosis stage, and may be a useful discriminating parameter compared with the fat fraction measured by in-phase/out-of-phase imaging.

Hepatocellular carcinoma in a North American population: does hepatobiliary MR imaging with Gd-EOB-DTPA improve sensitivity and confidence for diagnosis?

PURPOSE

To evaluate the value of hepatobiliary phase imaging for detection and characterization of hepatocellular carcinoma (HCC) in liver MRI with Gd-EOB-DTPA, in a North American population.

MATERIALS AND METHODS

One hundred MRI examinations performed with the intravenous injection of Gd-EOB-DTPA in patients with cirrhosis were reviewed retrospectively. Nodules were classified as HCC (n = 70), indeterminate (n = 33), or benign (n = 22). Five readers independently reviewed each examination with and without hepatobiliary phase images (HBP). Lesion conspicuity scores were compared between the two readings. Lesion detection, confidence scores, and receiver operating characteristic (ROC) analysis were compared.

RESULTS

Lesion detection was slightly improved for all lesion types with the inclusion of the HBP, and was substantially higher for small HCCs (96.0% versus 85.3%). Mean confidence scores for the diagnosis of HCC increased for HCCs overall and each size category (P < 0.001). Diagnostic performance improved with the addition of the HBP (aggregate AROC 87.7% versus 80.0%, P < 0.01), and sensitivity for characterization improved (90.9% versus 78.3%, P < 0.01) while specificity was unchanged.

CONCLUSION

Hepatobiliary phase imaging may improve small lesion detection (<1 cm) and characterization of lesions in general, in MRI of the cirrhotic liver with Gd-EOB-DTPA.

Primovist, Eovist: what to expect?

Gadolinium ethoxybenzyl dimeglumine (Gd-EOB-DTPA, Primovist in Europe and Eovist in the USA) is a liver-specific magnetic resonance imaging contrast agent that has up to 50% hepatobiliary excretion in the normal liver. After intravenous injection, Gd-EOB-DTPA distributes into the vascular and extravascular spaces during the arterial, portal venous and late dynamic phases, and progressively into the hepatocytes and bile ducts during the hepatobiliary phase. The hepatocyte uptake of Gd-EOB-DTPA mainly occurs via the organic anion transporter polypeptides OATP1B1 and B3 located at the sinusoidal membrane and biliary excretion via the multidrug resistance-associated proteins MRP2 at the canalicular membrane. Because of these characteristics, Gd-EOB-DTPA behaves similarly to non-specific gadolinium chelates during the dynamic phases, and adds substantial information during the hepatobiliary phase, improving the detection and characterization of focal liver lesions and diffuse liver disease. This information is particularly relevant for the detection of metastases, and for the detection and characterization of nodular lesions in liver cirrhosis, including early hepatocellular carcinomas. Finally, GD-EOB-DTPA-enhanced magnetic resonance imaging may provide quantitative assessment regarding liver perfusion and hepatocyte function in diffuse liver diseases. The full potential of GD-EOB-DTPA-enhanced magnetic resonance imaging has to be established further. It is already clear that GD-EOB-DTPA-enhanced magnetic resonance imaging provides anatomic and functional information in the setting of focal and diffuse liver disease that is unattainable with magnetic resonance imaging enhanced with non-specific contrast agents.

Gadolinium accumulation and fibrosis in the liver after administration of gadoxetate disodium in a rat model of active hepatic fibrosis

PURPOSE

To evaluate the effect of gadoxetate disodium on fibrosis in a rat model of active hepatic fibrosis.

MATERIALS AND METHODS

The local committee for animal research approved this study. Hepatic fibrosis was induced during 12 weeks of intraperitoneal injection of carbon tetrachloride (CCl(4)). Gadoxetate disodium was administered at 10 mmol/kg for 5 consecutive days starting after the final dose of CCl(4) (clinical dose of gadoxetate disodium is 0.25 mmol/kg). Three groups of Sprague-Dawley rats were studied. Group 1 consisted of six rats treated only with gadoxetate disodium, group 2 consisted of nine rats treated only with CCl(4), and group 3 consisted of nine rats treated with both gadoxetate disodium and CCl(4). Seven days after the final injection of gadoxetate disodium, the rats were sacrificed, and histologic findings and gadolinium deposition in the liver were examined. Fibrosis stage and gadolinium deposition were compared by using the Mann-Whitney test and Student t test.

RESULTS

Fibrosis grading in groups 2 and 3 did not differ significantly (mean Batts-Ludwig fibrosis stage in group 2 was 2.67 and in group 3 was 2.78, P = .70; mean Ishak fibrosis stage in group 2 was 3.89 and in group 3 was 4.11, P = .71). Gadolinium deposition in the liver was slightly increased in group 3 in comparison to group 1 (3.2 ppm versus 4.0 ppm, P = .01), although this reversed when corrected as a percentage of total injected dose (0.022% versus 0.017%, P = .003).

CONCLUSION

The high-dose administration of gadoxetate disodium in the setting of active hepatic fibrosis was not associated with increased fibrosis, suggesting that gadoxetate disodium does not incite a nephrogenic systemic fibrosis-like fibrotic change in the setting of active hepatic inflammation.

Simultaneous PET/MR body imaging in rats: initial experiences with an integrated PET/MRI scanner

OBJECTIVE

We recently developed an integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) (iPET/MRI) scanner for small animals, which had relatively large field-of-view (FOV) covering up to the size of a rat body. The purpose of this study was to report results of simultaneous PET/MRI of a rat body using this scanner with some radiotracers.

METHODS

C-11-methionine (MET), F-18-fluorodeoxyglucose (FDG), or F-18-sodium fluoride (NaF) was injected as a radiotracer for PET portion in addition to gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid, a hepatobiliary contrast agent, for MRI portion. Simultaneous PET/MRI was performed in normal rats. PET, MRI, and co-registered fusion images were evaluated regarding image quality and feasibility for rat imaging studies.

RESULTS

MET uptake was clearly shown in the liver and pancreas, which was confirmed with magnetic resonance (MR) and fused PET/MR images. PET/MR images depicted intense FDG uptake in the brain, Harderian glands, and myocardium. NaF uptake was observed in all bones and joints within FOV, except in ribs, which was well recognized with the help of MR and fused PET/MR images.

CONCLUSION

This study demonstrated that simultaneous PET/MRI with an integrated dual-modality molecular imaging scanner was a feasible technique for imaging studies targeting on a rat body. However, further developments including attenuation correction methods are required to use this technique routinely in rat imaging studies.

Diagnostic imaging of hepatocellular carcinoma: recent progress

The diagnostic imaging of hepatocellular carcinoma (HCC) has recently undergone marked progress. The advent of the ultrasound (US) contrast agent Sonazoid, approved in January 2007, and magnetic resonance imaging (MRI) with the liver-specific MRI contrast agent gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA-MRI), approved in January 2008, are of particular significance. Sonazoid contrast-enhanced US (Sonazoid-CEUS) is useful not only for the diagnosis of HCC, but also for guiding treatment and assessing treatment response. Sonazoid-CEUS has proven to be particularly effective for screening and staging, which used to be considered impossible with CEUS, through the introduction of the newly developed diagnostic technique of defect reperfusion imaging. It is still not possible if other vascular agents such as SonoVue and Definity are used. In particular, Gd-EOB-DTPA-MRI has been suggested to be much more reliable in the differentiation of early HCC from precancerous dysplastic nodules than any other modalities such as multidetector raw computed tomography, dynamic MRI, and superparamagnetic iron oxide-MRI. A decrease in contrast uptake in the hepatocyte phase observed on EOB-MRI is strongly suggestive of cancer, and the absence of early staining in the arterial phase suggests early HCC. The differential diagnostic capacity of Gd-EOB-DTPA-MRI is considered to far exceed that of what were previously the most useful imaging techniques, computed tomography (CT) during hepatic arteriography or CT during arterial portography, and to be comparable to that of the pathological diagnosis by pathologists specialized in liver.

Prediction of microvascular invasion of hepatocellular carcinoma: usefulness of peritumoral hypointensity seen on gadoxetate disodium-enhanced hepatobiliary phase images

PURPOSE

To determine whether peritumoral hypointensity seen on hepatobiliary phase images of preoperative gadoxetate disodium-enhanced magnetic resonance imaging (EOB-MRI) is useful for predicting microvascular invasion of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

This study was approved by the Institutional Review Board. In all, 104 HCC masses in 104 patients who had undergone EOB-MRI and liver surgery within 1 month after EOB-MRI were evaluated. Two radiologists independently recorded the presence of a peritumoral hypointensity on hepatobiliary phase. Interobserver agreement was assessed and consensus records were used. Tumor size was measured. A chi-square test and independent t-test were used for univariate analysis. Multiple logistic regression was performed to determine factors for predicting microvascular invasion. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of peritumoral hypointensity were calculated.

RESULTS

Sixty HCCs had microvascular invasion and 44 did not. Interobserver agreement in determining peritumoral hypointensity was excellent (κ = 0.83). By univariate analysis, peritumoral hypointensity and tumor size were significant for predicting microvascular invasion of HCC. On multiple logistic regression analysis, only peritumoral hypointensity was significant in predicting microvascular invasion of HCC (P = 0.013). The sensitivity, specificity, PPV, and NPV of peritumoral hypointensity were 38.3%, 93.2%, 88.5%, and 52.6%, respectively.

CONCLUSION

Peritumoral hypointensity on the hepatobiliary phase of EOB-MRI is not sensitive but has high specificity for predicting microvascular invasion of HCC.

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.

Signal profile on Gd-EOB-DTPA-enhanced MR imaging in non-alcoholic steatohepatitis and liver cirrhosis induced in rats: correlation with transporter expression

OBJECTIVES

To compare the transporter expression and signal profile on Gd-EOB-DTPA-enhanced MRI between non-alcoholic steatohepatitis (NASH) and cirrhotic liver induced in rats, and investigate the correlation of the transporter expression and fibrosis rate in both diseases.

METHODS

Forty-eight rats were divided into four groups of 12: TAA (cirrhosis), NASH 7- and 10-week, and control groups. Each group was divided into two subgroups: Group 1 for MRI and Group 2 for transporter examinations.

RESULTS

The relative enhancement of the TAA group was significantly lower than those of other groups (p < 0.01). The T(max) and T(1/2) of the NASH 10-week group was significantly prolonged in comparison with the TAA group (p < 0.01). There was no significant difference in the oatp1 expression, whereas the mrp2 expression of the TAA group was significantly higher than those of other groups (p < 0.01). There was no significant correlation between the fibrosis rate and oatp1 expression, whereas a paradoxical correlation was found between the fibrosis rate and mrp2 expression (NASH: negative correlation, r = 0.91, p < 0.01; TAA: positive correlation, r = 0.85, p < 0.01).

CONCLUSIONS

Our findings showed that the mrp2 expression in cirrhosis increases in comparison with NASH, and there was a paradoxical correlation between the fibrosis rate and mrp2 expression.

Consensus report of the 4th International Forum for Gadolinium-Ethoxybenzyl-Diethylenetriamine Pentaacetic Acid Magnetic Resonance Imaging

This paper reports on issues relating to the optimal use of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid magnetic resonance imaging (Gd-EOB-DTPA MR imaging) together with the generation of consensus statements from a working group meeting, which was held in Seoul, Korea (2010). Gd-EOB-DTPA has been shown to improve the detection and characterization of liver lesions, and the information provided by the hepatobiliary phase is proving particularly useful in differential diagnoses and in the characterization of small lesions (around 1-1.5 cm). Discussion also focused on advances in the role of organic anion-transporting polypeptide 8 (OATP8) transporters. Gd-EOB-DTPA is also emerging as a promising tool for functional analysis, enabling the calculation of post-surgical liver function in the remaining segments. Updates to current algorithms were also discussed.

Effect of change in transporter expression on gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging during hepatocarcinogenesis in rats

BACKGROUND AND AIMS

To analyze the difference in signal intensity on gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) among various hepatocellular nodules during hepatocarcinogenesis as correlated with the expressions of the transporters of Gd-EOB-DTPA.

METHODS

We received institutional animal review board approval prior to the commencement of all studies. Forty rats were divided into three groups. The rats in the tumor groups received N-nitrosomorpholine solution (n = 16), and rats in the cirrhosis group (thioacetamide [TAA] group) received thioacetamide solution (n = 12). As a control, the remaining 12 rats were fed normal water. Each group was divided into two sub-groups: Group 1 for Gd-EOB-DTPA-enhanced MRI (0.025 mmol Gd/kg, n =7) and Group 2 for reverse transcription-polymerase chain reaction to compare transporter (oatp1 and mrp2) expressions (n = 5 for control and TAA groups, n = 9 for tumor groups).

RESULTS

Signal enhancement of tumors decreased according to the progress of hepatocarcinogenesis. Although the relative enhancement of each tumor group was significantly lower than that of the control group (P < 0.01), and there was no significant difference between TAA, hyperplastic nodules (HPN), and HCC(well) groups. The relative enhancement of the HCC(mod) group was significantly lower than the other groups (P < 0.01). The oatp1 expression of HPN tended to be higher than those of HCC(well) and HCC(mod). The mrp2 expression of TAA was significantly higher than those of HCC(well), HCC(mod), HPN and control (P < 0.01). The mrp2 expression of HPN tended to be higher than those of HCC(well ) and HCC(mod).

CONCLUSION

It was suggested that the signal enhancement on Gd-EOB-DTPA-enhanced MRI would correlate with the transporter expression in various hepatocellular nodules during hepatocarcinogenesis.

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.