Superparamagnetic iron oxide enhanced magnetic resonance imaging of rat liver with hepatocellular carcinoma and benign hyperplastic nodule

SPIO-enhanced MRI findings of well-differentiated hepatocellular carcinomas: correlation with MDCT findings

Objective

This study was designed to assess superparamagnetic iron oxide (SPIO)-enhanced MRI findings of well-differentiated hepatocellular carcinomas (HCCs) correlated with their multidetector-row CT (MDCT) findings.

Materials and Methods

Seventy-two patients with 84 pathologically proven well-differentiated HCCs underwent triple-phase MDCT and SPIO-enhanced MRI at a magnetic field strength of 1.5 Tesla (n = 49) and 3.0 Tesla (n = 23). Two radiologists in consensus retrospectively reviewed the CT and MR images for attenuation value and the signal intensity of each tumor. The proportion of hyperintense HCCs as depicted on SPIO-enhanced T2- or T2^*-weighted images were compared in terms of tumor size (< 1 cm and > 1 cm), five CT attenuation patterns based on arterial and equilibrium phases and magnetic field strength, by the use of univariate and multivariate analyses.

Results

Seventy-eight (93%) and 71 (85%) HCCs were identified by CT and on SPIO-enhanced T2- and T2^*-weighted images, respectively. For the CT attenuation pattern, one (14%) of seven isodense-isodense, four (67%) of six hypodense-hypodense, four (80%) of five isodense-hypodense, 14 (88%) of 16 hyperdense-isodense and 48 (96%) of 50 hyperdense-hypodense HCCs were hyperintense (Cochran-Armitage test for trend, p < 0.001). Based on the use of multivariate analysis, the CT attenuation pattern was the only factor that affected the proportion of hyperintense HCCs as depicted on SPIO-enhanced T2- or T2^*-weighted images (p < 0.001). Tumor size or magnetic field strength was not a factor that affected the proportion of hyperintense HCCs based on the use of univariate and multivariate analysis (p > 0.05).

Conclusion

Most well-differentiated HCCs show hyperintensity on SPIO-enhanced MRI, although the lesions show various CT attenuation patterns. The CT attenuation pattern is the main factor that affects the proportion of hyperintense well-differentiated HCCs as depicted on SPIO-enhanced MRI.

Multidetector row CT and MR imaging in diagnosing hepatocellular carcinoma

It is important to diagnose hepatocellular carcinoma (HCC) correctly and in early stage, because viral hepatitis and liver cirrhosis are often complicated by HCC. Noncontrast and enhanced CT and MRI are very useful to visualize and diagnose HCC objectively. Especially, CT and MR imaging with dynamic study is essential to diagnose HCC, because it is usually hypervascular. Dynamic CT and MR study also improve differential diagnosis in the characterization of the tumor. However, to perform useful dynamic study, it is necessary to use a CT unit which can make a helical scan, or a MR system with fast imaging technique available that can obtain more than 15 slices within a single breath hold. Tissue specific contrast medium, such as superparamagnetic iron oxide that is available only on MRI, is also useful for diagnosis of HCC.

Effect of resovist on rats with different severities of liver cirrhosis

RATIONALE AND OBJECTIVES

Whether the degree of diffuse hepatic damage is correlated with the signal change on MR images after injection of superparamagnetic iron oxide (SPIO) particles was investigated. In addition, we investigated whether hepatic function deteriorates after injection of SPIO.

METHODS

Seventy-six female Sprague-Dawley rats aged 3 to 4 weeks were given drinking water containing 0.03% thioacetamide (TAA) for 4 or 12 weeks to induce two grades of liver injury. Seventeen normal rats were served as a control. Normal and model rats were administered Resovist (10 micromol Fe/kg), and signal intensities in the liver on MR images obtained at 4.7 T were measured up to 60 minutes after injection (n = 5). The model rats were injected with 10 times the envisaged dose of Resovist (100 micromol Fe/kg) or saline as a control substance, and blood parameters were measured at 4, 24, and 48 hours after injection (n = 5 or 6). At 4 hours after injection, iron and Kupffer cells in the liver were stained (n = 3).

RESULTS

Maximal signal reduction in the liver occurred 15 minutes after injection in all groups. The reduced signal persisted for 60 minutes after injection. However, the degree of maximal signal reduction in the model rats was significantly less than that in the normal rats (P < 0.05, 0.01). Signal reduction in the 12-week group was less than that in the 4-week group. In control rats, the number of iron-positive cells increased by 22 cells per area (0.065 mm(2)) following treatment with Resovist. In the 4-week and 12-week groups, numbers of iron-positive cells increased by 13 and 11 cells, respectively. There was no statistically significant difference in the number of Kupffer cells between control and model rats. No significant change was observed in blood parameters with Resovist.

CONCLUSION

The MR signal induced by Resovist depended on the degree of phagocytic activity in the liver. The safety profiles of Resovist remained unchanged even at 10 times the imaging dose.

Effect of superparamagnetic iron oxide-enhanced MRI of the liver with hepatocellular carcinoma and hyperplastic nodule

PURPOSE

To evaluate the possibility of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) of the liver in predicting the histologic grade of hepatocellular carcinoma (HCC) and differentiating HCC from benign hyperplastic nodule (HPN).

MATERIALS AND METHODS

Thirty patients with 31 histologically proved HCC and HPN underwent MRI (1.5 Tesla). HCCs were graded into well-differentiated HCC (HCCw; n = 10) and moderately to poorly differentiated HCC (HCCmp; n = 15). HPN was categorized into dysplastic nodule (DN; n = 1) and focal nodular hyperplasia (FNH; n = 6). T2-weighted fast spin echo images were obtained before and after administration of SPIO. Signal-to-noise ratios (SNR) of the lesion and surrounding liver parenchyma and contrast-to-noise ratios (CNR) were calculated pre- and postcontrast study. Relative enhancement ratios (RER), also known as signal intensity reduction ratios of the lesions, were also calculated.

RESULTS

HCCw, HCCmp, DN, and FNH decreased in SNR after injection of SPIO. RER of HCCw was 19.5 +/- 13.3%, that of HCCmp was 6.8 +/- 5.8%, DN was 44.0%, and FNH was 42.9 +/- 4.8%. Significant statistical differences were seen between HCCw and HCCmp and HCC and HPN in RER. HCCw, HCCmp, and DN increased in CNR, and FNH decreased in CNR, but no lesion showed a statistically significant difference in CNR.

CONCLUSION

SPIO-enhanced MR images may help to predict the histologic grade of HCC and distinguish HCC from HPN.

Dose-dependency and rate of decay of efficacy of Resovist on MR images in a rat cirrhotic liver model

RATIONALE AND OBJECTIVES

To investigate the dose-dependency and half-life of decay of the signal reduction by super-paramagnetic iron oxides on three different spin-echo images in a rat model of cirrhosis.

METHODS

For normal and cirrhotic liver, signal intensities were measured 15 minutes after injection of Resovist (range, 1-40 mumol Fe/kg) on three different spin-echo images. Subsequently, recovery of signal intensity was monitored up to 2 weeks after injection.

RESULTS

The dose-dependency of efficacy was somewhat less at all doses and imaging parameters in cirrhotic liver. However, the submaximal effect was obtained at a dose of 20 mumol Fe/kg, the same as in normal liver. The rate of decay of the efficacy in cirrhotic liver was similar to or faster than that in normal liver.

CONCLUSIONS

The dose-dependency and rate of decay of efficacy of Resovist in cirrhosis were similar to those in normal liver, although the efficacy was less in cirrhotic liver and both the dose-dependency and rate of decay of efficacy were dependent on imaging parameters.

Hepatitis, cirrhosis, and hepatoma

Virus hepatitis and liver cirrhosis are found at high incidence in Asia, and they require not only biochemical examination of blood but also subsequent imaging, because they are often complicated by hepatocellular carcinoma (HCC). It is, therefore, very important to know the specific appearances of hepatitis, liver cirrhosis, and HCC when we diagnose these diffuse liver diseases. Liver necrosis due to severe hepatitis is seen as high intensity on T2-weighted spin echo images. Regeneration is seen as low intensity on T2-weighted images. Morphologic and pathologic changes of cirrhotic liver are well demonstrated by MR imaging techniques. Fibrotic septum with inflammatory cell infiltration or rich pseudo bile duct show high intensity on T2-weighted images, and regenerating nodules shows low intensity. Gradient echo images show regenerating nodules with iron deposition as low-intensity nodules due to susceptibility artifact. MRI also has the potential to evaluate function of diffuse liver disease, cirrhosis, and hepatitis. MRI can visualize and diagnose HCC objectively. Dynamic MRI is very useful for diagnosing HCC. It is also applied for evaluation of effect after transcatheter arterial chemoembolization, because it shows enhancement only in the viable region at an arterial phase. MRI is less invasive and is thus an extremely important form of liver imaging.