Potential for Differential Diagnosis with Gadolinium-Ethoxybenzyl-Diethylenetriamine Pentaacetic Acid-Enhanced Magnetic Resonance Imaging in Experimental Hepatic Tumors

A gadoxetic-acid enhancement flux analysis of small liver nodules (≤2 cm) in patients at high risk of hepatocellular carcinoma

PURPOSE

To discriminate between benignities and hepatocellular carcinomas (HCCs) in patients at high risk of HCC using a novel enhancement flux analysis for gadoxetic-acid enhanced MRI.

METHOD

This study retrospectively collected 181 liver nodules in 156 patients at high risk of HCC who underwent gadoxetic acid-enhanced MRI examinations with following surgical resection from 1st August 2017 to 31st December 2021 as the training set; another 42 liver nodules in 36 patients were prospectively collected from 1st January 2022 to 1st October 2022 as the test set. The time-intensity curves (TICs) of liver nodules were formed with consecutive time points: 0 s, 20 s, 1 min, 2 min, 5 min, 10 min, 15 min, and 20 min since contrast injection. A novel enhancement flux analysis was applied by using a biexponential function fitting to distinguish benignities and HCC. Besides, previously published models including maximum enhancement ratio (ER_max), percentage signal ratio (PSR), and ER_max+PSR were compared. The areas under the receiver operating characteristic curves (AUCs) were compared among these methods.

RESULTS

The novel enhancement flux analysis showed the highest AUCs in the training set (0.897, 95%CI: 0.833-0.960) and the test set (0.859, 95%CI: 0.747-0.970) among all models. The AUCs of PSR, ER_max and ER_max+PSR were 0.801 (95%CI: 0.710-0.891), 0.620 (95%CI: 0.510-0.729), and 0.799 (95%CI: 0.709-0.889) in the training set, and were 0.701 (95%CI: 0.539-0.863), 0.529 (95%CI: 0.342-0.717), and 0.708 (95%CI: 0.549-0.867) in the test set.

CONCLUSIONS

The biexponential flux analysis for gadoxetic-acid enhanced MRI presents a better potential in accurate diagnosis of small HCC nodules.

Expression of Organic Anion Transporting Polypeptides in an H-Ras 12V Transgenic Mouse Model of Spontaneous Hepatocellular Carcinoma

PURPOSE

Expression of organic anion transporting polypeptides (OATPs) 1B1/1B3 in hepatocellular carcinoma (HCC) induces a paradoxical enhancement of gadoxetic acid on liver magnetic resonance imaging (MRI). We examined the expression profile of OATPs with regard to tumor differentiation in a genetically modified H-Ras 12V mouse model of spontaneous HCC that undergoes multistep hepatocarcinogenesis with minimal inter-individual variation.

MATERIALS AND METHODS

Tumor nodules were harvested from transgenic H-Ras 12V mice. Hematoxylin and eosin-stained slides were examined for tumor differentiation and high-grade pathological components (tumor necrosis, thickened trabeculae, or vascular invasion). Immunohistochemistry of OATP 1B1/1B3 was performed, and OATP expression was assessed.

RESULTS

We examined well-differentiated HCCs (n=59) in which high-grade pathological components were absent (n=49) or present (n=10). Among the well-differentiated HCCs without high-grade pathological components (n=49), OATP expression was negative, weak positive, and moderate positive in 23, 17, and nine cases, respectively. Among the well-differentiated HCCs with high-grade pathological components (n=10), OATP expression was negative, weak positive, and moderate positive in one, two, and seven cases, respectively. The ratio of positive OATP 1B1/1B3 expressing tumors was higher in HCCs with high-grade pathological components than in those without high-grade pathological components (p=0.004).

CONCLUSION

Our findings support those of previous clinical studies that have reported the frequent appearance of gadoxetic acid-enhanced MRI in moderately differentiated HCC.

An overview of hepatocellular carcinoma with atypical enhancement pattern: spectrum of magnetic resonance imaging findings with pathologic correlation

BACKGROUND

In the setting of cirrhotic liver, the diagnosis of hepatocellular carcinoma (HCC) is straightforward when typical imaging findings consisting of arterial hypervascularity followed by portal-venous washout are present in nodules larger than 1 cm. However, due to the complexity of hepatocarcinogenesis, not all HCCs present with typical vascular behaviour. Atypical forms such as hypervascular HCC without washout, isovascular or even hypovascular HCC can pose diagnostic dilemmas. In such cases, it is important to consider also the appearance of the nodules on diffusion-weighted imaging and hepatobiliary phase. In this regard, diffusion restriction and hypointensity on hepatobiliary phase are suggestive of malignancy. If both findings are present in hypervascular lesion without washout, or even in iso- or hypovascular lesion in cirrhotic liver, HCC should be considered. Moreover, other ancillary imaging findings such as the presence of the capsule, fat content, signal intensity on T2-weighted image favour the diagnosis of HCC. Another form of atypical HCCs are lesions which show hyperintensity on hepatobiliary phase. Therefore, the aim of the present study was to provide an overview of HCCs with atypical enhancement pattern, and focus on their magnetic resonance imaging (MRI) features.

CONCLUSIONS

In order to correctly characterize atypical HCC lesions in cirrhotic liver it is important to consider not only vascular behaviour of the nodule, but also ancillary MRI features, such as diffusion restriction, hepatobiliary phase hypointensity, and T2-weighted hyperintensity. Fat content, corona enhancement, mosaic architecture are other MRI feautures which favour the diagnosis of HCC even in the absence of typical vascular profile.

Quantitative evaluation of Gd-EOB-DTPA uptake in focal liver lesions by using T1 mapping: differences between hepatocellular carcinoma, hepatic focal nodular hyperplasia and cavernous hemangioma

Objectives

To investigate the difference of T1 relaxation time on Gd-EOB-DTPA-enhanced MRI in hepatocellular carcinoma (HCC), hepatic focal nodular hyperplasia (FNH) and cavernous hemangioma of liver (CHL), and to quantitatively evaluate the uptake of Gd-EOB-DTPA in these three focal liver lesions (FLLs).

Results

The T1_P of CHL was significantly higher than those of HCC and FNH (P < 0.05). Reduction of T1 relaxation time on hepatobiliary phase could be observed in all three types of lesions. There were significant differences of T1_P, T1_E, T1_D and T1_D% between FNH, CHL and HCC (P < 0.001). Spearman correlation analysis revealed that T1_D% was the best indicator for diagnostic differentiation, with a correlation coefficient of 0.702. Discriminant analysis using three variables (T1_P, T1_E, and T1_D%) showed that the classification accuracy was 88.2%.

Materials and Methods

74 patients diagnosed with focal liver lesions underwent Gd-EOB-DTPA-enhanced MRI including T1 mapping were enrolled, consisting of 51 HCCs, 10 FNHs, and 13 CHLs. T1 relaxation times of these lesions were measured on pre-contrast (T1_P) and on hepatobiliary phase images at 20 minute after contrast (T1_E). The reduction of T1 relaxation time on hepatobiliary (T1_D) and the percentage reduction (T1_D%) was calculated. The differences of T1_P, T1_E, T1_D and T1_D% in these FLLs were analyzed. The usefulness of these parameters for classification of FLLs was evaluated.

Conclusions

Uptake of Gd-EOB-DTPA is different between in HCC, FNH and CHL. These three lesions can be distinguished using T1 mapping.

Major and ancillary magnetic resonance features of LI-RADS to assess HCC: an overview and update

Liver Imaging Reporting and Data System (LI-RADS) is a system for interpreting and reporting of imaging features on multidetector computed tomography (MDCT) and magnetic resonance (MR) studies in patients at risk for hepatocellular carcinoma (HCC). American College of Radiology (ACR) sustained the spread of LI-RADS to homogenizing the interpreting and reporting data of HCC patients. Diagnosis of HCC is due to the presence of major imaging features. Major features are imaging data used to categorize LI-RADS-3, LI-RADS-4, and LI-RADS-5 and include arterial-phase hyperenhancement, tumor diameter, washout appearance, capsule appearance and threshold growth. Ancillary are features that can be used to modify the LI-RADS classification. Ancillary features supporting malignancy (diffusion restriction, moderate T2 hyperintensity, T1 hypointensity on hapatospecifc phase) can be used to upgrade category by one or more categories, but not beyond LI-RADS-4. Our purpose is reporting an overview and update of major and ancillary MR imaging features in assessment of HCC.

Gd-EOB-DTPA-enhanced magnetic resonance imaging combined with T1 mapping predicts the degree of differentiation in hepatocellular carcinoma

BACKGROUND

Variable degrees of differentiation in hepatocellular carcinoma(HCC)under Edmondson-Steiner grading system has been proven to be an independent prognostic indicator for HCC. Up till now, there has been no effective radiological method that can reveal the degree of differentiation in HCC before surgery. This paper aims to evaluate the use of Gd-EOB-DTPA-Enhanced Magnetic Resonance Imaging combined with T1 mapping for the diagnosis of HCC and assessing its degree of differentiation.

METHODS

Forty-four patients with 53 pathologically proven HCC had undergone Gd-EOB-DTPA enhanced MRI with T1 mapping before surgery. Out of the 53 lesions,13 were grade I, 27 were gradeII, and 13 were grade III. The T1 values of each lesion were measured before and at 20 min after Gd-EOB-DTPA administration (T1p and T1e). The absolute reduction in T1 value (T1d) and the percentage reduction (T1d %) were calculated. The one-way ANOVA and Pearson correlation were used for comparisons between the T1 mapping values.

RESULTS

The T1d and T1d % of grade I, II and III of HCC was 660.5 ± 422.8ms、295.0 ± 99.6ms、276.2 ± 95.0ms and 54.0 ± 12.2 %、31.5 ± 6.9 %、27.7 ± 6.7 % respectively. The differences between grade Iand II, grade Iand III were statistically significant (p < 0.05), but there was no statically significant difference between grade II and III. The T1d % was the best marker for grading of HCC, with a Spearman correlation coefficient of -0.676.

CONCLUSIONS

T1 mapping before and after Gd-EOB-DTPA administration can predict degree of differentiation in HCC.

Distinguishing intrahepatic cholangiocarcinoma from poorly differentiated hepatocellular carcinoma using precontrast and gadoxetic acid-enhanced MRI

PURPOSE

We aimed to gain further insight in magnetic resonance imaging characteristics of mass-forming intrahepatic cholangiocarcinoma (mICC), its enhancement pattern with gadoxetic acid contrast agent, and distinction from poorly differentiated hepatocellular carcinoma (pHCC).

METHODS

Fourteen mICC and 22 pHCC nodules were included in this study. Two observers recorded the tumor shape, intratumoral hemorrhage, fat on chemical shift imaging, signal intensity at the center of the tumor on T2-weighted image, fibrous capsule, enhancement pattern on arterial phase of dynamic study, late enhancement three minutes after contrast injection (dynamic late phase), contrast uptake on hepatobiliary phase, apparent diffusion coefficient, vascular invasion, and intrahepatic metastasis.

RESULTS

Late enhancement was more common in mICC (n=10, 71%) than in pHCC (n=3, 14%) (P < 0.001). A fat component was observed in 11 pHCC cases (50%) versus none of mICC cases (P = 0.002). Fibrous capsule was observed in 13 pHCC cases (59%) versus none of mICC cases (P < 0.001). On T2-weighted images a hypointense area was seen at the center of the tumor in 43% of mICC (6/14) and 9% of pHCC (2/22) cases (P = 0.018). Other parameters were not significantly different between the two types of nodules.

CONCLUSION

The absence of fat and fibrous capsule, and presence of enhancement at three minutes appear to be most characteristic for mICC and may help its differentiation from pHCC.

Evaluation of optimal scan delay for gadoxetate disodium-enhanced hepatic arterial phase MRI using MR fluoroscopic triggering and slow injection technique

OBJECTIVE

The purpose of this article is to prospectively evaluate the optimal scan delay for gadoxetate disodium-enhanced hepatic arterial phase MRI of hypervascular hepatocellular carcinoma (HCC) using MR fluoroscopic triggering and a slow-injection technique.

SUBJECTS AND METHODS

Sixty-three patients (37 men and 26 women; age range, 33-92 years; mean age, 68.2 years) underwent gadoxetate disodium-enhanced MRI; there were 33 hypervascular HCCs (size range, 8-57 mm; mean size, 19.8 mm) in 19 patients. The time from the start of contrast agent injection to its arrival in the abdominal aorta (time to arrival) and the time from contrast agent arrival to peak enhancement (time to peak) were determined using MR fluoroscopy using IV slow injection at 1 mL/s of contrast material and a saline chaser. All patients underwent four-phase whole-liver imaging with a 3D keyhole gradient-echo sequence during a single breath-hold immediately after confirmation of aortic peak enhancement. Delays from peak aortic enhancement to k-space filling were 5-9, 10-14, 15-19, and 20-28 seconds, respectively, in the four phases. Time to arrival, time to peak, and HCC-to-liver contrast were evaluated.

RESULTS

The time to arrival (range, 11-24 seconds; mean, 16.2 seconds) and the time to peak (range, 3-10 seconds; mean, 6.8 seconds) showed considerable variation among patients. HCC-to-liver contrast peaked at the first phase in 58% of cases, at the second phase in 42% of cases, and at the third and fourth phases in 0% of cases. Mean HCC-to-liver contrast in the first and second phases was significantly higher than that in the third and fourth phases (p<0.01).

CONCLUSION

Optimal scan delays for imaging hypervascular HCCs with gadoxetate disodium-enhanced hepatic arterial phase MRI was 7-12 seconds after the peak aortic enhancement using a slow-injection protocol.

Impact of gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance on the non-invasive diagnosis of small hepatocellular carcinoma: a prospective study

BACKGROUND

Gadoxetic acid (Gd-EOB-DTPA) is a 'hepatocyte-specific' contrast agent for magnetic resonance (MR) in both the vascular and the hepatobiliary phases.

AIM

To evaluate the contribution of the hepatobiliary phase of Gd-EOB-DTPA MR in the diagnosis of small hepatocellular carcinoma (HCC) in cirrhotic patients under surveillance.

METHODS

Between 2008 and 2011, 48 consecutive small (10-30 mm) liver nodules were detected in 33 patients, who prospectively underwent contrast-enhanced ultrasound (CEUS), Gd-EOB-DTPA-enhanced MR and helical-computed tomography (CT) in a blind study. The diagnosis of HCC was established according to AASLD 2005 criteria.

RESULTS

Of the 48 nodules, 38 (79%) were diagnosed as HCC, 24 (63%) of them based on AASLD non-invasive criteria, 11 diagnosed at histology and 3 during follow-up. The typical vascular pattern (arterial hypervascularisation and venous/late washout) was detected in 30 (79%) HCC nodules by MR, in 22 (58%) by CT and in 17 (45%) by CEUS. Hypointensity during the MR hepatobiliary phase was observed in all HCC nodules and in 3 nonmalignant nodules (sensitivity 100%, specificity 70%, positive predictive value 93%, negative predictive value 100%, positive likelihood ratio 3.33, negative likelihood ratio 0). Eight (21%) of the 38 HCC nodules, 7 of which lacked the typical vascular features at any of the imaging modalities, showed washout in the portal/venous phase and hypointensity in the hepatobiliary phase at MRI, while this pattern was not detected in any nonmalignant lesion.

CONCLUSIONS

Gadoxetic acid magnetic resonance may enhance the sensitivity of the non-invasive diagnosis of small hepatocellular carcinoma nodules in cirrhotic patients under surveillance. Double hypointensity in the portal/venous and hepatobiliary phases could be considered a new magnetic resonance pattern, highly suggestive of hypovascular hepatocellular carcinoma.

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.

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.

Hepatic hemangioma and metastasis: differentiation with gadoxetate disodium-enhanced 3-T MRI

OBJECTIVE

The purpose of this study was to evaluate the gadoxetate disodium-enhanced MRI findings of hepatic hemangioma and to investigate the diagnostic performance in differentiating hepatic hemangioma and metastasis.

MATERIALS AND METHODS

Images of 32 hepatic hemangiomas in 25 patients and of 29 hepatic metastatic lesions in 20 patients were retrospectively reviewed. Two independent readers interpreted hepatobiliary phase images alone, dynamic extracellular phase images alone, and combined hepatobiliary and dynamic extracellular phase images. MRI findings and performance with respect to the differential diagnosis of hemangioma and metastasis were assessed.

RESULTS

During the hepatic arterial phase, 11 of the 32 hemangiomas (34%) exhibited early total enhancement, and nine (28%) exhibited peripheral nodular enhancement. A bright dot sign or minimal peripheral enhancement during the late dynamic phase was observed for a small number of lesions (6% and 28%, respectively). Twenty-three of the 29 metastatic lesions (79%) exhibited ring enhancement during the hepatic arterial phase. Twenty-nine hemangiomas (91%) and all of the metastatic lesions exhibited homogeneous or heterogeneous hypointensity during the hepatobiliary phase. The sensitivity, specificity, and area under the receiver operating characteristic curve for the detection of hemangioma were 76%, 81%, and 0.87 for the hepatobiliary phase alone; 97%, 88%, and 0.97 for the dynamic extracellular phase alone; and 97%, 88%, and 0.98 for the combination. Five nodules smaller than 1 cm (four hemangiomas, one metastatic lesion) that exhibited no enhancement during the arterial phase and minimal enhancement during the late dynamic phase were not differentiated.

CONCLUSION

Gadoxetate disodium-enhanced MRI was found useful for differentiating hepatic hemangiomas and metastatic lesions, especially during the dynamic extracellular phase. Only a limited number of lesions smaller than 1 cm in diameter, which exhibited minimal enhancement on late dynamic phase images, were difficult to diagnose.

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.

Diffusion-weighted and Gd-EOB-DTPA-contrast-enhanced magnetic resonance imaging for characterization of tumor necrosis in an animal model

PURPOSE

To evaluate the role of diffusion-weighted magnetic resonance imaging (MRI) in determining tumor necrosis and contrast-enhanced MRI using gadoxetic acid disodium (Gd-EOB-DTPA) in determining maximum tumor size measurement and tumor delineation compared with criterion-standard histologic measurements in the rabbit VX2 liver tumor model.

MATERIALS AND METHODS

VX2 tumors were implanted in the livers of 13 rabbits. Magnetic resonance imaging was performed using a 1.5-T MRI scanner and an extremity coil. The imaging protocol included T2-weighted fast spin-echo images, 3-dimensional T1-weighted spoiled gradient-echo with and without fat suppression after administration of Gd-EOB-DTPA, and diffusion-weighted echo planar images. Rabbits were killed, and the tumor was harvested and sliced at 4-mm intervals in the axial plane. The MRI parameters evaluated were tumor size, tumor delineation, and tumor apparent diffusion coefficient (ADC) values. Histologic sections were evaluated to quantify tumor necrosis.

RESULTS

On contrast-enhanced MRI (obtained from 11 rabbits), the mean tumor sizes were 20, 19, and 20 mm in the arterial, portal venous, and delayed phases, respectively. Tumor delineation was most distinguishable in the delayed phase. On diffusion-weighted MRI (acquired in 13 rabbits), the mean tumor ADC value was 1.84 x 10 mm/s. The mean tumor size at pathology was 16 mm. The mean percent necrosis at the tumor's pathologic condition was 36%. The correlation between ADC value and percent necrosis showed an R value of 0.68.

CONCLUSIONS

Contrast-enhanced MRI using Gd-EOB-DTPA may provide additional information about tumor outline in the liver. Moreover, we showed a remarkable correlation between ADC values and tumor necrosis. Thus, diffusion-weighted imaging may be useful to assess tumor necrosis; nevertheless, the search for new modalities remains important.

Delay before the hepatocyte phase of Gd-EOB-DTPA-enhanced MR imaging: is it possible to shorten the examination time?

AIM

To examine if it is possible to shorten the examination time of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB)-enhanced MRI by omitting hepatocyte-phase images of 20-min delay time (Im-20) for detecting focal liver lesions.

MATERIALS AND METHODS

Four hundred ninety-five malignant focal liver lesions observed on Im-20 in 265 patients were included. The hepatocyte phase was obtained 10 min (Im-10) and 20 min (Im-20) after Gd-EOB injection. Liver enhancement was evaluated using a 4-point scale [excellent/good/poor/non-diagnostic; visual liver-spleen contrast (V-LSC)] and a quantitative liver-spleen contrast ratio (Q-LSC). Two radiologists evaluated lesion conspicuity for assessing the sensitivity of lesion detection. As Im-20 was used as the standard of reference for the lesions, Im-20 artificially had 100% sensitivity.

RESULTS

The results showed that although sensitivities and Q-LSC significantly increased from Im-10 to Im-20 (sensitivity/mean Q-LSC: Im-5, 81%/1.4 Im-10, 96%/1.7: Im-20, 100%/1.9), the sensitivity of Im-10 achieved 100% (the same as Im-20) in patients with good/excellent V-LSC or Q-LSC of more than 1.5. On Im-10, 202 patients (77%) were assigned as having good/excellent V-LSC (78%), and 161 (61%) were assigned as having Q-LSC of more than 1.5.

CONCLUSION

We concluded that Im-20 can be omitted in at least 61% of the patients.

Tumor models and specific contrast agents for small animal imaging in oncology

Despite the widespread use of various imaging modalities in clinical and experimental oncology without or with combined application of commercially available nonspecific contrast agents (CAs), development of tissue- or organ- or disease-specific CAs has been a continuing effort for pursuing ever-improved sensitivity, specificity, and applicability. This is particularly true with magnetic resonance imaging (MRI) due to its intrinsic superb spatial/temporal/contrast resolutions and adequate detectability for tiny amount of substances. In this context, research using small animal tumor models has played an indispensible role in preclinical exploration of tissue specific CAs. Emphasizing more on methodological and practical aspects, this article aims to share our cumulated experiences on how to create tumor models for evaluation and development of new tissue specific MRI CAs and how to apply such models in imaging-based research studies. With the results that are repeatedly confirmed by later clinical applications in cancer patients, some of our early preclinical studies have contributed to the designs of subsequent clinical trials on the new CAs, some studies have predicted new utilities of these CAs; and other studies have led to the discoveries of new tissue- or disease-specific CAs with novel diagnostic or even therapeutic potentials. Among commonly adopted tumor models, the chemically induced and surgically implanted nodules in the liver prove very useful to simulate primary and metastatic intrahepatic tumors, respectively in clinical patients. The methods to create tumor models have eased procedures and yielded high success rates. The specific properties of the new CAs could be outshined by intraindividual comparison to the commercial CAs as nonspecific controls. Meticulous imaging-microangiography-histology matching techniques guaranteed colocalization of the lesion on in vivo MRI and postmortem tissue specimen, hence correct imaging interpretation and longstanding conclusions. As exemplified in the real study cases, the present experimental set-up proves applicable in small animals for imaging-based oncological investigations, and may provide a platform for the currently booming molecular imaging in a multimodality environment.

Potential of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) for differential diagnosis of nonalcoholic steatohepatitis and fatty liver in rats using magnetic resonance imaging

RATIONALE AND OBJECTIVES

To investigate the potential of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) for the differential diagnosis of nonalcoholic steatohepatitis (NASH) and fatty liver (FL).

METHODS

Twenty-one male rats were divided into 3 groups. Seven rats in the NASH group were fed a choline-deficient diet for 10 weeks, and the 7 rats in the FL group were fed a standard diet also containing 1% (wt/wt) orotic acid for 4 weeks. As a control, 7 rats were fed a standard diet. After the feeding period, all rats were subjected to contrast-enhanced dynamic and delayed MRI with a 2D-FLASH technique. Gd-DTPA (0.1 mmol Gd/kg) and Gd-EOB-DTPA (0.025 mmol Gd/kg) were injected into the tail vein at 24-hour intervals. Signal intensities of the liver were measured for each MR image and the relative enhancement (RE) was calculated. In addition, the time of maximum RE (Tmax) and the half-life of RE (T1/2) in liver were compared. After MRI, the liver was histologically analyzed to evaluate steatosis, hepatitis, and fibrosis.

RESULTS

Diffuse macrovesicular steatosis and severe fibrosis were observed in the NASH group, whereas diffuse microvesicular steatosis and rare fibrosis were observed in the FL group. Immediately after the Gd-DTPA injection, the RE in the liver of each group temporarily increased, and thereafter, rapid RE reduction was observed. However, a continuous increase and subsequent slow reduction of RE were induced after the Gd-EOB-DTPA injection. Although there was no difference between the Tmax and T1/2 of each group after the Gd-DTPA injection, Tmax and T1/2 of the NASH group were significantly prolonged in comparison with FL and control groups after the Gd-EOB-DTPA injection (P < 0.01).

CONCLUSIONS

It was possible to differentiate NASH and FL by evaluating the SI time course on Gd-EOB-DTPA enhanced MRI.

Diffusion-weighted magnetic resonance imaging of focal hepatic nodules in an experimental hepatocellular carcinoma rat model

RATIONALE AND OBJECTIVES

We sought to investigate the value of diffusion-weighted MR imaging in evaluating focal hepatic nodules in an experimental hepatocellular carcinoma (HCC) rat model.

MATERIALS AND METHODS

Forty rats with chemically induced primary hepatic nodules ranging pathologically from regenerative nodules (RNs) to dysplastic nodules (DNs) to HCC were examined with diffusion-weighted imaging. The apparent diffusion coefficient (ADC) values of hepatic nodular lesions were calculated. Tukey's HSD post hoc test was used to compare the difference in ADC values between different hepatic nodular lesions.

RESULTS

Eight RNs, 16 DNs, 7 well-differentiated HCCs (HCCwell), 11 moderately differentiated HCCs (HCCmod), and 14 poorly differentiated HCCs (HCCpoor) were evaluated. There was no significant difference between RNs and DNs (P > 0.05). Although the ADC values of HCCwell were slightly lower than those of DNs, there was no significant difference between them (P > 0.05). The ADC values of HCCmod and HCCpoor were significantly higher (P < 0.05) than those of other nodules, and no significant difference was seen between HCCmod and HCCpoor (P > 0.05).

CONCLUSION

Diffusion-weighted magnetic resonance imaging can be useful in characterizing focal hepatic nodular lesions, but ADC values cannot be used efficiently to distinguish HCCwell from DNs.

Biliary and reticuloendothelial impairment in hepatocarcinogenesis: the diagnostic role of tissue-specific MR contrast media

The development and progression of a hepatocellular carcinoma (HCC) in a chronically diseased liver, i.e., the carcinogenesis, comprise a multistep and long-term process. Morphologically, this process is associated with the presence of distinct nodular lesions in the liver that are called 'preneoplastic lesions.' These preneoplastic lesions are associated with and can precede the growth and progression of well-differentiated HCCs . The characterization of nodular lesions and demonstration of the multistep development of HCC in the cirrhotic liver by imaging modalities represent a challenging issue. The arterial hypervascular supply, depicted by different dynamic studies, represents a fundamental radiological criterion for the diagnosis of HCC in cirrhosis. Magnetic resonance (MR) imaging performed with tissue-specific contrast media can help to investigate the "grey area" of carcinogenesis, in which significant histological changes are already present without any imaging evidence of neoangiogenesis. The purpose of this review is to provide information on the properties of tissue-specific MR contrast agents and on their usefulness in the demonstration of the pathologic changes that take place at the level of the biliary and reticuloendothelial systems during the carcinogenetic process in liver cirrhosis.

Targeted gene therapy toward astrocytoma using a Cre/loxP-based adenovirus system

The aim of this study was to establish a novel adenovirus-based gene therapy system targeting astrocytoma. For this purpose, the Cre recombinase (Cre)/loxP system together with the astrocytoma-specific promoter for GFAP were used. We constructed an adenovirus (Ad) vector that expressed Cre under the control of the GFAP promoter (AxGFAPNCre), as well as another Ad vector containing a switching unit. The latter vector contained a stuffer sequence encoding GFP (AxCALGLTK) with a functional polyadenylation signal between two loxP sites, followed by the herpes simplex virus thymidine kinase (HSV-TK) gene under the control of the CAG promoter. In this system, gene expression of either the stuffer sequence (GFP) or the downstream gene (HSV-TK) was switched on by co-expression of Cre recombinase. Western blot analysis demonstrated specific expression of high levels of TK protein in C6 glioma cells after co-infection of AxGFAPNCre and AxCALGLTK. In vivo, AxGFAPNCre/AxCALGLTK injection into C6 gliomas in the subcutaneous tissue of nude mice followed by intraperitoneal ganciclovir (GCV) treatment significantly suppressed tumor growth compared with control mice. Co-infection of AxGFAPNCre and AxCALNLLacZ resulted in LacZ expression in C6 glioma cells and some reactive astrocytes, whereas GFP was expressed in other cell types surrounding the injected site. Furthermore, a combination of AxGFAPNCre/AxCALGLTK and intraperitoneal GCV injection significantly regressed intracranial C6 gliomas in the rat striatum and prolonged the survival time compared with control rats. The present results indicate that this cell-type-specific gene therapy using a Cre/loxP adenovirus system is both operational and effective, at least against astrocytoma.

Evaluation of Gd-EOB-DTPA Uptake in a Perfused and Isolated Mouse Liver Model

OBJECTIVES

The aim of this work was to quantitatively evaluate the pharmacokinetic pattern of Gd-EOB-DTPA in a model of isolated and perfused mouse liver by using magnetic resonance imaging (MRI) and monochromatic quantitative computed tomography (MQCT).

MATERIALS AND METHODS

For MQCT, perfusions were realized with the gallbladder spared; for MRI, with gallbladder spared, severed, or clamped. Inductively coupled plasma (ICP) was performed at the end of the imaging protocols.

RESULTS

MQCT, MRI, and ICP showed that perfused mice livers with spared gallbladder can be divided in 2 groups depending on their uptake profile of the contrast agent. Livers with severed gallbladders behave as the group internalizing more contrast agent, whereas Gd-EOB-DTPA uptake looks impaired in the case of a clamped gallbladder.

CONCLUSIONS

For the first time, MQCT and MRI have been performed in parallel to investigate the same physiological problem. The existence of 2 liver groups seems to be the result of some instability of the protocol likely to be related to surgery.

Interstitial Magnetic Resonance Lymphography Using Gadolinium-Ethoxybenzyl-Diethylenetriamine Pentaacetic Acid in Rabbits With Lymph Node Metastasis

RATIONALE AND OBJECTIVES

To investigate the dose dependency of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) for interstitial magnetic resonance (MR) lymphography and the detection of lymph node metastasis in rabbits.

METHODS

Eighteen VX2 tumor-bearing rabbits were subjected to MR lymphography using clinical MRI equipment. The enhancement of popliteal lymph nodes was studied in these rabbits before and at 2.5 to 10 minutes after the subcutaneous administration of 4, 8, or 17 micromol Gd/kg of Gd-EOB-DTPA in TSE and 3D-FLASH (n = 6). Signal-to-noise ratio and contrast-to-noise ratio were statistically compared between each group by the Tukey test. After MR imaging, the popliteal lymph nodes were removed, and sections were prepared for microscopic examination.

RESULTS

In the histologic findings, all metastases (3-12 mm) in the popliteal lymph nodes were detected by 3D-FLASH images. Gd-EOB-DTPA-enhanced T1WI showed a hypointense region for metastasis and a hyperintense region for nontumor regions, although the lymph nodes containing metastasis were detected as a hyperintense region by conventional PDWI and T2WI. Signal enhancement of the nontumor regions and contrast between the nontumor regions and metastasis showed dose dependency and reached a plateau at 8 micromol Gd/kg on T1WI (signal-to-noise ratio: 13.9 +/- 1.6; contrast-to-noise ratio: -12.7 +/- 1.7).

CONCLUSIONS

This study showed that interstitial MR lymphography with Gd-EOB-DTPA can detect metastasis and that the optimal dose in rabbits is 8 micromol Gd/kg as a subcutaneous application.

Magnetic Resonance Imaging With Hepatospecific Contrast Agents in Cirrhotic Rat Livers

OBJECTIVE

During biliary cirrhosis in rats, organic anion-transporting peptides (Oatps) and ATP-dependent multidrug resistance-associated protein 2 (Mrp2) that are likely to transport the contrast agent Gd-BOPTA through hepatocytes are down-regulated. However, the consequences of such down-regulation on the signal intensity (SI) enhancement are unknown. Consequently, the aim of our study was to measure the hepatic SI enhancement during Gd-BOPTA perfusion as well as the Oatp and Mrp2 expression in normal and cirrhotic livers.

MATERIALS AND METHODS

The hepatic SI enhancement during Gd-BOPTA perfusion was measured in livers isolated from normal rats and rats that had a bile duct ligation (BDL) 15, 30, and 60 days before the perfusion. Hepatic injury and transporter expression were measured in control and cirrhotic rats.

RESULTS

BDL induced a severe hepatic injury that increased over time with a down-regulation of the transporter expression. The extracellular space (assessed by Gd-DTPA perfusion) increased with the severity of the disease. Gd-BOPTA-induced SI enhancement remained similar in BDL-15 and BDL-30 rats than in control rats but significantly decreased in severe cirrhosis (BDL-60 rats). In comparison, the Mn-DPDP-induced SI enhancement decreases proportionally to the severity of the disease.

CONCLUSION

During biliary cirrhosis, Gd-BOPTA-induced SI enhancement could not be related to the hepatic expression of transporters.

[Current status of MRI diagnostics with liver-specific contrast agents. Gd-EOB-DTPA and Gd-BOPTA]

The contrast agents Gd-EOB-DTPA and Gd-BOPTA can be administered by bolus injection and are appropriate for use in MRI both as vascularization markers and markers of hepatobiliary excretion. This contribution presents an overview of the specific characteristics of contrast media and the status of clinical development. In comparison to CT and to MRI with unspecific extracellular Gd-chelates, liver-specific contrast agents offer advantages in differentiating unclear liver lesions, increasing the detection rate, and examining the bile duct system.