Contrast-enhanced ultrasonography in the characterization of benign focal liver lesions: activity-based cost analysis

PURPOSE: The aim of this study was to perform a cost analysis of contrast-enhanced ultrasonography (CEUS) in the study of benign focal liver lesions (BFLL) with indeterminate appearance on ultrasonography (US). MATERIALS AND METHODS: A decision model of patients with suspected BFLL on baseline US who subsequently underwent CEUS between 2002 and 2005 was constructed. We analysed the cost effectiveness of CEUS, considering whether or not computed tomography (CT) was necessary for the diagnosis. There were 398 patients with 213 angiomas, 41 focal nodular hyperplasias (FNH) and 154 pseudolesions (focal fatty sparing, focal fatty areas). Each patient underwent CEUS, and 98 of them were also studied by CT. All lesions were followed up. RESULTS: The cost of a single CEUS examination was 101.51 euros, and that of a single CT scan was 211.48 euros. For diagnosis of haemangiomas, we saved 1,406.97 euros in 2002, 5,315.22 euros in 2003, 10,317.78 euros in 2004 and 9,536.13 euros in 2005. For diagnosis of focal nodular hyperplasias, we saved 781.65 euros in 2003, 781.65 euros in 2004 and 1,406.97 euros in 2005. For diagnosis of pseudolesions, we saved 2,813.94 euros in 2002, 5,158.89 euros in 2003, 5,158.89 euros in 2004 and 4,220.91 euros in 2005. In the period 2002-2005, the introduction of CEUS allowed us to save a total of 47,055.33 euros in the diagnosis of benign focal hepatic liver lesions. CONCLUSIONS: This cost analysis shows that CEUS is the least expensive second-line modality after baseline US for the diagnosis of BFLL.     

Tissue harmonic and contrast-specific imaging: back to gray scale in ultrasound

The development of new US techniques that produce images based on nonlinear acoustic effects of US interaction with matter or microbubble contrast agents has opened new prospects for gray-scale US in native tissue and contrast imaging. Tissue harmonic imaging uses higher frequencies generated on propagation of the US beam through matter to improve image quality and resolve small anatomic structures and details, and is becoming a routine approach in US examination of many abdominal districts. Contrast-specific imaging techniques display enhancement of US agents in gray-scale with optimal contrast and spatial resolution, and offer high sensitivity either to microbubble movement or to microbubble destruction in dependence of the level of the applied acoustic peak pressure. Owing to the ability to exploit the microcirculation, contrast-specific techniques have enabled the evolution of contrast US from vascular imaging to the imaging of perfused tissues. Several studies have shown that these methods can substantially improve US detection and characterization of focal liver lesions, and promising results have been reported in other areas of investigation. This article reviews physical principles, technical issues, and clinical applications of tissue harmonic and contrast-specific imaging. It is foreseen that the new gray-scale US techniques will rapidly become a tool in numerous clinical scenarios.     

Liver lesions: intermittent second-harmonic gray-scale US can increase conspicuity with microbubble contrast material-early experience

The authors investigated the effect of intermittent second-harmonic gray-scale (ISHGS) ultrasonography (US) with SH U 508A microbubbles on the conspicuity of focal liver lesions. Twenty-three patients were included in the study. Images were analyzed subjectively and quantitatively. Objective lesion conspicuity was increased. In 12 of the 15 patients with liver malignancy, gray-scale defects were seen in previously unsuspected areas. ISHGS US may improve the sensitivity of US for liver lesions.     

Focal liver lesions: role of contrast-enhanced ultrasound

The introduction of microbubble contrast agents and the development of contrast-specific techniques have opened new possibilities in liver imaging. Initially, only intermittent imaging with Doppler detection was available. Second-generation contrast agents and low mechanical index real-time scanning techniques are decisive advances that enable convenient liver examinations with high sensitivity and specificity. Hepatic lesions usually show typical perfusion and enhancement patterns through the various contrast phases, which help their characterization. Several published studies and the daily clinical routine show that, as opposed to conventional ultrasound (US), contrast-enhanced US can substantially improve detection and differentiation of focal liver lesions. Today, contrast-enhanced US is the dynamic imaging modality of choice for differentiation of focal liver lesions. Contrast uptake patterns of the most relevant liver lesions, as well as important clinical indications are presented and discussed.     

Ultrasonographic detection of focal liver lesions: increased sensitivity and specificity with microbubble contrast agents

Ultrasonography (US) is the first choice for screening patients with suspected liver lesions. However, due to a lack of contrast agents, US used to be less sensitive and specific compared with computed tomography (CT) and magnet resonance imaging (MRI). The advent of microbubble contrast agents increased both sensitivity and specificity dramatically. Rapid developments of the contrast agents as well as of special imaging techniques were made in recent years. Today numerous different US imaging methods exist which based either on Doppler or on harmonic imaging. They are using the particular behaviour of microbubbles in a sound field which varies depending on the energy of insonation (low/high mechanical index, MI) as well as on the properties of the agent themselves. Apart from just blood pool enhancement some agents have a hepatosplenic specific late phase. US imaging during this late phase using relatively high MI in phase inversion mode (harmonic imaging) or stimulated acoustic emission (SAE; Doppler method) markedly improves the detection of focal liver lesions and is also very helpful for lesion characterisation. With regards to detection, contrast enhanced US performs similarly to CT as shown by recent studies. Early results of studies using low MI imaging and the newer perfluor agents are also showing promising results for lesion detection. Low MI imaging with these agents has the advantage of real time imaging and is particularly helpful for characterisation of focal lesions based on their dynamic contrast behaviour. Apart from the techniques which based on the morphology of liver lesions there were some attempts for the detection of occult metastases or micrometastases by means of liver blood flow changes. Also in this field the use of US contrast agents appears to have advantages over formerly used non contrast-enhanced methods although no conclusive results are available yet.     

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

PURPOSE: To assess whether characterization of solid focal liver lesions could be improved by using ultrasonographic (US) contrast-specific modes after sulfur hexafluoride-filled microbubble contrast agent injection, as compared with lesion characterization achieved with preliminary baseline US. MATERIALS AND METHODS: Four hundred fifty-two solid focal hepatic lesions that were considered indeterminate at baseline gray-scale and color Doppler US were examined after microbubble contrast agent injection performed by using low-acoustic-power contrast-specific modes during the arterial (10-40 seconds after injection), portal venous (50-90 seconds after injection), and late (100-300 seconds after injection) phases. Two readers independently and retrospectively reviewed baseline and contrast material-enhanced US scans and classified each depicted lesion as malignant or benign according to standard diagnostic criteria. Sensitivity, specificity, accuracy, and positive and negative predictive values and areas under the receiver operating characteristic curve (Az) were calculated by considering histologic analysis (317 patients) or contrast-enhanced helical computed tomography followed by serial US 3-6 months apart (135 patients) as the reference standards. RESULTS: Different contrast enhancement patterns were observed according to lesion characteristics. During the late phase, benign lesions were predominantly hyper- or isoechoic relative to the adjacent liver parenchyma, whereas malignant lesions were predominantly hypoechoic. Review of the contrast-enhanced US scans after baseline image review yielded significantly improved diagnostic performance (P <.05). Overall diagnostic accuracy was 49% before versus 85% after review of the contrast-enhanced scan for reader 1 and 51% before versus 88% after review of the contrast-enhanced scan for reader 2. Diagnostic confidence-that is, the Az-was 0.820 before versus 0.968 after review of the contrast-enhanced scan for reader 1 and 0.831 before versus 0.978 after review of the contrast-enhanced scan for reader 2. CONCLUSION: The use of contrast-specific modes with a sulfur hexafluoride contrast agent led to improved characterization of solid focal liver lesions.     

Radiofrequency Ablation of Liver Cancer: Early Evaluation of Therapeutic Response with Contrast-Enhanced Ultrasonography

The early assessment of the therapeutic response after percutaneous radiofrequency (RF) ablation is important, in order to correctly decide whether further treatment is necessary. The residual unablated tumor is usually depicted on contrast-enhanced multiphase helical computed tomography (CT) as a focal enhancing structure during the arterial and portal venous phases. Contrast-enhanced color Doppler and power Doppler ultrasonography (US) have also been used to detect residual tumors. Contrast-enhanced gray-scale US, using a harmonic technology which has recently been introduced, allows for the detection of residual tumors after ablation, without any of the blooming or motion artifacts usually seen on contrast-enhanced color or power Doppler US. Based on our experience and reports in the literature, we consider that contrast-enhanced gray-scale harmonic US constitutes a reliable alternative to contrast-enhanced multiphase CT for the early evaluation of the therapeutic response to RF ablation for liver cancer. This technique was also useful in targeting any residual unablated tumors encountered during additional ablation.     

Ultrasound of focal liver lesions

This paper gives a comprehensive overview of ultrasound of focal liver lesions. Technical aspects such as examination technique and the use of Doppler modes as well as recent developments such as tissue harmonic imaging and microbubble contrast agents are discussed. The clinical significance and sonographic features of various liver lesions such as haemangioma, focal nodular hyperplasia, adenoma, regenerative nodule, metastasis, hepatocellular carcinoma and various types of focal infections are described. With the exception of cysts and typical haemangiomas, definitive characterisation of a liver lesion is often not possible on conventional ultrasound. This situation has changed with the recent advent of ultrasound contrast agents, which permit definitive diagnosis of most lesions. Contrast-enhanced sonography using recently developed contrast-specific imaging modes dramatically extends the role of liver ultrasound by improving its specificity in the detection and characterisation of focal lesions to rival CT and MRI.     

Comparison of diagnostic performance of unenhanced vs SonoVue - enhanced ultrasonography in focal liver lesions characterization. The experience of three Italian centers

PURPOSE: To evaluate the diagnostic performance of contrast-enhanced US with SonoVue (Bracco, Milan, Italy) compared to baseline US in focal hepatic lesions characterization. MATERIALS AND METHODS: A comprehensive number of four operators from 3 hospitals evaluated 57 consecutive patients with 60 focal hepatic lesions (28 hepatocellular carcinomas, 11 metastases, 13 hemangiomas, 1 hepatocellular adenoma and 7 focal nodular hyperplasias) by baseline gray-scale ultrasound (US) and color Doppler US. The same lesions were subsequently scanned by contrast-enhanced US after intravenous bolus administration of 2,4-4,8 ml of SonoVue by employing intermittent high or continuous low transmit power imaging. The diagnosis of lesions nature (benign or malignant) and histotype proposed by the on-site operator was finally compared to the definite diagnosis reached by reference procedures (multiphasic contrast-material enhanced helical-computed tomography or magnetic resonance in 24 lesions and fine needle US guided biopsy in 36 lesions). Diagnostic performance (sensitivity, specificity and overall accuracy expressed by the agreement with the reference procedures) of baseline and contrast enhanced US were compared. RESULTS: Differences in sensitivity (baseline vs contrast-enhanced US: 13/39 [33%] vs 32/39 [82%]), specificity (baseline vs contrast-enhanced US: 12/21 [57%] vs 16/21 [76%]) and overall accuracy (baseline vs contrast-enhanced US: 25/60 [41%] vs 47/60 [78%]) were significant (p<0.05; McNemar test). CONCLUSIONS: SonoVue-enhanced US determined a significant improvement in diagnostic performance in the characterization of focal liver lesions if compared to baseline US.     

Does the echogenicity of focal liver lesions on baseline gray-scale ultrasound interfere with the diagnostic performance of contrast-enhanced ultrasound?

The objective was to evaluate whether the echogenicity of focal liver lesions (FLLs) on baseline gray-scale ultrasound (US) interferes with the diagnostic performance of contrast-enhanced US (CEUS) for small FLLs. Three-hundred and eighty-eight patients were examined by real-time CEUS using a sulfur hexafluoride-filled microbubble contrast agent. The images of 114 hyperechoic lesions, 30 isoechoic lesions and 244 hypoechoic lesions were reviewed by two blinded independent readers. A five-point confidence level was used to discriminate malignant from benign lesions, and specific diagnoses were made. The diagnostic performances were evaluated by receiver-operating characteristic (ROC) analysis. The diagnostic performances of CEUS on hyperechoic lesions in terms of the areas (Az) under the ROC curve were 0.987 (reader 1) and 0.981 (reader 2), and were 0.987 (reader 1) and 0.984 (reader 2) for iso- and hypoechoic lesions, respectively. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 87.0–95.9%, 93.1–100%, 88.6–100%, 70.0–97.1% and 90.0–95.1%, respectively. The echogenicity of FLLs on baseline gray-scale US does not appear to interfere with the diagnostic ability of CEUS for small FLLs.     

US characterization of focal hepatic lesions with intermittent high-acoustic-power mode and contrast material

RATIONALE AND OBJECTIVES: This study was performed to determine whether ultrasound (US) performed with SonoVue, a contrast agent that contains microbubbles filled with sulfur hexafluoride vapor, depicts differential patterns of contrast enhancement in focal hepatic lesions. MATERIALS AND METHODS: Forty focal hepatic lesions (15 hepatocellular carcinomas [HCCs], 10 metastases, 11 hemangiomas, and four focal nodular hyperplasias) in 39 patients were evaluated by means of US, color Doppler US, and contrast-enhanced US performed by using intermittent high-acoustic-power mode. Contrast-enhanced helical computed tomography (11 patients) and US-guided fine needle aspiration (28 patients) were used as reference procedures. Contrast enhancement patterns were defined by means of both subjective and objective analysis, and baseline and contrast-enhanced US scans were reviewed offline. RESULTS: Thirteen of 15 HCCs, eight of 10 metastases, and all four hemangiomas with an atypical pattern at baseline US were correctly characterized after SonoVue injection. Two of 15 HCCs and two of 10 metastases remained indeterminate, with no characteristic baseline or contrast-enhanced patterns identified. Baseline US was essential in characterizing all hemangiomas with a typical pattern (n = 7), and color Doppler US with spectral analysis of tumoral vessels was essential in characterizing focal nodular hyperplasia. The percentage of diagnostic agreement with reference procedures was significantly increased (P < .001) for contrast-enhanced US compared with baseline US. CONCLUSION: Characteristic patterns of US contrast enhancement with SonoVue help in characterizing and differentiating focal hepatic lesions.     

The real capabilities of contrast-enhanced ultrasound in the characterization of solid focal liver lesions

Contrast-enhanced US (CEUS) using intravenous agents is a rapidly evolving field even though the main clinically recognized application is the characterization of focal liver lesions. Several reports have described the improvement provided by CEUS in the characterization of focal liver lesions in comparison to unenhanced US. CEUS with low transmit power insonation allows the real-time assessment of focal liver lesion contrast enhancement and vascularity during the different dynamic phases after injection of an intravenous contrast agent. CEUS allows the accurate characterization of focal liver lesions as benign or malignant based on the lesion contrast enhancement pattern during the arterial phase and lesion vascularity during portal--late phase in comparison to the adjacent liver parenchyma. During the portal--late phase, benign lesions present prevalently a sustained contrast enhancement with hyper or isovascular appearance to the adjacent liver while malignant lesions present prevalently microbubble washout with hypovascular appearance. On the other hand, the histology of focal liver lesions can only be confidently predicted in selected cases by CEUS, as in liver haemangiomas presenting typical nodular peripheral enhancement with subsequent centripetal fill-in and focal nodular hyperplasia with central spoke wheel-shaped contrast enhancement.     

Focal Hepatic Lesions: Evaluation with Contrast-Enhanced Gray-Scale Harmonic US

Objective

To determine the findings of various focal hepatic lesions at contrast-enhanced gray-scale ultrasound (US) using a coded harmonic angio (CHA) technique and emphasizing lesion characterization.

Materials and Methods

The study involved 95 patients with 105 focal hepatic lesions, namely 51 hepatocellular carcinomas (HCCs), 22 metastases, 22 hemangiomas, four cases of focal nodular hyperplasia (FNH), and six nontumorous nodules. After the injection of a microbubble contrast agent (SH U 508A), gray-scale harmonic US studies using a CHA technique were performed with a combination of continuous scanning to assess the intratumoral vasculature (vascular imaging) and interval-delay scanning to determine the sequential enhancement pattern (acoustic emission imaging). Each imaging pattern was categorized and analyzed.

Results

At vascular imaging, 69% of HCCs (35/51) showed irregular branching vessels, while in 91% of metastases (20/22) a peripherally stippled pattern was observed. Intratumoral vessels were absent in 95% of hemangiomas (21/22) and all nontumorous lesions (6/6), while in 75% of FNHs (3/4) a spoke-wheel pattern was evident. At acoustic emission imaging, 71% of HCCs (36/51) showed heterogeneous enhancement and 86% (19/22) of metastases showed rim- or flame-like peripheral enhancement during the early phase, with washout occurring in all HCCs and metastases (100%, 73/73) during the late phase. In hemangiomas, enhancement was either peripheral and nodular (19/22, 86%) or persistent and homogeneous (3/22, 14%), and 75% of FNHs (3/4) became isoechoic during the late phase.

Conclusion

At contrast-enhanced gray-scale US using a CHA technique, a period of continuous scanning depicted the intratumoral vasculature, and interval-delay scanning demonstrated the sequential enhancement pattern. The characteristic findings of various focal hepatic lesions were thus determined.     

Differential patterns of contrast enhancement in different focal liver lesions after injection of the microbubble US contrast agent SonoVue

PURPOSE: To identify differential contrast enhancement patterns in different focal hepatic lesions after injection of the microbubble contrast agent SonoVue using high or low acoustic power imaging. MATERIAL AND METHODS: Forty-seven focal hepatic lesions (1-8 cm) were detected in 45 patients at unenhanced gray-scale ultrasound (US) and evaluated by color Doppler (CD) US with spectral analysis of tumoral vessels. Lesions were subsequently evaluated by US contrast specific modes after IV bolus administration of 2,4-4,8 ml of SonoVue, by intermittent high acoustic power (18 patients) or by continous low acoustic power imaging (27 patients), during arterial, portal and late phase. Subjective evaluation of lesions appearance before and after SonoVue injection was performed. For final diagnosis multiphasic helical CT (21 patients) and/or fine needle US guided biopsy (24 patients) were considered as the reference procedures. RESULTS: Final diagnoses comprised 22 hepatocellular carcinomas (HCCs; 1,5-6 cm), 2 macroregenerative nodules (RNNs; 1-2 cm), 10 metastasis (2-3,5 cm), 10 hemangiomas (2-6 cm) and 3 focal nodular hyperplasias (FNHs; 1-3 cm). On CD evaluation HCCs revealed peripheral basket shaped (12/22) or intranodular (10/22) arterial pattern while, after SonoVue injection HCCs revealed diffuse contrast enhancement during arterial phase with contrast washout during portal and late phase. Metastases did not reveal flow signals on CD or contrast enhancement after SonoVue injection, except for 2 metastases which revealed peripheral and central vessels on CD and a diffuse contrast enhancement during arterial phase, appearing hypoechoic to the adjacent liver during portal and late phase. RNNs revealed dotted contrast-enhancement during portal and late phase with isoechoic appearance to the adjacent liver. Hemangiomas revealed some peripheral venous flows on CD and a peripheral nodular contrast enhancement during arterial phase with a centripetal fill-in during portal and late phase. FNHs revealed low resistance peripheral or central arterial vessels and a diffuse contrast enhancement during arterial phase, preceded or not by central spoke wheel shaped contrast enhancement, and a persistent iso-hyperechogenicity during portal and late phase. CONCLUSIONS: SonoVue injection has showed to identify differential contrast enhancement patterns in different focal hepatic lesions.     

Clinical value of MRI liver-specific contrast agents: a tailored examination for a confident non-invasive diagnosis of focal liver lesions

Screening of the liver for hepatic lesion detection and characterization is usually performed with either ultrasound or CT. However, both techniques are suboptimal for liver lesion characterization and magnetic resonance (MR) imaging has emerged as the preferred radiological investigation. In addition to unenhanced MR imaging techniques, contrast-enhanced MR imaging can demonstrate tissue-specific physiological information, thereby facilitating liver lesion characterization. Currently, the classes of contrast agents available for MR imaging of the liver include non-tissue-specific extracellular gadolinium chelates and tissue-specific hepatobiliary or reticuloendothelial agents. In this review, we describe the MR features of the more common focal hepatic lesions, as well as appropriate imaging protocols. A special emphasis is placed on the clinical use of non-specific and liver-specific contrast agents for differentiation of focal liver lesions. This may aid in the accurate diagnostic workup of patients in order to avoid invasive procedures, such as biopsy, for lesion characterization. A diagnostic strategy that considers the clinical situation is also presented.     

Contrast enhanced ultrasound of hepatocellular carcinoma

Sonazoid (Daiichi Sankyo, Tokyo, Japan), a second-generation of a lipid-stabilized suspension of a perfluorobutane gas microbubble contrast agent, has been used clinically in patients with liver tumors and for harmonic gray-scale ultrasonography (US) in Japan since January 2007. Sonazoid-enhanced US has two phases of contrast enhancement: vascular and late. In the late phase of Sonazoid-enhanced US, we scanned the whole liver using this modality at a low mechanical index (MI) without destroying the microbubbles, and this method allows detection of small viable hepatocellular carcinoma (HCC) lesions which cannot be detected by conventional US as perfusion defects in the late phase. Re-injection of Sonazoid into an HCC lesion which previously showed a perfusion defect in the late phase is useful for confirming blood flow into the defects. High MI intermittent imaging at 2 frames per second in the late phase is also helpful in differentiation between necrosis and viable hypervascular HCC lesions. Sonazoid-enhanced US by the coded harmonic angio mode at a high MI not only allows clear observation of tumor vessels and tumor enhancement, but also permits automatic scanning with Sonazoid-enhanced three dimensional (3D) US. Fusion images combining US with contrast-enhanced CT or contrast-enhanced MRI have made it easy to detect typical or atypical HCC lesions. By these methods, Sonazoid-enhanced US can characterize liver tumors, grade HCC lesions histologically, recognize HCC dedifferentiation, evaluate the efficacy of ablation therapy or transcatheter arterial embolization, and guide ablation therapy for unresectable HCC. This article reviews the current developments and applications of Sonazoid-enhanced US and Sonazoid-enhanced 3D US for diagnosing and treating hepatic lesions, especially HCC.     

Breast lesions: imaging with contrast-enhanced subharmonic US--initial experience

PURPOSE: To prospectively compare accuracy of gray-scale subharmonic imaging (SHI) with that of standard gray-scale ultrasonography (US), power Doppler US (with and without contrast material), and mammography for the diagnosis of breast cancer, with histopathologic or clinical follow-up results as the reference standard. MATERIALS AND METHODS: This HIPAA-compliant pilot study had institutional review board approval; all subjects gave written informed consent. Fourteen women (age range, 37-66 years) had 16 biopsy-proved breast lesions. In SHI, pulses are transmitted at one frequency, but only echoes at half that frequency (the subharmonic) are received. A US scanner was modified to perform gray-scale SHI (transmitting at 4.4 and receiving at 2.2 MHz). Precontrast imaging (gray-scale US and power Doppler) was followed by contrast material-enhanced power Doppler and gray-scale SHI. A reader blinded to mammographic and pathologic findings assessed diagnosis on a six-point scale. Sensitivity, specificity, accuracy, and receiver operating characteristic (ROC) curves were computed for mammography, gray-scale and power Doppler imaging (pre- and postcontrast), and SHI. RESULTS: Of the 16 lesions, four (25%) were malignant. Mammography had 100% sensitivity and 20% specificity. Sensitivity and specificity, respectively, were 50% and 92% for precontrast imaging and 75% and 75% for contrast-enhanced power Doppler. SHI had 75% sensitivity and 83% specificity. Specificity was higher for all US modes than for mammography (P<.04). There were no significant differences in specificity among US modes or in sensitivity (P>or=.50). Area under the ROC curve for the diagnosis of breast cancer was 0.64 for standard gray-scale US and power Doppler US, 0.67 for contrast-enhanced power Doppler US, 0.76 for mammography, and 0.78 for SHI (P>.20). Contrast enhancement was better with SHI than with power Doppler (100% vs 44% of lesions with good or excellent enhancement; P=.004). CONCLUSION: SHI appears to improve the diagnosis of breast cancer relative to conventional US and mammography, albeit on the basis of results in a very limited number of subjects.     

Initial clinical experience with oral manganese (CMC-001) for liver MR imaging

Recently, a new oral liver-specific manganese-based MR agent (CMC-001) has been introduced. This contrast medium is delivered to the liver in high concentrations in the portal vein and very low doses in the hepatic artery, as only small amounts of manganese enter the general circulation. It is taken up by the hepatocytes and excreted in the bile. Our initial experience with the new MR contrast medium in a variety of patients is reported. A total of 20 patients (11 males and 9 females) were studied with MR imaging 2 h after oral ingestion of the contrast agent. Sixteen patients were referred for evaluation of focal liver lesion(s), whereas in the remaining four patients, evaluation of the biliary tract was requested. In the 17 patients without biliary obstruction, there was an increased signal intensity of the liver parenchyma, whereas in the three patients with biliary obstruction, the uptake was delayed. There was excellent visualization of the biliary system on the T1-weighted images in the 16 patients without biliary obstruction referred for evaluation of a focal liver lesion. In seven patients, the uptake was patchy. In patients with focal liver lesions or biliary tract diseases, it is possible to increase the signal intensity of the liver parenchyma after the oral intake of CMC-001. In patients without biliary tract obstruction, the biliary system is easily visualized. Oral manganese seems to be useful in hepatobiliary MRI. Further research is strongly warranted. Financial disclosure: Thomsen HS. Manganese-containing magnetic resonance contrast agent. US patent no. 6,015,545/ 18 January 2000.     

Dynamic contrast-enhanced ultrasound with carbon dioxide microbubbles as adjunct to arteriography of liver tumors

Purpose The goal of the study is to evaluate utility of contrast enhanced ultrasound (US) with carbon dioxide microbubbles in evaluation of hepatic lesions.Methods Twenty eight patients with single or multiple t hepatic lesions (11 hepatocellular carcinoma, 8 hemangiomas, 5 metastases, 1 adenoma, 1 focal nodular hyperplasia, 2 regenerative nodules) were examined. US exam was performed during intraarterial injection of 10 ml of CO₂ through the same catheter employed for liver arteriography. The US exam was videotaped in its salient phases. Characteristics of enhancement were evaluated and correlated with histological findings or patient follow up.Results Sonographic angiography clearly demonstrated vascularization of the lesions. Hepatocellular carcinoma, hemangioma, metastases, focal nodular hyperplasia, and regenerative nodules had very characteristic patterns. The injection of CO₂ allowed detection of small additional nodules.Conclusion Sonographic angiography can improve characterization and staging of hepatic tumors. Low cost and the simplicity of the technique should encourage further experimentation.     

Contrast-enhanced ultrasound in diagnosis and characterization of focal hepatic lesions

The extensive use of imaging techniques in differential diagnosis of abdominal conditions and screening of hepatocellular carcinoma in patients with chronic hepatic diseases, has led to an important increase in identification of focal liver lesions. The development of contrast-enhanced ultrasound (CEUS) opens a new window in the diagnosis and follow-up of these lesions. This technique offers obvious advantages over the computed tomography and magnetic resonance, without a decrease in its sensitivity and specificity. The new second generation contrast agents, due to their intravascular distribution, allow a continuous evaluation of the enhancement pattern, which is crucial in characterization of liver lesions. The dual blood supply in the liver shows three different phases, namely arterial, portal and late phases. The enhancement during portal and late phases can give important information about the lesion's behavior. Each liver lesion has a different enhancement pattern that makes possible an accurate approach to their diagnosis. The role of emerging techniques as a contrast-enhanced three-dimensional US is also discussed. In this article, the advantages, indications and technique employed during CEUS and the different enhancement patterns of most benign and malignant focal liver lesions are discussed.