Prolongation and optimization of Doppler enhancement with a microbubble US contrast agent by using continuous infusion: preliminary experience

Predicting Long-Term Hepatocellular Carcinoma Response to Transarterial Radioembolization Using Contrast-Enhanced Ultrasound: Initial Experiences

Conventional cross-sectional imaging done shortly after radioembolization of hepatocellular carcinoma (HCC) does not reliably predict long-term response to treatment. This study evaluated whether quantitative contrast-enhanced ultrasound (CEUS) can predict the long-term response of HCC to yttrium-90 (Y-90) treatment. Fifteen patients underwent CEUS at three time points: immediately following treatment and 1 and 2 wk post-treatment. Response 3-6 mo after treatment was categorized on contrast-enhanced magnetic resonance imaging by two experienced radiologists using the Modified Response Evaluation Criteria in Solid Tumors. CEUS data were analyzed by quantifying tumor perfusion and residual fractional vascularity using time-intensity curves. Patients with stable disease on magnetic resonance imaging had significantly greater fractional vascularity 2 wk post-treatment (65.15%) than those with partial or complete response (13.8 ± 9.9%, p = 0.007, and 14.9 ± 15.4%, p = 0.009, respectively). Complete responders had lower tumor vascularity at 2 wk than at post-operative examination (-38.3 ± 15.4%, p = 0.045). Thus, this pilot study suggests CEUS may provide an earlier indication of Y-90 treatment response than cross-sectional imaging.

Cavitation Therapy Monitoring of Commercial Microbubbles With a Clinical Scanner

The ability to monitor cavitation activity during ultrasound and microbubble-mediated procedures is of high clinical value. However, there has been little reported literature comparing the cavitation characteristics of different clinical microbubbles, nor have current clinical scanners been used to perform passive cavitation detection in real time. The goal of this work was to investigate and characterize standard microbubble formulations (Optison, Sonovue, Sonazoid, and a custom microbubble made with similar components as Definity) with a custom passive cavitation detector (two confocal single-element focused transducers) and with a Philips EPIQ scanner with a C5-1 curvilinear probe passively listening. We evaluated three different methods for investigating cavitation thresholds, two from previously reported work and one developed in this work. For all three techniques, it was observed that the inertial cavitation thresholds were between 0.1 and 0.3 MPa for all agents when detected with both systems. Notably, we found that most microbubble formulations in bulk solution behaved generally similarly, with some differences. We show that these characteristics and thresholds are maintained when using a diagnostic ultrasound system for detecting cavitation activity. We believe that a systematic evaluation of the frequency response of the cavitation activity of different microbubbles in order to inform real-time therapy monitoring using a clinical ultrasound device could make an immediate clinical impact.

Delayed contrast enhancement of hepatic parenchyma after intravenous sonographic contrast agent: unusual phenomenon. Case report and review of literature

Aim

A case of heterogeneous late-phase hepatic enhancement (HLHE) using contrast‐enhanced ultrasound (CEUS) with SonoVue is presented, where HLHE lasted after 50 min of injection.

Methods

This study aims to review prior literature on this topic, to characterize the features of HLHE in the liver, and to find possible and reliable explanations for this phenomenon.

Results

From literature, thus far five publications discuss this phenomenon with a total of 21 patients.

Conclusion

We suggest that phagocytosis of contrast agent microbubbles by macrophages, and lymphocytosis of peripheral blood due to stress conditions of the patients might be in the background of HLHE.

The Continuing Evolution of Molecular Functional Imaging in Clinical Oncology: The Road to Precision Medicine and Radiogenomics (Part II)

The present era of precision medicine sees "cancer" as a consequence of molecular derangements occurring at the commencement of the disease process, with morphological changes happening much later in the process of tumourigenesis. Conventional imaging techniques, such as computed tomography (CT), ultrasound (US) and magnetic resonance imaging (MRI) play an integral role in the detection of disease at the macroscopic level. However, molecular functional imaging (MFI) techniques entail the visualisation and quantification of biochemical and physiological processes occurring during tumourigenesis. MFI has the potential to play a key role in heralding the transition from the concept of "one-size-fits-all" treatment to "precision medicine". Integration of MFI with other fields of tumour biology such as genomics has spawned a novel concept called "radiogenomics", which could serve as an indispensable tool in translational cancer research. With recent advances in medical image processing, such as texture analysis, deep learning and artificial intelligence, the future seems promising; however, their clinical utility remains unproven at present. Despite the emergence of novel imaging biomarkers, the majority of these require validation before clinical translation is possible. In this two part review, we discuss the systematic collaboration across structural, anatomical and molecular imaging techniques that constitute MFI. Part I reviews positron emission tomography, radiogenomics, AI, and optical imaging, while part II reviews MRI, CT and ultrasound, their current status, and recent advances in the field of precision oncology.

Contrast-Enhanced Hepatic Sonography

Hepatic applications of sonography include evaluation of the gallbladder and bile ducts, assessment of patients with suspected portal hypertension, and evaluation of focal and diffuse parenchymal liver disease. Ultrasound imaging (US) is generally a reliable and accurate method to diagnose a variety of hepatic abnormalities; however, in some cases there is a need to improve sonography's sensitivity and specificity, particularly for the detection and characterization of hepatic masses. Recent clinical experience has shown that the addition of a US contrast agent can enhance sonography's diagnostic capabilities including improving assessments of hepatic blood flow and the detection and characterization of hepatic neoplasms. One intravenously administered US contrast agent is now available in the United States, but its approved indication is limited to echocardiographic applications. Additional agents that have more diagnostic applications are likely to become available. Contrast-enhanced sonography may play a significant role in the diagnosis and management of patients with suspected hepatic abnormalities. This article describes two generic types of US contrast agents—vascular agents and tissue-specific agents—and includes a review of recent published reports on clinical applications of contrast-enhanced hepatic sonography.

Contrast sonovenography - Is this the answer to complex deep vein thrombosis imaging?

BACKGROUND

Deep vein thrombosis (DVT) is a potentially fatal condition causing significant morbidity and mortality in the patient population. Ultrasound (USS) is the mainstay for detecting DVT. This can sometimes be difficult in hostile limbs due to factors such as large body habitus and oedema. This pilot study investigated contrast-enhanced ultrasound (CEUS) as a viable method to improve visualisation of the venous system of the lower limb.

METHODS

Patients at high risk for DVT were selected after an initial negative USS. A follow-up scan was performed 1 week later utilising standard B-mode imaging with a curvilinear 3-5 MHz transducer array. After the fundamental scan, intravenous Sonovue™ contrast was administered and visualisation of the proximal limb veins and visualisation gains in distance were mapped onto a proforma.

RESULTS

Twelve patients were selected. Visualisation was not improved in the common femoral vein (CFV) but increases in full visualisation were demonstrated in the femoral vein (FV) and popliteal vein (Pop V) from (n = 8) 67% and (n = 10) 83-100% in both veins, respectively. Significant gains in visualisation distance were observed in the posterior tibial vein (PTV) (p = 0.0005) and peroneal vein (Per V) (p = 0.02) with increased full visualisation of the Per V from (n = 3) 25% to (n = 7) 58%.

CONCLUSION

CEUS is a viable and clinically safe method for increasing visualisation of the deep venous system. It has the potential to improve visualisation of the lower limb venous system, reducing follow-up costs and diagnostic uncertainty for patients and the clinician.

Effect of microbubble contrast on intracranial blood flow velocity assessed by transcranial Doppler

PURPOSE

Ultrasound contrast agents (UCA) salvage a considerable number of transcranial Doppler (TCD) exams which would have failed because of poor bone window. UCA bolus injection causes an undesirable increase in measured blood flow velocity (BFV). The effect of UCA continuous infusion on measured BFV has not been investigated, and some in vitro experiments suggest that gain reduction during UCA administration may also influence measured BFV. This study aimed to investigate the effect of UCA continuous infusion on BFV measured by TCD and the influence of gain reduction on these measurements in a clinical setting.

METHODS

The right middle cerebral artery of ten patients with optimal bone window was insonated using a 2 MHz probe. UCA were administered using an infusion pump. BFV was measured (1) at baseline, (2) during UCA infusion, (3) during UCA infusion with gain reduction, and (4) after UCA wash-out phase. Gain reduction was based on the agreement between two neurosonographers on the degree of gain reduction necessary to restore baseline Doppler signal intensity (DSI). Actual DSI was estimated offline by analysis of raw data.

RESULTS

BFV measured during UCA infusion with no gain adjustment was significantly higher than baseline BFV [peak systolic velocity (PSV): 85.1 ± 19.7 vs. 74.4 ± 19.7 cm/s, p < 0.0001; Mean velocity (MV): 56.5 ± 11.8 vs. 50.2 ± 12.3 cm/s, p < 0.0001]. BFV measured during UCA infusion with gain reduction was not significantly higher than baseline BFV (PSV: 74.3 ± 18.9 vs. 74.4 ± 19.4 cm/s, p = 0.8; MV: 49.4 ± 11.0 vs. 50.2 ± 12.3 cm/s, p = 0.8). Actual DSI during UCA infusion with gain reduction was not significantly higher than baseline DSI (13 ± 1 vs. 13 ± 1 dB).

CONCLUSION

This study shows that UCA continuous infusion leads to an increase in measured BFV which may be counteracted by reducing Doppler gain thus restoring pre-contrast DSI.

Qualitative and quantitative contrast enhanced ultrasonography of the pancreas using bolus injection and continuous infusion methods in normal dogs

Quantitative contrast enhanced ultrasound is a major breakthrough for ultrasound imaging in recent years. However, contrast enhancement of the pancreas is brief with bolus injection. To assess if continuous infusion of Sonazoid^® can prolong the duration of pancreatic enhancement over bolus injections, eight adult dogs received bolus injection and continuous infusion of Sonazoid^® on separate days. Contrast enhanced ultrasound of the pancreatic parenchyma and proximal descending duodenum was performed, and time intensity curves reflecting tissue perfusions were generated. Perfusion parameters- time to initial upslope, peak time, time to wash-out and peak intensity were calculated and evaluated. Fast wash-in to intense peak, followed by rapid wash-out was observed for time intensity curves of bolus injection. With continuous infusion, contrast wash-in to peak intensity was gradual, followed by long plateau and slow wash-out. Median contrast enhancement durations of the pancreas and duodenum were significantly prolonged by continuous infusion from 11 sec (range, 10 to 23 sec) and 16 sec (range, 3 to 43 sec) at bolus injection to 205 sec (range, 170 to 264 sec, P<0.01) and 193 sec (range, 169 to 216 sec, P<0.05), respectively. Median peak intensity of the pancreas was 100.9 MPV (range, 80.2 to 124.3 MPV) at bolus injection and 77.6 MPV (range, 58.2 to 99.5 MPV, P<0.05) at continuous infusion. Prolonged continuous imaging is afforded by continuous infusion of contrast agent. Peak intensity of the pancreas was slightly diminished in continuous infusion, but offered adequate imaging subjectively.

Evaluation of Carotid Plaque Neovascularization Using Contrast Ultrasound

Contrast-enhanced ultrasound (CEUS) is increasingly used to improve visualization of carotid arteries. However, its reproducibility and utility for clinical research are not well established. The aim of the present study was to assess reproducibility of detection of carotid artery wall neovascularization using CEUS. Complete sequenced CEUS images from 10 individuals were analyzed for the presence of carotid arterial wall neovascularization. The images were acquired using Philips CompactXtreme CX50 ultrasound unit with an L12-3 probe and Bracco SonoVue contrast agent. The carotid wall neovascularization was graded by 2 independent observers with inter-/intraobserver agreement (κ) calculated. Interobserver κ values for intraplaque neovascularization (mean [95% confidence interval]) were 0.67 (0.40-0.94) for the left side. Interobserver κ values for intraplaque neovascularization were 0.65 (0.38-0.92). No study-related complications were observed. The CEUS method although semiquantitative shows moderate-to-strong intra- and interagreement for the results and can be used for clinical research purpose.

Vascular patterns in nodules of intraductal papillary mucinous neoplasms depicted under contrast-enhanced ultrasonography are helpful for evaluating malignant potential

OBJECTIVES

The purpose of this study is to evaluate the feasibility of contrast-enhanced ultrasonography (CE-US) to differentiate between benign and malignant intraductal papillary mucinous neoplasms (IPMN).

PATIENTS AND METHODS

Contrast-enhanced ultrasonography with a contrast agent was performed on 22 consecutive patients with IPMN suspected of being malignant. This revealed 10 carcinomas, 1 borderline lesion and 11 adenomas. All patients underwent surgery, and the histological diagnosis was confirmed by examination of resected specimens. CE-US was performed using a contrast agent. The detection rates of mural nodules were compared between CE-US and contrast-enhanced computed tomography (CE-CT), and the imaging of mural nodules depicted under CE-US was analyzed.

RESULTS

Seventeen of 22 resected specimens (77.3%) had mural nodules. There was no significant difference in the detection rate between CE-US (n=15; 88.2%) and CE-CT (n=12; 70.6%). In 12 (80.0%) of these patients, CE-US revealed small vessels in the mural nodule. The spotty or linear-shaped pattern was detected in 4 patients and the branch-shaped pattern in 8. The branch-shaped pattern lesion was associated with carcinoma. These mural nodules were 10mm or more in height. In the perfusion image phase, cystic walls and mural nodules were also enhanced in all cases.

CONCLUSION

The vessel shapes of the mural nodules depicted under CE-US were associated with size and pathological findings. These results suggested that CE-US with a contrast agent is a powerful modality with which to evaluate the malignant potential of IPMN.

Contrast enhanced endoscopic ultrasound: More than just a fancy Doppler

Contrast enhanced endoscopic ultrasound (CEUS) is a new modality that takes advantage of vascular structure and blood flow to distinguish different clinical entities. Contrast agents are microbubbles that oscillate when exposed to ultrasonographic waves resulting in characteristic acoustic signals that are then converted to colour images. This permits exquisite imaging of macro- and microvasculature, providing information to help delineate malignant from non-malignant processes. The use of CEUS may significantly increase the sensitivity and specificity over conventional endoscopic ultrasound. Currently available contrast agents are safe, with infrequent adverse effects. This review summarizes the theory and technique behind CEUS and the current and future clinical applications.

[Assessment of tumour angiogenesis using contrast-enhanced ultrasound]

Microbubbles are useful for imaging tumour angiogenesis and relatively crude forms of this approach are now routinely used for subjective diagnosis, especially in the liver. More sophisticated methods use quantitative approaches to measure the amount and the time course of bolus or reperfusion curves and have shown great promise in revealing effective tumour response to anti-angiogenic drugs in humans before tumour shrinkage occurs. These are beginning to be accepted into clinical practice. In the long term, targeted microbubbles for molecular imaging and eventually for directed anti-tumour therapy are expected to be tested.

Quantitative assessment of synovial vascularity using contrast-enhanced power Doppler ultrasonography: correlation with histologic findings and mr imaging findings in arthritic rabbit knee model

Objective

To validate contrast-enhanced power Doppler ultrasonography (PD US) for the evaluation of synovial vascularity in an arthritic rabbit knee model in correlation with MR and histological findings.

Materials and Methods

Power Doppler ultrasonography was performed for carrageenin-induced arthritic left knee and control right knee of 13 rabbits, first without and then with sonic contrast agent enhancement (Levovist, Schering, Berlin Germany), followed by gadolinium-enhanced MR imaging. Synovial vascularity was quantitatively assessed by calculating the color pixel area in power Doppler sonography using a computer-aided image analysis program and by grading the enhancement on MR images: grade 1, enhancement of knee joint is less than one-third of the area; grade 2, one-third to two-thirds enhancement; and grade 3, more than two-thirds enhancement. Microvessel density (MVD) was measured on slides stained immunohistochemically for CD31 antigen for histological assessment.

Results

The mean area of color pixels in PD US changed from 4.37 to 16.42 mm² in the arthritic knee after enhancement (p < 0.05), whereas it changed from 0.77 to 2.31 mm² in the control knee (p < 0.05). Arthritic knees had greater power Doppler signal than control knees both before and after contrast administration (p < 0.05). The average MVD was 88 in arthritic knees and 46 in control knees. MVDs correlated with color pixel areas of contrast-enhanced power Doppler imaging in arthritic knees. In MR grading of arthritic knees, five were grade 2 and eight were grade 3. MVD and PD US revealed no significant difference between grade 2 and 3 arthritic knees (p > 0.05).

Conclusion

Sonic contrast-enhanced PD US improves the visualization of synovial vascularity and allows quantitative measurement in experimentally induced rabbit arthritic knees.

Assessment of cerebral autoregulation with transcranial Doppler sonography in poor bone windows using constant infusion of an ultrasound contrast agent

Cerebral autoregulation is an important pathophysiological and prognostic parameter for a variety of neurologic conditions. It can be assessed quickly and safely using transcranial Doppler sonography (TCD). In elderly patients, poor insonation conditions decrease the number of examinable patients and can cause a systematic bias in autoregulation parameters. The aim of this study was to investigate whether a constant infusion of an ultrasound contrast agent (Levovist((R))) can counteract these effects. We examined two cohorts of unselected neurologic patients. In 45 patients with good insonation windows (cohort 1), we used a thin aluminium foil between the skin and the TCD probe to artificially decrease the insonation quality. We determined two parameters of cerebral autoregulation (phase difference [PD] and a cross-correlation coefficient [Mx]) in native patients, with aluminium foil and with aluminium foil and a constant infusion of Levovist. In 30 patients with poor insonation windows (cohort 2), we measured the autoregulation twice, with and without an infusion of Levovist, to assess the reproducibility of the autoregulation parameters. In cohort 1, the foil model significantly decreased the Doppler signal quality, i.e., the mean spectrum energy decreased from 33.9 +/- 2.7 dB to 26.3 +/- 2.4 dB (p < 0.001). This introduced a significant bias to all autoregulation parameters (PD: decreased from 38.2 +/- 10.0 degrees to 27.9 +/- 12.5 degrees (p < 0.001); Mx: decreased from 0.308 +/- 0.170 to 0.254 +/- 0.162 (p < 0.01)). Both effects were compensated largely by a constant infusion of Levovist (300 mg/min). In cohort 2, infusion of the contrast agent at the same rate increased insonation quality, too, but to a lesser degree (27.4 +/- 2.4 dB to 32.0 +/- 3.7 dB, p < 0.001). This smaller increase did not cause a significant change in the autoregulation parameters, but the reproducibility of the PD was significantly improved (intraclass coefficient coefficient [ICC] 0.76, 95% confidence interval [0.59-0.87] in native poor bone window compared with ICC 0.90, 95% confidence interval [0.81-0.95] with infusion of the contrast agent). Our data show that constant infusion of an ultrasound contrast agent during the assessment of cerebral autoregulation can avoid potential bias introduced by poor insonation conditions. Furthermore, infusion of the contrast agent can improve reproducibility and contribute to the credibility of autoregulation assessment in the elderly. (E-mail: matthias.lorenz@em.uni-frankfurt.de).

Liver transplantation: vascular complications

Transplantation has become the method of choice for treatment of patients with irreversible severe liver dysfunction. Vascular thrombosis or stenosis, biliary obstruction, hemorrhage, posttransplantation neoplasm, and rejection are some of the most common potential complications. Most complications cause significant morbidity and mortality after liver transplantation. The appearance of vascular complications in posttransplantation patients is illustrated in this article.

Small renal masses: the value of contrast-enhanced colour Doppler imaging

OBJECTIVE

To assess the value of a microbubble-based ultrasonographic contrast agent for enhancing blood vessels in colour Doppler imaging (CDI) of small renal masses.

PATIENTS AND METHODS

Fifty-one patients with small renal masses (< 3 cm in diameter) had prospective CDI before and after intravenous administration of the contrast agent Levovist (Schering, Berlin, Germany). The degree of tumour vascularity was subjectively graded from 0 to IV (indicating an increasing vessel count). Furthermore, peak systolic velocity (PSV), resistive index, and pulsatility index were measured. The CDI findings were then compared with those obtained at histopathological examination.

RESULTS

Intra- and/or peritumoral vessels were detected in 26 lesions (51%) by unenhanced CDI and in 48 by enhanced CDI (94%; P = 0.006, McNemar test). Higher grades of tumour vascularity (grade III and IV) were more common in malignant renal masses (P < 0.01). There were PSVs of >80 cm/s only in malignant lesions. Based on receiver operating characteristic analysis, enhanced CDI (area under the curve 0.789) was more accurate than unenhanced CDI (0.576) for differentiating benign from malignant renal masses (P < 0.004).

CONCLUSION

Enhanced CDI is better than unenhanced CDI for detecting tumour vascularity, and for discriminating between benign and malignant small renal masses.

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.

Comparison of visual and quantitative analysis for characterization of insonated liver tumors after microbubble contrast injection

OBJECTIVE

The objective of our study was to compare diagnostic performance of visual and quantitative analysis for the characterization of liver tumors insonated at low transmit power after microbubble contrast agent injection.

SUBJECTS AND METHODS

This series comprised 166 liver tumors (1-5 cm in diameter) in 166 patients (99 men, 67 women; mean age +/- SD, 58 +/- 11 years) scanned at low transmit power (mechanical index: 0.1-0.14) after sulfur hexafluoride-filled microbubble injection. Digital cine clips recorded at the arterial phase (10-40 sec after contrast injection) and late phase (100-300 sec) were analyzed to characterize liver tumors as benign or malignant. Visual analysis was performed by three independent blinded reviewers who evaluated enhancement patterns at the arterial phase and subjective tumor conspicuity at the late phase. Quantitative analysis of videotape intensity (VI: gray-scale levels, 0-255) was performed to calculate objective tumor conspicuity at the late phase: (VI(tumor) - VI(liver)) / VI(liver).

RESULTS

Characteristic enhancement patterns were observed in malignant tumors (peripheral rimlike) and benign tumors (peripheral nodular or central and spoke-wheel-shaped). Malignant (n = 95) versus benign (n = 71) tumors differed for subjective (median value: -1 vs 1, respectively) and objective conspicuity at the late phase (-0.6 vs 0.15, respectively; p = 0.001, Mann-Whitney U test) due to persistent microbubble uptake in benign tumors. Diagnostic performance of visual (odds ratio: reviewer 1 = 4.28, reviewer 2 = 10.18, reviewer 3 = 9.56) and quantitative (odds ratio: 89.33) analyses differed significantly in the characterization of liver tumors (p = 0.01, chi-square test).

CONCLUSION

Quantitative analysis revealed higher diagnostic performance than visual analysis to characterize liver tumors insonated at low transmit power after microbubble contrast agent injection.

Prognostic value of angiogenesis evaluated with high-frequency and colour Doppler sonography for preoperative assessment of primary cutaneous melanomas: correlation with recurrence after a 5 year follow-up period

OBJECTIVE

To study the value of high-frequency sonography (HFS) and colour Doppler sonography (CDS) in evaluating the 5 year metastatic potential of primary cutaneous melanomas (CM).

MATERIALS AND METHODS

111 CM were studied before surgical resection and 107 were depicted on HFS. The maximal HFS thickness was measured and compared with the Breslow thickness. A CDS study was performed in each tumour.

RESULTS

HFS thickness ranged from 0.26 to 8.0 mm and Breslow thickness from 0.15 to 8.0 mm. HFS and Breslow thickness correlated strongly (r > 0.93). Intratumour vessels were depicted in 43 of the 107 CM, of which 40 were thicker than 2 mm. The median follow-up was 61 months and 27 patients developed relapses. In the univariate analyses, neovascularization visualized with CDS, sonographic thickness and the Breslow thickness were significantly linked to relapses (p < 0.0001), as were lymph node status and ulceration (p = 0.007 and 0.004).

CONCLUSION

Vascularization was observed mainly in thick primary melanoma. A median follow-up of 5 years showed the prognostic value of angiogenesis evaluated by CDS.

Diagnostic efficacy of SonoVue®, a second generation contrast agent, in the assessment of extracranial carotid or peripheral arteries using colour and spectral Doppler ultrasound: a multicentre study

The purpose of this study was to demonstrate the improvement in diagnostic quality and diagnostic accuracy of SonoVue microbubble contrast-enhanced ultrasound (CE-US) versus unenhanced ultrasound imaging during the investigation of extracranial carotid or peripheral arteries. 82 patients with suspected extracranial carotid or peripheral arterial disease received four SonoVue doses (0.3 ml, 0.6 ml, 1.2 ml and 2.4 ml) with Doppler ultrasound performed before and following each dose. Diagnostic quality of the CE-US examinations was evaluated off-site for duration of clinically useful contrast enhancement, artefact effects and percentage of examinations converted from non-diagnostic to diagnostic. Accuracy, sensitivity and specificity were assessed as agreement of CE-US diagnosis evaluated by an independent panel of experts with reference standard modality. The median duration of clinically useful signal enhancement significantly increased with increasing SonoVue doses (p< or =0.002). At the dose of 2.4 ml of SonoVue, diagnostic quality evaluated as number of inconclusive examinations significantly improved, falling from 40.7% at baseline down to 5.1%. Furthermore, SonoVue significantly (p<0.01) increased the accuracy, sensitivity and specificity of assessment of disease compared with baseline ultrasound. SonoVue increases the diagnostic quality of Doppler images and improves the accuracy of both spectral and colour Doppler examinations of extracranial carotid or peripheral arterial disease.

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.

Computer-assisted quantitative assessment of power Doppler US: effects of microbubble contrast agent in the differentiation of breast tumors

RATIONALE AND OBJECTIVES

To objectively quantify the effects of a microbubble contrast agent to differentiate breast tumors with power doppler ultrasound and to compare these results with color doppler ultrasound (CD US).

METHODS

In 47 patients a microbubble contrast agent was injected intravenously. Computer-assisted quantitative assessment of the color pixel density was performed to evaluate the increase in Doppler signals. Results were compared to previously published results of a color Doppler ultrasound study.

RESULTS

Peak color pixel density at contrast-enhanced power Doppler ultrasound was higher for carcinomas than for benign tumors (P < 0.03). Time to peak enhancement was shorter in carcinomas than in benign tumors (P < 0.01). For both parameters, diagnostic accuracy of power Doppler ultrasound was 69 and 78%, and for color Doppler ultrasound 62 and 76%, respectively.

CONCLUSIONS

Quantitative assessment of contrast-enhanced power Doppler ultrasound showed significant differences in malignant and benign breast tumors. Diagnostic accuracy of contrast-enhanced power Doppler ultrasound was higher compared to color Doppler ultrasound.

Ultraschallkontrastmittel: Substanzklassen, Pharmakokinetik, klinische Anwendungen, Sicherheitsaspekte

Ultrasound contrast agents (UCA) have undergone constant development and improvement in recent years. Greater mechanical stability and improved acoustic properties, combined with new contrast-specific ultrasound sequences, have broadened the potential fields for investigation considerably. Contrast-enhanced ultrasound studies will no longer be complementary investigations, but will be considered as primary techniques. This review article provides a survey of the different drugs used, their chemical properties, and their pharmacokinetic aspects. Summarized are the most important established and published indications for the use of UCA together with an outlook for future applications. Finally this paper discusses the safety profile of these agents, which has become important due to the increasing use of these agents.

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.

In vitro and in vivo studies on continuous echo-contrast application strategies using SonoVue in a newly developed rotating pump setup

With emerging imaging strategies for contrast sonography (CS), there is a rising demand for the precise control of ultrasound (US) contrast agent delivery. Constant delivery minimizes artefacts and improves efficacy. The aim of this study was to evaluate the physical properties of the new contrast agent SonoVue and to evaluate the feasibility and accuracy of a new infusion approach using an automated infusion system for contrast agitation and delivery of echo-contrast agents. In vitro testing of infusion properties of SonoVue were performed in a capillary phantom mimicking tissue perfusion. Nonagitated standard infusion setups were compared with hand agitation and the new pump system with respect to possible artefacts, constancy of contrast effect and efficacy. In three volunteers, the new pump system was tested for constancy of contrast in large vessels. Without continuous agitation, continuous infusion of SonoVue resulted in bolus-like signal-intensity curves, along with substantial imaging artefacts. Additionally, homogenization of SonoVue significantly improved efficacy (p < 0.0001). No significant differences were found between hand agitation and homogenization by the new pump. In clinical settings, constant agitation using the new pump resulted in constant signal conditions in the carotid artery 3.72 +/- 0.46 units (U) after 5 min. Continuous agitation of SonoVue is mandatory for quantitative approaches. By the new infusion technique, CS could be performed for a reasonably long time period and efficacy is significantly improved (p < 0.0001). The new infusion technique might thereby allow routine application of constant infusion scenarios in clinical CS.

Contrast-enhanced duplex scanning of crural arteries by means of continuous infusion of Levovist

OBJECTIVES

To estimate the dosage needed for continuous infusion and to investigate whether continuous infusion of the ultrasound contrast-enhancing agent Levovist (SH U 508A) can improve duplex scanning of crural arteries in patients with peripheral arterial obstructive disease (PAOD) eligible for distal bypass graft surgery.

DESIGN, PATIENTS, AND METHODS

The study design consisted of two parts. Part 1 investigated the color and spectral Doppler scan enhancement of three different Levovist dosages (200, 300, and 400 mg/mL) in one arterial segment of a patent lumen of a crural artery in seven patients with PAOD. Part 2 investigated the value of the optimum Levovist dosage in the assessment of 10 crural arteries in 10 consecutive patients with PAOD. Angiography was the reference standard.

RESULTS

Part 1: Levovist significantly enhanced color and spectral Doppler scan as compared with baseline ultrasound scan, but no differences were found between the Levovist dosages. Thus, the lowest Levovist dosage sufficed for application in part 2, because of its infusion volume and prolonged enhancement time. Part 2: The agreement between contrast-enhanced duplex scanning and angiography was moderate (kappa = 0.50; 95% confidence interval [CI], 0.03-0.97). Five (50%) of 10 crural arteries that could not adequately be visualized with routine duplex scanning could be visualized with contrast-enhanced duplex scanning.

CONCLUSION

Contrast-enhanced duplex scanning by means of continuous infusion of Levovist in patients with PAOD improves the ultrasound scan investigation of crural arteries in case routine duplex scanning is inconclusive and might reduce the need for angiography.

Echo-enhanced duplex sonography of extracranial vertebral arteries

We sought to investigate the potential benefit in examining extracranial vertebral arteries (ExVA) with an echo contrast agent. A total of 26 patients with insufficiently assessable ExVA underwent extracranial duplex sonography without and with an echo contrast medium. All examinations were recorded and analysed independently by two experienced sonographers. Interrater agreement was fair in assessment of B-mode quality, colour-coding, blooming artefacts, change of vmax, good to very good in all other rated categories. Using an echo contrast medium reduced overall inassessable ExVA by 48% and 36% according to the two raters, respectively. After contrast enhancement, diagnosis was clarified in ExVA formerly inassessable for hypoplasia in 60% vs. 56%, extracranial occlusion in 67% vs. 56% and resistance signal in 63% vs. 45%, respectively. Application of an echo contrast agent leads to clarification of ExVA sonographic diagnosis in approximately one third of poorly examinable patients (35% and 30%, respectively), and contributes in ruling out extracranial occlusion, hypoplasia and resistance signal.

Microbubble ultrasound contrast in the assessment of hepatic artery patency following liver transplantation: role in reducing frequency of hepatic artery arteriography

We prospectively evaluated the role of microbubble ultrasound contrast for detection of hepatic artery thrombosis following liver transplantation. The hepatic artery of adult liver transplant recipients with suspected thrombosis on surveillance Doppler ultrasound (US) were re-examined by a second observer. In patients with no hepatic spectral Doppler signal the microbubble contrast agent Levovist was used. The presence or absence of flow following microbubble contrast was evaluated against arteriography or repeated Doppler US findings. A total of 794 surveillance Doppler US examinations were performed in 231 patients. Hepatic artery flow was demonstrated in 759 of 794 (95.6%) examinations. Microbubble ultrasound contrast was administered in 31 patients (35 studies) with suspected hepatic artery thrombosis. Following microbubble US contrast the hepatic artery could not be demonstrated in 13 of 35 (37.1%) studies (12 patients). Eight patients had arteriography: there was hepatic artery thrombosis in 7 patients and 1 patient had a patent, highly attenuated artery. Detection of a patent hepatic artery increased from 759 of 794 (95.6%) to 781 of 794 (98.4%) with the addition of microbubble contrast. Upon independent reading of the data, the degree of operator confidence in the assessment of the hepatic artery patency prior to microbubble contrast was 4.7 (CI 1.92-7.5) but rose to 8.45 (CI 7.06-9.84) following microbubble contrast ( p<0.0001). In 22 of 35 (62.9%) of studies arteriography could potentially have been avoided. Ultrasound microbubble contrast media may reduce the need for invasive arteriography in the assessment of suspected hepatic artery thrombosis.

Assessment of Transcranial Color-coded Duplex Sonography for the Surveillance of Intracranial Aneurysms Treated with Guglielmi Detachable Coils

OBJECTIVE

We sought to evaluate the sensitivity and specificity of transcranial color-coded duplex sonography (TCCS) and the effect of an ultrasonographic contrast agent in the long-term surveillance of intracranial aneurysms treated with Guglielmi detachable coils.

METHODS

Forty-six studies were obtained in patients with intracranial aneurysms treated with coils. All studies were obtained within 2 months of surveillance digital subtraction angiograms, which was adopted as the standard for observing aneurysm refilling. For 34 of the studies, imaging was performed both before and after infusing an ultrasonographic contrast agent (Levovist). The remaining 12 studies were unenhanced. Aneurysms were described either as being fully occluded or as having residual flow. The degree of residual flow was quantified as minor, moderate, or extensive. The operator was blinded to the results of digital subtraction angiography during TCCS assessment.

RESULTS

TCCS correctly identified 19 of 20 aneurysms with complete occlusion (sensitivity, 95%; specificity, 84%). TCCS also identified all 16 of the clinically relevant aneurysms with either moderate or extensive residual flow visualized on digital subtraction angiograms and 5 aneurysms only after contrast enhancement (sensitivity, 100%; specificity, 97%). The overall accuracy of TCCS in identifying clinically relevant aneurysms was 85% without contrast enhancement and 96% with contrast enhancement.

CONCLUSION

Contrast-enhanced TCCS shows promise as a noninvasive imaging method for the surveillance of coiled intracranial aneurysms.

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.

Evaluation of liver parenchymal blood flow with contrast-enhanced US: preliminary results in healthy and cirrhotic patients

RATIONALE AND OBJECTIVES

To determine whether changes in hepatic parenchymal blood flow in cirrhotic patients can be evaluated with contrast-enhanced ultrasound (US) after Levovist administration.

MATERIALS AND METHODS

Ten normal volunteers, 16 Child A and 16 Child C cirrhotic patients were evaluated with contrast-enhanced US. Frames obtained at progressively increasing pulse intervals of 2, 4, 7, and 10 seconds in the same scan plane during infusion of Levovist (300 mg/mL, 150 mL/h) have been digitally recorded. Pulse intervals versus signal intensity (PI-SI) plots were fitted to a straight line whose slope is proportional to the speed of blood in the liver parenchyma. Enhancement differences in late phase have been evaluated measuring the SI after 7 minutes from the beginning of the infusion.

RESULTS

The slope of the PI-SI plot of the Child A cirrhotic patients was significantly lower than the slope of the normal controls (P < 0.05); conversely, no significant differences were found between the slope of the patients with Child C cirrhosis and that of the normal controls. In comparison with the normal subjects, the average SI at late phase decreased significantly both in patients with Child A (P < 0.05) and Child C (P < 0.001) cirrhosis.

CONCLUSION

Microbubble contrast agents could provide a noninvasive tool to detect and monitor hemodynamic changes that occur in the cirrhotic liver. Changes in the hepatospecific properties at late phase have also been demonstrated.

A review of nonconventional ultrasound techniques and contrast-enhanced ultrasonography of noncardiac canine disorders

Modern ultrasound contrast media are gas-containing stabilized microbubbles that remain intact in the circulating blood for several minutes after intravenous injection and increase the intensity of the backscattered ultrasound. When the microbubbles disappear from the blood, they can be detected in the parenchyma of the liver and the spleen for about 30 more minutes (late liver- and spleen-specific phase). The insonated microbubbles produce second harmonic ultrasound frequencies, whose detection requires nonconventional ultrasound modalities such as pulsed inversion imaging. Nonconventional ultrasound techniques can also be used without microbubbles because second harmonics can be generated by ultrasound in tissues as well. The physical principles and advantages of nonconventional ultrasound techniques are described. The circulating microbubbles can be used not only to enhance weak Doppler signals, but also to perform dynamic contrast studies. Contrast-enhanced dynamic ultrasound studies--similar to contrast-enhanced CT and MRI examinations--have been used in humans to characterize lesions noninvasively (i.e., without biopsies) found during conventional ultrasound examinations. To map the distribution of contrast medium in a nodule or in an organ, specific scanning techniques such as stimulated acoustic emission have been developed. Stimulated acoustic emission occurs when high acoustic pressure ultrasonic waves disrupt the stationary or slowly moving microbubbles. This results in the release of a large amount of harmonic ultrasound frequencies. When the stimulated acoustic emission technique is used for dynamic studies, scanning must be interrupted several times to allow the microvasculature of the lesion to refill with microbubbles (interval delay imaging). The contrast patterns of malignant and benign hepatic nodules in humans have been the most intensively studied. Another type of dynamic study in humans measures the transit time of the contrast medium; that is, how fast the peripherally injected microbubbles reach the hepatic veins. Hepatic cirrhosis can be differentiated from other diffuse parenchymal liver diseases by a shorter transit time. Introducing nonconventional ultrasound techniques and ultrasound contrast media in veterinary diagnostic imaging may have potential value; however, intensive research should be carried out before ultrasound contrast agents can routinely be used in clinical practice.

Multigated contrast-enhanced power Doppler to measure blood flow in mice tumors

This study evaluated an image-gating method using contrast-enhanced power Doppler ultrasound (US) to estimate blood perfusion in mice tumors. A mathematical model that compensates for the effect of bubble destruction by US pulses was used to determine contrast flow through an image plane. Multigated power Doppler images were obtained following contrast injection. Contrast flow index (CFI) was determined by measuring the area under the color level vs. time curve for each gating frequency. CFI was compared with true flow. The method was first evaluated using a flow phantom with variable flow rates, and then verified in a mouse model with implanted tumors. Color levels in Doppler images were modulated with gating frequency due to variable destruction of microbubbles by US pulses. CFI measured from the images correlated strongly with true flow in the flow phantom (r(2) = 0.87). The proposed method yielded reproducible CFI for mice tumors, suggesting that multigated contrast-enhanced power Doppler imaging may provide noninvasive measurement of tumor perfusion in mice.

Value of contrast-enhanced power Doppler sonography using a microbubble echo-enhancing agent in evaluation of small breast lesions

PURPOSE

The purpose of this study was to prospectively evaluate the usefulness of contrast-enhanced power Doppler sonography (PDUS) using a microbubble echo-enhancing agent in differentiating between malignant and benign small breast lesions.

PATIENTS AND METHODS

Between July 1, 2000, and September 30, 2001, we performed gray-scale sonographic examination of patients in whom diagnostic sonography or screening mammography had revealed solid breast lesions measuring less than 2 cm in the largest dimension. The patients were then examined on PDUS before and after injection of a microbubble contrast agent. The sonographic findings for all 3 techniques, as well as the morphologic features of the Doppler signals for each patient before and after injection of the contrast agent on PDUS, were independently assessed. Each lesion was classified as "benign" or "malignant" on the basis of specific criteria for sonographic interpretation. A hemodynamic study was performed in which time-transit profiles of the Doppler signals on contrast-enhanced PDUS were generated using a computer-assisted program, and the results for each patient were compared with the findings of a histopathologic examination of surgical specimens.

RESULTS

Thirty-six patients (35 women and 1 man) with a mean age of 43.5 years (range, 18-69 years) were evaluated. The tumors ranged from 4 to 19 mm in the largest dimension. Histopathologic examination revealed that 19 tumors were benign and 17 were malignant. For morphologic diagnosis of the malignant lesions, the sensitivity of gray-scale sonography was 100%, compared with 29% for PDUS without contrast enhancement. The specificity of gray-scale sonography was 47%, compared with 74% for PDUS without contrast enhancement. Contrast-enhanced PDUS had a sensitivity of 71% and a specificity of 58%. The diagnostic accuracy was 72% for gray-scale sonography, 53% for PDUS without contrast enhancement, and 64% for contrast-enhanced PDUS. The time-transit profiles of the hemodynamic study did not reveal a statistically significant difference in the accuracy rates of contrast-enhanced PDUS between benign and malignant breast lesions.

CONCLUSIONS

Compared with PDUS without contrast enhancement, contrast-enhanced PDUS provides better visualization of the morphology of vascular Doppler signals that is characteristic of malignancy and therefore has a higher sensitivity and diagnostic accuracy, albeit a lower specificity. In differentiating between benign and malignant small breast lesions, contrast-enhanced PDUS can be helpful when used with gray-scale sonography and PDUS without contrast enhancement.

Power Doppler sonography with and without echo-enhancing contrast agent and contrast-enhanced MRI for the evaluation of rheumatoid arthritis of the shoulder joint: differentiation between synovitis and joint effusion

OBJECTIVE

To evaluate patients with clinically active rheumatoid arthritis (RA) of the shoulder for joint effusion and synovitis using conventional sonography, power Doppler (PD) sonography with and without echo-enhancing contrast agent, and contrast-enhanced MRI.

DESIGN AND PATIENTS

Twenty-four patients (mean age 64 years) with known RA had one symptomatic shoulder evaluated by conventional gray-scale sonography and PD sonography before and after intravenous administration of the echo-enhancing contrast agent Levovist (300 mg/ml, 2.5 g). The degree and extent of the altered echo pattern in the subacromial bursa, axillary recess and glenohumeral joint seen by conventional gray-scale sonography and the intensity of vascular signals of PD sonography were compared with the findings of MRI obtained with T2-weighted turbo spin-echo sequences and contrast-enhanced T1-weighted fat-saturated spin-echo sequences. MRI was evaluated by two readers in consensus without knowledge of the sonographic findings.

RESULTS

MRI, which was used as the reference examination, detected joint effusion in 71% (17/24) and synovitis in 92% (22/24) of the patients. Conventional sonography revealed an abnormal articular echo pattern in 96% (23/24) of the patients, especially in the axillary recess and subacromial bursa, but failed to attribute the altered echo pattern to either fluid or specific synovitis. PD sonography allowed a specific diagnosis of synovitis in 33% (8 patients), which increased to 50% (12 patients) after administration of an echo-enhancing contrast agent. In 42% (10/24) of the patients, the findings of synovitis demonstrated by MRI corresponded to an altered echo pattern by conventional sonography, but vascular signals were absent by PD sonography with or without echo-enhancing contrast agent.

CONCLUSIONS

Using MRI as the "gold standard," PD sonography with and without echo-enhancing contrast agent cannot reliably identify synovitis or distinguish synovial inflammation from effusion in the shoulder joint.

Non-invasive detection of coronary artery stenosis: a comparison among power-Doppler contrast echo, 99Tc-Sestamibi SPECT and echo wall-motion analysis

BACKGROUND

Power-Doppler imaging is a recently developed method for myocardial contrast echocardiography (MCE). It can selectively evaluate the signal coming from an ultrasound contrast agent, allowing myocardial perfusion studies.

OBJECTIVE

To compare the ability of power-Doppler MCE with stress-echo wall-motion and nuclear scan imaging (SPECT) to assess myocardial ischaemia during pharmacological stress, using coronary angiography as reference.

METHODS

In 25 patients the three non-invasive imaging modalities were acquired during a single dipyridamole stress test (so as to avoid stress variations). Power-Doppler MCE was acquired using continuous intravenous infusion of Levovist. Echo wall-motion was acquired too. At peak stress 99Tc-Sestamibi was injected; stress SPECT images were acquired 30 min after injection.

RESULTS

Power-Doppler MCE and SPECT showed 84% concordance (21 of 25 patients; kappa=0.67) for detection of ischaemia. Concordance based on coronary artery territories for normal perfusion versus fixed defects versus reversible defects was 92% (69 of 75; kappa=0.81), with 100% for left anterior descending, 92% for right coronary artery and 84% for circumflex. Power-Doppler MCE had lower sensitivity than SPECT (89 versus 100%) but higher specificity (100 versus 88%) for identification of stenotic (> or = 70%) coronary arteries as assessed by angiography. Echo wall-motion analysis showed the lowest sensitivity (68%) with 100% specificity. Accuracy was 94% for both power-Doppler MCE and SPECT, and 83% for wall-motion analysis.

CONCLUSION

Power-Doppler MCE is a sensitive and specific method for identification of myocardial perfusion during pharmacological stress. Accuracy of power-Doppler MCE for stenotic coronary arteries appears to be slightly higher than stress-echo wall-motion and similar to SPECT.

Effect of Levovist on splanchnic hemodynamics in cirrhotic patients

This study was aimed to assess the effect of Levovist on Doppler parameters of splanchnic hemodynamics. A total of 12 patients with cirrhosis and 12 healthy subjects underwent Doppler ultrasound (US) examination of the portal vein and of the hepatic, splenic and superior mesenteric arteries before, 5 to 8 and 12 to 15 min after the start of an 8-min long IV infusion of 2.5 g of Levovist. Mean velocity and mean diameter were calculated for the portal vein. Resistance index was determined for the arteries. A significant increase of resistance index was observed in the hepatic (0.80 +/- 0.07 vs. 0.71 +/- 0.06; p < 0.01) and splenic arteries (0.72 +/- 0.06 vs. 0.64 +/- 0.06; p < 0.01) 5 to 8 min after contrast agent injection in patients with cirrhosis, but not in controls. Neither portal vein diameter nor portal flow mean velocity changed during the test in both controls and cirrhotic patients. This effect might be related to a selective trapping of microbubbles in the altered hepatic and splenic microvasculature in patients with cirrhosis rather than being artefactual. It might have implications on harmonic imaging US protocols designed to image the cirrhotic liver in the early arterial phase.

Microbubble-augmented ultrasound declotting of thrombosed arteriovenous dialysis grafts in dogs

PURPOSE

Transcutaneous low-frequency ultrasound (LFUS) can effectively lyse clots in the presence of microbubbles. This study was designed to test the commercially available human albumin microspheres injectable suspension octafluoropropane formulation, Optison, to establish efficacy and assess US parameters of intensity and wave modes in a canine model of a thrombosed arteriovenous (dialysis) graft.

MATERIALS AND METHODS

Arteriovenous grafts in five dogs were cannulated, temporarily ligated, and thrombosed. Different declotting techniques were randomized to treat nine groups. Control groups involved direct saline (4.5 mL) clot injection in 0.5-1.0-mL increments. One group underwent peripheral intravenous microbubble injection (13.5 mL). Six groups underwent direct incremental clot injection of 4.5 mL of microspheres with LFUS for 30 minutes in 3-5-minute increments with use of various intensity settings in continuous-wave and pulsed-wave (PW) modes. At each increment, angiography was used to grade flow, declotting, and overall success.

RESULTS

One hundred four procedures showed success in all 24 high-intensity PW modes (1.2-2.0 W/cm(2)); only one of 20 control experiments was successful (P <.0001). Medium-intensity modes yielded intermediate success rates. Lowest-intensity direct-injection groups and intravenous and control groups ranked lower. Results at 30 minutes were better than at 15 minutes (P <.0001).

CONCLUSIONS

LFUS with direct injection of microbubbles is effective in lysing moderate-sized clots and recanalizing thrombosed arteriovenous grafts. It best succeeds at the higher range of intensity settings tested in PW mode. Further development is justified.

Pulse-inversion harmonic imaging improves lesion conspicuity during US-guided biopsy

PURPOSE

To assess the feasibility of percutaneous biopsy of low-conspicuity focal liver lesions with use of pulse-inversion harmonic imaging (PIHI) guidance in the late phase after injection of microbubble contrast agent.

MATERIALS AND METHODS

Twelve patients referred for ultrasound (US)-guided biopsy had liver lesions lacking adequate conspicuity to undergo biopsy under conventional ultrasound (US) guidance. They underwent biopsy procedures performed with the use of PIHI guidance in the late phase after injection of Levovist. The conspicuity of lesions, procedure time, number of passes, and success and complication rates were documented and compared to a control group. The control group consisted of retrospective analysis of 19 patients who had undergone conventional US-guided biopsy procedures performed by the same radiologist.

RESULTS

After contrast material injection, all lesions had sufficient increases in conspicuity to be targeted under PIHI guidance. Procedure time was prolonged in the PIHI group (66 minutes; range, 30-120 min; vs control, 33 min; range, 15-77 min; P <.01, Wilcoxon signed-rank test). The number of passes was greater in the PIHI group (1.9 +/- 0.3; vs control, 1.4 +/- 0.6; P <.01, chi(2) test). No statistically significant difference was observed when comparing success and complication rates.

CONCLUSION

PIHI in the late phase after injection of Levovist generated clear delineation of focal liver lesions in all cases, allowing an accurate and safe sampling. This technique broadens the scope of US-guided biopsy to lesions lacking adequate conspicuity on conventional US.

Kinetics of a US contrast agent in benign and malignant adnexal tumors

PURPOSE

To evaluate the effects of a microbubble contrast agent on the power Doppler ultrasonographic (US) examination of adnexal tumors, with a special focus on the timing of the transit of the microbubble bolus.

MATERIALS AND METHODS

Seventy patients who were suspected of having ovarian tumors were examined preoperatively with contrast material-enhanced US. Images obtained during a 5-minute examination were stored digitally, and the behavior of the contrast agent was evaluated objectively with measurement of the time-dependent image intensity at the region of interest with a computer program. A time-intensity curve in each case was derived and analyzed. The Mann-Whitney U test was used to compare intensity changes and tumor parameters in benign and malignant adnexal tumors.

RESULTS

Both the baseline and maximum power Doppler intensities, as well as the absolute and relative (percent) rise in intensity, were significantly higher (P <.001) in malignant as compared with benign tumors. The arrival time was shorter (17.5 vs 22.5 seconds; P =.005) and the duration of contrast agent effect was longer (190.4 vs 103.6 seconds; P <.001) in malignant tumors than they were in benign tumors. The area under the time-intensity curve was significantly greater in malignant tumors compared with that in benign tumors (P <.001).

CONCLUSION

After microbubble contrast agent injection, malignant and benign adnexal lesions behave differently in degree, onset, and duration of Doppler US enhancement.