Hypervascular liver lesions: differentiation of focal nodular hyperplasia from malignant tumors with dynamic gadolinium-enhanced MR imaging

Benign liver tumors in pediatric patients - Review with emphasis on imaging features

Benign hepatic tumors are commonly observed in adults, but rarely reported in children. The reasons for this remain speculative and the exact data concerning the incidence of these lesions are lacking. Benign hepatic tumors represent a diverse group of epithelial and mesenchymal tumors. In pediatric patients, most benign focal liver lesions are inborn and may grow like the rest of the body. Knowledge of pediatric liver diseases and their imaging appearances is essential in order to make an appropriate differential diagnosis. Selection of the appropriate imaging test is challenging, since it depends on a number of age-related factors. This paper will discuss the most frequently encountered benign liver tumors in children (infantile hepatic hemangioendothelioma, mesenchymal hamartoma, focal nodular hyperplasia, nodular regenerative hyperplasia, and hepatocellular adenoma), as well as a comparison to the current knowledge regarding such tumors in adult patients. The current emphasis is on imaging features, which are helpful not only for the initial diagnosis, but also for pre- and post-treatment evaluation and follow-up. In addition, future perspectives of contrast-enhanced ultrasound (CEUS) in pediatric patients are highlighted, with descriptions of enhancement patterns for each lesion being discussed. The role of advanced imaging tests such as CEUS and magnetic resonance imaging, which allow for non-invasive assessment of liver tumors, is of utmost importance in pediatric patients, especially when repeated imaging tests are needed and radiation exposure should be avoided.

Tumors of the liver and intrahepatic bile ducts: radiologic-pathologic correlation

Primary tumors of the liver can be classified pathologically based on their cell of origin into epithelial tumors, arising from hepatocytes or biliary epithelium, and nonepithelial tumors, including mesenchymal tumors and lymphoma. Characteristic findings on MR imaging can be seen in many cases. This article reviews the MR imaging appearance of these tumors with pathologic correlation.

A Pictorial Review of the MRI Appearances of Focal Liver Lesions

The role of magnetic resonance imaging (MRI) in evaluating benign and malignant liver lesions has undergone significant expansion in recent years with the evolution and optimization of imaging sequences and contrast enhanced techniques. The aim of this article is first to summarize the various imaging sequences employed in the evaluation of liver pathology, with reference to the recent literature on the subject and second, to illustrate through pictorial review, the MRI characteristics of a number of benign and malignant lesions both in the normal liver and in those with chronic liver disease. We highlight the importance of availability of adequate clinical history in the interpretation of focal liver lesions on MRI, including the presence or absence of chronic liver disease, known history of primary malignancy and if applicable, serum alpha fetoprotein levels. In conclusion, MRI is the optimum imaging modality in the evaluation of focal liver lesions. Pattern recognition and knowledge of patient history enables characterization of the majority of liver lesions without the use of ionizing radiation.

Focal nodular hyperplasia of the liver in longterm survivors of neuroblastoma: how much diagnostic imaging is necessary?

OBJECTIVES

Focal nodular hyperplasia of the liver is a tumor-like lesion, uncommon in children, but it has recently been more frequently observed in children treated for malignant diseases, especially neuroblastoma. The aetiology is unclear, the pathogenesis remains controversial. Focal nodular hyperplasia of the liver is suspected to be a sequela of tumor therapy.

METHODS

Besides the clinical data we evaluated the imaging modalities needed to diagnose focal nodular hyperplasia of the liver in children with neuroblastoma who have been followed in our institution for more than 5 years.

RESULTS

Out of 60 children six developed focal nodular hyperplasia at a median time of 10.5 years after diagnosis of neuroblastoma and 9.4 years after the end of treatment. The diagnosis of focal nodular hyperplasia was based on imaging criteria which are variable in ultrasonography and specific in MRI. Only one child underwent surgical biopsies to rule out liver metastases.

CONCLUSIONS

Longterm survivors of neuroblastoma are at risk of developing focal nodular hyperplasia, especially if they underwent toxic chemotherapy and/or radiotherapy to the liver during initial treatment. The recommended diagnostic imaging tools are ultrasonography for detecting liver lesions and MRI for confirming and characterizing these lesions as focal nodular hyperplasia.

Distinguishing benign from malignant liver tumours

Liver masses are very common and most are benign. It is therefore important to avoid unnecessary interventions for benign lesions, while at the same time ensuring accurate diagnosis of hepatic malignancies. Many cancer patients, like the general population, have incidental benign liver lesions. In planning treatment for cancer patients, it is critical to avoid inappropriate treatment decisions based on misdiagnosis of a benign lesion as a metastasis or primary liver malignancy. This article describes the salient imaging features of the common benign liver masses and outlines a general approach to distinguishing between benign and malignant hepatic lesions.

Focal nodular hyperplasia: lesion characteristics on state-of-the-art MRI including dynamic gadolinium-enhanced and superparamagnetic iron-oxide-uptake sequences in a prospective study

PURPOSE

To image a cohort of patients with pathology-proven focal nodular hyperplasia (FNH) to assess which characteristics of state-of-the-art magnetic resonance imaging (MRI) of the liver are the most useful for improving the detection and characterization of FNH.

MATERIALS AND METHODS

In 14 patients, pathology-proven FNH (N=33) were prospectively examined using gadolinium (Gd) and superparamagnetic iron-oxide (SPIO) contrast media. All lesions were evaluated for signal intensity (SI), fatty infiltration, central scar, mode of enhancement with Gd, and uptake of SPIO. The percentage of dynamic contrast enhancement in the arterial, portal, and delayed phases was assessed. The contrast-to-noise ratio (CNR) before and after administration of SPIO contrast was calculated.

RESULTS

The SI of the lesions was low to isointense on T1-weighted (T1W) images, and intermediate to isointense on T2W images. Fatty infiltration of the lesions was present in 6%. The percentages of enhancement in the liver and lesion were 110%, 115%, and 95%, and 151%, 182%, and 160%, respectively (P<0.0001). All lesions showed uptake of SPIO with improved conspicuity of the central scar and septa. The CNR values precontrast and post-Gd/SPIO were significantly different for T1 in- and opposed-phase and black-blood echo-planar imaging (BBEPI).

CONCLUSION

Combining dynamic Gd-enhanced imaging with T1W and T2W sequences after administration of SPIO facilitates comprehensive evaluation of FNH.

Update on Colorectal Cancer Imaging

Colorectal cancer remains a leading cancer killer worldwide. The disease is both curable and preventable, and yet the importance of widespread screening is only now starting to be appreciated. This article reviews the variety of diagnostic tests, imaging procedures and endoscopic examinations available to detect colorectal cancer and polyps in their early stage and also presents details on various screening options. The critical role of the radiologist is elaborated on including accurate assessment of the tumor extent within the bowel wall and beyond and the detection of lymph node and distant metastases. Staging with CT, MR imaging, endorectal ultrasound, and positron emission tomography are of paramount importance in determining the most appropriate therapy and the risk of tumor recurrence and overall prognosis.

Hepatocellular carcinoma with a prominent vascular scar in the center: MR imaging findings

We report herein a case of hepatocellular carcinoma (HCC) with a prominent central scar. Dynamic CT and MRI studies revealed a hypervascular liver mass and a washout of contrast material in the delayed phase. The tumor center showed particular hyperintensity on T2-weighted images and delayed or prolonged enhancement. The surgical specimen revealed moderately differentiated HCC with a central scar. The central scar consisted of prominent vascular channels and loose fibrous tissue, indicative of a vascular scar. We should understand MR imaging findings of this type of central scar in the HCC.

Hepatocellular adenoma: findings at state-of-the-art magnetic resonance imaging, ultrasound, computed tomography and pathologic analysis

The purpose of this paper is to describe the most recent concepts and pertinent findings of hepatocellular adenomas, including clinical presentation, gross pathology and histology, pathogenesis and transformation into hepatocellular carcinoma (HCC), and imaging findings at ultrasound (US), computed tomography (CT), and magnetic resonance (MR) imaging.

Contrast-enhanced dynamic magnetic resonance imaging findings of hepatocellular carcinoma and their correlation with histopathologic findings

PURPOSE

To investigate the correlations of contrast-enhanced magnetic resonance (MR) imaging findings of large (> 5 cm) hepatocellular carcinomas with tumor size and histopathologic findings.

MATERIALS AND METHODS

MR imaging was performed in 30 patients with a histopathologic diagnosis of hepatocellular carcinoma. The imaging protocol included non-contrast, hepatic arterial, portal venous and late phases. The signal intensities relative to the liver, enhancement patterns and the morphologic features of the lesions were evaluated in relation to size and degree of differentiation.

RESULTS

On histopathologic examination, 12 of 30 (40%) tumors were well-differentiated (grade 1), 6 of 30 (20%) were moderately differentiated (grades 2 and 3) and 12 of 30 (40%) were poorly differentiated (grade 4). Tumor size, tumor boundry, serum alpha-fetoprotein level and portal vein invasion were found to have statistically significant correlations with the degree of differentiation (p < 0.05). Portal vein invasion, capsule formation and tumor surface characteristics showed statistically significant correlations with tumor size (p < 0.05).

CONCLUSION

MR imaging findings of hepatocellular carcinomas larger than 5 cm are partially dependent on tumor size and degree of differentiation.

Characterization of Hepatocellular Tumors

PURPOSE

To assess the value of mangafodipir trisodium-enhanced MR imaging for characterization of hepatocellular lesions.

MATERIALS AND METHODS

Magnetic resonance images of 41 patients with 48 histopathologically proven hepatocellular lesions (20 cases of focal nodular hyperplasia [FNH], 4 adenomas, 15 hepatocellular carcinomas [HCCs], 7 regenerative nodules, and 2 others) were retrospectively studied. Magnetic resonance imaging was performed on a 1.5-T unit (Vision, Siemens, Erlangen, Germany; ACS-NT, Philips, Best, The Netherlands) using T2-weighted, fat-saturation, turbo spin echo imaging and T1-weighted gradient echo imaging before and 20 minutes after infusion of 5 micromol/kg mangafodipir (Amersham Health, Oslo, Norway). Qualitative analysis by 4 blinded independent readers included assessment of unenhanced images and, in a second step, assessment of unenhanced and contrast-enhanced images together. Lesions were classified as benign or malignant using a 5-point scale, and readers made a specific diagnosis.

RESULTS

For characterization of hepatocellular lesions, mangafodipir-enhanced imaging was significantly superior to unenhanced imaging (P < 0.05). On receiver operating characteristic analysis, the area under the curve was 0.768 (95% confidence interval: 0.633-0.903) for unenhanced images and 0.866 (95% confidence interval: 0.767-0.966) for evaluation of unenhanced and contrast-enhanced images together (P < 0.05). Analysis of enhancement patterns aided in characterization and classification of tumors.

CONCLUSION

Administration of mangafodipir improves the differentiation between adenoma or HCC and "nonsurgical" lesions (FNH or regenerative nodules). The accuracy for arriving at a specific diagnosis is higher when unenhanced and mangafodipir-enhanced images are considered together than for unenhanced MR images alone.

Early-enhancing nonneoplastic lesions on gadolinium-enhanced magnetic resonance imaging of the liver following partial hepatectomy

PURPOSE

To assess the frequency, imaging findings, and significance of early-enhancing nonneoplastic (EN) lesions with gadolinium-enhanced magnetic resonance imaging (MRI) of the liver following partial hepatectomy.

MATERIALS AND METHODS

We retrospectively reviewed MR images after partial hepatectomy in 30 patients. Postoperative MRI was performed in 1-12 months (mean, 3.7 months) after partial hepatectomy. We defined the EN lesion as a lesion that was ill defined; irregular, wedge shaped, or serpiginous; located along the liver edge; not visible on unenhanced MR images; did not appear hypointense on portal venous- or equilibrium-phase images; or a combination of those imaging findings.

RESULTS

A total of 39 EN lesions (size range, 5-60 mm; mean, 25.2 mm) in 19 patients and 17 recurrent tumors (size range, 5-50 mm; mean, 16.8 mm) in 10 patients newly appeared after partial hepatectomy. The EN lesions were diagnosed as pseudolesions by the second postoperative follow-up MRI in 17 patients or contrast-enhanced computed tomography (CT) in two. A total of 13 EN lesions (33%) were located along the liver edge and 20 (51%) were adjacent to the resected area. The shape was circular in 11 (28%), oval in three (8%), irregular in 11 (28%), wedge shaped in five (13%), and serpiginous in nine (23%). No EN lesion showed hypointensity on gadolinium-enhanced portal venous-phase or equilibrium-phase images. A total of 14 EN lesions (36%) showed slight hyperintensity on T2-weighted images. The confidence levels for malignancy probability assigned by blinded radiologists were lower with EN lesions than with recurrent tumors (P < 0.001).

CONCLUSION

EN lesions are frequently seen in MRI following partial hepatectomy, and occasionally are slightly hyperintense on T2-weighted images, mimicking malignant tumors. However, most EN lesions can be correctly diagnosed with MRI findings.

High prevalence of hepatic focal nodular hyperplasia in subjects with hereditary hemorrhagic telangiectasia

A vascular pathogenesis of hepatic focal nodular hyperplasia (FNH) has been suggested; this study was aimed to evaluate in families with hereditary hemorrhagic telangiectasia (HHT) the prevalence of FNH, relating it to presence and stage of hepatic vascular malformations (VMs). Fifty-two HHT families underwent a screening program including abdominal Doppler sonography (US) searching for hepatic VMs; we classified them as minimal, moderate and severe, depending on the number and degree of abnormalities found by Doppler US. Presence of focal liver lesions was recorded. Diagnosis of FNH was made if at least two examinations, whether color Doppler US, liver scintigraphy, dynamic computed tomography (CT) or magnetic resonance (MR), showed suggestive findings. FNH was found in five out of 274 subjects (1.8%). All five were affected by HHT. Thus, percentage related to the group of affected patients increased to 2.9; 4/5 presented severe liver VMs. Female-to-male ratio was 4:1. FNH was single in three cases; tumor size ranged between 20 and 90 mm. During follow-up, no lesion showed a reduction in size, three showed an increase. Prevalence of FNH in patients with HHT is far greater than that reported in the general population; Doppler US role in its diagnosis and follow-up is highlighted.

MRI of atypical focal nodular hyperplasia of the liver: radiology-pathology correlation

OBJECTIVE

The purpose of our study was to determine the MRI features of atypical focal nodular hyperplasia of the liver and to compare them to pathology findings.

MATERIALS AND METHODS

We retrospectively reviewed MRI and pathology findings in 27 focal nodular hyperplasia lesions with atypical MRI features. Six criteria for typical focal nodular hyperplasia were required: iso- or hypointensity on T1-weighted sequences and iso- or slight hyperintensity on T2-weighted sequences; homogeneous signal intensity; central hyperintense area on T2-weighted sequences; marked lesion contrast enhancement; accumulation of gadolinium chelates within the central area on delayed contrast-enhanced T1-weighted sequences; and absence of capsule.

RESULTS

The most common atypical radiology features included absence of, or an atypical, stellate area; heterogeneity on both T1- and T2-weighted images; and high-intensity signal on T1-weighted sequences. MRI-pathology correlation showed that T1 hyperintensity with no other atypical MRI feature (n = 3) could be explained by steatosis, sinusoidal dilatation, or hemorrhage. In addition, in two patients with lesions smaller than 3 cm in diameter, the only atypical MRI feature was absence of a stellate area.

CONCLUSION

These findings suggest a lesion that is hyperintense on T1-weighted sequences or that lacks a stellate area but is smaller than 3 cm in diameter can be diagnosed as focal nodular hyperplasia provided all other MRI criteria for this diagnosis are present. In such cases, close monitoring on MRI without invasive diagnostic procedures may be warranted. However, in large lesions (> 3 cm) without a stellate area and in lesions with heterogeneity, histopathology examination is mandatory to rule out other diagnoses.

Assessment of Sequential Enhancement Patterns of Focal Nodular Hyperplasia and Hepatocellular Carcinoma on Mangafodipir Trisodium Enhanced MR Imaging

RATIONALE AND OBJECTIVES

Sequential contrast changes of mangafodipir trisodium (Mn-DPDP)-enhanced magnetic resonance imaging (MRI) were evaluated in the differentiation of focal nodular hyperplasias (FNH) and hepatocellular carcinomas (HCC).

METHODS

Patients with FNH (n = 16) or HCC (n = 12) underwent MRI: T2-weighted fast spin echo before and T1-weighted gradient echo before and 1, 4, 14, and 22 hours after 5 micromol/kg Mn-DPDP. Homogeneity of enhancement and delineation of fibrous scars of FNHs were assessed qualitatively. Lesion-to-liver contrast changes of FNHs and HCCs were compared quantitatively (Mann-Whitney U).

RESULTS

Mn-DPDP improved detection of characteristic scars of FNHs from 50% before to 90% after contrast agent. Apart from fibrous tissue enhancement of FNHs was mostly homogeneous (90%). Time-dependent contrast changes were up to 20 times higher (after 4 hours) for FNHs than HCCs (P < 0.0001).

CONCLUSIONS

Mn-DPDP-enhanced MRI helps to delineate characteristic morphologic features of FNHs and can provide quantitative data differentiating FNH and HCC.

Liver tumour MRI: what do we need for lesion characterization?

BACKGROUND

Hepatic lesions constitute a daily challenge to radiology in clinical settings, and non-invasive methods are valuable in the characterization of these liver tumours. We undertook our investigation to assess the lesion characterization potential of MRI by evaluating several unenhanced MR sequences and the dynamic gadolinium (Gd)-enhanced technique.

METHODS

A total of 116 focal liver lesions in 116 patients were included in our retrospective study, and histological verification was available for 107 lesions. Nine haemangiomas had a follow-up of 2 years. The 1.5-T MR system was used. T1- and T2-weighted sequences and dynamic Gd-enhanced studies were evaluated by two individual readers as separate sequences and also collectively. Lesions were classified into benign or malignant, and a specific diagnosis was proposed. The McNemar test was used in statistical analysis, and interobserver variation was measured using kappa statistics.

RESULTS

Lesion classification into benign and malignant tumours (by evaluating all images in concert) was assessed in 83% and 89% of cases by readers 1 and 2, respectively. From single sequences, best lesion classification was achieved with Gd-enhanced T1 by both readers. The difference in classification was statistically significant when all sequences were evaluated in comparison with any single sequence alone (P = 0.02). Specific diagnosis was correctly determined using all sequences together in 60% and 71% of cases by readers 1 and 2, respectively. For individual sequences, correct diagnosis was most frequently proposed with a Gd-enhanced T1-weighted sequence by both readers (59% and 65% for readers 1 and 2, respectively).

CONCLUSION

Multisequential MRI using Gd-enhanced imaging performs extremely well in liver lesion classification, and with moderate ability to determine a specific diagnosis.

Accelerated dynamic MR imaging with a parallel imaging technique for hypervascular hepatocellular carcinomas: usefulness of a test bolus in examination and subtraction imaging

PURPOSE

To assess the impact of the accelerated dynamic MR imaging (ADMRI) approach using parallel imaging for detecting hypervascular hepatocellular carcinomas (HCCs) and to evaluate the usefulness of a test bolus in examination and subtraction imaging in this setting.

MATERIALS AND METHODS

Thirty patients with 135 HCCs underwent ADMRI using a two-dimensional gradient-recalled echo sequence with parallel imaging. Seventeen patients were evaluated without a test bolus and 13 patients with a test bolus. The detectability of HCCs was calculated between the groups with and without a test bolus. ADMRI was evaluated regarding the signal-to-noise ratio (SNR) of the lesion and the liver, the contrast-to-noise ratio (CNR) of the lesion vs. the liver, and the feasibility of subtraction images.

RESULTS

ADMRI with and without a test bolus had almost equal sensitivity (92.5% and 92.6%). No significant difference was seen in the SNR of lesions and the CNR of lesions vs. livers between both groups. With a test bolus, ADMRI could depict the peak enhancement of nodules on the 2nd or 3rd dynamic phases and optimized the timing of peak lesion enhancement. Subtraction images could be obtained regarding minimal slice misregistration.

CONCLUSION

ADMRI had high detectability of HCCs with and without a test bolus.

Hepatic focal nodular hyperplasia in children previously treated for a solid tumor. Incidence, risk factors, and outcome

BACKGROUND

The detection of hepatic nodules, particularly in patients treated for a previous malignancy, raises a diagnostic dilemma. Focal nodular hyperplasia (FNH) of the liver is an uncommon, benign tumor in children and must be differentiated from malignant hepatic lesions. The etiology of FNH is obscure, and its pathogenesis is poorly understood. FNH may be a reaction to localized vascular abnormalities and circulatory disturbances. The goal of the current study was to identify risk factors for the occurrence of FNH in children who had received prior treatment for a malignant tumor.

METHODS

The current retrospective study examined 14 cases of FNH in pediatric patients who previously had been treated for a malignancy. Diagnosis was based on clinical and radiologic findings and was proven histologically in four cases.

RESULTS

FNH lesions were discovered by chance during routine examination in 78% of patients. The incidence of FNH was particularly high in the current series (0.45%) compared with the incidence in the general pediatric population. High doses of alkylating agents (e.g., busulfan or melphalan), venoocclusive disease, and liver radiotherapy may be responsible for injury to the vascular endothelium and subsequent localized circulatory disturbances. FNH is characterized by the absence of complications after its detection; therefore, only close follow-up is recommended.

CONCLUSIONS

FNH appears to be a late complication of an iatrogenic vascular disease in children with a history of malignancy.

Atypical focal nodular hyperplasia of the liver: imaging features of nonspecific and liver-specific MR contrast agents

OBJECTIVE

The objective of our study was to describe the functional and differential uptake features of atypical focal nodular hyperplasia using different MR contrast agents and to evaluate their potential role in the diagnosis and characterization of focal nodular hyperplasia.

MATERIALS AND METHODS

Contrast-enhanced MR images of 45 patients with 85 focal nodular hyperplasia lesions were retrospectively reviewed. In these patients, sonographic findings were nonspecific (n = 37), or CT features were inconclusive (n = 8). Non-liver specific gadolinium chelates were used in 18 patients (48 lesions) suspected of having either focal nodular hyperplasia or hemangioma. The following liver-specific agents were used in patients with suspected focal nodular hyperplasia or metastases: mangafodipir trisodium, 30 patients (55 lesions); ferumoxides, six patients (16 lesions); and SHU 555 A, six patients (six lesions). Individual lesions were quantified by signal intensity and assessed qualitatively by homogeneity, contrast enhancement, and presence of a central scar.

RESULTS

At unenhanced MR imaging, the triad of homogeneity, isointensity, and central scar was found in 22% of the focal nodular hyperplasia lesions. On mangafodipir trisodium-enhanced T1-weighted images, all focal nodular hyperplasia lesions showed contrast uptake: in 64% of the lesions, uptake was equal to parenchyma; 25%, greater than the parenchyma; and 11%, less than the parenchyma. On iron oxide-enhanced T2-weighted images, all focal nodular hyperplasia lesions showed uptake of the contrast agent, but contrast uptake in the lesions was less than in the surrounding parenchyma. Dynamic gadolinium chelate-enhanced MR imaging showed early and vigorous enhancement of focal nodular hyperplasia lesions with rapid washout in 88%. Atypical imaging features of the lesions included hyperintensity on T1-weighted images, necrosis and hemorrhage, and inhomogeneous or only minimal contrast uptake.

CONCLUSION

For patients in whom the diagnosis of focal nodular hyperplasia cannot be established on unenhanced or gadolinium-enhanced MR imaging, homogeneous uptake of liver-specific contrast agent with better delineation of central scar may help to make a confident diagnosis of focal nodular hyperplasia.

Gadolinium-enhanced MR imaging of the liver: optimizing imaging delay for hepatic arterial and portal venous phases--a prospective randomized study in patients with chronic liver damage

PURPOSE

To investigate the optimal imaging delays for hepatic arterial and portal venous phases of gadolinium-enhanced dynamic spoiled gradient-recalled-echo magnetic resonance (MR) imaging of the liver in patients with chronic liver damage.

MATERIALS AND METHODS

MR images were obtained after intravenous bolus injection of gadopentetate dimeglumine in 100 patients with chronic liver damage. Test bolus imaging was performed to determine the aortic transit time. A 26-second spoiled gradient-recalled-echo sequence was used. Patients were randomized into four groups so that the middle of k space was acquired at 5, 10, 15, and 20 seconds for the first phase and 45, 50, 55, and 60 seconds for the second phase, respectively, from the time of arrival of contrast material in the abdominal aorta. Mean signal intensities of the liver, spleen, and abdominal aorta were measured, and images were reviewed prospectively by three radiologists in consensus. Analysis of variance, the Scheffé criterion for continuous data, and the Kruskal-Wallis test for categorical data were used for statistical evaluation.

RESULTS

Intense splenic enhancement with the moiré pattern without intense hepatic enhancement occurred at 10-15 seconds. Aortic and splenic enhancement significantly decreased from 45 to 50 seconds (P <.05). Spleen-to-liver contrast-to-noise ratio began to decrease at 20 seconds and decreased constantly over time. Qualitative results correlated well with quantitative results.

CONCLUSION

Biphasic imaging with k space centered at 10-15 and 50 seconds or later after arrival of contrast material in the abdominal aorta may be the optimal technique to obtain ideal contrast enhancement. Empirically, delays of 28-34 and 68 seconds or later after initiating contrast material injection may be effective for biphasic imaging.

Radiologists' performance in the diagnosis of liver tumors with central scars by using specific CT criteria

PURPOSE

To determine the performance of radiologists with differing levels of expertise in the diagnosis of the most common types of liver tumors with central scars (ie, focal nodular hyperplasia [FNH], fibrolamellar hepatocellular carcinoma [HCC], and large hepatic hemangioma) by using specific computed tomographic (CT) findings.

MATERIALS AND METHODS

Review of medical records at the University of Pittsburgh Medical Center identified patients with a total of 64 liver tumors that had central scars-including 29 cases of FNH, 20 fibrolamellar HCCs, and 15 large (>3.5 cm in diameter) hemangiomas-and with CT scans available for review. Retrospective review of these scans was performed individually by six radiologists who were blinded to the diagnosis, including two faculty abdominal radiologists, one abdominal imaging fellow, and three radiology residents. Individual performance was evaluated by means of receiver operating characteristic analysis, and interobserver agreement was measured by using the Cronbach alpha. Individual CT findings that may allow differentiation of tumor types were identified with the Kruskal-Wallis test.

RESULTS

CT allowed good to excellent interobserver agreement in the diagnosis of tumor type and in recognition of differential findings among the three types. The individual accuracy of diagnosis was very good, with the average area under the receiver operating characteristic curve ranging from 0.81 to 0.90. Although the faculty radiologists performed the best, the differences in performance between the subgroups of readers and the levels of confidence in diagnosis were not statistically significant. The diagnosis of fibrolamellar HCC was the most accurate and had the highest sensitivity, followed by FNH and large hemangioma. Clinical and CT findings that were found to be statistically significant in differentiating tumor types were patient age and sex, tumor size larger than 10 cm, width of tumor scars, invasion of vessels, nodular centripetal enhancement, marked hyperattenuation on arterial phase images, lymphadenopathy, heterogeneity, extrahepatic metastases, surface lobulation, calcification, and isoattenuation with liver tissue on portal venous phase images.

CONCLUSION

CT allows accurate differentiation of the most common types of liver tumors with central scars, including FNH, fibrolamellar HCC, and large hemangioma.

Histologic scoring of liver biopsy in focal nodular hyperplasia with atypical presentation

The contribution of radio-guided transcutaneous biopsy in the diagnosis of focal nodular hyperplasia (FNH) of the liver was compared with the findings on surgical specimens to assess its contribution in clinical and radiologic atypical cases. This retrospective study involved 30 patients with atypical tumors on imaging who underwent liver biopsy and then surgery. All surgical specimens were diagnosed as FNH, either classical (n = 18) or nonclassical (n = 12). Imaging data were reviewed according to 4 radiologic criteria on magnetic resonance imaging (MRI) and/or computed tomography (CT) scan (hypervascularity, homogeneity, nonencapsulation, and presence of a central scar), and classified depending on the number of criteria found (group I, 4 of 4; group II, 3 of 4; group III, 2 or fewer). Histologic assessment of ultrasound (US)-guided liver biopsy recorded major diagnostic features (fibrous bands, thick-walled vessels, reactive ductules, and nodularity) and minor features (sinusoidal dilatation and perisinusoidal fibrosis). "Definite FNH" (3 or 4 major features) was diagnosed in 14 biopsies, "possible FNH" (2 major and 1 or 2 minor features) in 7 cases, and "negative for FNH" (2 or fewer major features without minor features) in 9 cases. The diagnosis of FNH on biopsy was reached in 14 cases (58.3%) in patients with 2 or fewer imaging criteria (group III; n = 24). Biopsies with a diagnosis of "possible FNH" corresponded to a large proportion of telangiectatic-type FNH on the specimen. In conclusion, liver biopsy does not appear to be necessary in cases in which imaging is typical. However, the absence of radiologic diagnostic criteria in FNH does not preclude a positive diagnosis on liver needle biopsy. Using the proposed histologic scoring system, surgical management may be avoided in these cases.

MR imaging of benign hepatic tumors

Use of a state-of-the-art pattern recognition approach and the combination of various MR sequences and contrast enhancement techniques makes it possible to diagnose most benign hepatic tumors with confidence.

MR imaging of intrahepatic cholangiocarcinoma with pathologic correlation

OBJECTIVE

The objective of this study was to determine the MR imaging features of intrahepatic cholangiocarcinoma.

MATERIALS AND METHODS

MR images of 50 patients with pathologically proven intrahepatic cholangiocarcinoma were reviewed retrospectively. T1- and T2-weighted spin-echo images were obtained in all patients. Contrast-enhanced T1-weighted imaging was performed in 25 patients. Signal intensity and enhancement pattern of the tumors were correlated with pathology findings. The frequency of central hypointense regions on T2-weighted images and the intrahepatic bile duct dilatation of several other hepatic tumor types were investigated. Results were compared with imaging results of cholangiocarcinoma.

RESULTS

On T2-weighted images, central hypo- and hyperintense regions were detected in tumors in 27 and 17 patients, respectively. Contrast-enhanced T1-weighted imaging revealed central hypointense areas exhibiting homogeneous, heterogeneous, and no enhancement in six, three, and five, respectively, of 14 patients. Regions of fibrosis displayed enhancement, whereas those of coagulative necrosis showed no enhancement. The signal intensity difference on T2-weighted images between the center and the edge of the tumor correlated well with the fibrotic ratio difference between those two areas corresponding to the MR image (Spearman's rank correlation test, r = 0.72, 95% confidence interval = 0.48-0.86). T2-weighted images revealed central hypointense regions in 16 of 34 instances of hepatic colorectal metastases. However, hypointensity was observed in only 26 of 234 other hepatic tumors. Intrahepatic bile duct dilatation was evident in 27 of 50 cases of cholangiocarcinoma but occurred in only a single case of 34 instances of hepatic colorectal metastases.

CONCLUSION

The combination of the signal intensity on T2-weighted images and the enhancement pattern on contrast-enhanced T1-weighted images showed good correlation with the pathologic findings of cholangiocarcinoma. The occurrence of a central hypointense area on T2-weighted images is not pathognomonic; however, this finding, which reflects severe fibrosis, appears to be a characteristic marker of intrahepatic cholangiocarcinoma. The presence of intrahepatic bile duct dilatation may indicate cholangiocarcinoma, although it is difficult to differentiate cholangiocarcinoma from hepatic colorectal metastasis.

Exophytic benign tumors of the liver: appearance on MRI

The purpose of our study was to determine the MR imaging appearance of exophytic benign liver tumors on precontrast and postgadolinium images. We reviewed our 9.5 year experience with MRI of the liver with dynamic gadolinium enhanced imaging to identify four patients with five histologically proven exophytic benign liver tumors. The histological diagnoses were cavernous hemangioma (2), focal nodular hyperplasia (FNH) (1), and hepatocellular adenoma (HCA) (2 exophytic adenomas in a patient with adenomatosis of the liver). All MRI studies were performed at 1.5 T and included: in-phase and out-of-phase T1-weighted spoiled gradient echo (SGE), T2-weighted fat-suppressed echo train spin echo, single shot T2-weighted sequences, and serial postgadolinium T1-weighted SGE sequences without and with fat-suppression. Prospective interpretations were reviewed and retrospective consensus readings of all MR images were performed assessing location, size, origin, morphology, visibility of the connection to the liver, signal characteristics on precontrast T1-weighted and T2-weighted images, and enhancement patterns on serial postgadolinium images. Three of the five tumors were pedunculated and connected to the liver by a thin stalk, which was prospectively identified in one patient. On precontrast and serial postgadolinium images, all exophytic tumors showed signal characteristics comparable to imaging features of standard intraparenchymal benign liver tumors. Our findings illustrate that the characteristic T1, T2, and postgadolinium imaging findings of these tumors permit correct identification of their liver origin despite their exophytic location, even if their connection with liver is not visualized.

Focal liver lesions: comparison of dual-phase CT and multisequence multiplanar MR imaging including dynamic gadolinium enhancement

The purpose of this study was to compare dual-phase spiral computed tomography (CT) and magnetic resonance imaging (MRI) using dynamic gadolinium enhancement for liver lesion detection and characterization. Twenty-two consecutive patients underwent dual-phase spiral CT and MRI for the evaluation of focal liver disease within a 1-month period. Spiral CT and MR images were interpreted prospectively, in a blinded fashion by separate, individual, experienced investigators, to determine lesion detection and characterization. Liver lesions were confirmed by surgery and pathology in 6 patients, and by clinical and imaging follow-up in the other 16 patients. Pathological correlation of a primary extrahepatic malignancy was available in 5 of the 16 patients who had metastatic liver disease. Spiral CT and MRI detected 53 and 63 lesions, and characterized 39 and 62 true positive lesions, respectively. A kappa statistic test was applied to assess agreement between MR and CT results. MR versus CT for lesion detection resulted in a kappa statistic of 0.54 (95% confidence interval), indicating moderate agreement, and 0.32 (95% confidence interval) for lesion characterization, indicating only slight agreement. More lesions were detected on MR images than CT images in 6 (27%) patients, with lesions detected only on MR images in 4 (18%) patients. More lesions were characterized on MR images in 9 (41%) patients. In 9 patients with a discrepancy between MR and CT findings, the MR images added information considered significant to patient management in all 9 cases. MRI was moderately superior to dual-phase spiral CT for lesion detection, and was markedly superior for lesion characterization, with these differences having clinical significance.

Dynamic contrast-enhanced three-dimensional MR imaging of liver parenchyma: source images and angiographic reconstructions to define hepatic arterial anatomy

PURPOSE

To assess the accuracy of an interpolated breath-hold T1-weighted three-dimensional (3D) gradient-echo (GRE) magnetic resonance (MR) imaging sequence with near-isotropic pixel size (</=2.3 mm) for evaluation of hepatic arterial anatomy variants during dynamic liver parenchymal imaging and to report patterns of hepatic arterial anatomy.

MATERIALS AND METHODS

Liver MR imaging, including an interpolated breath-hold 3D GRE sequence with fat suppression (4.2/1.8 [repetition time msec/echo time msec], 12 degrees flip angle), was performed in 207 consecutive patients before and after gadopentetate dimeglumine administration. Of the 207 patients, 202 (98%) had technically satisfactory studies clearly defining the hepatic arterial system. The first contrast material-enhanced GRE acquisition was timed for optimal arterial enhancement with a timing examination. In a retrospective review, hepatic arteries were evaluated on the basis of arterial phase images interpreted by two independent readers using transverse source images complemented by multiplanar reconstructions. Twenty-three patients also underwent digital subtraction angiography, which was a reference standard for comparison.

RESULTS

Conventional hepatic arterial anatomy was demonstrated in 135 (67%) of 202 patients. In the 23 patients with angiographic correlation, no discrepancy was noted between MR imaging and digital subtraction angiographic findings.

CONCLUSION

Hepatic arterial anatomy can be reliably demonstrated during liver parenchymal imaging with an optimally timed contrast-enhanced isotropic 3D GRE sequence.

Contrast agents for MR imaging of the liver

A variety of different categories of contrast agents, and within each category a number of individual agents, are currently available for clinical use in magnetic resonance (MR) imaging of the liver. In this review, the use of nonspecific extracellular gadolinium chelates, reticuloendothelial system-specific iron oxide particulate agents, hepatocyte-selective agents, and combined perfusion and hepatocyte-selective agents are described. Most clinical experience is with nonspecific extracellular gadolinium chelates. The relatively low cost, safety, good patient tolerance, and ability to help detect and characterize a wide range of liver diseases have rendered gadolinium chelates as commonly used agents. Reticuloendothelial system-specific agents improve lesion detection by decreasing the signal intensity of background liver on T2-weighted MR images, which increases the conspicuity of focal hepatic lesions with negligible reticuloendothelial cells (eg, metastases). Hepatocyte-selective agents increase the signal intensity of background liver on T1-weighted images, which increases the conspicuity of focal lesions that do not contain hepatocytes (eg, metastases). The clinical application of the different categories of contrast agents, techniques for their administration, sequences to be used, and appearances of common entities on contrast agent-enhanced studies are described.

Small renal masses: assessment of lesion characterization and vascularity on dynamic contrast-enhanced MR imaging with fat suppression

OBJECTIVE

The aim of our study was to characterize renal lesions equal to or smaller than 3.0 cm using dynamic contrast-enhanced MR imaging with fat suppression by means of quantitative analysis of signal intensity.

MATERIALS AND METHODS

We retrospectively reviewed the MR imaging examinations of 35 patients (20 with renal cell carcinoma, eight with angiomyolipoma, and seven with complicated cysts) who were studied with spin-echo and dynamic fat-suppressed gradient-recalled echo MR sequences, before and after the administration of gadopentetate dimeglumine. Every 30 sec after contrast injection, we measured the lesion percentage of enhancement and the ratio of contrast (lesion-renal cortex signal intensity difference) to noise.

RESULTS

Ten renal cell carcinomas were classified as hypervascular (enhancement greater than that of renal cortex) and 10 as hypovascular. The percentage of enhancement of hypervascular carcinomas was similar to that of renal cortex until 150 sec and greater in the late sequences (180-210 sec, p < 0.01). Hypovascular carcinomas had a lower percentage of enhancement than hypervascular carcinomas (60-210 sec, p < 0.005). Angiomyolipomas, after an early enhancement peak, showed values similar to those of hypovascular carcinomas. Complicated cysts had very low enhancement (p < 0.001). The baseline contrast-to-noise ratio was negative for all lesions (hypointensity with respect to renal cortex). After gadolinium injection, the contrast-to-noise ratio of hypervascular carcinomas rose, becoming positive after 150 sec. Until 60 sec, the contrast-to-noise ratio of hypovascular carcinomas declined slightly, whereas that of angiomyolipomas and cysts fell sharply; then the three curves remained stable (60-210 sec, p < 0.05 for all matches except angiomyolipomas versus cysts).

CONCLUSION

Quantitative analysis of signal intensity variations during dynamic contrast-enhanced MR imaging with fat suppression can be useful in the characterization of small renal lesions.

Enhancement characteristics of hepatic focal nodular hyperplasia and its scar by dynamic magnetic resonance imaging

RATIONALE AND OBJECTIVES

To determine the relationship between the lesion and the scar enhancement characteristic in a series of hepatic Focal Nodular Hyperplasia (FNH) lesions studied with dynamic MR imaging.

METHODS

Nine patients with FNH were studied. The slice showing the largest scar was selected for the dynamic single slice T1-weighted Gradient-echo sequence before and after contrast administration (15 images, one every 20 s). Analysis was performed with ROI measurements in the lesion and the scar. Signal-intensity and enhancement curves were obtained from both structures.

RESULTS

Dynamic MRI showed the typical homogeneous early enhancement of the lesion with delayed enhancement of the scar. The scar enhanced early and vigorously in all cases. Two patterns of enhancement curves were defined. In the parallel pattern, both curves started early, quickly reaching a plateau maintained over time (77.8%). In the divergent pattern the curve of the scar was above the curve of the FNH (22.2%), after the maximum slope was reached, with progressive separation of the curves.

CONCLUSION

There is a hypervascular scar enhancement within FNH lesions with either a parallel or divergent course after the maximum early enhancement.

Probability of hepatocellular carcinoma of small hepatocellular nodules undetectable by computed tomography during arterial portography

Recent advances in imaging modalities enable the identification of small hepatocellular nodules. Among the imaging techniques currently used for detecting hepatocellular carcinomas (HCC), computed tomography (CT) during arterial portography (CTAP) is one of the most sensitive techniques available for detecting hemodynamic change. Even so, well-differentiated HCCs that display only limited hemodynamic change, a feature shared with nonmalignant hepatocellular nodules, are not always detectable by CTAP. To improve our ability to distinguish well-differentiated HCCs from nonmalignant hepatocellular nodules, we have attempted to clarify how the characteristics of the nodules are shown by each imaging technique. We studied the imaging and pathological characteristics of 31 nodules (in 22 patients) detected by ultrasonography (US), but not by CTAP. Histological diagnoses were as follows: HCC, 17 of 31 nodules (55%); high-grade dysplastic nodules, 1 of 31 (3%); and nonmalignant nodules, 13 of 31 (42%). Neither digital substraction angiography (DSA) nor CT arteriography (CTA) were able to detect any of the nodules. Detection rates for plain CT were: 5 of 17 (29%) HCC, 1 of 1 (100%) high-grade dysplastic nodules, and 1 of 13 (8%) nonmalignant nodules. Detection rates for T1/T2-weighted magnetic resonance imaging (MRI) were: 4 of 17 (24%) HCC, 1 of 1 (100%) high-grade dysplastic nodules, and 3 of 13 (23%) nonmalignant nodules. Dynamic CT and dynamic MRI provided no additional information. In conclusion, there is some probability that hepatocellular nodules detected by US, but not by CTAP, are HCC. Presently, it is difficult to distinguish between benign nodules and malignant ones with these imaging techniques, and our findings indicate that biopsy may be advisable for nodules detected under these conditions.

Evolution from empirical dynamic contrast-enhanced magnetic resonance imaging to pharmacokinetic MRI

For chemotherapy to be effective against cancers which grow as solid tumors, agents must reach all tumor cells in effective quantities. Although many clinical trials include studies of the pharmacokinetics of the agents in body fluids such as blood or cerebrospinal fluid (CSF), there is presently no widely applicable way to determine access of chemotherapeutic agents to all regions of a solid tumor in an individual patient. This review discusses a relatively new methodology in MR imaging - dynamic contrast-enhanced imaging for exploring tumor microcirculation and drug access by imaging the uptake, or leakage, of contrast agent into tumor interstitial (extracellular and extravascular) space. The aims and methods of dynamic contrast-enhanced MRI evaluations to measure contrast uptake are distinguished from dynamic contrast-enhanced MRI to measure blood volume or flow, by MR imaging of the first-pass effects of a contrast bolus. Measures of contrast uptake by dynamic MRI have demonstrated a convincing ability to aid in diagnosing the presence of viable tumor and to measure response for a range of human tumors. This body of clinical results will be summarized. While questions remain to be answered about how to extract non-invasive pharmacokinetic measures of drug access from these novel dynamic imaging methods, we are optimistic that these methods can provide important new clinical measures that reflect the range of biological variation within and between naturally-occurring solid tumors.

Gadolinium-enhanced arterial-phase MR imaging of hypervascular liver tumors: comparison between tailored and fixed scanning delays in the same patients

The purpose of this study was to compare in the same patients tailored and fixed scanning delays during gadolinium-enhanced arterial-phase magnetic resonance imaging of hypervascular liver tumors. Tailored scanning delays were obtained with automated region of interest threshold triggering. A delay of 23 seconds between the start of contrast material injection and imaging was used for fixed delay examinations. Quantitative and qualitative evaluation was performed in 21 patients with normal cardiac function referred for MR assessment of hypervascular liver tumors. In the tailored examinations, the median time delay between the start of contrast material injection and the start of magnetic resonance imaging was 21 seconds (range, 18-34 seconds). The median tumor-to-liver contrast during tailored examinations was 19.1 versus 14.7 during fixed delay examinations. This difference, however, was not significant. Similarly, the enhancement in the aorta, the portal vein, the liver, and the tumor did not differ significantly between examinations performed with tailored and fixed delays. It is concluded that in our group of patients with hypervascular liver tumors and normal cardiac function, no significant improvement in tumor-to-liver contrast and enhancement during the arterial phase was found when gadolinium-enhanced magnetic resonance imaging was performed with a tailored scanning delay rather than with a fixed delay.

Two cases of focal nodular hyperplasia of the liver: value of scintigraphy with Tc-99m GSA and positron emission tomography with FDG

Focal nodular hyperplasia (FNH) of the liver is relatively rare, and can be difficult to differentiate from other benign tumors arising in the liver. We describe a 23-year-old woman and a 25-year-old man with FNH. They were hospitalized for further evaluation of a space-occupying lesion in the liver. Scintigraphy with Tc-99m diethylenetriaminepentaacetic acid galactosyl human serum albumin (Tc-99m GSA) revealed increased radioactivity in the tumor in one patient and radioactivity similar to that in the normal part of liver in the other. F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) showed uptake similar to that of the normal liver in both patients. FNH was diagnosed on the basis of angiographic findings and histological findings in liver biopsy specimens. Our results show that scintigraphy with Tc-99m GSA and FDG-PET may provide information helpful in the diagnosis of FNH.

MR imaging of the liver: techniques and clinical applications

With a recent advance of fast MR imaging techniques including fast gradient-echo (GRE), fast spin-echo (FSE), single shot FSE (SSFSE) and echo-planar imaging (EPI), and availability of a phased-array torso coil, there can be many possible pulse sequences for liver MR imaging. In clinical practice, optimization of pulse sequences is important for improving diagnostic performance of liver diseases. In this article, we review the current status of liver MR imaging, focusing on the description of standard pulse sequences, and the utility of fast scanning technique and contrast-enhancement studies.

Benign liver lesions: differentiation by magnetic resonance

Optimal hepatic imaging involves both detection and characterization of focal lesions. Detection involves both determination of the presence of lesions and of their segmental extent of liver involvement. In the evaluation of hypervascular lesions, magnetic resonance imaging (MRI) has a greater impact on patient management than ultrasound (US) and computed tomography (CT). Most benign tumors are incidental findings and do not produce clinical symptoms. They must be accurately diagnosed without using aggressive procedures. Knowledge of their imaging features is essential to avoid unnecessary work-up and to minimize patient anxiety. In this article, the MR appearance, vascular and functional behavior of the most common benign liver tumors will be discussed.

Contrast-enhanced hepatic MRI: comparison of half-dose and standard-dose gadolinium DTPA administration in lesion characterization with T1-weighted gradient echo sequences

The objective of this article was to compare half-dose (0.05 mm/kg) gadolinium-enhanced dynamic hepatic MR imaging to standard doses (0.10 mm/kg). Eighteen patients for follow-up hepatic MR received 0.05 mm/kg of gadolinium DTPA dynamically with gradient-echo imaging. Imaging parameters were identical to a 0.10-mm/kg study; patients were imaged during multiple phases of contrast enhancement. Two readers assessed for enhancement patterns and characterization. Quantitative signal-to-noise ratios (S/N) were obtained for abdominal viscera and contrast-to-noise ratios (C/N) were obtained on up to three lesions. No significant difference for the arterial dominant phase (P > 0.05) was found. Significant differences were found in all categories during the portal venous phase (except pancreas) and equilibrium phase (except liver). Lesion C/N ratios were not significant at any point (P > 0.05). Sixty-two out of 64 lesions (97%) were identically characterized. Therefore, half-dose dynamic gadolinium-enhanced MR may have diagnostic value.

A multicenter, randomized, double-blind study to evaluate the safety, tolerability, and efficacy of OptiMARK (gadoversetamide injection) compared with Magnevist (gadopentetate dimeglumine) in patients with liver pathology: results of a Phase III clinical trial

The purpose of this study was to evaluate the safety and efficacy of OptiMARK (gadoversetamide injection) compared with Magnevist (gadopentetate dimeglumine) in hepatic MRI of patients with suspected liver pathology. A Phase III, multicenter, randomized, double-blind, parallel group study was performed in adults with suspected liver pathology. All patients underwent contrast-enhanced computed tomography within 3 weeks prior to magnetic resonance scanning. Ninety-nine patients received OptiMARK, and 94 patients received Magnevist at a dose of 0.1 mmol/kg. Precontrast T1- and T2-weighted spin-echo imaging and T1-weighted gradient-echo imaging were performed, followed by T1-weighted gradient-echo imaging at 15-20 seconds, 1 minute, and 5 minutes after intravenous contrast injection. Three primary efficacy endpoints (confidence in lesion diagnosis, level of conspicuity, and lesion border delineation) were evaluated on the precontrast image set and compared with the pre plus postcontrast image set. Vital signs, physical examination, electrocardiograms (ECGs), and laboratory parameters (chemistry, hematology, and urinalysis) were measured at various time points. Adverse events were recorded. The study design and statistical analyses were chosen to demonstrate presumed equivalence of OptiMARK and Magnevist. There were no statistically significant differences in efficacy between OptiMARK and Magnevist as assessed by either blinded readers or the on-site principal investigators. No serious or unexpected adverse events were noted. Of the 193 patients receiving contrast media, 82 experienced a total of 154 adverse events. Thirty-three (21.4%) of these 154 adverse events were felt by the on-site investigators to be probably related to either study agent: 15 events in 9 patients in the OptiMARK group, and 18 events in 13 patients in the Magnevist group. Headache was the most common adverse event, occurring in 10.1% of the OptiMARK patients and 12.8% of the Magnevist patients. No clinically relevant trends were observed in any laboratory parameter or ECG findings in either treatment group. The results demonstrate the safety, efficacy, and equivalence of OptiMARK and Magnevist at a dose of 0.1 mmol/kg in hepatic magnetic resonance imaging of patients with suspected liver pathology.

Comparison of a 1.0 molar and a 0.5 molar formulation of gadobutrol in dynamic MR imaging of the liver in rats with hepatocellular carcinoma

The efficacy of a 1.0 molar formulation of gadobutrol was compared with that of a 0.5 molar formulation in dynamic magnetic resonance (MR) imaging of the liver in rats with hepatocellular carcinoma (HCC). Seven nodules histologically identified as moderately differentiated HCC underwent dynamic study. In the normal parenchyma surrounding these tumors, the 0.5 molar and 1.0 molar formulations yielded similar enhancement patterns, with maximum enhancement value of approximately 35% at 20 to 40 s after injection. In the tumors, the 0.5 molar formulation induced approximately 65% enhancement, whereas the 1.0 molar formulation, used at the same dose as the 0.5 molar formulation, induced significantly higher enhancement until 10 min after injection with maximum enhancement of approximately 90%. These findings indicate that the 1.0 molar formulation could be more efficacious than the 0.5 molar formulation in dynamic MR studies of moderately differentiated HCC even when injected at the same dose.

Power Doppler imaging of hepatic tumours: differential diagnosis between hepatocellular carcinoma and metastatic adenocarcinoma

We evaluated the usefulness of power Doppler imaging in the differential diagnosis between hepatocellular carcinoma and metastatic adenocarcinoma. Forty-seven patients with hepatocellular carcinoma and 18 patients with metastatic adenocarcinoma were evaluated using power Doppler imaging. The colour signals of hepatic tumours were graded as follows: 1, colour signals only in the marginal area; 2, small dot or dotted line colour signals within the tumours; 3, continuous solid line colour signals within the tumours. The grade 3 colour signals were classified in the following three patterns; winding line pattern, stretched line pattern and mixed pattern. The colour signals of hepatocellular carcinoma were grade 1 in seven patients, grade 2 in 11 and grade 3 in 29. The colour signals of metastatic adenocarcinoma were grade 1 in three patients and grade 3 in 15. Of the 29 hepatocellular carcinoma patients with a grade 3 signal, 26 patients had winding line patterns and three had mixed patterns. Of the 15 metastatic adenocarcinoma patients with a grade 3 signal, 12 patients had stretched line patterns and three had mixed patterns. In conclusion, power Doppler imaging is useful in the differential diagnosis between hepatocellular carcinoma and metastatic adenocarcinoma to evaluate the colour signal pattern within the tumour.

Sonographic evaluation of focal nodular hyperplasias (FNH) of the liver with a transpulmonary galactose-based contrast agent (Levovist)

Focal nodular hyperplasias (FNH) are hypervascular, benign focal liver lesions. Differentiation of FNH from other focal liver lesions is of clinical importance. The purpose of this study was to examine the impact of a new, transpulmonary echo-enhancing agent SHU 508A (Levovist) and recent Doppler techniques in the sonographic evaluation of FNH. 43 patients with 61 focal nodular hyperplasias of the liver were examined with grey scale ultrasound and power Doppler ultrasound. Levovist, a galactose-air-microbubble suspension was administered intravenously in all patients, either by bolus injection (400 mg ml-1) or continuous pump-infusion (300 mg ml-1). Visualization of the feeding vessels and vascularity of the lesions were evaluated. The resistance indexes (RI) in the feeding vessel and the hepatic artery were assessed and compared with the diameters of the FNH. The mean diameter of FNH was 4.3 cm (+/- 1.0). Echo enhanced power Doppler ultrasound was superior to unenhanced power Doppler ultrasound in the detection of the feeding artery (85% vs. 98%) in FNH and depicted the internal vascular architecture more clearly, especially in lesions located in the left lobe of the liver. Lesions smaller than 3 cm did not show a characteristic vascular architecture with echo enhanced Doppler ultrasound. The resistance index of the feeding artery (mean: 0.51 +/- 0.08) is significantly (p < 0.0001) lower than that of the hepatic artery (mean 0.65 +/- 0.06) with a mean difference of -0.14 +/- 0.01 in the same patient. The RI of the feeding artery significantly decreased as the size of the FNH increased, whereas RI differences between the hepatic artery and the feeding artery increased with lesion size. Intravenous (i.v.) bolus injection of the contrast agent will depict the hypervascular nature of FNH more clearly than i.v. infusion, although the latter will significantly prolong the diagnostic window. In conclusion, i.v. infusion of Levovist improves the visualization of the feeding artery and the radiating vascular architecture in FNH located in the left lobe of the liver due to improved signal-to-noise ratio and results in more effective suppression of motion artefacts. Although echo enhanced Doppler ultrasound improves the detection of the low resistance arterial feeding vessel in small FNH, it will not, however, reveal a specific vascular pattern in these lesions.