Liver metastases in cancer: detection with contrast-enhanced ultrasonography

Comparison of digital subtraction angiography and contrast-enhanced ultrasound in assessment of carotid stenosis

INTRODUCTION

The performances of contrast-enhanced ultrasound (CEUS) and digital subtraction angiography (DSA) were used to establish an efficient as well as non-invasive clinical technique for the diagnosis of extra-cranial internal carotid artery (ICA) stenosis.

MATERIALS AND METHODS

Thirty-six successive patients (11 women and 25 men, mean age: 65.0 ± 9.2, range: 43-78 years) with internal carotid artery (ICA) stenosis were tested by CEUS and DSA. These tests were carried out by means of Hitachi Preirus ultrasound machine for CEUS and Allura Xper FD20 system (Philips Medical Systems, Nederland B.V.) for DSA. 1.2 ml SonoVue (Bracco, Switzerland) was used a s contrast agent.

RESULTS

The results clearly indicated that there were no noteworthy variations among the distributions recorded by CEUS as well as DSA for the four tested groups. The percentage of diameter stenosis calculated by CEUS was clearly in accordance with the DSA images. CEUS showed accurate results with good specificity and sensitivity at 50%, 70%, and 100%. Also, CEUS performance was relatively better than DSA in the diagnosis of ICA and suitability of CEA.

CONCLUSION

CEUS proved to be a precise non-invasive testing method for the diagnosis of carotid artery stenosis which is more feasible and well-tolerated in patients with various stages of carotid stenosis.

Morphological and dynamic evaluation of complex cystic focal liver lesions by contrast-enhanced ultrasound: current state of the art

Complex cystic and cystic-like focal liver lesions (FLLs) encompass a spectrum of disorders ranging from non-neoplastic conditions to benign and malignant tumors. In this prospective, the possibility of non-invasive differentiation of these lesions is extremely important, because the clinical implications and therapeutic strategies vary considerably. Because of its advantageous cost/benefit ratio, widespread availability and easy execution, ultrasound (US) is the first-line imaging modality in most countries for the initial liver survey and represents the imaging technique that usually detects a complex liver cyst. However, US showed poor efficacy in the differential diagnosis of complex cystic FLLs. Thus, for years, computed tomography (CT) and magnetic resonance (MR) imaging have been used for further assessment of these lesions. Recently, the development of low mechanical index real-time contrast-enhanced ultrasound (CEUS) technique performed with the second generation of US contrast agents has led to an accurate depiction of macrovasculature and microvasculature. The technique yields information about contrast enhancement of the liver and FLLs almost as CT and MRI do, but in real time and without the use of ionizing radiation. To date, there is only a small amount of evidence about the role of CEUS in the less common setting of complex liver cysts. The aim of this review is to offer an up-to-date overview on the state of the art of CEUS in the study of the most common complex cystic focal liver lesions. To our knowledge, there are no literature comprehensive reviews on this topic.

The Use of Ultrasound in Palliative Care and Hospice

Palliative care aims to reduce symptom burden and enhance quality of life for those with terminal disease. Ultrasound has become an increasingly popular diagnostic and therapeutic modality due to its low cost, ease of portability, safety, and good patient acceptance. A review of the literature to date shows that as a diagnostic tool, as a therapeutic modality, and as a tool to accurately guide palliative procedures, ultrasound can have many roles in palliative care and hospice. Based on our clinical experience, musculoskeletal ultrasound can be of benefit to patients with terminal disease. Examples include adhesive capsulitis in advanced neurologic disease and chronic osteomyelitis in a patient with metastatic colon cancer. Ideally, further studies investigating the use of ultrasound in the palliative care population will be conducted in the future to enhance the availability of diagnostic and therapeutic capabilities of this particular modality.

Liver Contrast-Enhanced Ultrasound Improves Detection of Liver Metastases in Patients with Pancreatic or Periampullary Cancer

The aim of this study is to provide a diagnostic performance evaluation of contrast-enhanced ultrasonography (CEUS) in detecting liver metastases in patients with suspected of pancreatic or periampullary cancer. Computed tomography (CT) is often insufficient for detection of liver metastases, but their presence plays a crucial role in the choice of therapy. Eighty-nine patients with suspected pancreatic or periampullary cancer were included in this prospective study with retrospective analysis. Patients underwent an abdominal CT and CEUS. Fifteen patients had liver metastases. The CT sensitivity was 73.3% (11/15), the specificity 93.2% (69/74), the positive predictive value (PPV) 68.8% (11/16) and the negative predictive value (NPV) 94.6% (69/73). Based on CEUS, the sensitivity was 80% (12/15), specificity 98.6% (73/74), PPV 92.3% (12/13) and NPV 96.1% (73/76). CEUS improved characterization of liver lesions in patients with suspected pancreatic or periampullary cancer compared with CT. CEUS can better detect benign liver lesions and distinguish false-positive or indeterminate CT results.

Morphologic and Functional Imaging of Non-Colorectal Liver Metastases

Liver metastases are the most frequent malignant liver lesions. Besides colorectal carcinoma, gastric carcinoma, pancreatic carcinoma, breast cancer, lung cancer, and neuroendocrine tumors are the most common entities that metastasize to the liver. The morphology of these metastases depends on the primary tumor. For morphologic and functional imaging of non-colorectal liver metastases, multiple imaging techniques such as ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography coupled with CT or MRI are available. This review summarizes morphologic and functional characteristics of different non-colorectal liver metastases.

Liver metastases: Contrast-enhanced ultrasound compared with computed tomography and magnetic resonance

The development of ultrasound contrast agents with excellent tolerance and safety profiles has notably improved liver evaluation with ultrasound (US) for several applications, especially for the detection of metastases. In particular, contrast enhanced ultrasonography (CEUS) allows the display of the parenchymal microvasculature, enabling the study and visualization of the enhancement patterns of liver lesions in real time and in a continuous manner in all vascular phases, which is similar to contrast-enhanced computed tomography (CT) and contrast-enhanced magnetic resonance imaging. Clinical studies have reported that the use of a contrast agent enables the visualization of more metastases with significantly improved sensitivity and specificity compared to baseline-US. Furthermore, studies have shown that CEUS yields sensitivities comparable to CT. In this review, we describe the state of the art of CEUS for detecting colorectal liver metastases, the imaging features, the literature reports of metastases in CEUS as well as its technique, its clinical role and its potential applications. Additionally, the updated international consensus panel guidelines are reported in this review with the inherent limitations of this technique and best practice experiences.

Screening for liver metastases in women with mammary carcinoma: comparison of contrast-enhanced ultrasound and magnetic resonance imaging

OBJECTIVE

The objective of the present study was to compare conventional B-mode ultrasound (BMU), contrast-enhanced ultrasound (CEUS), and magnetic resonance imaging (MRI) in the detection of liver metastases at the primary staging and follow-up of women with histologically confirmed mammary carcinoma.

PATIENTS AND METHODS

Included in the study were 55 women (aged 57.5 ± 11.0 years, range 27-75 years; mean disease duration 57.5 months, range 5-168 months); of these, 17 women were examined as part of primary staging (staging group) and 38 women at follow-up (follow-up group). All patients underwent BMU (Philips HDI 5000), CEUS (Philips HDI 5000; 4.8 ml SonoVue), and MRI (Siemens Avanto 1.5 T) of the liver.

RESULTS

In the staging group (n = 17), a mass was detected by BMU in 24% (n = 4), by CEUS in 29% (n = 5), and by MRI in 47% (n = 8); masses suspicious for malignancy were identified in 6% of patients with BMU and in 12% each by CEUS and MRI. Malignancy was not confirmed in any case by cytology or surgery. In the follow-up group (n = 38), masses were identified by MRI in 53% of patients with suspicion of malignancy in 18%. Malignancy was confirmed in 16% of cases identified at MRI, in 13% of cases identified with CEUS, and in 11% of cases identified with BMU. The Pearson coefficients of correlation were r = .29 (P = .03) for MRI vs. BMU; r = .42 (P = .002) for MRI vs. CEUS; and r = .75 (P ≤ .001) for BMU vs. CEUS. With respect to malignancy, the Pearson coefficients of correlation were r = .40 (P = .099) for BMU vs. MRI and r = .71 (P = .0009) for CEUS vs. MRI.

CONCLUSIONS

Beginning in tumor stage III, the use of CEUS and MRI is associated with a significantly greater benefit in the detection of malignant tumors of the liver compared with conventional BMU. BMU appears to be adequate for primary staging and the follow-up of lower tumor stages.

Contrast-enhanced ultrasound vs multidetector-computed tomography for detecting liver metastases in colorectal cancer: a prospective, blinded, patient-by-patient analysis

AIM

This study compared the sensitivity and specificity of contrast-enhanced ultrasound (CEUS) and multidetector-computed tomography (MDCT) in the detection of liver metastases in patients with colorectal cancer.

METHOD

Between September 2004 and December 2008, 271 consecutive patients (146 men and 125 women; median age 68 years, range: 34-91 years) with primary colorectal cancer were evaluated. All underwent combined liver ultrasound and CEUS following intravenous injection of 2.4 ml of SonoVue(TM). The interval from injection to arrival time in the hepatic vein (ATHV) was noted. Contrast-enhanced MDCT in the portal phase was performed and interpreted blindly. In all patients, intra-operative ultrasound was used as the reference point. In addition, magnetic resonance imaging (MRI) or biopsy was performed on all suspicious lesions or if there was inconsistency in the results.

RESULTS

Liver metastases were detected in 21 (8%) patients. Both CEUS and MDCT had a sensitivity of 85.7%, with respective specificities of 97.6% and 95.6%, and positive predictive values of 75%vs 62%. The negative predictive value of both methods was 99%. In patients with and without liver metastases, ATHV was 18 and 22 s, respectively (P < 0.05).

CONCLUSION

CEUS has potential as a diagnostic alternative to MDCT in the detection of liver metastases. ATHV was shorter in patients with liver metastases.

Liver metastases: Sulphur hexafluoride-enhanced ultrasonography for lesion detection: a systematic review

This is a systematic review to evaluate the accuracy of contrast-enhanced ultrasonography (CEUS) performed with "SonoVue" (sulphur hexafluoride) in the detection of hepatic metastases. The MEDLINE, EMBASE and COCHRANE Databases were searched, regardless of language, for relevant articles published before December 2009. Two reviewers independently assessed study eligibility using a standardized form and methodological quality using the quality assessment of diagnostic accuracy studies (QUADAS) Checklist. Sensitivity estimates were calculated on a per-patient and/or per-lesion basis. The search for published articles yielded 718 potentially relevant abstracts. Of these, 14 papers were eligible but only three articles fulfilled the inclusion criteria, which comprised a total of 450 patients (patient sample number: range 12 to 365; cancer prevalence: 14.8 to 71.2%). Estimated per-patient sensitivity ranged from 79-100%. Although the quality assessment of diagnostic accuracy studies checklist showed the papers were of good quality, a meta-analysis was not applicable because of the lack of eligible studies. In conclusion, CEUS seems to be promising in the detection of liver metastases; however, there have not been enough studies to conduct meta-analysis. Further studies are required before this promising method can be widely used.

Detection of focal liver lesions: from the subjectivity of conventional ultrasound to the objectivity of volume ultrasound

PURPOSE

This study was undertaken to establish the reliability of automated volumetric liver scans in detecting focal liver lesions by evaluating the degree of agreement between conventional and volume ultrasound (US) examinations.

MATERIALS AND METHODS

Over a period of 3 months, we prospectively studied 100 consecutive patients (36 men and 64 women; age range 15-87 years; mean age 63 years) referred to our institute for US imaging of the liver. Volumetric acquisition of the liver was achieved with a 3D transducer (2.0-5.0 MHz) and a Logiq 9 US scanner. All patients underwent both 2- and 3D US studies performed by two expert radiologists. Volumetric acquisitions were subsequently reviewed by the second radiologist, who was blinded to the first radiologist's report. Three categories were established: 1=presence of focal liver lesions; 2=doubtful finding; 3=absence of focal liver lesions. Concordance between volume US and conventional US was calculated by using the k statistic.

RESULTS

Out of 100 patients examined, 39 were found to be affected by focal liver lesions. All volume US examinations were technically adequate, allowing exploration of all hepatic sectors, except for five cases that were marred by major respiratory motion artefacts. Conventional and volume US identified the same number of focal liver lesions, with the exception of four cases of doubtful findings at volume US. Concordance between automated volume US and conventional US of the liver was high (k=0.92).

CONCLUSIONS

The identification of focal liver lesions on automated volume US is possible, and the examination shows a high level of concordance with conventional US.

Benefits of contrast-enhanced sonography for the detection of liver lesions: comparison with histologic findings

OBJECTIVE

The objective of our study was to compare the usefulness of contrast-enhanced sonography with baseline sonography in detecting malignant liver lesions.

SUBJECTS AND METHODS

This prospective study included 116 patients. All patients underwent a preoperative conventional sonography examination followed by sonography after injection of contrast agent combined with the use of perfusion software (vascular recognition imaging or pulse subtraction imaging). Histopathologic analysis was the reference standard used to compare the diagnostic value of baseline sonography versus contrast-enhanced sonography.

RESULTS

Eighty-two patients underwent hepatic surgery, 31 did not because of disseminated lesions, and the remaining three patients did not meet inclusion criteria. Three hundred six surgically proven lesions were taken into account for comparison of the two techniques: 147 were detected on baseline sonography and 177 on contrast-enhanced sonography. Histopathologic analysis revealed 233 malignant and 73 benign lesions. Sensitivity and specificity were improved on contrast-enhanced sonography compared with baseline sonography for the detection of malignant lesions: 68.7% versus 58.8% and 67% versus 50.7%, respectively. Contrast-enhanced sonography detected 23 additional malignant lesions that had been seen as lacuna at the portal venous phase and characterized as 19 benign nodules, thus improving the performance of sonography in 13.7% of the cases.

CONCLUSION

Contrast injection improved the sensitivity and specificity of baseline sonography and should be performed in routine practice if hepatic surgery is being considered for the management of liver lesions.

Standardize and compare contrast-enhanced ultrasonographic digital images obtained with different technologies: how to overcome the subjectivity

OBJECTIVE

This study was conducted to compare digital images obtained with cadence contrast pulse sequencing (CPS) and coherent contrast imaging (CCI) technologies for contrast-enhanced ultrasonography (CEUS).

METHODS

A CEUS study on 17 focal liver lesions was performed using CPS and CCI technologies with a second-generation contrast media. The lesion/liver ratio and conspicuity index were then calculated and compared with Adobe Photoshop 6.0.

RESULTS

Lesion/liver ratio and conspicuity index using CCI ranged from 1.3 to 7.1 (mean value, 3) and 19 to 127 (mean value, 58), respectively; by using CPS, we obtained results ranging from 2 to 19.1 (mean value, 8.9) and 57 to 164 (mean value, 109.2). Lesion/liver ratio and the conspicuity index for the lesions using CPS showed significantly (p < 0.0001) superior results than those obtained using CCI.

CONCLUSION

The computed analysis with standardization allows an objective evaluation of digital images of CEUS. CPS technology resulted in better lesion conspicuity compared to CCI during CEUS study on focal liver lesions.

Evaluation of quantitative contrast harmonic imaging to assess malignancy of liver tumors: A prospective controlled two-center study

AIM: To establish the extent to which contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics facilitates the detection of hepatic tumors.

METHODS: One hundred patients with histologically confirmed malignant or benign hepatic tumor (maximum size 5 cm) were analyzed. Contrast-enhanced ultrasound (bolus injection 2.5 mL SonoVue) was carried out with intermittent breath-holding technique using a multifrequency transducer (2.5-4 MHz). Native vascularization was analyzed with power Doppler. The contrast-enhanced dynamic ultrasound investigation was carried out with contrast harmonic imaging in true detection mode during the arterial, portal venous and late phases. Mechanical index was set at 0.15. Perfusion analysis was performed by post-processing of the raw data [time intensity curve (TIC) analysis]. The cut-off of the gray value differences between tumor and normal liver tissue was established using Receiver Operating Characteristic (ROC) analysis 64-line multi-slice computed tomography served as reference method in all cases. Magnetic resonance tomography was used additionally in 19 cases.

RESULTS: One hundred patients with 59 malignant (43 colon, 5 breast, 2 endocrine metastases, 7 hepatocellular carcinomas and 2 kidney cancers) and 41 benign (15 hemangiomas, 7 focal nodular hyperplasias, 5 complicated cysts, 2 abscesses and 12 circumscribed fatty changes) tumors were included. The late venous phase proved to be the most sensitive for classification of the tumor type. Fifty-eight of the 59 malignant tumors were classified as true positive, and one as false negative. This resulted in a sensitivity of 98.3%. Of the 41 benign tumors, 37 were classified as true negative and 4 as false negative, which corresponds to a specificity of 90.2%. Altogether, 95.0% of the diagnoses were classified as correct on the basis of the histological classification. No investigator-dependency (P = 0.23) was noted.

CONCLUSION: The results show the possibility of accurate prediction of malignancy of hepatic tumors with a positive prognostic value of 93.5% using advanced contrast-enhanced ultrasound. Contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics is a valuable tool to discriminate hepatic tumors.

Are metastases really hypovascular in the arterial phase? The perspective based on contrast-enhanced ultrasonography

OBJECTIVE

The purpose of this study was to describe enhancement and vascularity characteristics of liver metastases on real-time low-mechanical index contrast-enhanced ultrasonography.

METHODS

This retrospective study was approved for chart review by our Research Ethics Board. Informed consent was waived. Fifty metastases (colorectal [n = 28], neuroendocrine [n = 6], pancreatic [n = 6], melanoma [n = 3], and other [n = 7]) in 50 patients (38-84 years, 24 male and 26 female) were analyzed. Contrast-enhanced ultrasonography was performed after intravenous injection of a microbubble contrast agent. Two radiologists independently reviewed digital cine clips and static images for the arterial phase intensity and pattern of enhancement and the presence of dysmorphic vessels. Observations on wash-out included its presence and completeness. Disagreement was resolved by consensus. The interval to peak arterial enhancement and beginning of wash-out were determined. Reader agreement was estimated with the kappa statistic.

RESULTS

All but 6 metastases (44/50 [88%]) showed arterial hypervascularity, with dysmorphic vessels in 21 (42%) of 50. The pattern of enhancement was rim in 21 (42%) of 50 and diffuse in 29 (58%) of 50. The time to peak arterial enhancement ranged from 8 to 27 seconds (mean, 15.1 seconds), and the beginning of wash-out ranged from 13 to 50 seconds (mean, 25.2 seconds). Although a thin margin of residual enhancement was seen in 27 (54%) of 50 lesions in the early wash-out phase, all lesions (50/50) showed uniform complete wash-out in the portal phase.

CONCLUSIONS

Contrary to popular belief based on computed tomography and magnetic resonance imaging studies, most hepatic metastases, including those thought to be hypovascular, show transient arterial hypervascularity on contrast-enhanced ultrasonography, followed by rapid and complete wash-out initiated within the conventional arterial phase.

Microbubbles assist goat liver ablation by high intensity focused ultrasound

High intensity focused ultrasound (HIFU) has been introduced to treat cancers. However, this therapy is a time-consuming procedure; destructing a deeper volume is also difficult as ultrasonic energy attenuates exponentially with increasing depth in tissues. The aim of the present study was to investigate the effects of introducing microbubbles on liver HIFU ablation. Seventeen goats were divided into groups A (n=8) and B (n=9). The livers in both groups were ablated using HIFU (1.0 MHz, 22,593 W/cm2) performed in the manner of a clinical regime using a clinical device. A microbubble agent was bolus-injected intravenously before HIFU exposure in group B. All animals in group A and seven goats in group B were euthanased to evaluate the ablation efficiency 24 h after HIFU. The necrosis rate (mm3/s), which was the volume of necrosis tissue per second of HIFU exposure, was used to judge the ablation efficiency. Pathological examinations were performed to determine whether there were residual intact tissues within the exposed volume. The other two goats in group B were used to determine the delayed pathological changes 7 days after ultrasonic ablation. The necrosis rate (mm3/s) was increased in group B (14.4647+/-4.1960 versus 33.5302+/-12.4484, P=0.0059). Pathological examinations confirmed that there were no residual unaffected tissue focuses within the exposed volume. Two remarkable changes occurred in the other two goats in group B 7 days after HIFU: there were ghost-cell islands at the periphery of the ablated tissues, and surrounding adjacent tissues outside the reactive zone necrotized. These findings showed that microbubbles could be used to assist liver HIFU ablation.

Focal liver lesions: sinusoidal phase of CEUS

Ultrasound examination is the first imaging modality for hepatic study in neoplastic and chronic liver diseases. Focal liver lesions frequently cause diagnostic problems in terms of characterization, especially when small and hypoechoic to the rest of the parenchyma. Contrast--enhanced ultrasonography (CEUS) has shown its value in the characterization of focal liver lesions. This study assessed the value of the sinusoidal phase of CEUS with a second-generation contrast agent in the characterization of focal liver lesions to distinguish benign from malignant. Two hundred hepatic lesions with suspicious features at baseline ultrasound were prospectively studied with CEUS. Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of the sinusoidal phase in the characterization of benign versus malignant liver lesions were evaluated. Hypoechogenicity of the focal liver lesion, during the sinusoidal phase of CEUS, allowed the diagnosis of malignancy with a sensitivity of 85%, specificity of 88%, positive predictive value of 92%, negative predictive value of 77%, and diagnostic accuracy of 86%. The diagnostic confidence in the diagnosis of malignancy significantly increased, with receiver operating characteristic curve areas from 0.536 for baseline ultrasound to 0.902 for the sinusoidal phase of CEUS.

Correlation between estimates of tumor perfusion from microbubble contrast-enhanced sonography and dynamic contrast-enhanced magnetic resonance imaging

OBJECTIVE

We compared measurements of tumor perfusion from microbubble contrast-enhanced sonography (MCES) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in an animal tumor model.

METHODS

Seven mice were implanted with Lewis lung carcinoma cells on their hind limbs and imaged 14 days later with a Philips 5- to 7-MHz sonography system (Philips Medical Systems, Andover, MA) and a Varian 7.0-T MRI system (Varian, Inc, Palo Alto, CA). For sonographic imaging 100 microL of a perfluoropropane microbubble contrast agent (Definity; Bristol-Myers Squibb Medical Imaging, Billerica, MA) was injected and allowed to reach a pseudo steady state, after which a high-mechanical index pulse was delivered to destroy the microbubbles within the field of view, and the replenishment of the microbubbles was imaged for 30 to 60 seconds. The MRI included acquisition of a T(10) map and 35 serial T(1)-weighted images (repetition time, 100 milliseconds; echo time, 3.1 milliseconds; alpha, 30 degrees ) after the injection of 100 microL of 0.2-mmol/kg gadopentetate dimeglumine (Magnevist; Berlex, Wayne, NJ). Region-of-interest and voxel-by-voxel analyses of both data sets were performed; microbubble contrast-enhanced sonography returned estimates of microvessel cross-sectional area, microbubble velocity, and mean blood flow, whereas DCE-MRI returned estimates of a perfusion-permeability index and the extravascular extracellular volume fraction.

RESULTS

Comparing similar regions of tumor tissue seen on sonography and MRI, region-of-interest analyses revealed a strong (r(2) = 0.57) and significant relationship (P < .002) between the estimates of perfusion obtained by the two modalities.

CONCLUSIONS

Microbubble contrast-enhanced sonography can effectively depict intratumoral heterogeneity in preclinical xenograft models when voxel-by-voxel analysis is performed, and this analysis correlates with similar DCE-MRI measurements.

Assessment of metastatic liver disease in patients with primary extrahepatic tumors by contrast-enhanced sonography versus CT and MRI

AIM

To evaluate contrast-enhanced ultrasonography (CEUS) using SonoVue in the detection of liver metastases in patients with known extrahepatic primary tumors versus the combined gold standard comprising CT, MRI and clinical/histological data.

METHODS

It is an international multicenter study, and there were 12 centres and 125 patients (64 males, 61 females, aged 59+/-11 years) involved, with 102 patients per protocol. Primary tumors were colorectal in 35%, breast in 27%, pancreatic in 17% and others in 21%. CEUS using SonoVue was employed with a low-mechanical-index technique and contrast-specific software using Siemens Elegra, Philips HDI 5000 and Acuson Sequoia; continuous scanning for at least five minutes.

RESULTS

CEUS with SonoVue increased significantly the number of focal liver lesions detected versus unenhanced sonography. In 31.4% of the patients, more lesions were found after contrast enhancement. The total numbers of lesions detected were comparable with CEUS (55), triple-phase spiral CT (61) and MRI with a liver-specific contrast agent (53). Accuracy of detection of metastatic disease (i.e. at least one metastatic lesion) was significantly higher for CEUS (91.2%) than for unenhanced sonography (81.4%) and was similar to that of triple-phase spiral CT (89.2%). In 53 patients whose CEUS examination was negative, a follow-up examination 3-6 mo later confirmed the absence of metastatic lesions in 50 patients (94.4%).

CONCLUSION

CEUS is proved to be reliable in the detection of liver metastases in patients with known extrahepatic primary tumors and suspected liver lesions.

The use of a micro-bubble agent to enhance rabbit liver destruction using high intensity focused ultrasound

Liver tissues in New Zealand rabbits were ablated using high intensity focused ultrasound (HIFU, 14300 W/cm(2), 1.0 MHz). The animals were intravenously administered 0.2 ml of micro-bubble agent in the experimental (n=20) group and an isovolumetric normal saline solution in the control (n=27) group before HIFU treatment which was performed as a linear scan. In both groups, the preselected tissue volumes were destroyed without harming the overlying tissues. Necrosis rate (NR, cm(3)/s) was used to reflect the ablation efficiency, which was the tissue volume of occurring coagulative necrosis per 1s HIFU exposure. NR was improved in the experimental group (0.0570+/-0.0433 vs 0.0120+/-0.0122, P=0.0002). Pathological studies confirmed that there were no residual intact targets within the exposed volume. These findings suggested that the introduction of the micro-bubble agent enhanced HIFU liver destruction.

Contrast Harmonic Imaging of Canine Hepatic Tumors

Six adult healthy Beagles were used to investigate the hepatic perfusion dynamics of Levovist, a contrast agent used in contrast harmonic imaging (CHI). In addition, 8 dogs with hepatocellular carcinoma (HCC) and 2 dogs with metastatic hepatic hemangiosarcoma (HSA) were used to characterize both the CHI findings with Levovist. In the Beagles, the start of intravenously injected Levovist into the aorta between the cranial mesenteric and renal arteries and the portal vein at the hepatic hilum were 5.47 +/- 1.52 sec and 16.03 +/- 3.39 sec, respectively. As a characteristic CHI finding in the 8 dogs with HCC, the early arterial phase showed a fine network of blood flow enhanced at the surrounding region and within the tumor in all the 8 dogs (100%), and the post vascular phase demonstrated a defect in the whole tumor and an enhancement of the surrounding hepatic tissues in 7 dogs (87.5%). In the 2 dogs with HSA, characteristic finding in which the early arterial and late vascular phases showed a rim contrast enhancement pattern, and the post vascular phase revealed that the whole tumor lacked contrast enhancement and the surrounding hepatic tissues was clearly enhanced. In dogs, the start of the early arterial and late vascular phases, and the characterizations of the CHI findings in HCC and HSA were suggested to be similar to those in humans. Therefore, CHI is thought to be useful for the diagnosis of HCC and metastatic hepatic HSA in dogs as well as in humans.

Ultrasonic contrast agent shell rupture detected by inertial cavitation and rebound signals

Determining the rupture pressure threshold of ultrasound contrast agent microbubbles has significant applications for contrast imaging, development of therapeutic agents, and evaluation of potential bioeffects. Using a passive cavitation detector, this work evaluates rupture based on acoustic emissions from single, encapsulated, gas-filled microbubbles. Sinusoidal ultrasound pulses were transmitted into weak solutions of Optison at different center frequencies (0.9, 2.8, and 4.6 MHz), pulse durations (three, five, and seven cycles of the center frequencies), and peak rarefactional pressures (0.07 to 5.39 MPa). Pulse repetition frequency was 10 Hz. Signals detected with a 13-MHz, center-frequency transducer revealed postexcitation acoustic emissions (between 1 and 5 micros after excitation) with broadband spectral content. The observed acoustic emissions were consistent with the acoustic signature that would be anticipated from inertial collapse followed by "rebounds" when a microbubble ruptures and thus generates daughter/free bubbles that grow and collapse. The peak rarefactional pressure threshold for detection of these emissions increased with frequency (e.g., 0.53, 0.87, and 0.99 MPa for 0.9, 2.8, and 4.6 MHz, respectively; five-cycle pulse duration) and decreased with pulse duration. The emissions identified in this work were separated from the excitation in time and spectral content, and provide a novel determination of microbubble shell rupture.

Adverse effects associated with SonoVue®use

Conventional ultrasonography (US) has limited accuracy in the detection and characterisation of solid focal liver lesions (FLL). Contrast-enhanced ultrasound (CEUS) significantly improves the diagnostic performance of US in the assessment of FLL. Rare reports of serious adverse events have been reported with CEUS. The rates of adverse reactions reported from the use of ultrasound contrast agents seem comparable to, or lower than, those observed for other imaging modalities that use contrast agents such as computed tomography and magnetic resonance imaging. Improved diagnostic results and diagnostic confidence achieved in conventional CEUS studies of the liver and during the investigational use in the intraoperative CEUS exploration appear to justify the use of this promising modality.