Hepatic malignancies: improved detection with pulse-inversion US in late phase of enhancement with SH U 508A-early experience

Artifacts and Technical Considerations at Contrast-enhanced US

Contrast-enhanced US (CEUS), similar to other radiologic modalities, requires specific technical considerations and is subject to image artifacts. These artifacts may affect examination quality, negatively impact diagnostic accuracy, and decrease user comfort when using this emerging technique. Some artifacts are related to commonly known gray-scale US artifacts that can also appear on the contrast-only image (tissue-subtracted image obtained with the linear responses from background tissues nulled). These may include acoustic shadowing and enhancement; reverberation, refraction, and reflection; and poor penetration. Other artifacts are exclusive to CEUS owing to the techniques used for contrast mode image generation and the unique properties of the microbubbles that constitute ultrasound-specific contrast agents (UCAs). UCA-related artifacts may appear on the contrast-only image, the gray-scale image, or various Doppler mode images. Artifacts related to CEUS may include nonlinear artifacts and unintentional microbubble destruction resulting in pseudowashout. The microbubbles themselves may result in specific artifacts such as pseudoenhancement, signal saturation, and attenuation and shadowing and can confound the use of color and spectral Doppler US. Identifying and understanding these artifacts and knowing how to mitigate them may improve the quality of the imaging study, increase user confidence, and improve patient care. The authors review the principles of UCAs and the sound-microbubble interaction, as well as the technical aspects of image generation. Technical considerations, including patient positioning, depth, acoustic window, and contrast agent dose, also are discussed. Specific artifacts are described, with tips on how to identify and, if necessary, apply corrective measures, with the goal of improving examination quality. ^© RSNA, 2022 Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

The Most Appropriate Time Delay after Microbubble Contrast Agent Intravenous Injection to Maximize Liver Metastasis Conspicuity on Contrast-Enhanced Ultrasound

PURPOSE

To identify the most appropriate time delay after microbubble contrast agent injection to maximize liver metastasis conspicuity on contrast-enhanced ultrasound (CEUS).

METHODS

Twenty-five consecutive patients (12 male and 13 female; age: 50 ± 13 years) with a known primary tumor and evidence of liver metastases on unenhanced ultrasound (US) underwent CEUS. CEUS consisted of continuous liver parenchyma scanning during arterial (15-35 s after microbubble injection), portal venous (40-120 s), and late phase (from 120 s up to microbubble disappearance). Subjective conspicuity index (ranging from 1 to 5) and objective conspicuity index (I_lesion-I_liver/I_liver, I = signal intensity) were calculated on reference frames selected on arterial phase and every 20 s on portal venous and late phase.

RESULTS

A total number of 40 liver metastases were identified after microbubble injection. The highest liver metastasis conspicuity was observed on early portal venous phase (40-60 s after microbubble injection) both on visual (mean subjective conspicuity index ± standard deviation [SD] = 4.36 ± 0.75, reader 1; 4.25 ± 0.65, reader 2) and quantitative analysis (mean objective conspicuity index ± SD = -0.99 ± 0.001).

CONCLUSION

The early portal venous phase (40-60 s after microbubble injection) provides the best liver metastases' conspicuity after microbubble contrast agent injection.

Artifacts in contrast-enhanced ultrasound: a pictorial essay

Although contrast-enhanced ultrasound (CEUS) has become a widely utilized and accepted modality in much of the world, the associated contrast agents have only recently received approval in the United States. As with all radiological techniques, image artifacts are encountered in CEUS, some of which relate to commonly encountered ultrasound artifacts, while others are unique to this technique. Image artifacts must be recognized when performing and interpreting examinations to improve technique and diagnostic accuracy. In this article, we review artifacts that may be encountered in CEUS, and where possible discuss how to minimize them or mitigate their effect on image quality and interpretation.

Evaluation of contrast Sonazoid-enhanced ultrasonography for the detection of hepatic metastases in breast cancer

Background

The present study was aimed to evaluate the usefulness of contrast Sonazoid-enhanced ultrasonography (US) for the detection of hepatic metastases in breast cancer patients and compare the clinical efficacy and sensitivity of this technique with conventional contrast unenhanced B-mode US in follow-up examinations of breast cancer patients with liver metastasis.

Methods

We assessed a total of 84 hepatic tumors from 24 patients diagnosed with or suspected of having metastatic cancer. These hepatic nodules were diagnosed through imaging, including dynamic magnetic resonance imaging (MRI), contrast-enhanced computed tomography (CECT) scan, B-mode US or contrast Sonazoid-enhanced US (SEUS). Differences in the sensitivity between US and SEUS were compared using MR imaging, CECT, and follow-up imaging.

Results

A total of 79 nodules were diagnosed as metastatic tumors. The remaining nodules were diagnosed as benign tumors (hepatic hemangioma: n = 3; local fatty change: n = 2). SEUS precisely detected the presence or absence of hepatic tumors in the 24 patients examined, showing a sensitivity of 98.8 % (83 of 84 lesions) for total imaged solid liver lesions, with an accuracy of 98.7 % (78 of 79 lesions) for total metastatic breast cancer lesions. In contrast, conventional B-mode US imaging revealed hepatic tumor lesions at a sensitivity of 66.7 % (56 of 84 lesions) and an accuracy of 64.6 % (51 of 79 lesions), respectively. Furthermore, the false positive and false negative rates were, respectively, 6.33 and 29.1 % for B-mode US and 0 and 1.3 % for SEUS. Moreover, twenty-seven metastatic tumors and five benign lesions (3 hemangiomas and 2 focal fatty changes/sparings) were imaged using SEUS but not conventional B-mode US. Significant differences in diagnostic accuracy rates between contrast Sonazoid-enhanced US and conventional B-mode US were observed (Wilcoxon signed rank test: p = 0.0009). No severe adverse events occurred during SEUS after the administration of Sonazoid, except for a grade 1 skin reaction and nausea in one patient.

Conclusion

These results suggested that Sonazoid could be safely administrated to breast cancer patients with liver metastatic disease. Thus, contrast Sonazoid-enhanced US is a feasible and more effective method than B-mode US for the detection of hepatic metastasis, particularly for small metastatic breast cancer lesions less than 14 mm in diameter, showing significant high sensitivity and accuracy.

Combining microbubbles and ultrasound for drug delivery to brain tumors: current progress and overview

Malignant glioma is one of the most challenging central nervous system (CNS) diseases, which is typically associated with high rates of recurrence and mortality. Current surgical debulking combined with radiation or chemotherapy has failed to control tumor progression or improve glioma patient survival. Microbubbles (MBs) originally serve as contrast agents in diagnostic ultrasound but have recently attracted considerable attention for therapeutic application in enhancing blood-tissue permeability for drug delivery. MB-facilitated focused ultrasound (FUS) has already been confirmed to enhance CNS-blood permeability by temporally opening the blood-brain barrier (BBB), thus has potential to enhance delivery of various kinds of therapeutic agents into brain tumors. Here we review the current preclinical studies which demonstrate the reports by using FUS with MB-facilitated drug delivery technology in brain tumor treatment. In addition, we review newly developed multifunctional theranostic MBs for FUS-induced BBB opening for brain tumor therapy.

Natural history of postvascular-phase iso-enhanced lesions on the sonogram in chronic liver diseases

BACKGROUND AND AIM

This study examined the natural history of postvascular-phase iso-enhanced lesions (PIELs) on contrast-enhanced sonograms to determine the potential risk and predictive factors for developing hepatocellular carcinoma (HCC) in chronic liver diseases.

METHODS

This prospective study included 87 PIELs on contrast-enhanced sonograms (postvascular-phase: 10 min post-injection of perflubutane microbubbles) in 72 patients with chronic liver diseases (45 males and 27 females; age 65.0 ± 10.8y; PIEL diameter 12.5 ± 4.2 mm). The PIELs were followed up by ultrasound/contrast-enhanced ultrasound, computed tomography, or magnetic resonance imaging at 3 to 6 months intervals.

RESULTS

Twenty patients developed HCCs during the study period (median, 22.0 months). The cumulative risk of HCC occurrence was 7.9% at 1 year and 36.0% at 3 years. The presence of coexistent HCC (hazard ratio [HR], 4.975; 95% confidence interval [CI], 1.729-14.316; P = 0.003) and alpha-fetoprotein > 20 ng/mL (HR, 4.104; 95% CI, 1.621-10.392; P = 0.003) were significant factors for the risk of HCC occurrence. Fourteen of these lesions were diagnosed as HCCs that developed from iso-enhanced lesions. Cumulative HCC occurrence rates from PIEL > 14 mm was 23.5% at 1 year and 46.3% at 3 years. Cox regression analysis showed that PIEL > 14 mm (HR, 6.780; 95% CI, 2.060-22.32; P = 0.002) and alpha-fetoprotein > 20 ng/mL (HR, 4.892; 95% CI, 1.559-15.350; P = 0.007) were statistically significant factors for HCC occurrence.

CONCLUSIONS

Patients with coexistent HCC, alpha-fetoprotein > 20 ng/mL, or PIEL > 14 mm should be carefully monitored because of the high potential for HCC occurrence.

Computer-aided diagnosis for contrast-enhanced ultrasound in the liver

Computer-aided diagnosis (CAD) has become one of the major research subjects in medical imaging and diagnostic radiology. The basic concept of CAD is to provide computer output as a second opinion to assist radiologists’ image interpretations by improving the accuracy and consistency of radiologic diagnosis and also by reducing the image-reading time. To date, research on CAD in ultrasound (US)-based diagnosis has been carried out mostly for breast lesions and has been limited in the fields of gastroenterology and hepatology, with most studies being conducted using B-mode US images. Two CAD schemes with contrast-enhanced US (CEUS) that are used in classifying focal liver lesions (FLLs) as liver metastasis, hemangioma, or three histologically differentiated types of hepatocellular carcinoma (HCC) are introduced in this article: one is based on physicians’ subjective pattern classifications (subjective analysis) and the other is a computerized scheme for classification of FLLs (quantitative analysis). Classification accuracies for FLLs for each CAD scheme were 84.8% and 88.5% for metastasis, 93.3% and 93.8% for hemangioma, and 98.6% and 86.9% for all HCCs, respectively. In addition, the classification accuracies for histologic differentiation of HCCs were 65.2% and 79.2% for well-differentiated HCCs, 41.7% and 50.0% for moderately differentiated HCCs, and 80.0% and 77.8% for poorly differentiated HCCs, respectively. There are a number of issues concerning the clinical application of CAD for CEUS, however, it is likely that CAD for CEUS of the liver will make great progress in the future.

Role of contrast enhanced ultrasonography in the assessment of hepatic metastases: A review

Contrast enhanced ultrasonography (CEUS) has improved both the detection and characterization of focal liver lesions. It is now possible to evaluate in real time the perfusion of focal liver lesions in the arterial, portal and late contrast phases, and thus to characterize focal liver lesions with high diagnostic accuracy. As a result, CEUS has taken a central diagnostic role in the evaluation of focal liver lesions that are indeterminate upon computed tomography (CT) and magnetic resonance imaging. The combined use of second generation contrast agents and low mechanical index techniques is essential for the detection of liver metastases, and it now allows the examination of the entire liver in both the portal and late phases. Several studies have shown that using CEUS instead of conventional ultrasonography without contrast agents significantly improves sensitivity in detection of liver metastases. Furthermore, the detection rate with CEUS seems to be similar to that of CT. This review describes the clinical role of CEUS in detecting liver metastases, including details about examination techniques, features of metastases observed with CEUS, and clinical results and guidelines.

Detection Of Focal Liver Lesions In Cirrhotic Liver Using Contrast-Enhanced Ultrasound

Patients with liver cirrhosis are at increased risk of hepatocellular carcinoma (HCC). Conventional or baseline ultrasound (BUS) is often used as the first-line tool for HCC surveillance or detection, but the accuracy of BUS in HCC detection or differentiation from other focal liver lesions (FLLs) is limited. Contrast-enhanced ultrasound (CEUS) represents a recent revolution in the field of ultrasonography and it has become increasingly important in the detection and evaluation of FLLs. In CEUS, HCC typically exhibits arterial hyper-enhancement and portal-venous washout represented by hypo-enhanced lesions in the portal venous and late phases. The detection rate of HCC was significantly higher with CEUS compared with BUS. Even regenerative or some dysplastic nodules may exhibit arterial hyper-enhancement as they are differentiated from HCC by its iso-enhancing pattern in portal and late phases. The contrast-enhancement patterns of other different types of benign and malignant FLLs, as well as their detection rates with CEUS, were also discussed.

Improved detection of hepatic metastases with contrast-enhanced low mechanical-index pulse inversion ultrasonography during the liver-specific phase of sonazoid: observer performance study with JAFROC analysis

RATIONALE AND OBJECTIVES

To compare B-mode ultrasonography (US) alone with the combination of B-mode and contrast-enhanced (Sonazoid) late-phase pulse-inversion US for the detection of hepatic metastases by use of jackknife free-response receiver-operating characteristic (JAFROC) analysis.

MATERIALS AND METHODS

Twenty-seven patients with 57 hepatic metastases and 6 patients without hepatic metastases underwent B-mode and contrast-enhanced US. We used the diagnoses established by contrast-enhanced computed tomography and contrast-enhanced US as the standard of reference. All ultrasonographic scanning was performed by an experienced radiologist with a routine clinical procedure. All scanning data were archived with digital cine clips. A review system, which can display pairs of cine clips for B-mode and contrast-enhanced US side by side, was developed for off-site observer study. Seven radiologists interpreted each case individually first by B-mode US only, and then by the combination with contrast-enhanced US by identifying locations of possible candidates for hepatic metastasis with their confidence ratings. The figure-of-merit (FOM) values, sensitivity, and false-positives per case were estimated for B-mode US alone, and for the combination of B-mode and contrast-enhanced US.

RESULTS

The sensitivities of the combined ultrasonographic imaging (mean, 72.2%) were clearly improved from that of B-mode US alone (mean, 41.6%) while reducing the average number of false positives from 1.1 to 0.5 per case. In the jackknife analysis, there was a statistically significant difference between mean FOM values for the combined imaging (0.76) and for B-mode US alone (0.44, P < .00001).

CONCLUSION

Evaluating cine clips of contrast-enhanced liver US together with B-mode US could improve physicians' accuracy for detection of hepatic metastases.

Computer-aided diagnosis of focal liver lesions by use of physicians' subjective classification of echogenic patterns in baseline and contrast-enhanced ultrasonography

RATIONAL AND OBJECTIVES

To develop a computer-aided diagnostic (CAD) scheme for classifying focal liver lesions (FLLs) by use of physicians' subjective classification of echogenic patterns of FLLs on baseline and contrast-enhanced ultrasonography (US).

MATERIALS AND METHODS

A total of 137 hepatic lesions in 137 patients were evaluated with B-mode and NC100100 (Sonazoid)-enhanced pulse-inversion US; lesions included 74 hepatocellular carcinomas (HCCs) (23: well-differentiated, 36: moderately differentiated, 15: poorly differentiated HCCs), 33 liver metastases, and 30 liver hemangiomas. Three physicians evaluated single images at B-mode and arterial phases with a cine mode. Physicians were asked to classify each lesion into one of eight B-mode and one of eight enhancement patterns, but did not make a diagnosis. To classify five types of FLLs, we employed a decision tree model with four decision nodes and four artificial neural networks (ANNs). The results of the physicians' pattern classifications were used successively for four different ANNs in making decisions at each of the decision nodes in the decision tree model.

RESULTS

The classification accuracies for the 137 FLLs were 84.8% for metastasis, 93.3% for hemangioma, and 98.6% for all HCCs. In addition, the classification accuracies for histological differentiation types of HCCs were 65.2% for well-differentiated HCC, 41.7% for moderately differentiated HCC, and 80.0% for poorly differentiated HCC.

CONCLUSIONS

This CAD scheme has the potential to improve the diagnostic accuracy of liver lesions. However, the accuracy in the histologic differential diagnosis of HCC based on baseline and contrast-enhanced US is still limited.

Ultrasound contrast microbubbles in imaging and therapy: physical principles and engineering

Microbubble contrast agents and the associated imaging systems have developed over the past 25 years, originating with manually-agitated fluids introduced for intra-coronary injection. Over this period, stabilizing shells and low diffusivity gas materials have been incorporated in microbubbles, extending stability in vitro and in vivo. Simultaneously, the interaction of these small gas bubbles with ultrasonic waves has been extensively studied, resulting in models for oscillation and increasingly sophisticated imaging strategies. Early studies recognized that echoes from microbubbles contained frequencies that are multiples of the microbubble resonance frequency. Although individual microbubble contrast agents cannot be resolved-given that their diameter is on the order of microns-nonlinear echoes from these agents are used to map regions of perfused tissue and to estimate the local microvascular flow rate. Such strategies overcome a fundamental limitation of previous ultrasound blood flow strategies; the previous Doppler-based strategies are insensitive to capillary flow. Further, the insonation of resonant bubbles results in interesting physical phenomena that have been widely studied for use in drug and gene delivery. Ultrasound pressure can enhance gas diffusion, rapidly fragment the agent into a set of smaller bubbles or displace the microbubble to a blood vessel wall. Insonation of a microbubble can also produce liquid jets and local shear stress that alter biological membranes and facilitate transport. In this review, we focus on the physical aspects of these agents, exploring microbubble imaging modes, models for microbubble oscillation and the interaction of the microbubble with the endothelium.

Use of contrast ultrasonography in the diagnosis of metastatic feline visceral haemangiosarcoma

A 12-year-old cat was presented for investigation of weight loss and inappetence. Radiography and conventional grey-scale ultrasonography showed a large mid-body splenic mass. Contrast enhanced ultrasonography of the liver demonstrated a hypoechoic left lateral lobe nodular mass during the peak and late portal-phases of liver enhancement. Histopathology of the splenic mass and hepatic nodular mass confirmed haemangiosarcoma. The use of ultrasound microbubble contrast media in the diagnosis of hepatic metastasis in the cat has not been previously reported in the cat.

Can contrast-enhanced ultrasonography replace multidetector-computed tomography in the detection of liver metastases from colorectal cancer?

PURPOSE

To compare the sensitivity and specificity of contrast-enhanced ultrasonography (CEUS) and 4-slice multidetector-computed tomography (MDCT) in the detection of liver metastases in patients with colorectal cancer (CRC).

MATERIALS AND METHODS

Candidates for this prospective study were 461 consecutive patients referred to the Department of Colorectal Surgery, Aarhus University Hospital with primary or local recurrence of CRC. The patients underwent liver ultrasonography (US), CEUS, MDCT and intraoperative ultrasonography (IOUS). Fine-needle biopsy was performed on all suspicious lesions. The examinations were interpreted blindly and the combination of US, CEUS, biphasic MDCT, IOUS, follow up and biopsy was the gold standard.

RESULTS

Three hundred and sixty-five patients were included. All patients had undergone preoperative US, CEUS and MDCT and 65.5% had received IOUS. The gold standard found liver metastases in 54 patients (14.8%). Multidetector CT found significantly more metastases than CEUS in 15 (28%) of the patients (p=0.02). In a patient-by-patient analysis MDCT had a non-significantly higher sensitivity in the detection of liver metastases compared to CEUS (0.89 versus 0.80, p=0.06). The specificity of CEUS (0.98) was slightly better than that of MDCT (0.94) (p=0.02).

CONCLUSION

Multidetector CT found significant more metastases than CEUS, and MDCT had in patient-by-patient analysis a non-significant better sensitivity (p=0.06) in detecting liver metastases in patients with CRC.

Real time contrast enhanced ultrasonography in detection of liver metastases from gastrointestinal cancer

Background

Contrast enhanced ultrasound (CEUS) is an imaging technique which appeared on the market around the year 2000 and proposed for the detection of liver metastases in gastrointestinal cancer patients, a setting in which accurate staging plays a significant role in the choice of treatment.

Methods

A total of 109 patients with colorectal (n = 92) or gastric cancer prospectively underwent computed tomography (CT) scan and conventional US evaluation followed by real time CEUS. A diagnosis of metastases was made by CT or, for lesions not visibile at CT, the diagnosis was achieved by histopathology or by a malignant behavior during follow-up.

Results

Of 109 patients, 65 were found to have metastases at presentation. CEUS improved sensitivity in metastatic livers from 76.9% of patients (US) to 95.4% (p <0.01), while CT scan reached 90.8% (p = n.s. vs CEUS, p < 0.01 vs US). CEUS and CT were more sensitive than US also for detection of single lesions (87 with US, 122 with CEUS, 113 with CT). In 15 patients (13.8%), CEUS revealed more metastases than CT, while CT revealed more metastases than CEUS in 9 patients (8.2%) (p = n.s.).

Conclusion

CEUS is more sensitive than conventional US in the detection of liver metastases and could be usefully employed in the staging of patients with gastrointestinal cancer. Findings at CEUS and CT appear to be complementary in achieving maximum sensitivity.

Application of percutaneous ultrasound-guided treatment for ultrasonically invisible hypervascular hepatocellular carcinoma using microbubble contrast agent

AIM

To evaluate the efficacy of contrast-enhanced ultrasound for the localization of ultrasonically invisible hypervascular lesions in the liver to facilitate percutaneous ultrasound-guided treatment.

MATERIALS AND METHODS

Forty patients with 47 ultrasonically invisible hypervascular lesions (5-20mm) diagnosed on contrast-enhanced computed tomography were enrolled in the retrospective study. Contrast-enhanced ultrasound (CEUS) with Levovist was performed to localize the lesions both in the early phase and liver-specific phase. Diagnosis of was confirmed by percutaneous needle biopsy where feasible, and on the basis of on treatment outcomes or changes in computed tomography findings in those not amenable to biopsy.

RESULTS

Thirty-two lesions were diagnosed as hepatocellular carcinoma (HCC). Contrast-enhanced ultrasound localized hepatocellular carcinoma in 24/32 (75%) lesions, the mean diameter (15.1+/-4.9mm), as measured using computed tomography, being significantly larger than that of the remaining eight lesions (10.5+/-2.1mm). Ultrasound-guided treatment was performed in 19 of the 24 lesions, and transarterial chemoembolization (TACE) was applied for the other five lesions because of difficult percutaneous access. Five of the eight non-visualised lesions were treated by transarterial chemoembolization, and the other three by surgical resection. The beneficial effect of CEUS was significantly greater when the reason for poor initial visualisation was the coarse liver architecture (17/17) than when it was due to adverse location (seven of 15, p<0.005). Fifteen of the CT-detected hypervascular lesions were considered to represent false positives for HCC, based on their behaviour during follow-up.

CONCLUSION

Contrast-enhanced ultrasound with Levovist facilitates the application of percutaneous ultrasound-guided treatment by improving localization of ultrasonically invisible hypervascular hepatocellular carcinomas in the liver.

New perspectives for the use of contrast-enhanced liver ultrasound in clinical practice

The introduction of second-generation microbubble ultrasound contrast agents and the development of contrast specific ultrasound techniques have improved the ability of contrast enhanced ultrasound in detecting and characterising liver lesions, offering new perspectives for its exploitation in clinical hepatology. Indeed, several studies have demonstrated a high diagnostic accuracy in focal lesion characterisation (85-96%) in patients either with or without underlying chronic liver disease. This review article describes the basic principles of contrast enhanced ultrasound, defines the different vascular features of benign and malignant liver lesions, and assesses its clinical impact in different clinical scenarios, according to the guidelines of the European Federation of Societies for Ultrasound in Medicine and Biology, contrast enhanced ultrasound enables the characterisation of focal liver lesions, regardless of the presence or absence of underlying chronic liver disease. Contrast enhanced ultrasound is also useful in staging and follow-up of cancer patients and in monitoring local ablative treatment. Contrast enhanced ultrasound is expected to be considerably increased and replace many computed tomography and magnetic resonance imaging examinations in near future, according to the European Federation of Societies for Ultrasound in Medicine and Biology guidelines. Therefore, it is necessary to take measures in order to meet the demand for an increasing number of these procedures.

Recent applications of ultrasound: diagnosis and treatment of hepatocellular carcinoma

Ultrasound (US) has the advantages of real-time observation, simple technique, and a noninvasive procedure compared to other imaging modalities. The recent development of digital technologies has enabled the observation of sonograms with improved signal-to-noise ratio, penetration, and spatial and contrast resolutions. Furthermore, microbubble contrast agents have increased the diagnostic ability of US examination, and the use of three-dimensional sonograms is now not unusual. These advances have furthered the usefulness of US for liver tumors in clinical practice. This article reviews the recent applications of US in the diagnosis and treatment of hepatocellular carcinoma.

Detection of colorectal cancer hepatic metastases with contrast-enhanced ultrasound: comparison with conventional B-mode ultrasound

The aim of this study was to assess whether contrast-enhanced ultrasound (CE-US) could provide improved diagnostic information in detecting liver metastases from colorectal cancer as compared to B-mode non-enhanced ultrasound (B-US). 32 patients (M/F 23/9, age range 48-82 years, mean 58.2 years) under chemotherapy for colorectal cancer were examined with B-US and CE-US using a second-generation ultrasound contrast agent and a dedicated protocol for contrast detection. The presence of focal liver lesions along with the number, size, pre- and post-contrast sonographic features were recorded digitally. Lesion conspicuity with a three-grade scoring scale was performed on both techniques and contrast intensity measurements were calculated for each focal lesion. CE-US detected 17% more metastases in patient-by-patient and lesion-by-lesion analysis. A statistically significant difference was found between the scoring mean values with regard to conspicuity of the lesions. Accurate characterization of the liver lesions was achievable only with contrast-enhanced technique. A quantitative contrast intensity measurement method confirmed the invariably washing-out vascular pattern in all metastases at sinusoidal-parenchymal liver phase. In conclusion, CE-US is superior to B-US and provides an effective tool in the investigation of colorectal cancer liver metastases.

The value of contrast enhanced ultrasonography in detection of liver metastases from colorectal cancer: a prospective double-blinded study

OBJECTIVE

To compare sensitivity and specificity of contrast enhanced ultrasonography (CEUS) with conventional ultrasonography (US) in detection of liver metastases in patients with colorectal adenocarcinoma (CRC) in a patient-by-patient analysis.

MATERIALS AND METHODS

A prospective study of 461 consecutive patients referred to the Department of Colorectal Surgery, Aarhus University Hospital with primary or local recurrence of CRC. In order to detect possible liver metastases all patients underwent liver US, followed by CEUS by another investigator. Multislice CT scanning (MDCT), and intraoperative ultrasonography (IOUS) were then performed. Fine-needle biopsy was performed on all suspicious lesions. Each examination was interpreted blindly and the combination of biphasic MDCT, IOUS, follow up and biopsy was the gold standard.

RESULTS

Standard of reference found liver metastases in 54 patients (14.8%). Contrast enhanced ultrasonography improved the sensitivity significantly in detection of liver metastases from 0.69 by US to 0.80 (p=0.031). In 24 patients, CEUS found a higher number of metastases than US (p<0.001). The specificity (0.98) and the positive predictive value (0.86) was the same.

CONCLUSION

Contrast enhanced ultrasonography improves sensitivity in detection of liver metastases in patients with CRC and in nearly half of the cases CEUS found a higher number of metastases than US.

Contrast-enhanced triggered harmonic sonography for assessment of periarticular hemodynamic changes in experimental arthritis

BACKGROUND

Objective quantification is critical for assessment of functional sonography in inflammatory arthritis. To create a microbubble contrast-enhanced image of vessels that lie below the resolution of a standard US system, a technique is required that detects preferentially the contrast agent echo, rejecting that from background tissue: harmonic imaging.

OBJECTIVES

To investigate the ability of contrast-enhanced triggered harmonic sonography (CETHS) to evaluate periarticular hemodynamic changes over the course of experimental arthritis and to discriminate presence and absence of arthritis based on measurement values obtained at specific time-points.

MATERIALS AND METHODS

Arthritis was induced in rabbits knees by intra-articular injection of serum bovine albumin, which acted as an antigen. A total of 11 rabbits (8 with unilateral arthritis and 3 control animals) were imaged at 0, 1, 7, 14, 21 and 28 days of antigen-induced arthritis and euthanized at 28 days. A continuous infusion protocol was performed (triggering times 30.0, 20.0, 10.0, 5.0, 2.0, 1.0, and 0.5 s). Hemodynamic indices of synovial microvasculature (vascular volume, mean velocity and flow rate) were obtained and compared with clinical, laboratory, and histological surrogate markers.

RESULTS

Although interval CETHS changes were noted for flow rate (P=0.007) and vascular volume (P=0.003) ratios in albumin-injected knees, no significant differences in ratios were identified over time between albumin-injected and non-injected knees for flow rate (P=0.52), vascular volume (P=0.23) and mean velocity (P=0.19). Flow rate most accurately differentiated between presence and absence of arthritis according to clinical measurements in early (day 1) arthritis, and mean velocity in mid-term arthritis (day 14; both P=0.02).

CONCLUSION

Although the measurement properties of CETHS indices were poor in the evaluation of hemodynamic differences over time in albumin-injected knees compared with non-injected knees, they enabled discrimination between presence and absence of arthritis at specific time-points in different stages.

Microbubble disappearance-time is the appropriate timing for liver-specific imaging after injection of Levovist

Contrast enhancement in the portal vein was repeatedly observed at 1 min intervals with wide-band Doppler ultrasonography in 152 consecutive patients (132 with liver cirrhosis and HCC, 20 controls), 5 min after the injection of Levovist. The duration time of contrast enhancement in the portal vein (microbubble disappearance-time; MD-T) was measured in all patients and contrast-enhanced appearances were compared between the 5 min phase and MD-T phase in 68 HCC nodules. MD-T in patients with liver cirrhosis (572.4 +/- 117.9 s) was significantly longer than in controls (481.6 +/- 89.3 s, p < 0.05). MD-T was prolonged in patients with Child B and C compared with Child A (p < 0.05). The contrast-enhanced appearances between the two phases were different in 30 of 68 HCC nodules (44.1%), showing positive enhancement in the 5 min phase and negative enhancement in the MD-T phase. The proposed MD-T may become an essential factor for the evaluation of liver-specific sonograms.

The role of late-phase pulse inversion harmonic imaging in the detection of occult hepatic metastases

OBJECTIVE

The purpose of this study was to investigate the efficacy of late-phase pulse inversion harmonic imaging (PIHI) in detecting occult metastases and to compare the results with helical computed tomography (CT) in a group of patients whose fundamental liver sonographic results were normal.

METHODS

Thirty-two patients (21 women and 11 men; age range, 20-87 years) with a known primary malignancy were enrolled in the study. The patients were evaluated with conventional sonography, unenhanced PIHI, and PIHI 3 minutes after the injection of Levovist (SH U 508A; Schering AG, Berlin, Germany). All patients also underwent triphasic helical CT within 1 week after sonography. In 1 patient, mangafodipir-enhanced magnetic resonance imaging was performed as part of the clinical workup.

RESULTS

After Levovist injection, in 4 (12.5%) of 32 patients, at least 1 hypoechoic lesion was detected by PIHI; multiple lesions were shown in 1 patient. The mean diameter of newly detected lesions was 12 mm. Triphasic helical CT also showed all of the lesions that were detected by PIHI. The diagnoses were confirmed by biopsy and CT findings in 2 patients and by the typical CT and magnetic resonance imaging findings in 1 patient. For the fourth patient, the diagnosis was confirmed by follow-up and CT. Conclusions. Late-phase PIHI is comparable to helical CT for detecting occult hepatic metastases, but it protects patients from the potentially hazardous effects of radiation and iodinated contrast agents. Further series involving a larger number of patients are needed to determine its place in the evaluation of cancer staging and treatment planning.

Pulse-Inversion US Imaging of Testicular Ischemia: Quantitative and Qualitative Analyses in a Rabbit Model

PURPOSE

To quantitatively and qualitatively assess perfusion with pulse-inversion (PI) ultrasonography (US) in rabbit model of acute testicular ischemia.

MATERIALS AND METHODS

Institutional animal care committee approval was obtained. After 35 rabbits underwent unilateral spermatic cord occlusion, testicular Doppler US and contrast material-enhanced PI imaging were performed. Enhancement data yielded perfusion measurements including mean value during the first 10 seconds, mean value over entire recorded replenishment curve, and curve slope during the first 5 seconds. Calculated perfusion ratios were compared with radiolabeled microsphere-derived perfusion ratios. Two readers assessed testicular perfusion as none, possible, or definite and relative perfusion as greater to the right testis than to the left, greater to the left testis than to the right, or as equal to both testes. With kappa statistics, interobserver agreement for all imaging methods was determined. Association between qualitative perfusion categories and radiolabeled microsphere-based perfusion measurements was assessed. Quantitative and qualitative determinations of relative perfusion were compared with radiolabeled microsphere-based measurements.

RESULTS

Correlations between calculated and radiolabeled microsphere-based perfusion ratios were determined (r=0.49-0.64). Interobserver agreement for presence of perfusion was excellent (kappa=0.76), and that for relative perfusion assessment was good (kappa=0.55). Neither kappa value varied significantly with imaging method. The percentage of times a testis classified as having definite perfusion had greater perfusion as measured with radiolabeled microspheres than a testis classified as having no perfusion or possible perfusion was higher with PI imaging than with Doppler US (85%-98% vs 72%-89%). Identification of the testis with less perfusion was better with quantitative methods than with qualitative assessment of images by the readers (75%-79% vs 34%-60%, P<.004).

CONCLUSION

PI imaging, compared with conventional Doppler US methods, provides superior assessment of perfusion in the setting of acute testicular ischemia.

Comparison of contrast-enhanced ultrasonography versus baseline ultrasound and contrast-enhanced computed tomography in metastatic disease of the liver: diagnostic performance and confidence

AIM

The aim of this study was to compare contrast-enhanced ultrasonography (CEUS) to baseline US and contrast-enhanced computed tomography (CT) in metastatic disease of the liver diagnosed or suspected by US during presurgical staging or postsurgical follow-up for primary malignancies.

MATERIALS AND METHODS

Two hundred-fifty-three patients considered suitable for US due to the complete explorability of the liver and with one to five proven or suspected liver metastases at baseline US were included. All patients underwent US before and after microbubble injection, and multiphase contrast-enhanced CT. Independent panels of readers reviewed US and CT scans and recorded liver metastases according to a 5-grade scale of diagnostic confidence. Sensitivity, specificity (diagnostic performance) and area under the receiver operating characteristics (ROC) curve (diagnostic confidence) were calculated.

RESULTS

Reference standards revealed no metastases in 57/253, more than five in 59/253, and one to five in 137/253 patients. In patients with one to five metastases, CEUS versus baseline US revealed more metastases in 64/137 and the same number in 73/137 patients while CEUS versus CT revealed more metastases in 10/137, the same number in 99/137, and lower number in 28/137. Sensitivity, specificity, and area under ROC curve of CEUS (83%, 84%, 0.929, respectively) differed from baseline US (40%, 63%, 0.579, respectively; P<0.01) while did not differ from CT (89%, 89%, 0.945, respectively; P>0.05).

CONCLUSION

CEUS improved liver metastases diagnosis in comparison with baseline US while it revealed similar diagnostic performance and confidence to contrast-enhanced CT in patients considered suitable for US and with proven or suspected liver metastases at baseline US.

Ultrasonographic detection of hepatocellular carcinoma: correlation of preoperative ultrasonography and resected liver pathology

AIM

The aim of this study was to determine the sensitivity of ultrasonography for detecting hepatocellular carcinoma in patients who underwent surgical liver resection.

MATERIALS AND METHODS

The preoperative ultrasonography reports of 103 patients who underwent hepatic resection surgery were retrospectively reviewed. The patients had chronic liver disease with good liver function and a relatively normal liver echo-texture. The presence of a mass or masses in the resected part of the liver segments on preoperative ultrasonography was regarded as possible hepatocellular carcinoma, and these results were compared with the surgically resected hepatic lobes or segments. Accuracy for detection was assessed on a lesion-by-lesion basis, on a segment-by-segment basis, and on a patient basis.

RESULTS

One hundred and fifty-seven hepatocellular carcinomas were found in 244 hepatic segments of 103 patients. One hundred and one of 157 hepatocellular carcinomas were detected using ultrasonography in 97 patients resulting in a sensitivity of 64%. In six patients, a solitary hepatocellular carcinoma was missed in each patient, a patient sensitivity being 94%. Using ultrasonography, 87 of 100 (87%) hepatocellular carcinomas larger than 2 cm in diameter, and 14 of 57 (25%) hepatocellular carcinomas 2 cm or smaller in diameter were revealed. On the basis of segment-by-segment analysis, the sensitivity was 78% (99 of 127 segments), specificity was 97% (114 of 117 segments), accuracy was 87% (213 of 244 segments), positive predictive value was 97% (99 of 102 segments), and negative predictive value was 80% (114 of 142 segments).

CONCLUSION

In patients with chronic liver disease and good hepatic function, ultrasonography has a sensitivity of 94% in the identification of affected patients, but for individual lesions, the sensitivity is only 64%.

Bolus versus Continuous Infusion of Microbubble Contrast Agent for Liver US: Initial Experience

Institutional review board approval and informed consent were obtained. To prospectively assess if continuous infusion of galactose-palmitic acid can prolong the duration of hepatic enhancement at ultrasonography over bolus injection, 11 patients received two injections--one bolus injection (2 mL/sec) and one continuous infusion (1.5 mL/min)--with the same dose of galactose-palmitic acid (4 g, 300 mg/dL). Two unenhanced baseline sweep scans (mechanical index of 0.7 and 1.3) of the relevant liver lobe were acquired followed by contrast-enhanced sweeps after bolus injection and continuous infusion. Each sweep was saved as cine loops and analyzed with a personal computer. Duration of enhancement more than 3 dB was prolonged by continuous infusion from 4.3 minutes +/- 2.4 (+/-standard deviation) at bolus injection to 10.1 minutes +/- 3.0 (P < .005). Maximal parenchymal enhancement was 11.0 dB +/- 3.2 (bolus injection) and 9.2 dB +/- 3.8 (infusion, P < .05). Peak liver-to-lesion contrast was 14.2 dB +/- 6.3 (bolus injection) and 13.2 dB +/- 7.1 (infusion, not significant). Continuous infusion of galactose-palmitic acid markedly prolongs but slightly diminishes hepatic enhancement; liver-to-lesion contrast remains unchanged.

Comparison of IV Contrast-Enhanced Sonography and Histopathology of Pancreatic Cancer

OBJECTIVE

We compared contrast-enhanced sonography findings with pathologic findings in pancreatic cancer to evaluate the ability of contrast-enhanced sonography to depict the pathologic changes associated with pancreatic cancer.

SUBJECTS AND METHODS

Thirty-four patients with pancreatic cancer who underwent surgery were investigated. Sonography was performed with contrast material (Levovist) for all patients before surgery. Pathologic findings were evaluated on the basis of the resected cancer specimens. We compared contrast-enhanced sonography findings with pathologic findings.

RESULTS

All tumors that were hyperechoic on contrast-enhanced sonography were papillary adenocarcinoma, and all tumors that were hypoechoic on contrast-enhanced sonography were ductal adenocarcinoma. Among ductal adenocarcinomas, five (71.4%) of seven tumors for which the size of the hypoechoic area was unchanged on contrast-enhanced sonography had clear tumor margins with no infiltration or inflammation in the margin. In contrast, all tumors for which the size of the hypoechoic area was reduced on contrast-enhanced sonography had unclear tumor margins with infiltration of cancerous cells and inflammation. Nine (90%) of 10 tumors that showed partial contrast enhancement or a vascular shadow in a hypoechoic area had large or medium-sized vessels within a tumor at pathology. In contrast, only one (4.8%) of 21 tumors that did not show the vascular shadow in a hypoechoic area had no large or medium-sized vessels in a tumor.

CONCLUSION

Contrast-enhanced sonography well reflects the pathologic changes of pancreatic cancer and will provide useful information in a pretreatment evaluation. Further studies with a large number of patients will be required to confirm this finding.

1.5 Harmonic Imaging Sonography with microbubble contrast agent improves characterization of hepatocellular carcinoma

AIM: To investigate the usefulness of 1.5 Harmonic Imaging Sonography with the use of the contrast agent Levovist for the diagnosis of hepatocellular carcinoma (HCC) and for the evaluation of therapeutic response.

METHODS: Phantom experiments were performed to compare the contrast effects of 2^nd harmonic imaging and 1.5 Harmonic Imaging Sonography. 1.5 Harmonic Imaging Sonography was employed to examine 36 patients with HCC (42 nodules) before and after the treatment and to compare against the findings obtained using other diagnostic imaging modalities.

RESULTS: In 1.5 Harmonic Imaging Sonography, the tumor vessels of HCCs were clearly identified during the early phase, and late-phase images clearly demonstrated the differences in contrast enhancement between the tumor and surrounding hepatic parenchyma. Blood flow within the tumor was detected in 36 nodules (85.7%) during the early phase and in all 42 nodules (100%) during the late phase using 1.5 Harmonic Imaging Sonography, in 38 nodules (90.5%) using contrast-enhanced CT, in 34 nodules (81.0%) using digital subtraction angiography (DSA), and in 42 nodules (100%) using US CO₂ angiography. Following transcatheter arterial embolization, 1.5 Harmonic Imaging Sonography detected blood flow and contrast enhancement within the tumors that were judged to contain viable tissue in 20 of 42 nodules (47.6%). However, 6 of these 20 cases were not judged in contrast-enhanced CT. 1.5 Harmonic Imaging Sonography was compared with the US CO2 angiography findings as the gold standard, and the sensitivity and specificity of these images for discerning viable and nonviable HCC after transcatheter arterial embolization were 100% and 100%, respectively.

CONCLUSION: 1.5 Harmonic Imaging Sonography permits the vascular structures of HCCs to be identified and blood flow within the tumor to be clearly demonstrated. Furthermore, 1.5 Harmonic Imaging Sonography is potentially useful for evaluating the therapeutic effects of transcatheter arterial embolization on HCC.

Intrahepatic venous anastomosis formation of the right liver in living donor liver transplantation: evaluations by Doppler ultrasonography and pulse-inversion ultrasonography with Levovist

BACKGROUND

Our aim was to investigate the development of intrahepatic venous anastomoses between the middle hepatic vein (MHV) and the right hepatic vein (RHV) in adult-to-adult, living donor, liver transplantation.

METHODS

Using Doppler ultrasonography, we studied the formation of venous anastomoses between the MHV tributaries for segments 5 and 8 (V5, V8) and the RHV in the liver remnants of 7 donors of a left liver, including the MHV, and in the liver grafts of 8 recipients of a right liver, without including the MHV. In 1 donor and 5 recipients, we performed pulse-inversion ultrasonography with a microbubble contrast agent to evaluate hepatic parenchymal perfusion in the drainage region of the MHV.

RESULTS

We observed 15 MHV tributaries of V5 and 13 of V8 among the 15 adult transplant patients. During the first postoperative week, we detected venous anastomosis between V5 and the RHV in 4 patients and in 10 patients between V8 and the RHV. After the 1st week, we observed the formation of anastomosis between V5 and the RHV in 10 patients, and between V8 and the RHV in 3. In both MHV tributaries, the mean flow velocities increased (P < .01). By the end of the 1st week, the formation rate in V8 was higher than in V5 (77% vs 27%, P < .03). In the parenchymal phase of the pulse-inversion ultrasonography with the microbubble contrast agent, the V5 drainage region had low intensities, while the V8 drainage territory revealed high intensities in 4 of 6 patients (66.7%).

CONCLUSIONS

Functional venous anastomoses between either V5 or V8 and the RHV developed in most of the donors of left hepatic lobes and in recipients of right hepatic lobes; however, anastomoses developed earlier in V8 than in V5. Furthermore, perfusion was decreased in the drainage area of V5, compared with V8.

Real-time blood-pool images of contrast enhanced ultrasound with Definity in the detection of tumour nodules in the liver

Lower mechanical index (MI) technique with newer microbubble agents has been introduced into clinical practice as a newer ultrasound (US) imaging. However, the efficacy in detecting tumour nodules has not been proven scientifically. The aim of this study was to elucidate the efficacy of a blood-pool image of real-time contrast-enhanced US under low MI in detecting liver tumours. 15 rabbits with VX-2 tumour were used; the number of implantations was none in two rabbits, one in four, two in five and three in four. US equipment was APLIO (Toshiba) with linear probe (3.5/7.0 MHz). The number, location and size of tumour nodules were examined by non-contrast tissue harmonic imaging (NC-US) or contrast-enhanced pulse subtraction harmonic imaging (C-US) under extra-low MI (MI 0.065) with the injection of Definity (30 microl kg(-1)). The number of tumour nodules detected by both NC-US and C-US were consistent with the histopathological results in five rabbits - two with none, two with one nodule and one with two nodules. In the other 10 rabbits, C-US showed all the implanted tumours and small daughter nodules around them that were confirmed by histopathology. However, NC-US failed to demonstrate two implanted nodules and all the daughter nodules. On the basis of the histopathological results, detectability of implanted tumour was not significantly different between NC-US (24/26, 92.3%) and C-US (26/26, 100%). However C-US was superior to NC-US in delineating the nodules and in detecting small daughter nodules. The sizes of the implanted tumour nodules measured by histopathology correlated closely with those measured by C-US. Real-time blood-pool images by pulse subtraction harmonic imaging under extra-low MI with Definity will contribute to the improvement of the ultrasound delineation and detection of liver tumours.

MRI in detection of hepatocellular carcinoma (HCC)

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

[Contrast ultrasound imaging in focal liver lesions: diagnostic value and guidelines]

The recent introduction of high quality scanners and contrast agents for ultrasound deeply modifies diagnosis strategy in focal liver lesions by using validated criteria. Non-linear imaging methods using low mechanical index (MI<0.2) and second generation contrast agents allow real-time continuous imaging with concomitant limitation in background tIssue signal and also in agent collapse for a high quality contrast imaging giving dramatic improvement in detection and characterization of lesions. Interpretation is based on the presence of contrast agent within the lesion or not (hyper-, hypo- or isosignal) and the delay after injection (arterial, portal or parenchymal or late phase) as previously used by non-ultrasound methods. This allows an easy differentiation of benign from malignant lesions. Moreover, this allows complete characterization in 85 to 95% of all focal liver lesions and 75% in hepatocellular carcinomas. Those results markedly improve ultrasound accuracy compared to conventional sonography and so put contrast-enhanced sonography among recommended non-invasive imaging methods for focal liver lesions with changes in diagnostic strategy according to the lesion type and actual place of US methods. It is recommended to use contrast ultrasound methods in cancer staging for an optimal detection of liver metastases as well as in characterization of lesions detected during conventional sonography with a consecutive decrease of cost-diagnosis ratio.

Characterization of hyperechoic focal liver lesions: quantitative evaluation with pulse inversion harmonic imaging in the late phase of levovist

OBJECTIVE

The aim of this study was to evaluate hyperechoic focal liver lesions with pulse inversion harmonic imaging in the late phase of SH U 508A (Levovist; Schering AG, Berlin, Germany) and to determine whether quantitative evaluation improves the characterization of the lesions.

METHODS

Twenty-six patients with hyperechoic liver lesions were enrolled in this study. Pulse inversion harmonic imaging was performed before and after administration of Levovist. Scan data were digitally stored, and each lesion was analyzed with a personal computer-based quantification package. All lesions were confirmed by histologic or triphasic spiral computed tomographic examinations. The intensity was measured in decibels in regions of interest drawn within the lesion and surrounding liver parenchyma. The lesion-liver ratios were than calculated. After contrast agent administration, a ratio equal to or greater than 1 was presumed benign, whereas a ratio of less than 1 was considered malignant.

RESULTS

Nine malignant (7 metastases, 1 hepatocellular carcinoma, and 1 cholangiocarcinoma) and 17 benign (14 hemangioma, 1 focal nodular hyperplasia, 1 focal fatty change, and 1 inflammatory pseudotumor) hyperechoic lesions were quantitatively evaluated. All malignant (n = 9) and 2 benign lesions (1 hemangioma and 1 inflammatory pseudotumor) had ratios of less than 1. In 15 of 17 benign lesions, the ratios were equal to or greater than 1. The intensity ratios calculated for benign and malignant lesions showed a statistically significant difference (P < .05).

CONCLUSIONS

Pulse inversion harmonic imaging with quantitative evaluation facilitates the differential diagnosis of hyperechoic focal liver lesions. A lesion-liver ratio equal to or greater than 1 predicts a benign nature, assuming that malignant lesions show a ratio of less than 1.

CONTRAST HARMONIC ULTRASOUND OF SPONTANEOUS LIVER NODULES IN 32 DOGS

Thirty-two dogs with spontaneous hepatic nodules were given intravenous ultrasound contrast medium (Definity or Sonovue) and imaged with contrast harmonic software on a conventional ultrasound machine system. Digital video images were initially reviewed to describe the perfusion pattern of malignant nodules. The images were reviewed again to test this pattern against all individual nodules. Subjectively, there was improved conspicuity of malignant nodules after contrast enhancement compared with conventional imaging and increased numbers of malignant nodules were often noted. There was decreased conspicuity of benign nodules and no additional nodules were seen after contrast enhancement. There was a highly significant (P < 0.0001) association of malignancy with a hypoechoic nodule at surrounding normal liver peak contrast enhancement. Benign nodules were isoechoic to the surrounding normal liver at peak contrast enhancement. Only one benign nodule (hepatoma) had regions of hypoechogenicity compared with the surrounding normal liver at peak liver contrast enhancement. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were highly significant (P < 0.0001) (100%, 94.1%, 93.8%, 100%, and 96.9%, respectively). No complications or morbidity was noted throughout the course of the study. Contrast harmonic ultrasound appears to be accurate at discriminating between naturally occurring benign and malignant nodules in the liver of dogs.

The application of ultrasound contrast agents in the characterization of renal tumors

The aim of this article is to describe the current ultrasound (US) contrast agents employed in the characterization of renal tumors and to report our experience in the use of a contrast-specific ultrasound technique pulse inversion harmonic imaging (PIHI).A total of 23 renal masses were prospectively evaluated by conventional US, CDUS, PIHI and finally by helical-CT (HCT). The study was performed using a wideband convex array 2-5 MHz transducer and a US digital apparatus . PIHI scanning of each renal mass was performed before and after the injection of Levovist. To reach a definitive diagnosis HCT and/or histological findings were considered as the reference procedures. Eleven solid renal cell carcinomas (RCCs), one embryonal metanephric adenoma (EMA), seven angiomyolipomas (AMLs), and four cystic RCCs were analyzed. Solid RCCs revealed a higher contrast enhancement than AMLs with a typical pattern on conventional US. The EMA and AML with an atypical pattern revealed intense contrast enhancement during the arterial phase, progressively decreasing during the delayed phase. Cystic RCCs showed intense contrast enhancement on the peripheral thick wall during the arterial phase decreasing during the delayed phase. PIHI with Levovist may differentiate solid RCCs from AMLs with no hypervascular pattern while solid RCCs show a higher intensity of contrast enhancement than hypervascular AML.

Different behaviors of microbubbles in the liver: time-related quantitative analysis of two ultrasound contrast agents, Levovist and Definity

The differences in time-related changes of liver images were compared quantitatively between Levovist and Definity. A total of 40 rabbits were assigned to eight groups according to the timing of taking enhanced liver images at 1, 3, 5, 7, 9, 11, 13 and 15 min by intermittent harmonic imaging using Levovist or Definity (30 microL/kg) and another 40 rabbits for Definity (50 microL/kg). Intensity changes between before and after enhancement in the portal vein (I-PV) and liver parenchyma (I-LP) were analyzed. I-PV was greater than I-LP at the 1- and 3-min phases of enhancement and I-LP became greater than I-PV with Levovist after 5 min. However, I-PV was higher than I-LP in all phases with Definity. Different time-intensity curves of these two agents will indicate discrete behaviors of microbubble hemodynamics in the liver; Levovist becomes accumulated in the liver, whereas Definity acts as a blood pool contrast agent, without accumulation.

Liver metastases in cancer: detection with contrast-enhanced ultrasonography

In patients with known or suspected malignancy, ultrasonography (US) is often the first choice for liver imaging because of its widespread availability and low cost. Compared with contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI), the sensitivity of conventional US for detecting hepatic metastases is relatively poor. The advent of microbubble contrast agents changed this situation. Sensitivity and specificity increased substantially with the use of these contrast agents and contrast-specific imaging modes in recent years. Currently, numerous US imaging methods exist, based on Doppler techniques or harmonic imaging. They exploit the complex nonlinear behavior of microbubbles in a sound field to achieve marked augmentation of the US signal. Although microbubble contrast agents are essentially blood pool agents, some have a hepatosplenic specific late phase. Imaging during this late phase is particularly useful for improving the detection of malignant liver lesions and allows US to perform similarly to spiral CT as shown by recent studies. In addition, this late phase imaging is very helpful for lesion characterization. Low mechanical index imaging with the newer perfluor agents permits real-time imaging of the dynamic contrast behavior during the arterial, portal venous, and late phases and is particularly helpful for lesion characterization. The use of US for hemodynamic studies of the liver transit time may detect blood flow changes induced by micrometastases even before they become visible on imaging. In this field of functional imaging, further research is required to achieve conclusive results, which are not yet available.

Pyogenic hepatic abscesses: distinctive features from hypovascular hepatic malignancies on contrast-enhanced ultrasound with SH U 508A; early experience

The aim of this study was to investigate the feasibility of contrast-enhanced US (conE US) in differentiating pyogenic hepatic abscesses (PyHAs) from hypovascular hepatic malignancies. conE US images of 16 PyHAs in 12 patients were evaluated retrospectively and were compared with those of 22 hypovascular hepatic malignancies in 12 patients. The conE US images were obtained at 30, 90, 150 and 270 s after a bolus injection of 4 g of SH U 508A (Levovist, Schering; 300 mg/mL). The images were specifically analyzed for the shape (round or ovoid, lobulating or coalescent according to the complexity), the margin (sharp or ill-defined), and the pattern of contrast agent enhancement of the lesion (internal and rim enhancement). In our experience, as to the shape of the lesion, PyHAs were usually coalescent (94%), and hepatic malignancies were more frequently round or ovoid (36%) or lobulating (50%) (p < 0.0001). The margin of the lesion was usually sharp in PyHAs (81%), whereas it was more commonly ill-defined (59%) in hepatic malignancies (p = 0.02). Whereas PYHAs usually produced no internal enhancement (94%), diffuse (73%) or peripheral (27%) hypoechoic intratumoral enhancement was seen in hepatic malignancies (p < 0.0001). This study shows that conE US is potentially useful in differentiation of PyHAs from hypovascular hepatic malignancies. PyHAs usually produce characteristic features, such as coalescent appearance, sharp boundary of necrotic cavity, and lack of internal enhancement on conE US.

[Ultrasound contrast agents]

Ultrasound contrast agents consist of tiny gas bubbles encapsulated by a stabilising membrane or shell. When combined with recent contrast-specific ultrasound techniques, they provide substantial enhancement of vessels and solid organs. The clinical use and the diagnostic value of ultrasound contrast agents are in principle comparable to those of contrast agents for CT and MRI. They add an additional dimension of information to sonography, which results in considerable improvement of diagnostic accuracy in many cases. This paper reviews the physicochemical properties of various microbubble contrast agents, discusses non-linear bubble behaviour and contrast-specific imaging techniques. An overview of the most important radiological clinical applications in the liver, kidney and spleen is given.

Imaging of paediatric splenic injury with contrast-enhanced ultrasonography

We report two children who sustained traumatic parenchymal splenic injury and were monitored with contrast-enhanced ultrasound (CEUS). In both cases, unenhanced US failed to diagnose splenic haematoma, but the injury was well demonstrated after injection of contrast agent. In one case agreement with CT was excellent; in the other, CT was not performed due to the comprehensive information provided by CEUS.

Differential diagnosis of cardiac masses using contrast echocardiographic perfusion imaging

OBJECTIVES

We investigated the usefulness of echocardiographic contrast perfusion imaging in differentiating cardiac masses.

BACKGROUND

Two-dimensional echocardiography is the primary diagnostic modality for cardiac masses. However, differentiation between the different types of cardiac masses may be difficult at times. We hypothesized that echocardiographic contrast perfusion imaging would differentiate the neo-vascularization of malignancies from the avascularity of thrombi and the sparse vascularity of stromal tumors.

METHODS

Sixteen patients with cardiac masses underwent power-modulation imaging after echocardiographic intravenous contrast administration. Pixel intensities in the mass and an adjacent section of myocardium were analyzed visually and by dedicated software. All masses had a pathologic diagnosis or resolved after anticoagulation. In a subset of patients, video-intensity curves of contrast replenishment in the mass and myocardium over time were generated. The post-impulse steady-state pixel intensity (A) and initial rate of contrast replenishment after impulse (beta) were compared with an index of blood vessel area on pathology.

RESULTS

In seven of 16 patients, contrast enhancement resulted in greater pixel intensity in the mass than in the adjacent myocardium. All of these masses were classified pathologically as malignant (n = 6) or benign and vascular (n = 1). Nine masses demonstrated decreased pixel intensity, compared with the myocardium, and were diagnosed pathologically as myxomas (n = 2) or thrombi (n = 5), or they resolved with anticoagulation (n = 2). For the subset of patients, beta correlated with the vessel area index (r = 0.60).

CONCLUSIONS

Echocardiographic contrast perfusion imaging aids in the differentiation of cardiac masses. Compared with the adjacent myocardium, malignant and vascular tumors hyper-enhanced, whereas stromal tumors and thrombi hypo-enhanced.

Extra-low acoustic power harmonic images of the liver with perflutren: novel imaging for real-time observation of liver perfusion

OBJECTIVE

The features of images below the extra-low mechanical index level were studied to elucidate a suitable mechanical index level for observing real-time and continuous harmonic images of rabbit livers with VX-2 tumors with the use of perflutren.

METHODS

Eight New Zealand White rabbits, 2 with healthy livers and 6 with VX-2 tumors, were examined by harmonic imaging (1.85 and 3.7 MHz) at a frame rate of 17 Hz under various mechanical index levels.

RESULTS

Real-time enhanced images of the liver were observed continuously in all rabbits. Vascular images were more clearly visualized at the low mechanical index level (mechanical index, 0.18) than at any other level. However, predominant enhanced images of the whole liver were observed only at the extra-low mechanical index level (mechanical index, 0.06). In VX-2 tumors, tumor vessels were shown more clearly at a low acoustic power level than at an extra-low level. The histologically proved area of viable tumor was enhanced as a stain in the tumor nodule at an extra-low mechanical index level.

CONCLUSIONS

Harmonic imaging under extra-low mechanical index levels with perflutren could provide real-time and continuous enhanced images of the liver, which would contribute to improvement of the diagnostic ability of contrast-enhanced sonography in liver diseases.