Dysplastic nodules and hepatocellular carcinoma: thin-section MR imaging of explanted cirrhotic livers with pathologic correlation

Imaging of multistep human hepatocarcinogenesis

In Japan, there are approximately 32 000 deaths ( approximately 30 deaths per 100 000) per year due to hepatocellular carcinoma (HCC), and it is the third most common cancer in men and fifth in women. Approximately 90% of them are associated with chronic liver diseases due to hepatitis C or B virus infection. Therefore, it has become possible to detect small early stage HCC by the periodic screening in these high-risk patients group. During the screening imaging diagnosis of HCC, various kinds of hepatocellular nodules are also frequentlydetected. To characterize them is very important for the early diagnosis and treatment of HCC. For this purpose, it is necessary to understand the concept of multistep hepatocarcinogenesis and the sequential changes of imaging findings.

Recent advances in the diagnosis of hepatocellular carcinoma

In the last decade, new imaging techniques have become available, offering the possibility of investigating contrast perfusion of liver nodules in cirrhosis. It is now accepted that a non-invasive diagnosis of hepatocellular carcinoma (HCC) can be established based on the vascular pattern, obtained with pure blood pool contrast agents. The diagnostic pattern includes: hypervascularity in the arterial phase (15-35 s after contrast injection), consisting in a contrast signal in the nodule greater than in the surrounding parenchyma, followed by contrast wash out, which leads the nodule to show the same, or, more specifically, a lower contrast signal, than the surrounding parenchyma in the portal and late phases (>40 s after injection). Such a pattern can be obtained not only by computed tomography or magnetic resonance imaging, but also by contrast-enhanced ultrasonography, most simply with real-time low mechanical index harmonic imaging ultrasound equipment with second-generation ultrasound contrast agents. The risk of false-positive diagnosis of malignancy isnearly abolished when the functional vascular pattern is not the only feature, but is superimposed on a nodule visible also without contrast. One single contrast imaging technique may suffice to make a diagnosis of HCC if the nodule is >1 cm in diameter and has developed during a surveillance program. Other types of contrast agents, such as those taken up by the reticular-endothelial system cells, may offer additional diagnostic clues, but definitive evidence of their efficacy is still to be produced. In conclusion, contrast-enhanced imaging techniques now offer the possibility of a non-invasive diagnosis of HCC in a large number of cases, reducing the need of invasive investigations, such as ultrasound-guided biopsy or angiography.

Enhancement patterns and signal-intensity characteristics of small hepatocellular carcinoma in cirrhosis: pathologic basis and diagnostic challenges

Recent pathologic studies of hepatic resection and transplantation specimens have elucidated the morphologic features of the precancerous lesions and small hepatocellular carcinomas (HCCs) arising in cirrhotic livers. Small HCCs measuring less than 2 cm in diameter are of two types: vaguely nodular, well-differentiated tumors, also known as "early" HCCs, and distinctly nodular tumors, with histologic features of "classic" HCC. The precancerous lesions include dysplastic foci and dysplastic nodules. "Classic" small HCCs are supplied by nontriadal arteries, whereas early HCCs and dysplastic nodules may receive blood supply from both portal tracts and nontriadal arteries. The similarities in blood supply of these three types of nodular lesions result in significant overlap of findings on dynamic imaging. Nevertheless, small HCCs sometimes display characteristic radiologic features, such as "nodule-in-nodule" configuration and "corona enhancement" pattern. Moreover, various histologic features of these nodular lesions may also be related to a variety of signal intensities and attenuation coefficients, while the presence of cirrhosis is known to limit the sensitivity and specificity of any imaging modality, due to liver inhomogeneity. Because of these reasons, imaging findings of nodular lesions in cirrhotic livers are often inconclusive, emphasizing the need for a better understanding of these imaging features.

Small hyperintense hepatic lesions on T1-weighted images in patients with cirrhosis: evaluation with serial MRI and imaging features for clinical benignity

PURPOSE

The aim of this study was to evaluate the frequency and magnetic resonance imaging (MRI) features of clinically benign, small (<2 cm) hyperintense hepatic lesions in the cirrhotic liver on T1-weighted MR images seen at serial MRI.

MATERIALS AND METHODS

This study included 189 patients with cirrhosis, who underwent hepatic MRI more than twice with an interval of at least 12 months. The initial MR images were reviewed for the presence of small hyperintense lesions on T1-weighted images. The size, location and signal intensity on T2-weighted images as well as enhancement patterns of the corresponding lesions were recorded.

RESULTS

On the initial T1-weighted MR images, 43 small hyperintense hepatic lesions were detected in 23 (12%) of 189 patients. Twelve (28%) of 43 lesions showed early enhancement and were pathologically diagnosed as hepatocellular carcinoma (HCC) during the follow-up period. Thirty-one (72%) of 43 lesions showed no early enhancement with various signal intensity on T2-weighted images (hyperintensity=4, isointensity=20, hypointensity=7). Among these 31 lesions, 12 showed no interval change, while 11 disappeared (n=10) or decreased in size (n=1). In the remaining eight lesions, seven were diagnosed as HCC on the basis of pathologic confirmation or the interval growth.

CONCLUSION

Small hyperintense hepatic lesions on T1-weighted magnetic resonance (MR) images without early enhancement on the arterial-phase contrast-enhanced dynamic studies in patients with cirrhosis usually showed no interval growth or disappeared during the serial MRI. These lesions with additional findings of iso- or hypointensity on the T2-weighted MR images without "washout effect" on the contrast-enhanced equilibrium-phase images may more frequently be clinically benign or hyperplastic nodules than HCCs.

Stepwise carcinogenesis of hepatocellular carcinoma in the cirrhotic liver: demonstration on serial MR imaging

PURPOSE

To demonstrate imaging findings of stepwise carcinogenesis of hepatocellular carcinoma (HCC) in cirrhosis at serial state-of-the-art MR imaging exams.

MATERIALS AND METHODS

In a retrospective search of the hospital archives, three patients were identified in which developing HCC was observed in serial MR examinations, with histopathology or alpha-fetoprotein (AFP) correlation. Image findings were assessed for signal intensity of the lesions at multiple sequences, including dynamic gadolinium-enhanced imaging.

RESULTS

Initial findings in patient A showed a small nodule with fatty infiltration that developed in HCC in follow-up MRI, comprised of low-grade dysplastic nodule (DN; DN I), high-grade DN (DN II), and eventually classic HCC. In patient B, increased signal intensity on T2-weighted images in a single DN among numerous regenerative nodules was the only initial sign. Follow up MRI showed further increase in signal intensity and increased neovascularity, which suggested focal HCC in a DN II. Patient C demonstrated gradually increasing neovascularity as only initial sign, with development of classic HCC over time.

CONCLUSION

MR imaging provides insight in various pathways of stepwise carcinogenesis of developing HCC in cirrhosis. This may further explain the genetic heterogeneity, and may facilitate early detection and better selection of patients for follow-up.

Hyperintense nodules on non-enhanced T1-weighted gradient-echo magnetic resonance imaging of cirrhotic liver: fate and clinical implications

PURPOSE

To investigate the fate of hyperintense hepatic nodules on nonenhanced T1-weighted (T1w) gradient-echo (GRE) magnetic resonance (MR) images in cirrhotic patients.

MATERIALS AND METHODS

A total of 79 cirrhotic patients with hyperintense nodules (>5 mm) on precontrast opposed-phase (repetition time (TR)/echo time (TE) = 140/2.7 msec) GRE images from initial MRI without T2-weighted (T2w) hyperintensity or arterial hypervascularity were subjected to analysis of subsequent MR images obtained at intervals of 12-56 months (mean = 24.5 months). Multiplicity of hyperintense nodules (group A, up to 8; group B, >8) was correlated with follow-up changes.

RESULTS

Group B patients were younger (P = 0.003) than group A patients (mean = 47.5 and 56.2 years, respectively). In 66 group A patients, 39 out of 143 lesions (27%) were enlarged, including 20 malignantly transformed or borderline lesions. Of the 104 lesions (the eight largest lesions in each patient) in 13 group B patients, only three (2.9%) were enlarged. The results of best- and worst-case analyses showed that overall the lesions were benign in 91% and 82% of patients, respectively.

CONCLUSION

T1w hyperintense nodules without T2w hyperintensity or arterial hypervascularity in the cirrhotic liver are benign in most cases. In younger patients with numerous macronodules, almost all of these lesions follow a benign course.

In vivo 1H MR spectroscopy in the evaluation of the serial development of hepatocarcinogenesis in an experimental rat model

RATIONALE AND OBJECTIVES

We used a 1.5-T MR scanner to investigate in vivo hydrogen 1 ((1)H) MRS to evaluate metabolic changes in the hepatocarcinogenesis experimental rat model.

MATERIALS AND METHODS

Hepatocellular carcinoma (HCC) was induced by diethylnitrosamine in 70 treated rats with 20 normal rats used as controls. Single-voxel (1)H MRS is performed to obtained the relative choline-to-lipid (Cho/lipid) ratio. The liver and tumor tissues are incised for the histologic examination. Based on the histologic result, the progression of hepatocarcinogenesis of the animal model was divided into three stages: fibrosis stage, cirrhosis stage, and HCC stage. The mean (+/-SD) ratio values are calculated and compared at various stages between the treated group and the control group.

RESULTS

In control group, the calculated mean (+/-SD) Cho/lipid ratio was 0.15 +/- 0.05. With the progression of hepatocarcinogenesis, the Cho/lipid ratio increased significantly, to 0.18 +/- 0.05, 0.24 +/- 0.07, and 0.38 +/- 0.19, respectively.

CONCLUSION

The (1)H MRS is technically feasible for evaluation of the metabolic changes in the animal model. A significant increase in choline-containing compounds level was observed in the HCC stage in the treated group.

Newly Developed Hepatocellular Carcinoma (HCC) in Chronic Liver Disease

PURPOSE

The purpose of this work was to describe the initial magnetic resonance (MR) imaging findings obtained before an imaging diagnosis of overt hepatocellular carcinoma (HCC) in the chronically damaged liver.

METHODS

One hundred fifty-two newly diagnosed HCCs diagnosed by dynamic computed tomography (n = 111) or by MR imaging (n = 41), in addition to digital subtraction hepatic arteriography, in 96 patients were subjected to analysis of their MR imaging features within the previous 2 years.

RESULTS

Ninety-seven (64%) HCC cases showed no focal lesions distinguishable from background hepatic parenchyma in MR images taken before the indication of typical HCC. The remaining 55 (36%) lesions were readily identified in earlier images and were categorized into 3 groups: nonhypervascular lesions (category I, n = 6), lesions with partially hypervascular foci of "nodule-within-nodule" appearance (category II, n = 12), and homogeneously hypervascular and/or T2-weighted hyperintense lesions (category III, n = 37). The size and doubling time of category III lesions (0.7 cm, 154 days) were smaller and shorter than those of the other lesions (1.2 cm, 377 days).

CONCLUSIONS

Before the imaging diagnosis of HCCs, the premalignant or early malignant lesions can be found on the prior MR images just in the minority of the lesions in the cirrhotic liver.

Magnetic Resonance Imaging Appearance of Well-differentiated Hepatocellular Carcinoma

OBJECTIVE

To investigate the magnetic resonance imaging (MRI) features of well-differentiated hepatocellular carcinoma (HCC).

METHODS

We reviewed the MRI of 32 patients with 33 pathologically confirmed well-differentiated HCC. The MRI protocol included T2-weighted imaging with and without fat saturation, dual-phase T1-weighted imaging, and gadolinium-enhanced dynamic study. The signal intensity of each lesion was categorized as hyperintense, isointense, and hypointense with reference to the surrounding liver parenchyma.

RESULTS

Thirty-one (93.9%) of 33 well-differentiated HCC were demonstrated on the MRI. The remaining 2 were isointense in all magnetic resonance sequences and, therefore, could not be identified. Most of them were hyperintense (n = 15 [45.4%]) or isointense (n = 16 [48.5%]) on T1-weighted imaging, and hyperintense (n = 12 [36.4%]) or isointense (n = 17 [51.5%]) on T2-weighted imaging. On the dynamic study, 17 lesions (51.5%) were enhanced.

CONCLUSIONS

MRI may identify most well-differentiated HCC; however, the imaging appearance is diverse. Biopsy should be performed if magnetic resonance study is inconclusive.

Hepatocellular carcinoma in the cirrhotic liver: gadolinium-enhanced 3D T1-weighted MR imaging as a stand-alone sequence for diagnosis

PURPOSE

To retrospectively assess the usefulness of contrast material-enhanced T1-weighted magnetic resonance (MR) imaging alone and with T2-weighted MR imaging in the diagnosis of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

A waiver of informed consent and institutional review board approval for this retrospective study were granted. The study was HIPAA compliant. Twenty-eight men (mean age, 49 years; range, 23-70 years) and 10 women (mean age, 53 years; range, 42-72 years) with cirrhosis underwent T2-weighted and contrast-enhanced T1-weighted MR imaging at 1.5 T within 90 days of liver transplantation. Three readers reviewed the T1-weighted images alone and then the T2-weighted and T1-weighted images together. Lesion detection, characterization, and reader confidence levels were recorded.

RESULTS

At liver explantation, 57 lesions were present in 18 patients: 19 HCCs, 33 dysplastic nodules, and five cysts. Contrast-enhanced T1-weighted imaging depicted 13 of 19 HCCs with an overall sensitivity of 68.4% (13 of 19) and specificity of 65.7% (23 of 35). The sensitivity and specificity for detection of dysplastic nodules (sensitivity, 9%; specificity, 68.4%) and HCCs (sensitivity, 68.4%; specificity, 65.7%) were nearly identical for T1-weighted images read alone or read with T2-weighted images. The only difference was the specificity for T1-weighted images read alone (65.7%) and read with T2-weighted images (62.9%). The addition of T2-weighted images altered the diagnosis in one of 90 (1.1%) cases and provided an increase in diagnostic confidence in four of 258 (1.6%) cases for independent readers and three of 90 (3.3%) cases at consensus reading.

CONCLUSION

Contrast-enhanced T1-weighted imaging can be used as a stand-alone sequence for the diagnosis of HCC in patients with cirrhosis prior to liver transplantation.

Dysplastic nodules frequently develop into hepatocellular carcinoma in patients with chronic viral hepatitis and cirrhosis

BACKGROUND

Advances in imaging technology have enhanced the detection of small nodular lesions during the course of chronic liver disease.

METHODS

Between 1995 and 2002, the authors examined 154 consecutive patients with small hepatic nodules without hepatocellular carcinoma (HCC) over a median duration of 2.8 years. The median size of these nodules was 14 mm (range, 7-40 mm). The initial histopathologic diagnosis included high-grade dysplastic nodule (HGDN) (n=13), low-grade dysplastic nodule (LGDN) (n=42), and regenerative nodule (RN) (n=99).

RESULTS

A total of 29 (18.8%) nodules developed into HCC during the observation period. Cumulative HCC development rates at the first, third, and fifth year were 46.2%, 61.5%, and 80.8% for HGDN; 2.6%, 30.2%, and 36.6% for LGDN; and 3.3%, 9.7%, and 12.4% for RN, respectively. The rate of HCC development was significantly higher in the HGDN group than for other types (P<0.001). Multivariate analysis disclosed that histopathologic diagnosis (P<0.001) and findings on computed tomographic arterial portography (CT-AP) (P=0.004) were significantly associated with future HCC development. The hazard ratios of HGDN and LGDN were 16.8 (95% confidence interval [CI], 6.19-45.6) and 2.96 (95% CI, 1.20-7.31), respectively. A decrease in portal blood flow also showed a significantly high hazard ratio of 3.04 (95% CI, 1.42-6.50). Approximate annual development rate to HCC was 20% in patients with HGDN and 10% in LGDN.

CONCLUSION

HGDN should be considered a precancerous lesion when it appears during follow-up of chronic viral hepatitis or cirrhosis. Reduced portal blood flow in the nodule on computed tomography-AP is also an important predictor for development of hepatocellular carcinoma.

The risk of hepatocellular carcinoma in cirrhotic patients with small liver nodules on MRI

BACKGROUND AND AIM

The presence of hepatocellular carcinoma (HCC) has important implications for patients with cirrhosis. Studies have not compared the risk of cancer in cirrhotic patients with small liver nodules to cirrhotic patients without nodules. Our aim was to determine the risk of HCC in cirrhotic patients with small liver nodules on MRI compared to those without nodules.

METHODS

We conducted a prospective study to determine the rate of HCC in cirrhotic patients with and without liver nodules. Cases were patients with liver nodule(s) less than 2 cm on MRI and controls were cirrhotic patients without nodules. Kaplan-Meier estimates and multivariate analysis were performed to estimate the risk of HCC in the two groups.

RESULTS

A total of 310 liver transplant candidates with a mean follow-up of 663 days were included in the study and 133 underwent liver transplant during follow-up. The 1-yr incidence of HCC in the liver nodule group and control group was 11% and 0.5%, respectively, p < 0.001. The adjusted risk for HCC in the liver nodule group was 25 times higher compared to the control group, HR = 25.1 [95% CI 8.0, 78.9]. In 133 candidates who underwent transplant with and without liver nodules the rate of HCC was 11 (50%) and 4 (3.6%), respectively, p < 0.001.

CONCLUSION

The incidence of HCC in patients with small liver nodules is significantly higher compared to patients with cirrhosis without liver nodules. The presence of small liver nodules warrants increased imaging surveillance for HCC.

Importance of small (< or = 20-mm) enhancing lesions seen only during the hepatic arterial phase at MR imaging of the cirrhotic liver: evaluation and comparison with whole explanted liver

PURPOSE

To retrospectively assess the importance and imaging appearance of small (< or = 20 mm in diameter) hepatic arterial phase-enhancing (HAPE) lesions that are occult during portal and/or equilibrium phases and at unenhanced T1- and T2-weighted magnetic resonance (MR) imaging and to determine the gross pathologic diagnosis with whole-liver explant comparison.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board and compliant with HIPPA. Forty-six patients with cirrhosis who underwent MR imaging and transplantation within 90 days were evaluated with breath-hold T2-weighted and volumetric three-dimensional gadolinium-enhanced gradient-echo MR imaging in the hepatic arterial, portal venous, and equilibrium phases at 1.5 T. Three readers, who were blinded to the pathologic results, retrospectively reviewed the MR images in consensus for small HAPE nodules that were occult at T2-weighted and portal and/or equilibrium phase MR imaging. Only patients with nodules that enhanced during the arterial phase were included in the final study group, which included 16 patients (12 men and four women) aged 18-66 years (median age, 51.5 years). Explanted livers were serially sliced into 5-8-mm-thick sections to evaluate dysplastic nodules and hepatocellular carcinomas (HCCs). The Fisher exact test was performed to determine whether there was a relationship between HCC and the presence of a neoplastic HAPE-only lesion. The Mann-Whitney test was used to determine if patients with at least one neoplastic HAPE-only lesion had a larger number of non-HAPE-only lesions.

RESULTS

The 16 patients had 45 HAPE-only lesions; three (7%) of which were neoplastic, including one overt HCC, one HCC arising in a dysplastic nodule, and one dysplastic nodule. None of the remaining 42 HAPE-only lesions (93%) had correlative pathologic findings. All three neoplastic lesions seen only during the arterial phase were found in eight patients with concomitant HCC, who also had an additional 13 pathologically proved nonneoplastic HAPE-only lesions. In eight patients without HCC, none of the HAPE-only lesions were neoplastic. A concomitant non-HAPE-only neoplastic lesion was not a significant (P = .2) predictor for the presence of at least one neoplastic HAPE-only lesion. There was a preliminary but insignificant (P = .13) indication that the number of non-HAPE-only lesions tends to be higher in patients with neoplastic HAPE-only lesions.

CONCLUSION

The majority (93%) of HAPE-only lesions that are occult at T2-weighted and portal and/or equilibrium phase MR imaging are nonneoplastic, even in patients with pathologically proved HCC.

Cirrhotic nodules: association between MR imaging signal intensity and intranodular blood supply

PURPOSE

To retrospectively determine whether there is a relationship between the intranodular blood supply evaluated at computed tomography (CT) during arterial portography (CTAP) and CT during hepatic arteriography (CTHA) and the magnetic resonance (MR) imaging signal intensity of nodules associated with cirrhosis.

MATERIALS AND METHODS

Neither institutional review board approval nor informed consent was required for retrospective reviews of medical records and images. One hundred fourteen hepatocellular nodules 10 mm or greater in largest diameter in 58 patients (39 men, 19 women; mean age, 61 years) with cirrhosis were evaluated at CTAP, CTHA, and MR imaging. The CTAP and CTHA nodule findings were divided into three main types: Type A nodules were isoattenuating at CTAP and hypoattenuating at CTHA; type B nodules, slightly hypoattenuating at CTAP and hypoattenuating at CTHA; and type C nodules, strongly hypoattenuating at CTAP and hyperattenuating at CTHA. The relationships between the CTAP and CTHA findings and the MR imaging signal intensity among these nodules were analyzed by using the chi(2) test.

RESULTS

On T1-weighted MR images, 27 (63%) of 43 type A nodules were hyperintense, nine (39%) of 23 type B nodules were isointense, and 19 (48%) of 40 type C nodules were hypointense; differences were not significant. On T2-weighted MR images, 31 (72%) of 43 type A nodules were hypointense (P < .05), 12 (52%) of 23 type B nodules were isointense, and 34 (85%) of 40 type C nodules were hyperintense (P < .05).

CONCLUSION

There was a significant association between intranodular blood supply and nodule signal intensity on T2-weighted MR images. However, study findings did not show whether the blood itself (ie, blood volume or blood flow amount) directly influenced the signal intensity.

Sonography-Guided Percutaneous Microwave Ablation of High-Grade Dysplastic Nodules in Cirrhotic Liver

OBJECTIVE

Our objective was to evaluate the effect of sonography-guided percutaneous microwave ablation of high-grade dysplastic nodules in the cirrhotic liver.

MATERIALS AND METHODS

From July 1997 to May 2003, 49 histologically proven high-grade dysplastic nodules in 30 patients with liver cirrhosis were treated by microwave ablation. Three patients had concomitant small hepatocellular carcinomas (D < 3.0 cm), whereas another three had undergone liver segmentectomy for hepatocellular carcinoma 1 year earlier. The mean size of the nodules was 1.8 cm (range, 0.9-4.6 cm). Sixty-eight insertions with 78 applications were administered to the 49 nodules.

RESULTS

The follow-up period was 12-82 months (mean, 45.1 +/- 19.0 months). Five patients died during this study: three from advanced hepatocellular carcinoma, one from bleeding in the upper gastrointestinal tract, and another from cerebral hemorrhage. All nodules showed decreased density on unenhanced CT and no enhancement on contrast-enhanced CT after microwave ablation. Posttreatment biopsy performed in 16 patients with 18 nodules 1-3 months after microwave ablation showed no evidence of viable tissue but replacement by fibrotic tissue in all nodules.

CONCLUSION

Percutaneous microwave ablation as a minimally invasive therapy is effective for ablating high-grade dysplastic nodules, thus preventing their potential malignant transformation, which may improve survival. The preliminary data warrant further prospective, randomized studies.

Hepatic nodules in liver transplantation candidates: MR imaging and underlying hepatic disease

OBJECTIVE

To assess by MR imaging the frequency of hepatic nodules in patients waiting on the liver transplant list and to determine whether certain underlying hepatic diseases were more often associated with the development of such hepatic nodules.

MATERIAL AND METHODS

We reviewed the MR and clinical records in all patients seen by the liver transplant service at our center since its inception in January 1998 until September 2002. A total of 371 patients (207 men and 164 women, age range 18-68 years, mean 45 years) were included in the study. The presence of hepatic nodules, size, number and underlying hepatic diseases were determined in all patients. Magnetic resonance imaging was performed on a 1.5-T MR imager using T1-weighted, T2-weighted and multi-phase gadolinium-enhanced sequences. Odds ratio (OR) and 95% confidence intervals (CIs) were computed to evaluate the association between the underlying hepatic disease and the development of hepatic nodule.

RESULTS

Among 371 liver transplantation candidates, the most common underlying hepatic disease was hepatitis C virus (HCV) infection, either alone (n=93; 25%) or associated with other hepatic diseases (n=40; 10.8%). Of all patients, 33 (8.9%) had regenerative nodules (RNs), 40 (10.7%) dysplastic nodules (DNs) and 57 (15.3%) hepatocellular carcinomas (HCCs). Hepatocellular carcinoma was observed in 35.3% of patients with HCV infection and alcohol abuse combined, 24.5% with cryptogenic cirrhosis, 25% with hemochromatosis and 19% with alcohol abuse. Patients who had either DNs or HCC were 2.5 times more likely to have either alcohol abuse or HCV, alone or combined, as the substrate of their liver disease (OR 2.54, 95% CI 1.56-4.13). Our data suggest a supra-additive interaction between HCV infection and ethanol in their association with MR imaging detected lesions.

CONCLUSION

Patients with cryptogenic cirrhosis, alcohol abuse, HCV infection (alone or combined) and hemochromatosis had the greatest likelihood of having HCC, with the combination of HCV infection and alcohol abuse having the highest of all.

MRI in detection of hepatocellular carcinoma (HCC)

Hepatocellular carcinoma (HCC) is the commonest malignancy of the liver and is usually due to cirrhosis. Early detection of HCC and the premalignant dysplastic nodules has implications on the management options of tumor ablation, liver resection and transplantation. Magnetic resonance imaging is useful for the detection and characterization of lesions, in the identification of dysplastic nodules and their malignant transformation into HCC.

Non-invasive diagnosis of liver cirrhosis: magnetic resonance imaging presents special features

OBJECTIVE

Liver cirrhosis and its complications constitute a daily clinical challenge. The diagnosis of cirrhosis is traditionally established with the invasive method of liver biopsy. We undertook the present study in order to investigate the sensitivity and specificity of magnetic resonance imaging (MRI) in diagnosing cirrhosis.

MATERIAL AND METHODS

A total of 56 patients were included in our retrospective study. The liver cirrhosis group comprised 30 patients and the control group 26 patients. All cases were histologically verified. A 1.5T MRI unit was used. Twelve radiological features of cirrhosis (enlargement of segment one, narrowing of hepatic veins, enlargement of spleen, fibrosis, nodular liver surface, ascites, regenerative nodules, enlargement of hilar periportal space, atrophy of right lobe, portosystemic collaterals, expanded gallbladder fossa, iron depositions) and tumour-load were evaluated by consensus reading. The ratio between segment one and right lobe was measured and the livers were classified as cirrhotic or non-cirrhotic. The chi2-test and t-test were used to indicate statistical difference.

RESULTS

The sensitivity of MRI in diagnosing liver cirrhosis was 87% and the specificity 92%. The most characteristic MRI features were enlargement of segment one (83%), narrowing of hepatic veins (83%), signs of portal hypertension (77%), fibrosis (77%), and nodular liver margin (67%). There were statistical differences in all MRI signs between the cirrhosis and control groups. The ratio between segment one and right lobe also showed statistical significance between the two groups. All occult hepatocellular carcinomas were detected in the cirrhosis group.

CONCLUSION

MRI has high sensitivity and specificity in the diagnosis of liver cirrhosis.

Nodule-in-nodule appearance of hepatocellular carcinomas: comparison of gadolinium-enhanced and ferumoxides-enhanced magnetic resonance imaging

PURPOSE

To perform comparison of gadolinium-enhanced and ferumoxides-enhanced magnetic resonance imaging (MRI) in the detection of nodule-in-nodule appearance of hepatocellular carcinomas (HCCs).

MATERIALS AND METHODS

During a recent 45-month period, we had eight patients (five men and three women; age range, 63-84 years; mean, 71 years) with HCCs with nodule-in-nodule appearance who underwent gadolinium-enhanced MRI, ferumoxides-enhanced MRI, and computed tomography during arterial portography (CTAP) and computed tomography during hepatic arteriography (CTHA), combined and separately, within an interval of two weeks. Two blinded radiologists in consensus retrospectively evaluated three sets of sequences: unenhanced T1- and T2-weighted MR, gadolinium-enhanced MR, and ferumoxides-enhanced MR images in random order of patients and imaging sequences. The depiction degree of nodule-in-nodule appearance of HCC was evaluated in a semiquantitative fashion. The sensitivities of unenhanced T1- and T2-weighted, gadolinium-enhanced, and ferumoxides-enhanced MR images were compared with McNemar's test.

RESULTS

The eight HCCs with nodule-in-nodule appearance ranged in size from 16-26 mm (mean, 20.0 +/- 4.0 mm), and there existed nine internal HCC foci ranging in size from 5-14 mm (mean, 7.9 +/- 3.5 mm). On gadolinium-enhanced MR images, the nodule-in-nodule appearance of HCC was typically seen as hypervascular foci in an iso- or hypovascular area: the depiction degree of nodule-in-nodule appearance was distinct in two lesions, equivocal in three, and absent in three. On ferumoxides-enhanced MR images, it was typically seen as hyperintense foci in a hypointense area: the depiction degree was distinct in four, moderate in one, and absent in three. The sensitivities for detection of nodule-in-nodule appearance were 25%, 25%, and 63% on T1- and T2-weighted, gadolinium-enhanced, and ferumoxides-enhanced MR images, respectively, but there was no significant difference in sensitivity.

CONCLUSION

Nodule-in-nodule appearance of HCCs can be seen on ferumoxides-enhanced MR images, in some cases more clearly than on gadolinium-enhanced MR images, particularly when the background nodule shows hyperintensity on precontrast T1-weighted images. Ferumoxides-enhanced MRI may be considered when development of malignant foci is suspected during routine examinations.

Iron-containing nodules of cirrhosis

In the absence of genetic hemochromatosis and systemic hemosiderosis, patients with cirrhosis can accumulate focal iron within regenerative or dysplastic hepatic nodules, commonly referred to as 'siderotic nodules'. Siderotic dysplastic nodules are premalignant lesions while siderotic regenerative nodules are a marker for severe viral or alcoholic cirrhosis. The relationship of hepatic iron deposition to hepatic cirrhosis and neoplasia has not been fully clarified. This article will review the current literature regarding selective iron accumulation in siderotic nodules in chronic liver disease, followed by a discussion of current MR imaging techniques for detection and characterization of these nodules.

Magnetic resonance imaging of hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the most common primary hepatic malignancy, usually develops in patients with cirrhosis, growing sequentially from low-grade dysplastic nodules to frank malignant HCC. Its recognition is critical because curative treatment and prognosis require early diagnosis. Survival in patients with HCC relates directly to the number, size, and extent of lesions at diagnosis. Imaging of HCC is complicated because the tumor has a varied imaging appearance and frequently coexists with other cirrhotic nodules. Magnetic resonance imaging (MRI), the best available diagnostic technique, offers good contrast resolution and diagnostic sensitivity ranging from 33% to 77%. The main difficulty is not in diagnosing large tumors, but rather small tumors (<2 cm), because of considerable overlap on imaging between benign (regenerative), borderline (dysplastic), and malignant nodules. Increasing degrees of histological malignancy are associated with increasing arterialization and loss of portal blood supply; therefore, recognition of HCC requires dynamic imaging with gadolinium-enhanced T1-weighted sequence. Typically, HCC is a focal lesion with high signal intensity on T2-weighted images, variable signal intensity on T1-weighted images, intense arterial phase enhancement after gadolinium injection, and isointensity or hypointensity at the portal venous phase. The sensitivity of MRI for detecting small lesions is low, and improvement is still needed. Newer contrast agents, higher field strength (3 Tesla) imaging, and perfusion and diffusion MRI techniques possibly will provide greater sensitivity and specificity for detecting small HCCs in the future.

Hepatocellular carcinoma - issues in imaging

The imaging diagnosis of hepatocellular carcinoma is challenging as benign hypervascular lesions and arterioportal shunts (pseudolesions) often mimic it. There is also overlap in the imaging appearance from dysplastic and regenerating nodules. This article addresses the above imaging problems, examines proposed non-invasive imaging criteria for the diagnosis of hepatoma and discusses the optimal imaging modality.

Characterization of focal liver lesions with contrast-specific US modes and a sulfur hexafluoride-filled microbubble contrast agent: diagnostic performance and confidence

PURPOSE

To assess whether characterization of solid focal liver lesions could be improved by using ultrasonographic (US) contrast-specific modes after sulfur hexafluoride-filled microbubble contrast agent injection, as compared with lesion characterization achieved with preliminary baseline US.

MATERIALS AND METHODS

Four hundred fifty-two solid focal hepatic lesions that were considered indeterminate at baseline gray-scale and color Doppler US were examined after microbubble contrast agent injection performed by using low-acoustic-power contrast-specific modes during the arterial (10-40 seconds after injection), portal venous (50-90 seconds after injection), and late (100-300 seconds after injection) phases. Two readers independently and retrospectively reviewed baseline and contrast material-enhanced US scans and classified each depicted lesion as malignant or benign according to standard diagnostic criteria. Sensitivity, specificity, accuracy, and positive and negative predictive values and areas under the receiver operating characteristic curve (Az) were calculated by considering histologic analysis (317 patients) or contrast-enhanced helical computed tomography followed by serial US 3-6 months apart (135 patients) as the reference standards.

RESULTS

Different contrast enhancement patterns were observed according to lesion characteristics. During the late phase, benign lesions were predominantly hyper- or isoechoic relative to the adjacent liver parenchyma, whereas malignant lesions were predominantly hypoechoic. Review of the contrast-enhanced US scans after baseline image review yielded significantly improved diagnostic performance (P <.05). Overall diagnostic accuracy was 49% before versus 85% after review of the contrast-enhanced scan for reader 1 and 51% before versus 88% after review of the contrast-enhanced scan for reader 2. Diagnostic confidence-that is, the Az-was 0.820 before versus 0.968 after review of the contrast-enhanced scan for reader 1 and 0.831 before versus 0.978 after review of the contrast-enhanced scan for reader 2.

CONCLUSION

The use of contrast-specific modes with a sulfur hexafluoride contrast agent led to improved characterization of solid focal liver lesions.

Hepatocellular nodules in cirrhosis: focus on diagnostic criteria on liver biopsy. A Western experience

The spectrum of so-called space-occupying small (0.5-2.5 cm) sizable nodules arising in the cirrhotic liver includes a series of hyperplastic (large regenerative), dysplastic (low- and high-grade dysplastic), and malignant hepatocellular (well-differentiated hepatocellular carcinoma, HCC) nodules. Major progress in their classification and understanding was achieved through image analysis techniques and careful histological dissection of explanted native livers. Needless to say, the actual understanding of their natural history is crucial to a proper histological classification. The differential diagnosis of these hepatocellular nodules is difficult, particularly on biopsy specimens of focal liver lesions revealed by ultrasound (US), taken during the follow-up of cirrhotic patients. In this study we attempted to summarize, on the basis of our experience, essential clinicopathological features useful to distinguish the different nodules on needle biopsy. Synoptic tables of differential diagnosis and figures of elementar lesions, which have to be looked for, are provided. Only the continuous integration of clinical features, image analysis information of pathological findings, and follow-up data allows establishing the autonomy of these polymorphic and controversial entities and the boundaries between them.

T2-weighted MR imaging in the assessment of cirrhotic liver

PURPOSE

To assess if T2-weighted magnetic resonance (MR) imaging provides added diagnostic value in combination with dynamic gadolinium-enhanced MR imaging in the detection and characterization of nodular lesions in cirrhotic liver.

MATERIALS AND METHODS

Two readers retrospectively and independently analyzed 54 MR imaging studies in 52 patients with cirrhosis. In session 1, readers reviewed T1-weighted and dynamic gadolinium-enhanced images. In session 2, readers reviewed T1-weighted, dynamic gadolinium-enhanced, and respiratory-triggered T2-weighted fast spin-echo images. Readers identified and characterized all focal lesions by using a scale of 1-4 (1, definitely benign; 4, definitely malignant). Multireader correlated receiver operating characteristic (ROC) analysis was employed to assess radiologist performance in session 2 compared with session 1. The difference in the areas under the ROC curves for the two sessions was tested. In a third session, readers assessed conspicuity of biopsy-proved lesions on T2-weighted MR images by using a scale of 1-3 (1, not seen; 3, well seen) and identified causes of reduced conspicuity.

RESULTS

Two additional benign lesions were detected by each reader in session 2. Fifty-five lesions had pathologic verification, including 32 malignant, three high-grade dysplastic, and 20 benign nodules. There was no significant difference in the area under the ROC curves between the two sessions (P =.48). Thirty-two lesions were inconspicuous on T2-weighted MR images because of parenchymal heterogeneity, breathing artifacts (particularly in patients with ascites), and lesion isointensity with liver parenchyma. T2-weighted MR imaging was useful in the evaluation of cysts and lymph nodes.

CONCLUSION

T2-weighted MR imaging does not provide added diagnostic value in the detection and characterization of focal lesions in cirrhotic liver.

Angiogenesis in hepatocellular nodules: Correlation of MR imaging and vascular endothelial growth factor

PURPOSE

To assess the correlation between magnetic resonance (MR) imaging findings and angiogenetic activity in hepatocellular nodules evaluated by immunohistochemical staining with antibody of vascular endothelial growth factor (VEGF).

MATERIALS AND METHODS

We searched the pathologic records of our institution from December 1999 to April 2002, and included 16 patients with hepatocellular carcinoma (N = 14), large regenerative nodule (N = 1), and dysplastic nodule (N = 1) who underwent orthotopic liver transplantation (10 patients) or partial hepatectomy (six patients) and MR imaging within an interval of two weeks. The MR images were retrospectively assessed qualitatively and quantitatively. Angiogenetic activity of the hepatic nodules was evaluated by means of immunohistochemical study for VEGF. Analysis of variance and the Scheffé criterion were used for statistical evaluation.

RESULTS

Hepatic nodules with moderate to strong immunoreactivity for VEGF showed higher signal intensity on T1-weighted images (P < 0.05) and those with intense immunoreactivity for VEGF showed higher signal intensity on T2-weighted images (P < 0.05). No correlation was found between the immunoreactivity for VEGF and tumor vascularity on postcontrast early- and late-phase images.

CONCLUSION

Our current results suggest that signal intensity on unenhanced T1- and T2-weighted MR images may correlate with immunoreactivity for VEGF. Correlation was not found between immunoreactivity for VEGF and signal intensity on gadolinium-enhanced MR images.

Impact of large regenerative, low grade and high grade dysplastic nodules in hepatocellular carcinoma development

BACKGROUND/AIMS

The natural outcome of ultrasound-detected macronodules in cirrhosis is still poorly understood. In this study we assessed the incidence and predictors of malignant transformation in a prospective study of 90 consecutive ultrasound-detected macronodules in cirrhosis.

METHODS

Macronodules classification was based on recently proposed histological criteria. Extranodular large (LCC) and small cell changes were also evaluated. The follow-up included ultrasound and serum alfa-fetoprotein determination every 3 months. Independent predictors of hepatocellular carcinoma were evaluated by Cox proportional hazards regression analysis.

RESULTS

During a mean follow-up of 33 months, 28 (31%) nodules transformed into hepatocellular carcinoma. The incidence of hepatocellular carcinoma per 100 person-years of follow-up was 11.3%, with a malignant transformation rate of 3.5, 15.5, 31 and 48.5% at 1, 2, 3, and 5 years respectively. High-grade dysplastic nodules (HGDN) (hazard risk=2.4; CI 95%=1.1-5.0) and LCC (hazard risk=3.1; CI 95%=1.2-7.8) were independent predictors of malignant transformation. Eight additional hepatocellular carcinomas developed outside the original lesions raising the overall malignant transformation rate to 40% while 15 macronodules (17%) became undetectable at ultrasound (US).

CONCLUSIONS

Macronodules characterize a cirrhotic subpopulation with high risk of hepatocellular carcinoma. HGDN and LCC are strong predictors of malignant transformation; subjects with simultaneous presence of both these two conditions are at highest risk of cancer development. The management of cirrhotics with macronodules should be based on morphologic features detected on liver microsamples.

Nondysplastic nodules that are hyperintense on T1-weighted gradient-echo MR imaging: frequency in cirrhotic patients undergoing transplantation

OBJECTIVE

Our objective was to determine the frequency and MR imaging findings of nondysplastic nodules that are hyperintense on T1-weighted gradient-echo imaging in patients with cirrhosis who undergo liver transplantation.

MATERIALS AND METHODS

Two observers retrospectively evaluated in-phase (4-5 msec), opposed-phase gradient-echo (2.0-2.4 msec), and turbo short tau inversion recovery (STIR) MR images in 68 patients with cirrhosis--but without dysplastic nodules or hepatocellular carcinoma--who underwent MR imaging at 1.5 T within 150 days before liver transplantation. The size, number, signal characteristics, and arterial enhancement pattern of nodules that appear hyperintense on T1-weighted gradient-echo images were evaluated as well as the presence or absence of signal loss on opposed-phase imaging. These imaging findings were correlated with pathologic findings of whole explanted livers.

RESULTS

Eleven (16%) of 68 patients had at least one nondysplastic nodule that was hyperintense on T1-weighted MR imaging. Three patients had diffuse nondysplastic hyperintense nodules (>10 nodules) measuring less than 0.5 cm, and the remaining eight patients had 22 nondysplastic hyperintense nodules ranging in size from 0.5 to 2.5 cm (mean, 1.2 cm), of which 13 were isointense and nine were hypointense on turbo STIR images. No lesion lost signal on opposed-phase imaging or enhanced during the hepatic arterial phase.

CONCLUSION

In cirrhotic patients undergoing liver transplantation, nondysplastic nodules that are hyperintense are common findings on T1-weighted gradient-echo MR imaging and do not lose signal intensity on opposed-phase imaging or enhance during the hepatic arterial phase. These nodules may be indistinguishable from dysplastic nodules.

Developing a prediction rule to assess hepatic malignancy in patients with cirrhosis

OBJECTIVE

The objectives of our study were to identify independent clinical, demographic, and MR imaging correlates of malignancy in patients with cirrhosis and to develop a predictive model based on identified correlates of malignancy.

MATERIALS AND METHODS

Sixty examinations of 58 patients with biopsy proof of lesions suggestive of hepatocellular carcinoma on MR imaging were retrospectively reviewed. The signal intensity of the lesion on T2-weighted imaging and dynamic gadolinium-enhanced imaging, the size of the lesion, and the number of suspicious lesions were recorded; in addition, patient age and sex, alpha-fetoprotein level, and hepatitis C viral genotype were noted. The association between malignancy and each predictor variable was evaluated using the chi-square test or the two-group t test. The final logistic regression model included the variables that were shown to have a significant association with malignancy and the clinically relevant predictors. We used the adjusted odds ratios to measure the strength of each association. The discriminant ability of the model for detecting hepatic malignancy was assessed using receiver operating characteristic curve analysis.

RESULTS

The prevalence of hepatic malignancy in our study population was 64%. The area under the receiver operating characteristic curve for the logistic regression model was 0.82. Venous washout (odds ratio = 9.2), alpha-fetoprotein level (odds ratio = 3.2), and number of lesions (odds ratio = 1.5) were significant predictors for malignancy (p < 0.05). When arterial enhancement and venous washout were either both present or both absent, alpha-fetoprotein level contributed little to the prediction of malignancy.

CONCLUSION

The MR characteristics of hepatic lesions during the dynamic venous phase in conjunction with the serum alpha-fetoprotein level and number of lesions are predictors of hepatic malignancy. The use of these predictors can facilitate explicit estimation of malignancy in individuals with underlying cirrhosis, potentially improving clinical decision-making.

Hepatocellular carcinoma in cirrhotic livers: double-contrast thin-section MR imaging with pathologic correlation of explanted tissue

OBJECTIVE

The aim of our study was to determine the sensitivity of double-contrast MR imaging in the detection of hepatocellular carcinomas in patients with a cirrhotic liver.

SUBJECTS AND METHODS

Thirty-one patients underwent double-contrast MR imaging and subsequent liver transplantation. Breath-hold T1- and T2-weighted MR images were obtained before and after administration of superparamagnetic iron oxide, and three-dimensional T1-weighted gradient-recalled echo MR images were obtained 10, 40, and 120 sec after a bolus injection of gadolinium. Hypervascular lesions that failed to take up superparamagnetic iron oxide were regarded as showing typical characteristics of hepatocellular carcinoma; lesions that had only one of these two characteristics (either hypervascularity or failure to take up superparamagnetic iron oxide) were regarded as highly suspicious for hepatocellular carcinoma. Radiology reports were correlated with pathology reports for the explanted livers.

RESULTS

Thirty-two hepatocellular carcinomas were found in 14 of the 31 patients. Combining the number of MR imaging reports citing lesions that were "typical of hepatocellular carcinoma" with the number of those citing lesions that were "highly suspicious," we found that for 25 of 32 lesions, an accurate MR imaging diagnosis of hepatocellular carcinoma was made (overall sensitivity, 78%). These lesions included 10 of the 11 lesions that were larger than 20 mm (sensitivity, 91%), 12 of the 13 lesions that were 11-20 mm (sensitivity, 92%), and three of the eight lesions that were 10 mm or less (sensitivity, 38%). Nineteen (76%) of 25 lesions had characteristics considered typical of hepatocellular carcinoma; the remaining six lesions either failed to take up superparamagnetic iron oxide and were hypovascular or were hypervascular but showed some uptake of superparamagnetic iron oxide.

CONCLUSION

In patients with a cirrhotic liver, double-contrast MR imaging is highly sensitive in the diagnosis of hepatocellular carcinomas of 10 mm or larger, but success in the identification of tumors smaller than 10 mm is still limited.

Assessment of cancer cell differentiation in small hepatocellular carcinoma by computed tomography and magnetic resonance imaging

AIM

To study whether cancer cell differentiation in small hepatocellular carcinoma (HCC) can be assessed by computed tomography (CT) and magnetic resonance (MR) imaging.

METHODS

We retrospectively evaluated the relationship between cancer cell differentiation in 127 HCC 3 cm or less in diameter (113 patients) and CT and MR images. Images were reviewed in a consensus conference by three authors (SA, TY, and ME). Histopathological diagnosis of HCC was made from liver specimens obtained by sonographically guided biopsy.

RESULTS

The degree of histological differentiation of cancer cells was significantly different between HCC that were isodense with liver parenchyma in both artery-dominant and equilibrium phases in contrast-enhanced CT and tumors that were hyperdense in the artery-dominant phase and iso- or hypodense in the equilibrium phase (P = 0.0054), as well as tumors that were iso- or hypodense artery-dominant and hypodense equilibrium (P = 0.0002). Histological differentiation of lesions that were hyperintense in T1-weighted images and hypointense in T2-weighted images differed significantly from those with the opposite MR characteristics (P = 0.0122). In T1-weighted fat-suppression images and T2-weighted images, respectively, the degree of histological differentiation was significant between the hypointense/hyperintense and the hyperintense/hypointense patterns (P < 0.0001), as well as the hyperintense/isointense (P = 0.0296), the hyperintense/hyperintense (P = 0.0434), and the isointense/hyperintense (P = 0.0171). Using these differences an equation was developed that could determine with 76% accuracy whether the tumors were well or less-well differentiated.

CONCLUSION

CT and MR imaging patterns were useful in predicting the degree of histological differentiation of cancer cells in HCC.

Selective approach to major hepatic resection for hepatocellular carcinoma in chronic liver disease

For large HCCs, partial liver resection remains the best therapeutic option for cure because neither liver transplantation nor percutaneous treatments are indicated. In specialized centers, a better selection of at-risk patients and technical procedures, including the use of intermittent inflow occlusion and the anterior approach, have contributed to improve dramatically the outcome of major liver resection for HCC in CLD. In addition, portal vein embolization has become an important tool to hypertrophy the future liver remnant before major liver resection in cirrhotic patients with apparently normal liver function.

MnDPDP enhanced magnetic resonance imaging of focal liver lesions

Mangafodipir trisodium (MnDPDP) is a contrast agent for use in magnetic resonance imaging (MRI) of the liver. The agent is taken up by normal hepatocytes resulting in increased signal on T1-weighted imaging, and is excreted in the biliary system. Hepatocyte-containing liver neoplasms such as hepatomas or focal nodular hyperplasia (FNH), take up MnDPDP and demonstrate varying degrees of enhancement. Metastatic liver deposits and primary liver tumours of non-hepatocyte origin do not typically enhance with MnDPDP thus increasing their conspicuity compared with pre-contrast T1-weighted images. Metastases may demonstrate rim enhancement particularly on delayed imaging at 24 h, which can increase their conspicuity, thus allowing better visualization of small lesions. Functional biliary obstruction due to liver metastases can also result in wedge shaped areas of parenchymal enhancement. The MRI features of various focal liver after continuance with lesions following MnDPDP are discussed and illustrated including primary lesions such as hepatoma and secondary metastases.

Transplantation for hepatocellular carcinoma and cirrhosis: sensitivity of magnetic resonance imaging

The sensitivity of magnetic resonance imaging (MRI) in patients who undergo transplantation for hepatocellular carcinoma (HCC) and cirrhosis is not known. We prospectively evaluated 24 patients with known HCC who underwent MRI and subsequent transplantation within 60 days (mean, 20 days). Using a phased-array coil at 1.5T, breath-hold turbo STIR and T2-weighted MR images were performed. Dynamic gadolinium-enhanced MRI was performed using a two- or three-dimensional gradient echo pulse sequence with images obtained in the hepatic arterial, portal venous, and equilibrium phases. The prospective interpretation of the MR study was directly compared with thin-section pathology evaluation of the explanted livers. All 24 patients had at least one HCC, and MR diagnosed tumor in 21 (88%) of these patients. On a lesion-by-lesion basis, MRI depicted 39 of 118 HCC for an overall sensitivity of 33%. MRI detected five (100%) of five lesions >5 cm, 20 (100%) of 20 lesions >2 cm but not exceeding 5 cm, 11 (52%) of 21 lesions between 1 and 2 cm, and three (4%) of 72 lesions <1 cm. Of the nine patients with carcinomatosis (innumerable lesions less than 1 cm), MR detected three lesions in one patient. Of the 15 dysplastic nodules found at pathology, MRI depicted a single 1.8-cm high-grade lesion, for a sensitivity of 7%. In conclusion, MRI is sensitive for the detection of HCC measuring at least 2 cm in diameter but is insensitive for the diagnosis of small HCC (<2 cm) and carcinomatosis.

Benign versus malignant hepatic nodules: MR imaging findings with pathologic correlation

According to the currently used nomenclature, there are only two types of hepatocellular nodular lesions: regenerative lesions and dysplastic or neoplastic lesions. Regenerative nodules include monoacinar regenerative nodules, multiacinar regenerative nodules, cirrhotic nodules, segmental or lobar hyperplasia, and focal nodular hyperplasia. Dysplastic or neoplastic nodules include hepatocellular adenoma, dysplastic foci, dysplastic nodules, and hepatocellular carcinoma (HCC). Many of these types of hepatic nodules play a role in the de novo and stepwise carcinogenesis of HCC, which comprises the following steps: regenerative nodule, low-grade dysplastic nodule, high-grade dysplastic nodule, small HCC, and large HCC. State-of-the-art magnetic resonance (MR) imaging facilitates detection and characterization in most cases of hepatic nodules. State-of-the-art MR imaging includes single-shot fast spin-echo imaging, in-phase and opposed-phase T1-weighted gradient-echo imaging, T2-weighted fast spin-echo imaging with fat saturation, and two-dimensional or three-dimensional dynamic multiphase contrast material-enhanced imaging.

Hepatocellular carcinoma: predisposing conditions and precursor lesions

The global incidence of HCC is rising; in the United States, its rise is in parallel to that of cirrhosis due to the HCV and obesity epidemics. The lack of adequate treatment for advanced HCC mandates both prevention and early detection of these lesions. The limitations of currently available histopathologic evaluations, serologic markers, and radiographic imaging modalities in detecting HCC and its precursors have been outlined in this review. Refinements of all of these may lead to better HCC detection, earlier intervention, and successful treatment. Randomized controlled trials are necessary to evaluate the most efficacious and cost-effective approach to screening.

Small (<20 mm) enhancing hepatic nodules seen on arterial phase MR imaging of the cirrhotic liver: clinical implications

OBJECTIVE

To determine the significance in patients with cirrhosis of small (<20 mm) hepatic nodules that show no hyperintensity on T2-weighted MR images but that enhance during arterial phase MR imaging, we reviewed the cases of patients with such nodules.

MATERIALS AND METHODS

Our review of radiology reports yielded 68 nodules in 40 patients with cirrhosis that showed no hyperintensity on T2-weighted MR images but had rapid enhancement during arterial phase MR imaging after administration of a gadolinium contrast agent. Thirty-four patients (60 nodules) had multiple follow-up MR imaging examinations (range of length of follow-up, 1-72 months; average length of follow-up, 15 months 2 weeks). The final diagnosis of the nodule was determined by pathology reports or after at least 2 years of follow-up to ensure nodule stability and, therefore, benignity. Two radiologists independently reviewed MR images of the nodules, noting the size, signal intensity on T1- or T2-weighted images, and homogeneity of contrast enhancement.

RESULTS

Nine (13%) of the 68 nodules were hepatocellular carcinomas (HCCs). The size of nodules on the first MR examination was between 4 and 20 mm (mean size, 9.5 mm). No significant correlation between the diagnosis of HCC and nodule signal intensity (p = 0.48) or contrast enhancement homogeneity (p = 0.56) on first MR examination was found. Positive predictive value (PPV) and negative predictive value (NPV) for diagnosing HCC on the basis of nodule growth were 100% and 98%, respectively. For diagnosing HCC on the basis of a change in nodule signal intensity, the PPV was 60% and the NPV was 91%. For diagnosing HCC on the basis of a change of enhancement homogeneity, the PPV was 63%, and the NPV was 94%.

CONCLUSION

A finding of growth in small, early-enhancing nodules in patients with cirrhosis is highly predictive of HCC. When small nodules are observed on a single examination, close follow-up of the patient appears appropriate.

Contrast agents for hepatic magnetic resonance imaging

The current availability of liver-specific contrast media (LSCM) allows the possibility to obtain an accurate diagnosis when studying focal liver lesions (FLL). It is necessary to have an in-depth knowledge of the biologic and histologic characteristics of FLL and the enhancement mechanism of LSCM to gain significant accuracy in the differential diagnosis of FLL. It is possible to subdivide FLL into three main groups according to the kinetics of contrast enhancement: hypervascular FLL, hypovascular FLL, and FLL with delayed enhancement. Dynamic contrast-enhanced magnetic resonance imaging is an important tool in the identification and characterization of FLL. LSCM with a first phase of extracellular distribution give both dynamic (morphologic) and late phase (functional) information useful for lesion characterization. With LSCM it is possible to differentiate with high accuracy benign from malignant lesions and hepatocellular from nonhepatocellular lesions. To understand contrast behavior after injection of LSCM, it is necessary to correlate contrast enhancement with the biologic and histologic findings of FLL.

Low-grade siderotic dysplastic nodules: determination of premalignant lesions on the basis of vasculature phenotype

RATIONALE AND OBJECTIVES

The authors performed this study to determine whether, on the basis of the vascular profile, low-grade siderotic dysplastic nodules are premalignant lesions.

MATERIALS AND METHODS

The authors used a monoclonal antibody specific for smooth muscle actin to stain 18 siderotic low-grade dysplastic nodules (mean size, 0.7 cm) from nine patients. Two pathologists counted the number of unpaired arteries per high-power field in siderotic dysplastic nodules and background siderotic regenerative nodules by using two techniques (conventional and hot spot).

RESULTS

The number of unpaired arteries seen with the conventional counting technique in low-grade siderotic dysplastic nodules (range, 1-14; mean, 3.8) was significantly greater (P = .004) than that seen in background siderotic regenerative nodules (range, 0-3; mean, 1.2). Similarly, the number of unpaired arteries seen with the hot spot technique in low-grade siderotic dysplastic nodules (range, 0-14; mean, 5.2) was significantly greater (P = .005) than that seen in background siderotic regenerative nodules (range, 0-6; mean, 1.9).

CONCLUSION

On the basis of the vascular profile, low-grade siderotic dysplastic nodules should be considered premalignant lesions. Further research is needed to help differentiate these lesions from siderotic regenerative nodules with magnetic resonance imaging.

Magnetic resonance imaging techniques

In this article we describe state-of-the art techniques for magnetic resonance imaging of the liver. T1-weighted, T2-weighted, and heavily T2-weighted pulse sequences are discussed. Gadolinium-enhanced hepatic parenchymal imaging and magnetic resonance angiography are also described. A comprehensive MR imaging examination of the liver affords evaluation of focal and diffuse hepatic parenchymal disease, biliary disease, and vascular pathology.

MR imaging of hepatocellular carcinoma

In this article, MR imaging features of hepatocellular carcinoma (HCC) are described. To better understand the MR imaging features of HCC, recent progress regarding its etiology, treatment, carcinogenesis, histology, and gross pathology will be described. Currently, T2-weighted fast spin-echo with fat saturation, and multiphasic dynamic gadolinium-enhanced two-dimensional and three-dimensional T1-weighted gradient echo imaging provides excellent results for detection and characterization of HCC.

MR contrast agents in hepatic cirrhosis and chronic hepatitis

Chronic liver disease alters the gross architecture of the liver and its arterial and portal blood supply. The relative proportion of regenerative hepatocytes, necrosis, extracellular interstitial space, and fibrosis is responsible for liver enhancement after the administration of a contrast agent. Because contrast agents can be directed toward either the extracellular or the intracellular spaces, knowledge of the different parenchymal enhancement alterations seen after the administration of these agents is necessary to understand how chronic liver disease pathologic changes influence contrast-enhanced magnetic resonance (MR) images. This article reviews the effect of chronic liver disease on MR contrast enhancement, as well as the effect of altered enhancement on lesion detection and characterization. Both extracellular and intracellular contrast agents are considered.

Magnetic resonance of focal liver lesions in hepatic cirrhosis and chronic hepatitis

Detection of focal liver nodules in patients with cirrhosis continues to be a radiologic challenge despite progressive advances in liver imaging in the past 2 decades. Patients with hepatic cirrhosis have a high predisposition to develop hepatocellular carcinoma (HCC), and the early detection and diagnosis of this tumor is very important because the most effective treatment is surgical resection, transplantation, or local ablation therapy when the tumor is small. Cirrhotic livers are mainly composed of fibrosis, together with a broad spectrum of focal nodular lesions ranging from regenerative nodules to premalignant dysplastic nodules to overt HCC. Awareness of such lesions and interpretation of imaging studies in these patients requires a critical review to detect subtle tumors, and a thorough understanding of the imaging appearance of the malignant and benign masses that can occur in the cirrhotic liver. Although the recent advances in liver imaging techniques, especially computed tomography (CT) and magnetic resonance (MR), have facilitated the detection and characterization of focal liver nodules in cirrhotic patients, discriminating between HCC and precancerous nodules remains problematic with all available imaging techniques. Nevertheless, MR imaging appears to have more potential than other imaging techniques in the study of cirrhotic patients and MR may be more appropriate than the other imaging modalities for the detection of small HCCs. In this article we review the imaging characteristics of nodular focal lesions that arise in cirrhotic livers, with special attention to MR imaging features.

Detection of nodules in liver cirrhosis: spiral computed tomography or magnetic resonance imaging? A prospective study of 88 nodules in 34 patients

Detection and characterization of all focal lesions in the liver are critical for screening patients with chronic liver disease. The aim of this prospective study was to investigate the accuracy of magnetic resonance imaging (MRI) and spiral computed tomography for the diagnosis of hepatic nodules in cirrhotic patients when compared with pathological findings of the explanted liver. From February 1997 to July 1999, 34 cirrhotic patients waiting for orthotopic liver transplantation (OLT) (mean age, 53.5 +/- 9.3 years; 24 males) were included. All patients had MRI and spiral computed tomography examinations, and findings were matched with the histological findings. Data analyses were made using the McNemar chi-square test. Mean time between radiological examination (MRI or spiral computed tomography) and OLT was 43.8 +/- 39 days. A total of 88 nodules were found in the 34 patients: 54 hepatocellular carcinoma (HCC) (mean size, 18 +/- 10 mm) in 21 patients, 22 dysplastic nodules (mean size, 10.7 +/- 4.3 mm) in 11 patients, and 12 macroregenerative nodules in 13 patients. Lesion-by-lesion analyses showed that sensitivity of MRI and spiral computed tomography for nodule, HCC or dysplastic nodule diagnosis was 44.3 and 31.8% (P = 0.02), 61.1 and 51.9% (P = 0.2), and 27.3 and 0% (P = 0.04), respectively. Patient-by-patient analyses showed no statistical difference between spiral computed tomography and MRI for nodule diagnosis. In conclusion, in patients with liver cirrhosis, MRI is more accurate than spiral computed tomography for the detection of liver nodules and dysplastic nodules. However, tumour size is always a restricting factor for these two techniques, which are unable to detect small HCC in more than 60% of cases.

Radiology in liver transplantation

Imaging studies are becoming essential in the management of orthotopic liver transplantation (LT). They have a very important role in the preoperative evaluation and selection of suitable candidates. At the same time, they are essential in the early detection of postoperative complications, the recognition of which allows the prompt institution of appropriate therapeutic measures. Timely recognition of complications improves the success of LT; furthermore, some complications can be treated with interventional radiologic procedures, avoiding additional surgery. This article reviews the current application of diagnostic and interventional imaging in liver transplantation, both for cadaveric and living donor transplants.