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

T1 relaxation: Chemo-physical fundamentals of magnetic resonance imaging and clinical applications

A knowledge of the complex phenomena that regulate T1 signal on Magnetic Resonance Imaging is essential in clinical practice for a more effective characterization of pathological processes. The authors review the physical basis of T1 Relaxation Time and the fundamental aspects of physics and chemistry that can influence this parameter. The main substances (water, fat, macromolecules, methemoglobin, melanin, Gadolinium, calcium) that influence T1 and the different MRI acquisition techniques that can be applied to enhance their presence in diagnostic images are then evaluated. An extensive case illustration of the different phenomena and techniques in the areas of CNS, abdomino-pelvic, and osteoarticular pathology is also proposed. CRITICAL RELEVANCE STATEMENT: T1 relaxation time is strongly influenced by numerous factors related to tissue characteristics and the presence in the context of the lesions of some specific substances. An examination of these phenomena with extensive MRI exemplification is reported. KEY POINTS: The purpose of the paper is to illustrate the chemical-physical basis of T1 Relaxation Time. MRI methods in accordance with the various clinical indications are listed. Several examples of clinical application in abdominopelvic and CNS pathology are reported.

Liver Lesions at Risk of Transformation into Hepatocellular Carcinoma in Cirrhotic Patients: Hepatobiliary Phase Hypointense Nodules without Arterial Phase Hyperenhancement

Recent technical advances in liver imaging and surveillance for patients at high risk for developing hepatocellular carcinoma (HCC) have led to an increase in the detection of borderline hepatic nodules in the gray area of multistep carcinogenesis, particularly in those that are hypointense at the hepatobiliary phase (HBP) and do not show arterial phase hyperenhancement. Given their potential to transform and advance into hypervascular HCC, these nodules have progressively attracted the interest of the scientific community. To date, however, no shared guidelines have been established for the decision management of these borderline hepatic nodules. It is therefore extremely important to identify features that indicate the malignant potential of these nodules and the likelihood of vascularization. In fact, a more complete knowledge of their history and evolution would allow outlining shared guidelines for their clinical-surgical management, to implement early treatment programs and decide between a preventive curative treatment or a watchful follow-up. This review aims to summarize the current knowledge on hepatic borderline nodules, particularly focusing on those imaging features which are hypothetically correlated with their malignant evolution, and to discuss current guidelines and ongoing management in clinical practice.

Magnetism of materials: theory and practice in magnetic resonance imaging

All substances exert magnetic properties in some extent when placed in an external magnetic field. Magnetic susceptibility represents a measure of the magnitude of magnetization of a certain substance when the external magnetic field is applied. Depending on the tendency to be repelled or attracted by the magnetic field and in the latter case on the magnitude of this effect, materials can be classified as diamagnetic or paramagnetic, superparamagnetic and ferromagnetic, respectively. Knowledge of type and extent of susceptibility of common endogenous and exogenous substances and how their magnetic properties affect the conventional sequences used in magnetic resonance imaging (MRI) can help recognize them and exalt or minimize their presence in the acquired images, so as to improve diagnosis in a wide variety of benign and malignant diseases. Furthermore, in the context of diamagnetic susceptibility, chemical shift imaging enables to assess the intra-voxel ratio between water and fat content, analyzing the tissue composition of various organs and allowing a precise fat quantification. The following article reviews the fundamental physical principles of magnetic susceptibility and examines the magnetic properties of the principal endogenous and exogenous substances of interest in MRI, providing potential through representative cases for improved diagnosis in daily clinical routine.

Utility of endoscopic ultrasound and endoscopy in diagnosis and management of hepatocellular carcinoma and its complications: What does endoscopic ultrasonography offer above and beyond conventional cross-sectional imaging?

Hepatocellular carcinoma constitutes over 90% of the primary liver tumors, the rest being cholangiocarcinoma. It has an insidious presentation, which is responsible for the delayed presentation. Hence, the management strategy relies on screening to diagnose it an early stage for curative resection and/or treatment with local ablative techniques or chemotherapy. However, even with different screening programs, more than 60% of tumors are still detected at an advanced stage, leading to an unchanged mortality rate, thereby implying a room for improvement in the screening and diagnostic process. In the last few years, there has been evolution of utility of endoscopy, specifically endoscopic ultrasonography along with Fine needle aspiration, for this purpose, which we comprehensively review in this article.

Magnetic resonance imaging of the cirrhotic liver: diagnosis of hepatocellular carcinoma and evaluation of response to treatment - Part 1

Magnetic resonance imaging (MRI) is the modern gold standard for the noninvasive evaluation of the cirrhotic liver. The combination of arterial phase hyperenhancement and delayed wash-out allows a definitive diagnosis of hepatocellular carcinoma (HCC) in patients with liver cirrhosis or chronic liver disease, without the requirement for confirmatory biopsy. That pattern is highly specific and has been endorsed in Western and Asian diagnostic guidelines. However, the sensitivity of the combination is relatively low for small HCCs. In this two-part review paper, we will address MRI of the cirrhotic liver. In this first part, we provide a brief background on liver cirrhosis and HCC, followed by descriptions of imaging surveillance of liver cirrhosis and the diagnostic performance of the different imaging modalities used in clinical settings. We then describe some of the requirements for the basic MRI technique, as well as the standard MRI protocol, and provide a detailed description of the appearance of various types of hepatocellular nodules encountered in the setting of the carcinogenic pathway in the cirrhotic liver, ranging from regenerative nodules to HCC.

Bone Metastases of Hepatocellular Carcinoma: Appearance on MRI Using a Standard Abdominal Protocol

OBJECTIVE

The purpose of this study is to describe the MRI features of hepatocellular carcinoma (HCC) bone metastases.

MATERIALS AND METHODS

Thirty-three consecutive patients were included. Two radiologists performed qualitative and quantitative analysis. The coordinator searched for clinical and epidemiologic features related to patients and their primary liver tumors. Earlier MRI studies were also reviewed to determine whether bone metastases were already present and prospectively identified. Descriptive statistics and the Lin concordance correlation coefficient were used.

RESULTS

Chronic hepatitis C virus infection was the most common cause of liver disease (20/32; 62.5%), and diffuse and multifocal HCC were the most frequent types of liver HCCs (28/33; 84.8%). Most lesions were located at the spine (109/155; 70.3%), with high signal intensity on fat-suppressed T1-weighted (54/62; 87.1%) and T2-weighted (53/62; 85.5%) images. Bone metastases were predominantly nodular (48/62; 77.4%), confined to the vertebral body (40/60; 66.7%), and best visualized at the arterial phase (40/62; 64.5%). The ring pattern of enhancement was present in 23 of 62 lesions, and the remaining lesions showed diffuse enhancement. Thirty-five of 62 (56.4%) bone metastases showed arterial peak of enhancement. In 13 of 33 (39.9%) patients, bone metastases were not prospectively reported.

CONCLUSION

Most patients with bone metastases had chronic hepatitis C virus infection and diffuse or multifocal HCC. Metastases are most commonly appreciated as hypervascular focal moderately intensely enhancing nodular masses on the hepatic arterial dominant phase images, with concomitant moderately high signal intensity on fat-suppressed T1- and T2-weighted images.

Hypovascular hypointense nodules on hepatobiliary phase without T2 hyperintensity on gadoxetic acid-enhanced MR images in patients with chronic liver disease: long-term outcomes and risk factors for hypervascular transformation

PURPOSE

To evaluate the long-term outcomes and imaging features associated with hypervascularization of hypovascular nodules that show T2 iso-/hypointensity and hypointensity on hepatobiliary phase (HBP) of gadoxetic acid-enhanced magnetic resonance (MR) images in patients with chronic liver disease.

MATERIALS AND METHODS

Sixty patients and 114 nodules, which were hypovascular and iso-/hypointense on T2-weighted images and hypointense on HBP of gadoxetic acid-enhanced MRI, were included. We evaluated the effect of baseline clinical features, baseline MR features and growth rate on subsequent hypervascularization.

RESULTS

Twenty-seven nodules in 21 patients transformed to hypervascular hepatocellular carcinoma (HCC). Using multivariate Cox analysis, T1 hyperintensity (hazard ratio [HR] = 2.69, P = 0.021), previous history of HCC (HR = 2.64, P = 0.021), and initial nodule size (HR = 1.09, P = 0.046) were identified to be associated with hypervascularization. The growth rate of nodules was a more powerful determinant of subsequent hypervascularization than baseline clinical and MR features. At long-term follow-up after >3 years, only one nodule with T1 isointensity showed hypervascularization.

CONCLUSION

Careful follow-up or diagnostic procedures, such as biopsy, should be considered for up to 3 years after detection of hypointense nodules on HBP with T1 hyperintensity or a higher growth rate.

KEY POINTS

• T1 hyperintensity is a baseline MR predictive factor for subsequent hypervascularization. • A higher growth rate is a more powerful determinant of subsequent hypervascularization. • Management of patients with these predictive factors requires more attention.

Magnetic resonance imaging of the cirrhotic liver: An update

Noninvasive imaging has become the standard for hepatocellular carcinoma (HCC) diagnosis in cirrhotic livers. In this review paper, we go over the basics of MR imaging in cirrhotic livers and describe the imaging appearance of a spectrum of hepatic nodules marking the progression from regenerative nodules to low- and high-grade dysplastic nodules, and ultimately to HCCs. We detail and illustrate the typical imaging appearances of different types of HCC including focal, multi-focal, massive, diffuse/infiltrative, and intra-hepatic metastases; with emphasis on the diagnostic value of MR in imaging these lesions. We also shed some light on liver imaging reporting and data system, and the role of different magnetic resonance imaging (MRI) contrast agents and future MRI techniques including the use of advanced MR pulse sequences and utilization of hepatocyte-specific MRI contrast agents, and how they might contribute to improving the diagnostic performance of MRI in early stage HCC diagnosis.

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

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

Magnetic resonance imaging in cirrhosis: what's new?

Cirrhosis is the main risk factor for the development of hepatocellular carcinoma (HCC). The major causative factors of cirrhosis in the United States and Europe are chronic hepatitis C infection and excessive alcohol consumption with nonalcoholic steatohepatitis emerging as another important risk factor. Magnetic resonance imaging is the most sensitive imaging technique for the diagnosis of HCC, and the sensitivity can be further improved with the use of diffusion-weighted imaging and hepatocyte-specific contrast agents. The combination of arterial phase hyperenhancement, venous or delayed phase hypointensity "washout feature," and capsular enhancement are features highly specific for HCC with reported specificities of 96% and higher. When these features are present in a mass in the cirrhotic liver, confirmatory biopsy to establish the diagnosis of HCC is not necessary. Other tumors, such as cholangiocarcinoma, sometimes occur in the cirrhotic at a much lower rate than HCC and can mimic HCC, as do other benign lesions such as perfusion abnormalities. In this article, we discuss the imaging features of cirrhosis and HCC, the role of magnetic resonance imaging in the diagnosis of HCC and other benign and malignant lesions that occur in the cirrhotic liver, and the issue of nonspecific arterially hyperenhancing nodules often seen in cirrhosis.

Imaging of hepatocellular carcinoma: current concepts

Hepatocellular carcinoma (HCC) is the most common primary hepatic malignancy, and usually develops in the setting of liver cirrhosis. The early diagnosis of HCC is essential as curative treatment (including surgical resection and liver transplantation) improves survival. While screening and surveillance are traditionally performed with ultrasound, reported accuracies of ultrasound vary greatly, and poor sensitivity for small nodules is a uniformly recognized concern. Advances in computed tomography (CT) and magnetic resonance imaging (MRI), including multidetector technology and fast breath hold sequences now allow dynamic multiphasic enhanced imaging of the liver with excellent spatial and temporal resolution, holding much promise for improved HCC detection.

Characterization of hyperintense nodules on precontrast T1-weighted MRI: utility of gadoxetic acid-enhanced hepatocyte-phase imaging

PURPOSE

To evaluate the utility of gadoxetic acid-enhanced hepatocyte-phase magnetic resonance imaging (MRI) in characterization of T1-weighted hyperintense nodules within cirrhotic liver.

MATERIALS AND METHODS

This retrospective study was approved by our Institutional Review Board. Thirty-four nodules hyperintense in unenhanced T1-weighted MRI with histopathological confirmation from a collection of 19 patients were included. Tumor size, signal intensity on T1-weighted, and T2-weighted imaging as well as enhancement patterns on contrast-enhanced dynamic/hepatocyte-phase imaging were recorded. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic performance of hepatocyte-phase imaging.

RESULTS

Evaluation of the nodules with standard of reference revealed 15 dysplastic nodules (DN), seven well-differentiated hepatocellular carcinomas (wHCC), and 12 moderately differentiated HCCs (mHCC). The mean size of dysplastic nodules was smaller than that of HCCs (P < 0.001). Using the HCC criteria (T2W or arterial enhancement followed with portal venous washout), 11/19 HCC were correctly characterized. Using solely hypointensity (compared to the surrounding liver parenchyma) during the hepatocyte phase as the criterion, 18/19 HCC were correctly characterized. There were seven additional HCCs diagnosed with hepatocyte-phase imaging (P = 0.02).

CONCLUSION

Gadoxetic acid-enhanced MRI with hepatocyte-phase imaging is superior to gadoxetic acid-enhanced MRI with conventional criteria alone in characterization of T1W hyperintense nodules.

MR imaging of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common malignancy typically associated with chronic liver disease and is a leading cause of mortality among these patients. Prognosis is improved when detected early. MRI is the best imaging examination for accurate diagnosis. Although arterial enhancement with delayed washout, increased T2-weighted signal intensity, delayed capsular enhancement, restricted diffusion, and tumor thrombus are typical features, not all lesions demonstrate these findings. The radiologist must be familiar with these typical imaging characteristics, and less common appearances and associated findings of HCC, and must be able to differentiate them from those of lesions that mimic HCC. Knowledge of therapeutic options and how those are related to imaging findings is imperative to assist clinicians in managing these patients.

Focal liver lesions hyperintense on T1-weighted magnetic resonance images

This article reviews focal liver lesions hyperintense on T1-weighted magnetic resonance (MR) images and describes the underlying etiologies associated with their T1 signal intensity. Although focal liver lesions are commonly detected because of their iso- or hypointensity on T1-weighted images, lesions (benign or malignant) may present with T1 hyperintensity when they contain T1 shortening elements--such as fat, hemorrhage, copper, melanin, and highly concentrated proteins. Our discussion includes the description of state-of-the-art T1-weighted MR sequences and the imaging features of lesions on pre- and postcontrast MR images that are characteristic for lesion composition and useful for making accurate diagnosis.

Large (>or=2 cm) non-hypervascular nodules depicted on MRI in the cirrhotic liver: fate and implications

AIM

To determine the fate and clinical implication of large (>or=2 cm), non-hypervascular nodules depicted on magnetic resonance imaging (MRI) in the cirrhotic liver.

MATERIALS AND METHODS

In 21 patients with cirrhosis (14 hepatitis B, two ethanol abuse, four cryptogenic, one Wilson's disease), 25 large (>or=2 cm in the longest dimension) non-hypervascular nodules were identified on dynamic MRI. The implications for diagnosis of the initial size, contour, and signal characteristics on MRI in addition to patients' age and cause of cirrhosis were assessed in our analysis.

RESULTS

Twelve (75%) out of 16 lesions were malignant or potentially-malignant from 14 hepatitis B patients, while seven (78%) of the nine lesions from other patients were benign (p=0.016). The mean age of the patients who had malignant or potentially malignant lesions (57 years) was older than that for the other patients (47 years; p=0.039). The ratio of the short-to-long diameter was higher in malignant or potentially malignant lesions (mean 0.86) than in benign lesions (mean 0.69; p=0.008). There was no discriminative signal intensity characteristic (p>0.2 for all factors) that indicated the malignant potential for each non-hypervascular nodule. For all 10 lesions in the hepatitis B patients who were older than 52 years with a short-to-long diameter ratio of more than 0.75, the positive predictive value for malignant potential based on these three combined factors was 100%.

CONCLUSION

In older patients with cirrhosis from hepatitis B, large (>or=2 cm), non-hypervascular nodules with a spherical contour have a high malignant potential.

MR Imaging of hepatocellular carcinoma in the cirrhotic liver: challenges and controversies

The incidence of hepatocellular carcinoma (HCC) is expected to increase in the next 2 decades, largely due to hepatitis C infection and secondary cirrhosis. HCC is being detected at an earlier stage owing to the implementation of screening programs. Biopsy is no longer required prior to treatment, and diagnosis of HCC is heavily dependent on imaging characteristics. The most recent recommendations by the American Association for the Study of Liver Diseases (AASLD) state that a diagnosis of HCC can be made if a mass larger than 2 cm shows typical features of HCC (hypervascularity in the arterial phase and washout in the venous phase) at contrast material-enhanced computed tomography or magnetic resonance (MR) imaging or if a mass measuring 1-2 cm shows these features at both modalities. There is an ever-increasing demand on radiologists to detect smaller tumors, when curative therapies are most effective. However, the major difficulty in imaging cirrhosis is the characterization of hypervascular nodules smaller than 2 cm, which often have nonspecific imaging characteristics. The authors present a review of the MR imaging and pathologic features of regenerative nodules and dysplastic nodules and focus on HCC in the cirrhotic liver, with particular reference to small tumors and lesions that may mimic HCC. The authors also review the sensitivity of MR imaging for the detection of these tumors and discuss the staging of HCC and the treatment options in the context of the guidelines of the AASLD and the imaging criteria required by the United Network for Organ Sharing for transplantation. MR findings following ablation and chemoembolization are also reviewed.

Radiological diagnosis of hepatocellular carcinoma

Treatment of hepatocellular carcinomas (HCC) is often complicated by the fact that early HCCs are mostly asymptomatic and the carcinoma is often discovered at an advanced stage. The aim of diagnostic imaging is to detect HCC at an early stage, when curative options are available. In recent years, there have been many efforts to improve early detection of small HCC. The purpose of this article is to describe the pertinent findings of HCCs in non-invasive, diagnostic imaging, including ultrasound, computed tomography, as well as modern magnetic resonance imaging techniques. Special emphasis is given to the frequently addressed difficulties of differentiation of precancerous lesions and small HCCs. A non-invasive diagnostic approach is considered with a review of the literature.

Early hepatocellular carcinoma: pathology, imaging, and therapy

BACKGROUND

In 1987, Japanese researchers proposed to define the pathological concept of early hepatocellular carcinoma (HCC). However, there are some conceptual differences between the East and the West in the diagnosis and treatment of early HCC.

METHODS

To provide up-to-date data for making a worldwide consensus, this article has collected six papers focused on the management of early HCC, which were presented in the Fifth International Meeting of "Hepatocellular Carcinoma: Eastern and Western Experiences" in Houston in January 2007.

RESULTS

In the pathological perspective, the common criteria to discriminate early HCC from dysplastic nodule included hepatocytic invasion of portal triads and septa (stromal invasion). The current imaging modalities such as contrast-enhanced ultrasound (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI) with the use of intravenous contrast material with multiphasic imaging could enhance their ability to accurately characterize early HCC. From the treatment perspective, a single early HCC had a high chance for cure by resection, ablation, or transplantation, which proved to be the earliest clinical entity (Stage 0 HCC).

CONCLUSIONS

Early HCC is characterized by its incipient malignant nature and by an extremely favorable clinical outcome, thereby justifying its definition.

Gadolinium-enhanced MRI for tumor surveillance before liver transplantation: center-based experience

OBJECTIVE

The purpose of this study was to evaluate prospectively acquired institutional results to determine the accuracy of gadolinium-enhanced MRI in liver tumor surveillance before transplantation.

SUBJECTS AND METHODS

One hundred fifteen patients underwent MRI of the abdomen within 90 days before liver transplantation. Images were acquired with gadolinium-enhanced 3D gradient-echo sequences in the arterial, venous, and delayed phases. Detection of hepatocellular carcinoma (HCC) was based on the imaging criteria arterial phase enhancement, delayed phase hypointensity, and development of an enhancing outer margin capsule. Imaging findings were compared with findings at histopathologic evaluation of the explanted liver.

RESULTS

Thirty-six HCCs in 27 patients were detected at histopathologic evaluation. Patient-based analysis showed the sensitivity of MRI was 88.9% (24/27); specificity, 97.7% (false-positive findings in two patients); and accuracy, 95.7%. MRI depicted 28 of 36 HCCs, resulting in a lesion-based sensitivity of 77.8%. Although all 18 HCCs 2 cm or larger were depicted with MRI, only 10 of 18 HCCs smaller than 2 cm were correctly diagnosed. However, two HCCs measuring smaller than 2 cm at pathologic examination were rated as dysplastic nodules on MRI.

CONCLUSION

Contrast-enhanced MRI can be used as a primary diagnostic method for accurate detection and characterization of HCC 2 cm or larger as required by the criteria of the Model for End-Stage Liver Disease used by the United Network for Organ Sharing. MRI can be considered a standard tool for surveillance before liver transplantation. Reduction in cost and risk may be derived from the diminished need for other diagnostic imaging studies and biopsy and the avoidance of use of iodinated contrast agents in imaging of patients with cirrhosis, many of whom have impaired renal function.

EUS for detection of the hepatocellular carcinoma: results of a prospective study

BACKGROUND

Early detection of hepatocellular carcinoma (HCC) and accurate determination of the number of lesions are critical in determining eligibility for liver transplantation or resection. Current diagnostic modalities (CT and magnetic resonance imaging [MRI]) often miss small lesions.

OBJECTIVE

To compare the accuracy of the EUS with CT for the detection of primary tumors of the liver.

DESIGN

Prospective single-center study.

SETTING

Academic medical center.

PATIENTS

Subjects at high risk of HCC (hepatitis B, hepatitis C, or alcoholic cirrhosis) were enrolled.

INTERVENTIONS

US, CT, MRI, and EUS examinations of the liver were performed. Liver lesions identified during EUS underwent EUS-guided FNA (EUS-FNA).

RESULTS

Seventeen patients were enrolled in the study. Nine of these patients had liver tumors (HCC, 8; cholangiocarcinoma, 1). EUS-FNA established a tissue diagnosis in 8 of the 9 cases. The diagnostic accuracy of US, CT, MRI, and EUS/EUS-FNA were 38%, 69%, 92%, and 94%, respectively. EUS detected a significantly higher number of nodular lesions than US (P = .03), CT (P = .002), and MRI (P = .04). For HCC lesions, a trend was observed in favor of EUS for the detection of more lesions than US (8 vs 2; P = .06) and CT (20 vs 8; P = .06). No complications were observed as a result of EUS-FNA.

LIMITATIONS

Small sample size.

CONCLUSIONS

EUS-FNA is a safe and accurate test for the diagnosis of HCC. EUS increases the accuracy of intrahepatic staging of the HCC by delineation of lesions, which are missed by CT and MRI. We recommend EUS for suspected HCC, particularly in cases that are being considered for liver transplantation.

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.

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.

Improving the prediction of hepatocellular carcinoma in cirrhotic patients with an arterially-enhancing liver mass

In the United States, cirrhotic patients with known or suspected hepatocellular carcinoma (HCC) are prioritized for liver transplantation. Noninvasive criteria for the diagnosis of HCC rely on arterial enhancement of a mass. The aim of this study was to determine whether clinical, laboratory, and / or radiologic data can improve the prediction of HCC in cirrhotic patients with an arterially-enhancing mass. Between May 2002 and June 2003, dynamic gadolinium-enhanced magnetic resonance imaging (MRI) of consecutive patients with liver cirrhosis and a solid mass were reviewed by 2 radiologists blinded to the clinical diagnosis. Clinical, laboratory, and radiologic data were recorded for all patients. A total of 94 patients with cirrhosis and an arterially-enhancing liver mass were studied, 66 (70%) of whom had HCC. Alpha-fetoprotein (AFP) >20 ng/mL (P = .029), tumor size >2 cm (P = .0018), and delayed hypointensity (P = .0001) were independent predictors of HCC. Delayed hypointensity of an arterially-enhancing mass had a sensitivity of 89% and a specificity of 96% for HCC. The presence of delayed hypointensity was the only independent predictor of HCC among patients with arterially-enhancing lesions <2 cm (odds ratio, 6.3; 95% confidence interval [CI], 1.8-13), with a sensitivity of 80% and a specificity of 95%. In conclusion, delayed hypointensity of an arterially-enhancing mass was the strongest independent predictor of HCC, regardless of the size of the lesion. If additional studies confirm our results, the noninvasive criteria utilized to make a diagnosis of HCC should be revised.

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.