The safety of deFinity and Optison for ultrasound image enhancement: a retrospective analysis of 78,383 administered contrast doses

Contrast-enhanced ultrasound for assessing carotid atherosclerotic plaque lesions

OBJECTIVE

Contrast-enhanced ultrasound that is used to assess atherosclerotic carotid plaques improves visualization of vessel wall irregularities and provides direct visualization of intraplaque neovascularization. This article illustrates the use of contrast-enhanced ultrasound in the assessment of carotid atherosclerotic lesions.

CONCLUSION

Contrast-enhanced ultrasound is a new, noninvasive, and safe procedure for imaging carotid atherosclerotic lesions. It is a valuable tool for evaluating the vulnerable plaque at risk for rupture and for evaluating both the development and severity of systemic atherosclerotic disease.

Rapid Detection of Coronary Artery Stenoses With Real-Time Perfusion Echocardiography During Regadenoson Stress

Background—

Real-time myocardial contrast echocardiography permits the detection of myocardial perfusion abnormalities during stress echocardiography, which may improve the accuracy of the test in detecting coronary artery stenoses. We hypothesized that this technique could be used after a bolus injection of the selective A2A receptor agonist regadenoson to rapidly and safely detect coronary artery stenoses.

Methods and Results—

In 100 patients referred for quantitative coronary angiography, real-time myocardial contrast echocardiography was performed during a continuous intravenous infusion of 3% Definity at baseline and at 2-minute intervals for up to 6 minutes after a regadenoson bolus injection (400 μg). Myocardial perfusion was assessed by examination of myocardial contrast replenishment after brief high mechanical index impulses. A perfusion defect was defined as a delay (>2 seconds) in myocardial contrast replenishment in 2 contiguous segments. Wall motion was also analyzed. The overall sensitivity/specificity/accuracy for myocardial perfusion analysis in detecting a >50% diameter stenosis was 80%/74%/78%, whereas for wall motion analysis it was 60%/72%/66% ( P <0.001 for differences in sensitivity). Sensitivity for myocardial perfusion analysis was highest on images obtained during the first 2 minutes after regadenoson bolus ( P <0.001 compared with wall motion), whereas wall motion sensitivity was highest at the 4-to-6–minute period after the bolus. No significant side effects occurred after regadenoson bolus injection.

Conclusions—

Regadenoson real-time myocardial contrast echocardiography appears to be a feasible, safe, and rapid noninvasive method for the detection of significant coronary artery stenoses.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT0087369.

A pilot study of contrast harmonic endosonography using DEFINITY™ in the evaluation of suspected pancreatic and peri-ampullary malignancies

AIM: Contrast harmonic endosonography (CHEUS) is not widely available. This study assessed the utility of CHEUS using DEFINITY™, a second generation ultrasonic contrast agent, in the evaluation of suspected pancreatic and peri-ampullary malignancies. METHODS: Prospectively enrolled patients with suspected pancreatic and peri-ampullary malignancies underwent EUS followed by CHEUS. The incremental yield of CHEUS over EUS was analyzed. The gold standard for diagnosis of malignancy was positive cytology or histology; a negative diagnosis for malignancy was based on negative cytology or histology and benign clinical course. RESULTS: Twenty-nine patients were enrolled and underwent CHEUS. The final diagnoses were: pancreatic adenocarcinoma (16/29); metastases to pancreas (4/29); pancreatitis with inflammatory mass (4/29); normal pancreas with focal fat sparing (1/29); ampulla adenocarcinoma (2/29); serous cystic neoplasm (1/29); peri-pancreatic lymph node due to lymphoma (1/29). One bengin case of chronic pancreatitis had calcification casting artifacts that prevented accurate EUS examination and was excluded, leaving 28 cases for comparative analysis between EUS and CHEUS. CHEUS enhanced tumor margins. CHEUS detected vascular invasion missed by EUS in 2/16 patients with pancreatic adenocarcinoma. Masses appeared hypoechoic with EUS. With CHEUS malignant masses had an inhomogeneous hypoechoic pattern associated with abnormal vessels while lesions due to focal pancreatitis or fat sparing were characterized by diffuse enhancement (p<0.001). CONCLUSION: CHEUS improved the visualization of tumor margins and vascular invasion, and differentiated benign from malignant masses.

Contrast-enhanced sonographic characterization of the vascularity of the repaired rotator cuff: utility of maximum intensity projection imaging

OBJECTIVES

To characterize the distribution of vascularity of the postoperative rotator cuff tendon using a maximum intensity projection technique after contrast-enhanced sonography.

METHODS

We retrospectively evaluated image data on 23 patients (11 male and 12 female) with intact rotator cuff repairs who had previously undergone contrast-enhanced sonography of their shoulders using lipid microspheres before and after a standardized exercise protocol. The patients were on average 3 months out from their surgery. Using offline image analysis software, a maximum intensity projection image was obtained for each patient, reflecting the regional vascular distribution within the repair and adjacent soft tissue. Subjective analysis was performed in 4 regions of interest: peribursal, articular medial, articular lateral, and suture anchor, independently by 2 musculoskeletal radiologists using a semiquantitative scale ranging from 0 to 4 for each region (0, no enhancement; 1, 1%-25% enhancement; 2, 26%-50%; 3, 51%-75%; and 4, 76%-100%). A combined vascularity score (0-8) was produced for each region and formed the basis for the subjective analysis.

RESULTS

Using a Mann-Whitney nonparametric test, the data showed significantly higher regional enhancement in the peribursal and suture anchor regions compared to the tendon (P < .001). Exercise resulted in a statistically significant increase in the extent of enhancement in all regions (P < .002). Inter-rater reliability analysis using a weighted κ statistic showed strong agreement (0.63-0.64) for the suture anchor site and moderate agreement for the others (peribursal, 0.35-0.39; articular medial, 0.45-0.55; and articular lateral 0.32-0.33).

CONCLUSIONS

The maximum intensity projection technique after contrast-enhanced sonography provides a topographic map of rotator cuff vascularity; the latter has been implicated as an important factor in promoting bone-tendon healing. Approximately 3 months after rotator cuff repair, the suture anchor and peribursal regions showed the most robust vascularity. Maximum intensity projection imaging further establishes that there is a global increase in vascular response at the repair site after exercise.

Renal perfusion evaluation with contrast-enhanced ultrasonography

BACKGROUND

Contrast-enhanced ultrasonography (CEUS) is a novel imaging technique that is safe and applicable on the bedside. Recent developments seem to enable CEUS to quantify organ perfusion. We performed an exploratory study to determine the ability of CEUS to detect changes in renal perfusion and to correlate them with effective renal plasma flow.

METHODS

CEUS with destruction-refilling sequences was studied in 10 healthy subjects, at baseline and during infusion of angiotensin II (AngII) at low (1 ng/kg/min) and high dose (3 ng/kg/min) and 1 h after oral captopril (50 mg). Perfusion index (PI) was obtained and compared with the effective renal plasma flow (ERPF) obtained by parallel para-aminohippurate (PAH) clearance.

RESULTS

Median PI decreased from 188.6 (baseline) to 100.4 with low-dose AngII (-47%; P < 0.02) and to 66.1 with high-dose AngII (-65%; P < 0.01) but increased to 254.7 with captopril (+35%; P > 0.2). These changes parallelled those observed with ERPF, which changed from a median of 672.1 mL/min (baseline) to 572.3 (low-dose AngII, -15%, P < 0.05) and to 427.2 (high-dose AngII, -36%, P < 0.001) and finally 697.1 (captopril, +4%, P < 0.02).

CONCLUSIONS

This study demonstrates that CEUS is able to detect changes in human renal cortical microcirculation as induced by AngII infusion and/or captopril administration. The changes in perfusion indices parallel those in ERPF as obtained by PAH clearance.

The role of poly(ethylene glycol) brush architecture in complement activation on targeted microbubble surfaces

Complement fixation to surface-conjugated ligands plays a critical role in determining the fate of targeted colloidal particles after intravenous injection. In the present study, we examined the immunogenicity of targeted microbubbles with various surface architectures and ligand surface densities using a flow cytometry technique. Targeted microbubbles were generated using a post-labeling technique with a physiological targeting ligand, cyclic arginine-glycine-asparagine (RGD), attached to the distal end of the poly(ethylene glycol) (PEG) moieties on the microbubble surface. Microbubbles were incubated in human serum, washed and then mixed with fluorescent antibodies specific for various serum components. We found that complement C3/C3b was the main human serum factor to bind in vitro to the microbubble surface, compared to IgG or albumin. We also investigated the effect of PEG brush architecture on C3/C3b fixation to the microbubble surface. RGD peptide was able to trigger a complement immune response, and complement C3/C3b fixation depended on microbubble size and RGD peptide surface density. When the targeting ligand was attached to shorter PEG chains that were shielded by a PEG overbrush layer (buried-ligand architecture), significantly less complement activation was observed when compared to the more traditional exposed-ligand motif. The extent of this protective role by the PEG chains depended on the overbrush length. Taken together, our results confirm that the buried-ligand architecture may significantly reduce ligand-mediated immunogenicity. More generally, this study illustrates the use of flow cytometry and microbubbles to analyze the surface interactions between complex biological media and surface-engineered biomaterials.

Contrast echocardiography: what have we learned from the new guidelines?

A new consensus statement on the clinical applications of ultrasound contrast agents was published in November 2008 in the Journal of the American Society of Echocardiography. These guidelines provide the rationale for contrast use, and specifically highlight a number of clinical scenarios in which contrast should always be considered. These include the 1) assessment of left ventricular (LV) systolic function--especially when quantitative LV volumes and ejection fraction, or serial assessments are required, and during stress echocardiography; 2) evaluation of the LV apex; 3) evaluation of mechanical complications of myocardial infarction; 4) evaluation of suspected intracardiac mass; and 5) to enhance Doppler signals in the systemic circulation. Furthermore, detailed outlines on contrast administration, logistics, personnel requirements, and responsibilities are provided. Recent data published in the past 2 years to support these recommendations, and contrast agent safety data, are reviewed in this article.

Bench-to-bedside review: contrast enhanced ultrasonography--a promising technique to assess renal perfusion in the ICU

Acute kidney injury (AKI) is common in critically ill patients and associated with important morbidity and mortality. Although alterations in renal perfusion are thought to play a causative role in the pathogenesis of AKI, there is, to date, no reliable technique that allows the assessment of renal perfusion that is applicable in the ICU. Contrast-enhanced ultrasound (CEUS) is an ultrasound imaging technique that makes use of microbubble-based contrast agents. These microbubbles, when injected into the bloodstream, allow visualization of vascular structures and, with contrast-specific imaging modes, detection of blood flow at the capillary level. Some recent CEUS-derived approaches allow quantification of blood flow in several organs, including the kidney. Current generation ultrasound contrast agents have strong stability and safety profiles. Along with post-marketing surveillance, numerous studies report safe administration of these agents, including in critically ill patients. This review presents information on the physical principles underlying CEUS, the methods allowing blood flow quantification and the potential applications of CEUS in critical care nephrology, currently as a research tool but perhaps in the future as a way of monitoring renal perfusion.

Emerging diagnostic and therapeutic molecular imaging applications in vascular disease

Assessment of vascular disease has evolved from mere indirect and direct measurements of luminal stenosis to sophisticated imaging methods to depict millimeter structural changes of the vasculature. In the near future, the emergence of multimodal molecular imaging strategies may enable robust therapeutic and diagnostic ('theragnostic') approaches to vascular diseases that comprehensively consider structural, functional, biological and genomic characteristics of the disease in individualized risk assessment, early diagnosis and delivery of targeted interventions.This review presents a summary of recent preclinical and clinical developments in molecular imaging and theragnostic applications covering diverse atherosclerosis events such as endothelial activation, macrophage inflammatory activity, plaque neovascularization and arterial thrombosis. The main focus is on molecular targets designed for imaging platforms commonly used in clinical medicine including magnetic resonance, computed tomography and positron emission tomography. A special emphasis is given to vascular ultrasound applications, considering the important role this imaging platform plays in the clinical and research practice of the vascular medicine specialty.

Noninvasive imaging of the vulnerable atherosclerotic plaque

Atherosclerosis is an inflammatory disease, complicated by progressively increasing atherosclerotic plaques that eventually may rupture. Plaque rupture is a major cause of cardiovascular events, such as unstable angina, myocardial infarction, and stroke. A number of noninvasive imaging techniques have been developed to evaluate the vascular wall in an attempt to identify so-called vulnerable atherosclerotic plaques that are prone to rupture. The purpose of the present review is to systematically investigate the accuracy of noninvasive imaging techniques in the identification of plaque components and morphologic characteristics associated with plaque vulnerability, assessing their clinical and diagnostic value.

A retrospective comparison of mortality in critically ill hospitalized patients undergoing echocardiography with and without an ultrasound contrast agent

OBJECTIVES

To compare acute mortality in critically ill hospitalized patients undergoing echocardiography with and without an ultrasound contrast agent (UCA).

BACKGROUND

Because of serious cardiopulmonary reactions reported immediately after administration of perflutren-containing UCAs, the FDA required a black box safety warning for this class of agents, including perflutren protein-type A microspheres injectable suspension.

METHODS

This study used the largest hospital service-level database in the U.S. All adult patients undergoing in-patient echocardiography between January 2003 and October 2005 were identified (n = 2,588,722, of which 22,499 received perflutren protein-type A microspheres injectable suspension). Of the 22,499 contrast echocardiography patients, 2,900 had diagnoses meeting criteria for critical illness (heart failure, acute myocardial infarction, arrhythmia, respiratory failure, pulmonary embolism, emphysema, and pulmonary hypertension). To control for the differences between the contrast and noncontrast patients, we used propensity score matching. Variables used in the construction of the propensity score included comorbidities, demographic factors, hospital-specific factors, level of care, and mechanical ventilation status. Patients receiving contrast echocardiography were matched to 4 control patients who received noncontrast echocardiography. Conditional logistic regression was used to estimate mortality effects.

RESULTS

There were 167 deaths in the study among critically ill patients, 38 of 2,900 from the contrast group and 129 of 11,600 from the control group. The contrast agent was not associated with an increase in same-day mortality (odds ratio: 1.18; 95% confidence interval: 0.82 to 1.71; p = 0.37). Before matching, contrast patients showed greater morbidity than noncontrast patients (Deyo-Charlson comorbidity score 2.45 vs. 2.25, p < 0.0001). After propensity score matching, these differences were significantly reduced, showing that both groups were well balanced.

CONCLUSIONS

There is no increase in mortality in critically ill patients undergoing echocardiography with the UCA compared with case-matched control patients.

Meta-analysis of adverse cardiovascular events associated with echocardiographic contrast agents

In October 2007, the Federal Drug Agency issued a black box warning for contrast agents used in patients undergoing echocardiography and restricted their use in patients with acute coronary syndrome, a decompensated heart, and respiratory failure. We performed a systemic review and meta-analysis to study the adverse effects of contrast agents used with respect to myocardial infarction and all-cause mortality. MEDLINE, EMBASE, BIOSIS, and Cochrane databases from inception to October 2009 were searched for studies that reported myocardial infarction and all-cause mortality after the use of contrast agents for echocardiography. A total of 8 studies were included in the present meta-analysis. A random-effect model was used, and between-studies heterogeneity was estimated with I(2). A total of 8 studies reported death as an outcome and only 4 reported myocardial infarction. The incidence of death in the contrast group was 0.34% (726 of 211,162 patients) compared to 0.9% (45,970 of 5,078,666 patients) in the noncontrast group. The pooled odds ratio was 0.57 (95% confidence interval 0.32 to 1.01, p = 0.05). The reported incidence of myocardial infarction in the contrast group was 0.15% (86 of 57,264 patients) compared to 0.2% (92 of 44,503 patients) in the noncontrast group. The pooled odds ratio was 0.85 (95% confidence interval 0.35 to 2.05, p = 0.72). Significant heterogeneity was seen among the studies. In conclusion, the cumulative evidence has suggested that the use of contrast agents for echocardiography is safe and not associated with a greater incidence of myocardial infarction or and mortality.

Preclinical acute toxicology study of surfactant-stabilized ultrasound contrast agents in adult rats

Gas-filled microbubbles are used as contrast agents in diagnostic ultrasound imaging. A preclinical, acute toxicity study of 2 surfactant-stabilized ultrasound contrast agents (ST68 and ST44) was conducted. Subjects were 104 Sprague-Dawley rats (experimental doses, 0.1, 0.2, 0.8, and 1.0 mL/kg; control, 1.0 mL/kg saline) that were studied for 14 days after contrast; clinical signs, weight, blood, and urine were evaluated. Histopathology was performed following euthanasia. Of the 40 animals receiving ST44, 4 died prematurely and a dose dependency was demonstrated (P = .011), whereas in the ST68 groups only 1 death occurred (no dose dependency; P = .48). Only the weight of rats injected with ST44 varied significantly (P = .0003). This dependency was also found for 3 of 5 urine parameters and 4 of 36 blood parameters (P < .05). For ST68, only 1 urine parameter showed significance (P < .0001). Giant cell infiltration in the lungs was significantly higher than controls in the ST44 0.1 mL/kg and the ST68 0.8-1.0 mL/kg groups (P < .01). It is concluded that the prudent choice for future nonrodent, toxicology studies and potentially for human clinical trials is ST68 (given the deaths in the ST44 groups).

Contrast echocardiography: an update

Despite the advent of tissue harmonic imaging, echocardiography fails to produce diagnostically useful images in a significant proportion of patients. This often leads to inaccurate assessment of left ventricular function, necessitating the use of other, more expensive and laborious imaging techniques, purely for diagnostic purposes. This has facilitated the development of microbubbles, which together with ultrasound, produce opacification of the left ventricular cavity, thus enabling clear visualization and accurate quantification of left ventricular function. Contrast agents have also facilitated the development of myocardial contrast echocardiography. This allows assessment of cardiac anatomy, function, and perfusion, all in one sitting, by the bedside. Contrast ultrasound imaging also has now been applied to newer techniques (eg, real-time three-dimensional echocardiography) and is also showing promise in other cardiovascular scans (eg, carotid ultrasound for intima-media thickness). Thus, contrast agents play a pivotal role in noninvasive cardiovascular imaging and its use worldwide is likely to increase.