BR1: a new ultrasonographic contrast agent based on sulfur hexafluoride-filled microbubbles

The effects of Levovist and DD-723 in activating platelets and damaging hepatic cells of rats

OBJECTIVE

The purpose of this study was to compare platelet activation and hepatic cell damage produced by 2 ultrasonographic contrast agents with flow cytometric and ultrastructural analysis.

METHODS

Suspension samples were made by mixing Levovist (SH U508A; Schering AG, Berlin, Germany) or DD-723 (Nycomed; Amersham Health, Princeton, NJ) with whole blood. The final concentrations of Levovist in citrated whole blood were 0, 15, and 75 mg/mL, and those of DD-723 were 0, 5, and 50 microL/mL. After exposure to ultrasound in vitro, flow cytometric analysis was performed to determine the concentration of the CD62P activation-specific antigen. To compare the hepatic cell damage associated with these 2 agents, we divided 15 rats into 5 groups as follows: group 1, sham operation; group 2, Levovist injection only; group 3, DD-723 injection only; group 4, Levovist injection (contrast agent) and ultrasound exposure; and group 5, DD-723 injection and ultrasound exposure. The ultrasonographic contrast agents Levovist and DD-723 were administered through the femoral vein and sonicated continuously for the first minute; this was followed by sweeping for 5 minutes 10 seconds after the contrast agent was injected. The rats were perfused via the heart with a fixative solution immediately after the sweeping, and then the liver was excised; the specimens were studied with electron and light microscopy.

RESULTS

The percentage of CD62P-expressing platelets increased in both contrast agent-ultrasound exposure groups, and the percentage of CD62P-expressing platelets was greater in the Levovist group. We observed vacuolation and round deposits in the hepatocytes in both contrast agent-ultrasound exposure groups. Microbubbles were observed in the rat Kupffer cells, and a few hepatocytes were seen unexpectedly in the DD-723 group but were found in neither the Kupffer cells nor the hepatocytes in the Levovist group.

CONCLUSIONS

Both contrast agents, Levovist and DD-723, produced platelet activation and structural change in the rat hepatic cells, but only the microbubbles of DD-723 were taken up by the Kupffer cells and a few hepatocytes.

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.

Normal anatomy of the heel entheses: anatomical and ultrasonographic study of their blood supply

The purpose of this study was first to determine the normal blood supply of the heel entheses with cadaver injection, and second, to identify by means of ultrasound (US) this blood supply in healthy volunteers before and after the intravenous injection of a US contrast agent (SonoVue). Twenty cadaver lower limbs were cut into sagittal, coronal, or axial sections after the injection of a red-colored gelatin solution. Ten anatomical samples were selected for histology. Then 10 healthy volunteers were enrolled in a contrast-enhanced ultrasonography study (CUS). Calcaneal tendon and plantar aponeurosis entheses were studied first without any contrast-agent (B-mode, power Doppler). A single dose (2.4 ml) of the contrast agent was then administered for studying each enthesis of the right foot. The operators had to look for blood flow within the entheses and in the adjacent soft tissues. Anastomotic transverse branches were seen macroscopically at the back of the calcaneal tendon, giving some capillaries penetrating the enthesis. None of these vessels could be seen with CUS. In contrast, a high-density vascular network could be detected in Kager's triangle with CUS. No blood vessel could be seen within the plantar aponeurosis enthesis, either macroscopically or microscopically. No evidence of entheseal vascularization was found with any contrast-enhanced imaging technique. Inferior branches of the lateral plantar artery were seen on coronal and sagittal sections of the hindfoot, and could be detected with CUS. These arterioles were running toward the anterior aspect of the calcaneal tuberosity, near the plantar aponeurosis insertion. In conclusion, no vascularization was detected with CUS at the cortical bone insertion of normal heel entheses. However, some vascularization could be seen in the immediate vicinity of heel entheses. The latter feature has to be kept in mind, as it may represent a pitfall for the diagnosis of early inflammatory changes in patients, especially those with seronegative spondylarthropathies.

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.

Imaging of focal liver lesions: low-mechanical-index real-time ultrasonography with SonoVue

OBJECTIVE

The purpose of this study was to evaluate the usefulness of a contrast-enhanced contrast-specific ultrasonographic technique with a low mechanical index for characterization of focal liver lesions.

METHODS

Contrast-specific ultrasonography was used to assess 144 patients with 147 focal liver lesions: 87 primary liver carcinomas, 27 hemangiomas, 16 focal nodular hyperplasias, 5 hepatic abscesses, 3 inflammatory pseudotumors of the liver, and 9 metastases. A sulfur hexafluoride gas-based contrast agent was used with a mechanical index of 0.08 to 0.11.

RESULTS

On contrast-enhanced ultrasonography, the typical hemodynamic pattern of primary liver carcinoma was the whole-lesion enhancement or mosaic enhancement in the arterial phase with an enhancement defect in the late phase (sensitivity, 92.0%; specificity, 86.7%). The most common enhancement pattern of hemangioma was that enhancement appeared in the periphery first and progressively filled into the lesion center (sensitivity, 96.3%; specificity, 97.5%). The enhancement pattern of focal nodular hyperplasia was that the whole lesion enhanced early and rapidly in the arterial phase with a centrifugal radiating configuration and appeared isoechoic or hyperechoic until the late phase (sensitivity, 87.6%; specificity, 94.5%). The central scar was detected in 31.3% of cases in the late phase. The specific enhancement of a hepatic abscess was the honeycomblike enhancement in all phases (sensitivity, 80.0%; specificity, 100%). No enhancement of a lesion in all phases was specific for an inflammatory pseudotumor of the liver.

CONCLUSIONS

Contrast-enhanced real-time ultrasonography is a promising approach in the noninvasive characterization of focal liver lesions and can be useful as a first-line imaging technique clinically when a focal liver lesion is detectable on ultrasonography.

Liver haemangiomas undetermined at grey-scale ultrasound: contrast-enhancement patterns with SonoVue and pulse-inversion US

The objective of this study was to describe the spectrum of contrast-enhancement patterns of hepatic haemangiomas undetermined at grey-scale ultrasound (US) on SonoVue-enhanced pulse-inversion (PI) US. Twenty patients (11 women, nine men) with 35 haemangiomas (size range: 1-7 cm; mean: 3.1 cm) undetermined at baseline US underwent PI at low M.I. (0.05-0.08) after i.v. injection of SonoVue. All haemangiomas were confirmed by typical helical computed tomography (CT) and/or magnetic resonance imaging (MRI) findings. US examinations were videotaped and then reviewed by two experienced radiologists blinded to the final diagnosis. Readers evaluated by consensus the baseline echogenicity and the dynamic enhancement pattern of each lesion, in comparison with adjacent liver parenchyma. After administration of SonoVue, 31/35 (88%) haemangiomas showed peripheral hyperechoic nodules in the arterial phase, followed by progressive centripetal fill-in, which was complete in 25/35 cases and incomplete in 6/35 cases. Three out of 35 (9%) haemangiomas showed rapid and complete fill-in in the arterial phase, which persisted in the portal and delayed phases. Finally, 1/35 haemangiomas (3%) showed a rim of arterial contrast enhancement with progressive and complete centripetal fill-in in portal-venous and delayed phases. In conclusion, PI after the administration of SonoVue enabled the depiction of typical contrast-enhancement patterns in haemangiomas undetermined at baseline US.

A review of the sonographic assessment of tumor metastases in liver and superficial lymph nodes

Diagnostic imaging techniques are an important part of the diagnostic workup and staging of cancer patients. Ultrasound is of particular interest in this respect. In so far as tumor metastases are concerned, ultrasonography of regional lymph nodes and of the liver can provide valuable information. In humans many criteria, some of them objective, have been evaluated as indicators of malignancy. The most diagnostically helpful of these include the short/long axis ratio of the lymph node, the pattern of distribution of the blood vessels within the lymph node, and to some extent the calculated values for resistive and pulsatility indices. Putative objective criteria to improve the specificity of ultrasound for metastases detection in the liver have also been evaluated. These include perfusion indices, primarily using analysis of Doppler frequencies (Doppler perfusion index) and hepatic venography using an ultrasound contrast agent. Contrast-enhanced ultrasonography is a new and promising area to help the initial diagnosis and characterization of malignancy, particularly for focal lesions in the liver. This review discusses the use of ultrasound for detection of metastases and presents material from four veterinary cases.

Real-time imaging with the sonographic contrast agent SonoVue: differentiation between benign and malignant hepatic lesions

OBJECTIVE

We investigated the ability of contrast-enhanced sonography with SonoVue (Altana Pharma, Konstanz, Germany), a sulfur hexafluoride microbubble contrast agent, to reveal differences between benign and malignant focal hepatic lesions.

METHODS

One hundred twenty-six lesions in 124 patients with focal hepatic lesions detected by B-mode sonography (hepatocellular carcinoma, n = 36; metastasis, n = 25; cholangiocellular carcinoma, n = 1; lymphoma, n = 2; focal nodular hyperplasia, n = 9; adenoma, n = 4; regenerative cirrhotic nodule, n = 13; hemangioma, n = 29; and focal hyposteatosis, n = 7) were examined in a prospective study. After intravenous injection of 2.4 mL of SonoVue, the liver was examined continuously for 3 minutes by low-mechanical index pulse inversion sonography.

RESULTS

For the discrimination of malignant versus benign liver lesions, SonoVue-enhanced sonography improved sensitivity from 78% to 100% and specificity from 23% to 92% compared with baseline sonography. Receiver operating characteristic analysis revealed a significant improvement in this discrimination (area under the receiver operating characteristic curve, 0.510 +/- 0.054 [SD] at baseline sonography, 0.998 +/- 0.003 with SonoVue-enhanced sonography; P < .001). The following flow patterns in the early phase were diagnosis specific: early central starlike pattern for focal nodular hyperplasia, peripheral globular-nodular pattern for hemangioma, and diffuse arterial enhancement for malignant lesions. Homogeneous enhancement in the late phase was predictive for benign lesions (P < .001). Conversely, 93% of patients without contrast enhancement in the late phase had malignant lesions (P < .001).

CONCLUSIONS

SonoVue-enhanced sonography has greater specificity and sensitivity than baseline sonography for the differentiation of benign and malignant liver lesions.

Contrast-enhanced ultrasound for extrahepatic lesions: preliminary experience

Ultrasound imaging (US) is a convenient, inexpensive and non-invasive investigation. Its use is limited by low sensitivity in the detection of a number of parenchymal lesions, especially those produced by trauma, such as infarctions. Contrast enhancement with SonoVue improves the sensitivity of ultrasound in the detection and characterization of focal liver lesions to such an extent, that it may replace computed tomography (CT) and magnetic resonance imaging (MRI). Preliminary experience suggests that SonoVue-enhanced sonography may be useful in the detection of lesions in which blood flow is severely reduced as compared to surrounding parenchyma, such as infarctions, lacerations, hematomas, necrotic tissue and non-vascular cysts, especially in the spleen, kidney and pancreas. This technique can also rule out occlusion of the superior mesenteric, splenic and portal veins, and dilation of the biliary tree. Clinical trials comparing contrast-enhanced sonography with contrast-enhanced computed tomography are warranted to establish the role of this inexpensive and non-invasive technique in the routine work-up of patients with abdominal trauma or presenting with sudden flank pain.

Immunological evaluation of the new stable ultrasound contrast agent LK565: a phase one clinical trial

Background

Ultrasound contrast agents (UCAs) allow the enhancement of vascular definition, thereby providing more diagnostic information. LK565 is a new second-generation UCA based on synthetic polymers of aspartic acid which is eliminated from the blood stream via phagocytosis. LK565 forms very stable air-filled microspheres and is capable of repeated passage through the pulmonary capillary bed after peripheral intravenous injection. This characteristic allows examination of the cardiac function or extracardiac vessel abnormalities up to 15 minutes.

Methods

A phase one clinical study was conducted on 15 healthy volunteers to identify the development of an undesirable immune response. Phagocytosis capacity, TNF-α secretion, and MHC class II upregulation of monocytes was monitored, as well as microsphere specific antibody development (IgM, IgG). Furthermore, the kinetics of the activation surface markers CD69, CD25, CD71, and CD11b on leukocytes were analyzed.

Results

Due to LK565-metabolism the administration of the UCA led to saturation of phagocytes which was reversible after 24 hrs. Compared to positive controls neither significant TNF-α elevation, neither MHC class II and activation surface markers upregulation, nor specific antibody development was detectable.

Conclusion

The administration of LK565 provides a comfortable duration of signal enhancement, esp. in echocardiography, without causing a major activation cascade or triggering an adaptive immune response. To minimize the risk of undesirable adverse events such as anaphylactoid reactions, immunological studies should be included in clinical trials for new UCAs. The use of LK565 as another new ultrasound contrast agent should be encouraged as a safe means to provide additional diagnostic information.

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

PURPOSE

To assess whether characterization of solid focal liver lesions could be improved by using ultrasonographic (US) contrast-specific modes after sulfur hexafluoride-filled microbubble contrast agent injection, as compared with lesion characterization achieved with preliminary baseline US.

MATERIALS AND METHODS

Four hundred fifty-two solid focal hepatic lesions that were considered indeterminate at baseline gray-scale and color Doppler US were examined after microbubble contrast agent injection performed by using low-acoustic-power contrast-specific modes during the arterial (10-40 seconds after injection), portal venous (50-90 seconds after injection), and late (100-300 seconds after injection) phases. Two readers independently and retrospectively reviewed baseline and contrast material-enhanced US scans and classified each depicted lesion as malignant or benign according to standard diagnostic criteria. Sensitivity, specificity, accuracy, and positive and negative predictive values and areas under the receiver operating characteristic curve (Az) were calculated by considering histologic analysis (317 patients) or contrast-enhanced helical computed tomography followed by serial US 3-6 months apart (135 patients) as the reference standards.

RESULTS

Different contrast enhancement patterns were observed according to lesion characteristics. During the late phase, benign lesions were predominantly hyper- or isoechoic relative to the adjacent liver parenchyma, whereas malignant lesions were predominantly hypoechoic. Review of the contrast-enhanced US scans after baseline image review yielded significantly improved diagnostic performance (P <.05). Overall diagnostic accuracy was 49% before versus 85% after review of the contrast-enhanced scan for reader 1 and 51% before versus 88% after review of the contrast-enhanced scan for reader 2. Diagnostic confidence-that is, the Az-was 0.820 before versus 0.968 after review of the contrast-enhanced scan for reader 1 and 0.831 before versus 0.978 after review of the contrast-enhanced scan for reader 2.

CONCLUSION

The use of contrast-specific modes with a sulfur hexafluoride contrast agent led to improved characterization of solid focal liver lesions.

Usefulness of contrast-enhanced perfusional sonography in the assessment of hepatocellular carcinoma hypervascular at spiral computed tomography

BACKGROUND/AIMS

Diagnosis of hepatocellular carcinoma (HCC) relies strongly on the detection of hypervascularity in the arterial phase and, in this setting, spiral computed tomography (CT) is the most widely used method. This prospective study aimed to investigate the usefulness of low mechanical index harmonic ultrasound (US), using a second generation contrast-enhanced technique, in the assessment of vascular pattern of HCC shown to be hypervascular at spiral CT.

METHODS

A total of 79 cirrhotic patients with 103 nodules (mean+/-SD 28+/-13 mm) with arterial hypervascularity at spiral CT were studied. US examination was performed by perfusional sonography, using a new dedicated technology (CnTI-Esaote trade mark ), operating at low mechanical index, after injection of a second generation contrast agent (SonoVue trade mark -Bracco), allowing detection of tumoral flow during arterial phase.

RESULTS

Selective arterial enhancement on perfusional sonography was observed in 94 /103 nodules (91.3%), with a sensitivity of 66.6, 87.5, 91.7, and 97.3% in nodules </=1 cm, >1</=2 cm, >2</=3 cm, and >3 cm respectively.

CONCLUSIONS

Perfusional sonography shows good diagnostic agreement with spiral CT in hypervascular HCC and may be proposed for the immediate vascular characterization of nodules detected at US and used as second imaging technique to confirm hypervascularity in cirrhotic nodules.

Micromanipulation of endothelial cells: ultrasound-microbubble-cell interaction

Ultrasound (US) in combination with contrast microbubbles has been shown to alter the permeability of cell membranes without affecting cell viability. This permeabilisation feature is used to design new drug delivery systems using US and contrast agents. The underlying mechanisms are still unknown. One hypothesis is that oscillating microbubbles cause cell deformation resulting in enhanced cell membrane permeability. This technical note reveals the interaction between oscillating microbubbles and endothelial cells under a microscope recorded with a fast framing camera at 10 million frames per second. A microbubble expansion of 100% resulted a 2.3-mum displacement of the cell membrane. During the insonification, changes of approximately 15% in the cross-sectional distance of the endothelial cells were observed due to microbubble vibrations. In conclusion, the use of such a camera makes it possible to reveal the mechanisms of interactions between ultrasound, microbubbles and cells.

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 harmonic transesophageal echocardiography: a feasibility study

Ultrasound (US) contrast agents serve as tracers for the noninvasive quantification of blood flow, and many of them are now approved for left ventricular opacification and for enhanced endocardial border delineation. The availability of more stable contrast bubbles has stimulated many new classes of imaging methods, such as harmonic imaging, which is already employed in commercial systems for transthoracic imaging. However, transesophageal echocardiography (TEE) still lacks appropriate technology, mainly transducer technology, to be able to take advantage of contrast harmonic benefits. We investigate, in this study, a new TEE transducer that has a frequency bandwidth wide enough to be able transmit at a lower fundamental frequency and to receive the second harmonic frequency. The transducer characteristics are measured, as well as the optimal transmit settings that allow the achievement of a high contrast-to-tissue ratio. The transducer has a center frequency of 3.5 MHz with a bandwidth ranging from 2.3 MHz to 3.9 MHz. For optimal harmonic imaging, transmit settings consisted of a transmit pulse at 2.5 MHz containing two periods. The transducer, using these settings, was then evaluated in patients to investigate myocardial contrast perfusion imaging using TEE in the operating theater.

Evidence for spleen-specific uptake of a microbubble contrast agent: a quantitative study in healthy volunteers

PURPOSE

To evaluate the pharmacokinetics of the microbubble contrast agent BR1.

MATERIALS AND METHODS

Twenty healthy volunteers were injected via arm vein with a 1.2-mL bolus of BR1. Ultrasonographic images of liver and right kidney and of spleen and left kidney were obtained intermittently for 5 minutes with low-mechanical-index software (to minimize microbubble destruction) that shows stationary microbubbles in green. Percentage total uptake was calculated as the number of green pixels in the region of interest for each organ over time, divided by the total pixels. Relative uptake, the ratio of total uptake in liver to that in right kidney and of total uptake in spleen to that in left kidney, and differential uptake, the difference in total uptake between liver and right kidney and between spleen and left kidney, were calculated. Total uptake for each organ was plotted against time, and the gradient of a best-fit straight line was calculated. Wilcoxon signed rank test was used to compare mean uptake values in each subject. Mann-Whitney U test was used for comparisons in sex and age.

RESULTS

Total uptake declined over 5 minutes in left and right kidney and in liver (from 88% +/- 10% [1 minute] to 67% +/- 14% [5 minutes]), but not in spleen (range, 90%-99%). Mean relative uptake +/- 1 SD for spleen increased from 2.3 +/- 0.7 (1 minute) to 3.7 +/- 2.3 (5 minutes) (P =.005) but for liver was constant: 2.1 +/- 0.9 (1 minute) and 2.3 +/- 0.4 (5 minutes) (P =.06). Mean differential uptake +/- 1 SD for spleen increased from 51.3% +/- 14.9% (1 minute) to 65.0% +/- 9.1% (5 minutes) (P =.002). Significant difference was seen over time in total uptake gradients between spleen and left kidney (P =.014) but not between liver and right kidney or right and left kidney. No difference was seen between men and women or with age.

CONCLUSION

BR1 produces spleen-specific enhancement that is longer (5 minutes) than the blood pool phase.

Evaluation of hepatocellular carcinoma using SonoVue, a second generation ultrasound contrast agent: correlation with cellular differentiation

The appearance of hepatocellular carcinoma (HCC) with contrast-enhanced ultrasound (CEUS) in the vascular phase is described and evaluated as to whether the enhancement pattern correlates with the degree of cellular differentiation. One hundred four HCCs were prospectively evaluated with CEUS using coherent-contrast imaging (CCI) and SonoVue with a low mechanical index (<0.2). The enhancement of HCCs in the vascular phase was analyzed according to the degree of pathological differentiation obtained by fine-needle biopsy. In the arterial phase, all HCCs except for four well differentiated ones (96.2%) showed enhancement ( P<0.05). Histological differentiation of hypoechoic lesions in the early portal phase (7 HCCs; 16%) significantly differed from hyperechoic (1 HCC; 1%) or isoechoic lesions (87 HCCs; 83.6%) ( P<0.05), with a significant probability of a worse differentiation in hypoechoic lesions. Histological differentiation of isoechoic lesions in the late phase (30 HCCs; 28.8%) significantly differed from hypoechoic lesions (74 HCCs; 71.2%) ( P<0.05), with a significant probability of a better differentiation in isoechoic lesions. CEUS using CCI and SonoVue revealed enhancement in the arterial phase in >95% of HCCs, with a few well-differentiated cases not being diagnosed due to the absence of enhancement. Echogenicity in the portal and late phases correlated with cellular differentiation.

Sonovue improves endocardial border detection and variability in assessing wall motion score and ejection fraction during stress echocardiography

BACKGROUND

Stress echocardiography is useful for assessing patients with coronary artery disease unable to undergo formal exercise testing. Considerable skill is required to avoid large intra- and inter-observer variability due to poor endocardial definition. Intravenous ultrasound contrast agents are now available which may improve this variability.

AIM

To study intravenous Sonovue in assessing wall motion score and ejection fraction (EF) during stress echocardiography.

METHODS

Thirty-eight patients undergoing arbutamine stress echocardiography for known or suspected coronary artery disease were studied. Echocardiographic analysis of wall motion score index, endocardial border detection (EBD) and EF was performed at rest and at peak stress before and after intravenous injection of Sonovue, by experienced and inexperienced observers.

RESULTS

All three observers noted an improvement in endocardial border definition following Sonovue (p=<0.001). At baseline, there was a significant difference in wall motion score index between experienced and inexperienced observers at rest (p=0.01) and at peak stress (p=0.001). Following Sonovue administration this was no longer significant (p=0.07, p=0.114). Intra-observer variability of end diastolic, end systolic volumes (ESV) and EF improved following contrast (p<0.05) at rest and during stress.

CONCLUSION

Sonovue significantly improved EBD and reduced intra-observer variability of EF at rest and during peak arbutamine infusion.

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.

Detection of resting myocardial perfusion defects by SonoVue myocardial contrast echocardiography

BACKGROUND

SonoVue is a new microbubble contrast agent containing sulfur hexafluoride. We assessed the efficacy of SonoVue myocardial contrast echocardiography (MCE) to detect resting perfusion abnormalities.

METHODS

Nineteen adult patients with a wall motion abnormality in a screening echocardiogram were studied. Each patient received up to four bolus injections of 2.0 mL SonoVue (Bracco Diagnostics, Inc.) during echocardiographic examination using either B-mode(n = 12)or power Doppler(n = 7)imaging. Each patient also had SPECT nuclear perfusion imaging performed. Segmental assessment of myocardial perfusion from SonoVue MCE images were compared with corresponding SPECT nuclear images.

RESULTS

Using B-mode imaging, the mean number of views obtained with a single SonoVue injection ranged from 1.4 to 1.9, with 2 or 3 injections required for a complete examination. Ninety-four percent of segments were scored as diagnostic. Agreement between B-mode and SPECT images was 72% for segments with a perfusion defect, 86% for normal perfusion, and 80% for segments with either perfusion defect or normal perfusion (all views combined). Using power Doppler imaging, the mean number of views obtained with a single SonoVue injection ranged from 1.0 to 1.3, with 2 to 4 injections required for a complete examination. Sixty-eight percent of segments were scored as diagnostic. Agreement between power Doppler and SPECT images was 67% for perfusion defects, 53% for segments with normal perfusion, and 59% for segments with either perfusion defect or normal perfusion (all views combined).

CONCLUSIONS

SonoVue MCE has the potential to assess myocardial perfusion at rest. B-mode imaging was more accurate than power Doppler imaging when compared with SPECT nuclear imaging.

Blood flow quantification with contrast-enhanced US: "entrance in the section" phenomenon--phantom and rabbit study

PURPOSE

To investigate changes in destruction-replenishment curves (in vitro and in vivo) that result from microbubble destruction in feeding vessels that pass through the imaging plane before microbubbles enter the region of interest (ROI).

MATERIALS AND METHODS

During continuous injections of an ultrasonographic contrast agent, nonlinear gray-scale images were obtained in vitro in the longitudinal plane of a renal dialysis cartridge flow phantom (flow rates of 100, 200, and 400 mL/min) and in vivo in the coronal plane of the left kidneys of two rabbits (two kidneys). Destruction-replenishment curves were obtained for the dialysis cartridge in ROIs located immediately after the entrance of the microbubbles into the image plane and further from the entrance, after microbubbles had traveled across the complete length of the imaging plane. Replenishment curves were also obtained from ROIs in the rabbit kidneys at the level of segmental arteries, distal interlobar arteries, and the cortex.

RESULTS

The ROIs immediately after the entrance of the microbubbles in the image plane of the dialysis cartridge and in the segmental artery of the kidney followed a typical exponential function, A(1 - e-alphat). Early portions of curves obtained in ROIs filled with microbubbles that had already passed through the image plane of the dialysis cartridge or in the renal cortex were not well described by such a function. The shape of the curve and the variations as a function of flow rate can be explained by means of a mathematical model based on indicator-dilution theory.

CONCLUSION

When the feeding vessels of an ROI travel across the ultrasound field before they reach the measurement region, the typical shape of the replenishment curve is modified (reduced velocity parameter and plateau).

Myocardial contrast echocardiography in the assessment of patients with chronic coronary artery disease

The development of new contrast agents and new imaging methods has lead to an emerging field of applications for myocardial contrast echocardiography (MCE) in patients suffering from chronic ischemic heart disease. Echo contrast allows the assessment of myocardial perfusion (MP) by imaging the coronary microcirculation. Several echocardiographic modalities are available, the main difference between them being the acoustic power needed to perform the study. MP is evaluated by assessing the changes in myocardial videointensity that occur after intravenous contrast injection. Evaluation of these patients is performed by using different techniques. Evaluation of coronary stenosis may be performed by using stress tests or without its use. Coronary artery stenosis > 50% of the coronary luminal diameter reveals a decreased hyperemic response when myocardial oxygen demand is increased. Different methods to evaluate the presence of relevant coronary stenosis have been developed: evaluation of myocardial blood flow reserve, evaluation of myocardial blood volume, and evaluation of the transmural distribution of myocardial blood flow. The combination of wall motion analysis with MCE assessment has been demonstrated to achieve the best balance between sensitivity (86%) and specificity (88%), with the highest accuracy (86%). Without the need of any stress, the ratio systolic/diastolic myocardial blood volume has been described to increase with the presence of a epicardial coronary stenosis and it may be measured by MCE. Myocardial viability is also one of the potentials of MCE. Microvascular integrity, demonstrated by MCE, is an indicator of preserved viability and predicts functional recovery that has been validated in the setting of chronic left ventricular dysfunction secondary to chronic coronary artery disease and in the setting of post acute myocardial infarction left ventricular dysfunction.

IN CONCLUSION

contrast echocardiography provides an interesting tool that offers the potential of a complete evaluation of patients with chronic coronary artery disease. This includes both diagnostic and prognostic evaluation.

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

RATIONALE AND OBJECTIVES

This study was performed to determine whether ultrasound (US) performed with SonoVue, a contrast agent that contains microbubbles filled with sulfur hexafluoride vapor, depicts differential patterns of contrast enhancement in focal hepatic lesions.

MATERIALS AND METHODS

Forty focal hepatic lesions (15 hepatocellular carcinomas [HCCs], 10 metastases, 11 hemangiomas, and four focal nodular hyperplasias) in 39 patients were evaluated by means of US, color Doppler US, and contrast-enhanced US performed by using intermittent high-acoustic-power mode. Contrast-enhanced helical computed tomography (11 patients) and US-guided fine needle aspiration (28 patients) were used as reference procedures. Contrast enhancement patterns were defined by means of both subjective and objective analysis, and baseline and contrast-enhanced US scans were reviewed offline.

RESULTS

Thirteen of 15 HCCs, eight of 10 metastases, and all four hemangiomas with an atypical pattern at baseline US were correctly characterized after SonoVue injection. Two of 15 HCCs and two of 10 metastases remained indeterminate, with no characteristic baseline or contrast-enhanced patterns identified. Baseline US was essential in characterizing all hemangiomas with a typical pattern (n = 7), and color Doppler US with spectral analysis of tumoral vessels was essential in characterizing focal nodular hyperplasia. The percentage of diagnostic agreement with reference procedures was significantly increased (P < .001) for contrast-enhanced US compared with baseline US.

CONCLUSION

Characteristic patterns of US contrast enhancement with SonoVue help in characterizing and differentiating focal hepatic lesions.

Influence of contrast ultrasonography with perflutren lipid microspheres on microvessel injury

Microbubbles have been reported to enhance ultrasound (US)-related side effects in animal systems. The present study investigated the influence of contrast ultrasonography (US) with perflutren lipid microspheres, a recently developed second-generation contrast agent, on microvessels. Rat mesentery was exposed to 1.8-MHz pulsed US with intravenous injection of perflutren (0.1 or 1.0 ml/kg) or Levovist (300 mg/kg), and the microvessel bleeding and endothelial cell injury was examined. Impaired endothelial cells were identified by the fluorescence of propidium iodide. Microvessel bleeding was examined also in the rat myocardium. The interaction between 0.1 ml/kg of perflutren and US exposure did not cause microvessel bleeding, and did not increase endothelial cell injury compared with the sham operation, unless frequent, strong US exposure occurred. When the dose was increased to 1.0 ml/kg, the combination of perflutren and US exposure resulted in capillary bleeding and increased endothelial cell injury in capillaries and venules (p<0.01). However, the incidence of microvessel bleeding and endothelial cell injury did not exceed that with Levovist microbubbles. In the myocardium, microvessel bleeding was not observed under any conditions. In conclusion, perflutren lipid microspheres enhanced US-related microvessel injury as with other contrast agents at the dose of 1.0 ml/kg, but not with 0.1 ml/kg and the appropriate US setting.

Contrast superharmonic imaging: a feasibility study

Harmonic imaging provided significant improvement in image quality by taking advantage of the scattered second harmonic (2H) component from contrast bubbles. However, differentiation between contrast and tissue (usually termed contrast-to-tissue ratio, CTR) is sometimes cumbersome and this is mainly due to tissue contamination. We have previously demonstrated, using simulations and in vitro measurements, that CTR increases as a function of the order of the harmonic number. A new contrast imaging method based on the detection of the higher harmonics was developed and termed superharmonic (SH). This technique has been shown to be more sensitive to contrast by increasing the signal from contrast and suppressing that from tissue (high CTR). The purpose of this study was to determine the clinical feasibility and usefulness of SH in patients using a commercially available contrast agent (SonoVue(R)) for quantification of myocardial perfusion. A total of 10 patients with various cardiac diseases were assessed. Apical four-chamber views were acquired using SH in triggered mode before and after contrast injection. The superharmonic was performed with a newly developed probe transmitting at 0.8 MHz with a mechanical index of 0.2. Myocardial perfusion was determined visually and analyzed quantitatively using radiofrequency (RF) processing from different regions of interest. The results showed that, before contrast injection, SH was totally blinded to tissue and no superharmonic components were generated in the image view. After administration of SonoVue(R), myocardial opacification was visualized by SH after contrast entered the myocardium. An increase of more than 15 dB in the myocardial bubbles echo compared to tissue echo was measured. In addition, the technique was used to visualize myocardial perfusion after myocardial septal ablation for hypertrophic cardiomyopathy. The clinical results showed the ability of contrast SH imaging in differentiating low and normal perfusion areas, demonstrating the high sensitivity and specificity of the technique.

Microbubbles induce renal hemorrhage when exposed to diagnostic ultrasound in anesthetized rats

The generation of ultrasound (US) bioeffects using a clinical imaging system is controversial. We tested the hypothesis that the presence of microbubbles in the US field of a medical imager induces biologic effects. Both kidneys of anesthetized rats were insonified for 5 min using a medical imaging system after the administration of microbubbles. One kidney was insonified using a continuous mode (30 Hz) and the opposite kidney was insonified using an intermittent (1 Hz) technique. The microbubbles were exposed to three different transducer frequencies and four transducer output powers. After insonification, the animals were euthanized, the kidneys were removed and their gross appearance scored under "blinded" conditions using a defined scale. After the administration of microbubbles, US imaging of the kidney caused hemorrhage in the renal tissue. The severity and area of hemorrhage increased with an increase in the transducer power and a decrease in the transducer frequency. Intermittent insonification in the presence of microbubbles produced a greater degree of renal hemorrhage than continuous imaging techniques.

Targeted-microbubble binding selectively to GPIIb IIIa receptors of platelet thrombi

RATIONALE AND OBJECTIVES

New targeted microbubbles directed to the GPIIb IIIa receptor have been developed. The objective was to determine whether targeting microbubbles to clots would enhance ultrasound imaging. Systematic studies were designed to determine whether in vitro methodology is an acceptable predictor of in vivo efficacy.

MATERIALS AND METHODS

Bioconjugate ligands were inserted into lipid-coated membranes of perfluorocarbon gas microbubbles and binding studies performed on activated platelets immobilized on cell culture plates. Targeted microbubble binding to clots in a flow through chamber was also assessed. Finally, microbubble binding studies on arteriolar and venular clots in a mouse cremasteric muscle model were conducted.

RESULTS

Binding studies on platelet-immobilized plates demonstrated an affinity for targeted microbubbles versus untargeted microbubbles. Semiquantitative light obscuration techniques helped to measure extent of targeted microbubble binding. Targeted microbubbles similarly bound to platelet clots in the flow model. Finally, studies in the mouse model confirmed binding of targeted microbubbles in both venules and arterioles.

CONCLUSION

The use of receptor selective targeted microbubbles improved binding to vascular thrombi in both in vitro and in vivo settings.

Endothelial cell injury in venule and capillary induced by contrast ultrasonography

The aim of the present study was to test the hypothesis that microvascular endothelial cells (EC) are subject to the bioeffects induced by contrast ultrasound (US) because of their proximity to the circulating microbubbles. We examined EC injury in each microvessel section (arteriole, capillary or venule) in rat mesenteries among the following five groups: three controls (sham operation, microbubble injection alone, US exposure with saline injection), and two contrast-US groups (US exposure at a 1-Hz or 30-Hz frame rate with microbubble injection). Propidium iodide (PI), a fluorescent indicator of cell injury, was employed to visualize impaired EC. PI-positive nuclei were equally few among the three controls. Contrast-US increased PI-positive cells in capillaries (1-Hz frame rate, 2.4 +/- 2.2 cells per 0.1-mm vessel length, p = 0.09; 30-Hz frame rate, 4.3 +/- 1.8 cells, p < 0.01) and in venules (1-Hz frame rate, 4.1 +/- 2.5 cells, p < 0.05; 30-Hz frame rate, 13.8 +/- 3.6 cells, p < 0.01) compared with sham operation (0.10 +/- 0.22 cells). The finding indicates that diagnostic contrast US potentially causes EC injury, particularly in venules and capillaries.

Multi-centre clinical study evaluating the efficacy of SonoVue (BR1), a new ultrasound contrast agent in Doppler investigation of focal hepatic lesions

OBJECTIVES

SonoVue is a new ultrasound contrast agent, which consists of stabilised microbubbles of a sulphur hexafluoride gas. The aim of the study was to assess its efficacy in the Doppler investigation of focal hepatic lesions.

MATERIALS AND METHODS

Seventy patients with focal liver tumours were studied. Four doses (0.3, 0.6, 1.2 and 2.4 ml) of SonoVue were administered intravenously with at least 10 min delay between each injection. A complete colour/power and spectral Doppler imaging investigation of the lesions was performed at baseline pre-dosing and after each SonoVue injection. All examinations were recorded on SVHS videotapes. Baseline and post contrast videotapes were reviewed by the on-site (un-blinded) investigators and by two off-site blinded readers (a) to grade the global quality of the Doppler scans of the focal lesions vascularity and the normal parenchymal vessels (b) to measure the duration of clinically useful Doppler signal enhancement and (c) to determine the diagnostic accuracy and performance of the enhanced versus unenhanced scans using histopathology, tumour markers, CT and/or MR as the reference standard.

RESULTS

A statistically significant improvement was observed at all four SonoVue doses in the off site assessment of global quality of the Doppler examination of tumoral and normal parenchymal vessels in comparison with the baseline (P < 0.05). The median duration of clinically useful enhancement was significantly increased with increasing doses (P < 0.001), ranging between 1.4-2.2 min for the lowest dose and 3.2-3.8 min for the highest dose for the off-site readers. On-site assessment of diagnostic accuracy showed a significant increase in the specificity of the Doppler diagnoses (P < 0.0016) with an increase in the positive and negative predictive values and in the likelihood ratio in differentiating between benign and malignant lesions. Off-site evaluation showed a significant increase in the accuracy of enhanced Doppler diagnosis in comparison with the baseline performance.

CONCLUSION

The results suggest that SonoVue is effective in improving the display of tumoral vascularisation and may be useful in the characterisation of focal liver lesions.

Quantification of ultrasound contrast agent response: comparison of continuous wave Doppler and power Doppler to backscattered radiofrequency data

Our goal was to compare two quantification methods of ultrasound contrast agents available in clinical practice [continuous wave Doppler intensity (CWDI) and power Doppler intensity (PWDI)] to the reference technique (radio-frequency analysis) with a simple recirculating flow phantom using a renal dialysis cartridge. Measurements were made at different doses of perflenapent emulsion and BR1. Cineloops of power Doppler images were recorded using a clinically available ultrasound unit (HDI 3000). Simultaneously, integrated backscatter (IBS) was measured by analysis of radiofrequency signals, whereas Doppler signal intensity was measured with a continuous wave Doppler device. A linear relationship was found between CWDI and IBS and between PWDI and IBS when R(2) was calculated for each pair of parameters injection-by-injection. Results are summarized by the average R(2) for all injections between CWDI and IBS (BR1: R(2) = 0.93 +/- 0.05, perflenapent emulsion: R(2) = 0.94 +/- 0.03) and between PWDI and IBS (BR1: R(2) = 0.88 +/- 0.07, perflenapent emulsion: R(2) = 0.79 +/- 0.09). However, for all data obtained from all different injected doses and for both contrast agents, there was considerable variation of CWDI and PWDI values measured for a given value of IBS. In conclusion, for a fixed microbubble population, CWDI and PWDI can be proposed for quantification of USCA. However, their important variations observed at each dose make it difficult to link a single value of PWDI or CWDI or IBS to a single microbubble distribution composition.

MR perfusion imaging using encapsulated laser-polarized 3He

In this work, the use of a new carrier agent for intravascular laser-polarized 3He imaging is reported. Lipid-based helium microbubbles were investigated. Their average diameter of 3 microm, which is smaller than that of the capillaries, makes it possible to conduct in vivo studies. The NMR relaxation parameters T1, T2, and T2* of a microbubble suspension were measured as 90 s, 300 ms, and 4.5 ms, respectively, and in vivo images of encapsulated 3He with signal-to-noise ratios (SNRs) larger than 30 were acquired. Dynamic cardiac images and vascular images of encapsulated 3He were obtained in rats using intravenous injections of microbubble suspensions. Excellent preservation of 3He polarization through the lung capillaries and heart cavities was observed. The first images of 3He microbubble distributions in the lungs were obtained. Additionally, the potential of this technique for lung perfusion assessment was validated through an experimental embolism model with the visualization of perfusion defects.

Pharmacokinetics of echocontrast agent infusion in a dog model

Ultrasound contrast agents (UCAs) have a distinct diagnostic impact on transcranial Doppler (TCD) and duplex sonography. In addition to the properties of the UCA and ultrasound imaging modes, the duration of contrast enhancement depends on the administration mode. Infusion of UCAs may be appropriate for prolonging the diagnostically useful time of elevated Doppler intensity. Five sedated dogs were investigated by TCD during infusion with SonoVue, a new UCA consisting of sulfur hexafluoride microbubbles. The infusion rate was varied, and the time-intensity curves were analyzed. Infusion rate of 70 ml/h provided a stable mean level of increased Doppler intensity up to 24 to 26 dB over baseline, whereas a rate of 35 ml/h did not result in a stable plateau (range 8-19 dB over baseline [5 minutes after starting time]). The maximum increases in Doppler mean intensity (18.2 dB [35 ml/h] and 25.6 dB [70 ml/h]) were significantly different (P = .025). Pharmacokinetic analysis of SonoVue during inflow (by exponential functional fitting of the time-mean intensity curves) and elimination (by linear regression analysis) revealed no dose-related differences. This study demonstrated a dose-dependent level of increased Doppler mean intensity within the brain circulation during infusion of SonoVue. Unlike the bell-shaped course of Doppler signal enhancement seen after bolus injection, infusion generates a stable plateau, which is an important prerequisite for more advanced contrast applications.

SonoVue in transcranial Doppler investigations of the cerebral arteries

BACKGROUND AND PURPOSE

The authors investigated the safety and diagnostic potential of a new ultrasound contrast agent (SonoVue) using transcranial color-coded duplex sonography (TCCS).

METHODS

Forty patients were enrolled in a multicenter, open-label (on-site), blind (off-site), randomized, dose-ranging crossover study. SonoVue was administered as an intravenous bolus injection of 4 different dosages (0.3, 0.6, 1.2, and 2.4 mL). Efficacy was evaluated as (1) off-site assessment of global quality of the Doppler investigation (based on color or power Doppler images and spectral analysis) at baseline and following each dose of SonoVue according to a 4-point scale (from very poor to excellent imaging of blood flow) and (2) duration of clinically useful signal enhancement and color or power Doppler visualization of blood flow. Additional on-site efficacy assessments performed following each dose of SonoVue included confidence in diagnosis and global consequences of contrast enhancement on diagnosis. Safety evaluations included clinical laboratory tests, neurological examination, injection site tolerability, and incidence of adverse events and their relationship to the study agent.

RESULTS

All doses of SonoVue significantly improved the global quality of Doppler examinations (P < .05). The median duration of clinically useful enhancement was dose related (P < .001) and ranged from 2 to 6 minutes at the highest dose. The administration of the contrast agent changed a nondiagnostic study to a diagnostic one in 66% of patients and increased the confidence in diagnosis in 74% of cases. No serious adverse events were recorded following SonoVue administration. The observed adverse reactions were all transient and mild in intensity.

CONCLUSIONS

The results obtained from this multicenter study demonstrate that the administration of SonoVue to patients with ischemic cerebrovascular disease who undergo TCCS examination of cerebral vessels improves the visualization of intracranial arteries, providing a dose-dependent contrast enhancement and a clinically useful duration of signal enhancement related to the dose. During this multicenter study, SonoVue proved to be a safe and well-tolerated compound.

Quantification of renal blood flow with contrast-enhanced ultrasound

OBJECTIVES

The goal of this study was to determine the ability of contrast-enhanced ultrasound (CEU) to quantify renal tissue perfusion.

BACKGROUND

The kinetics of tracers used to assess renal perfusion are often complicated by countercurrent exchange, tubular transport or glomerular filtration. We hypothesized that, because gas-filled microbubbles are pure intravascular tracers with a rheology similar to that of red blood cells, CEU could be used to quantify renal tissue perfusion.

METHODS

During a continuous venous infusion of microbubbles (SonoVue), regional renal perfusion was quantified in nine dogs using CEU by destroying microbubbles and measuring their tissue replenishment with intermittent harmonic imaging. Both renal blood volume fraction and microbubble velocity were derived from pulsing-interval versus video-intensity plots. The product of the two was used to calculate renal nutrient blood flow. Renal arterial blood flow was independently measured with ultrasonic flow probes placed directly on the renal artery and was increased using dopamine and decreased by placement of a renal artery stenosis.

RESULTS

An excellent correlation was found between cortical nutrient blood flow using microbubbles and ultrasonic flow probe-derived renal blood flow (r = 0.82, p < 0.001) over a wide range (2.5 fold) of flows.

CONCLUSIONS

Ultrasound examination during microbubble infusion can be used to quantify total organ as well as regional nutrient blood flow to the kidney.

Air-filled polymeric microcapsules from emulsions containing different organic phases

Air-filled polymeric microcapsules for use as a contrast agent in ultrasonography have been prepared by the freeze-drying of different oil-in-water emulsions. The water phases consisted of a block copolymer in water. The organic phases consisted of a biodegradable polyester dissolved in (-)-camphene, cyclooctane, cyclohexane or tricyclene, which were relatively poor solvents for the polyester. A polymeric wall was, therefore, precipitated at the droplet surface early in the process, i.e. during freezing. Removing the solvent during freeze-drying, resulted in air-filled microcapsules. The microcapsules were suspended in saline after freeze-drying. All the suspensions contained echogenic microcapsules with a volume mean diameter of approximately 5-7 microm. Microscopic investigations showed that the microcapsules were spherical and hollow. Tricyclene and, to some degree, (-)-camphene were found unsuitable for industrial production due to melting points above 30 degrees C. Cyclooctane and cyclohexane were investigated as replacements for the initially chosen (-)-camphene, since they are liquids over a wider temperature range. These solvents gave improved yields, measured both as particle volume concentration per amount of polymer in suspension and acoustic attenuation at 3.5 MHz per amount of polymer in suspension, although the freeze-drying cycle was not optimized for these systems.

Clinical safety of SonoVue, a new contrast agent for ultrasound imaging, in healthy volunteers and in patients with chronic obstructive pulmonary disease

RATIONALE AND OBJECTIVES

To evaluate the safety profile of SonoVue, a new echo-contrast agent based on stabilized sulfur hexafluoride (SF6) microbubbles, in healthy volunteers and in patients with chronic obstructive pulmonary disease (COPD).

METHODS

Safety and tolerability of SonoVue were evaluated in 66 healthy volunteers during two placebo-controlled phase I studies (a single intravenous ascending-dose study in 36 volunteers given SonoVue doses of 0.003 to 0.12 mL/kg and a multiple-dose study in 30 subjects given cumulative doses of 0.15 to 0.6 mL/kg) and in 12 patients with COPD of various degrees of clinical severity, who were given SonoVue at a dosage of 4 mL (corresponding to 0.057 mL/kg in a 70-kg patient). Adverse events were monitored up to 48 to 72 hours after administration. All volunteers underwent extensive safety assessments (monitoring of vital signs, electrocardiogram, blood oxygen saturation, laboratory assessments, and Mini-Mental test) up to 24 to 72 hours after administration. In addition, patients with COPD underwent specific lung function tests, such as forced expiratory volume, forced vital capacity, and forced midexpiratory flow.

RESULTS

No serious adverse events occurred throughout the study. All nonserious adverse events were minor, mild, and rapidly self-resolving. No difference in the incidence of adverse events was observed among the various dosages of SonoVue and between SonoVue and placebo. There were no clinically significant changes in any of the safety assessments. No statistically significant differences between SonoVue and placebo were observed in mean forced expiratory volume, forced vital capacity, or forced midexpiratory flow levels. No substantial changes from baseline in blood oxygen saturation were observed for either study agent at any postinjection time point.

CONCLUSIONS

SonoVue showed a good safety profile both in healthy subjects and in patients with COPD.

A new Doppler signal enhancing agent for flow assessment in breast lesions

OBJECTIVE

To determine the diagnostic performance of SonoVue (Bracco) in the enhancement of Doppler signals in breast lesions and in the improvement of diagnostic accuracy.

METHODS

This multicenter study included 220 patients undergoing investigations of parenchymal lesions, 40 of which had breast tumors. After a baseline Doppler examination, intravenous doses of 0.3, 0.6, 1.2 and 2.4 ml SonoVue were injected. Doppler signal quality before and after injection was compared. Off-site assessment of the global quality of Doppler signal and duration of clinical useful enhancement, as well as off-site and on-site evaluation of quality of color and spectral Doppler, were performed. On-site evaluation of diagnostic accuracy was also carried out. Safety assessments included monitoring of adverse events up to 24 h following the last injection of SonoVue.

RESULTS

On-site evaluations: baseline Doppler was conclusive in only 4/21 carcinomas and in 2/17 benign lesions. Enhanced Doppler improved differential diagnosis in 20/21 carcinomas and in 9/12 benign lesions. Time to color enhancement was 0.55 min for the lowest and 0.35 min for the highest dose. The total duration of enhancement was 3.47 min for the lowest and 5.62 min for the highest dose, respectively. Off-site assessment: SonoVue improved the quality of Doppler blood flow information both in parenchymal and focal lesions. Statistically significant changes from baseline in global quality of Doppler investigations were observed at all four SonoVue doses (P<0.05). The duration of clinically useful signal enhancement increased with doses and a significant dose relationship was obtained (P<0.001). Mild adverse events were observed in two patients only.

CONCLUSION

The results obtained from this study, following both off-site and on-site assessment, demonstrate that the administration of SonoVue to patients with focal breast lesions provides significant improvement over the baseline of Doppler signal quality and a clinically useful duration of signal enhancement, related to the dose. SonoVue was shown to be a safe and well-tolerated compound.

Influence of bubble size distribution on the echogenicity of ultrasound contrast agents: a study of SonoVue

RATIONALE AND OBJECTIVES

To study the relative contributions of different bubble size classes to SonoVue's echogenicity in fundamental acoustic imaging modes. SonoVue is a contrast agent, previously known as BR1, with a bubble size distribution extending from approximately 0.7 to 10 microm.

METHODS

A model for the acoustic response of SonoVue was determined and validated for a set of experimental data. This model was used to simulate the acoustic response of a standard batch of SonoVue as the sum of responses of non-overlapping bubble size classes.

RESULTS

The simulation was first validated for a standard SonoVue bubble size distribution. When this distribution was considered as five size classes with equal numbers of bubbles, it was found that bubbles smaller than 2 microm accounted for 60% of the total number but contained only 5% of the total gas volume. The simulation results indicated marked differences in the acoustic contributions from these classes, with 80% of the acoustic efficacy provided by bubbles 3 to 9 microm in diameter. The study also compared bubble distributions in number, surface, and volume, with the distribution computed in terms of acoustic efficacy.

CONCLUSIONS

This study shows why bubble volume is a much better indicator of SonoVue's efficacy than is bubble count. A low threshold in diameter was found for SonoVue microbubbles at approximately 2 microm, under which size bubbles do not contribute appreciably to the echogenicity at medical ultrasound frequencies.

Diagnostic efficacy of SonoVue

SonoVue is a second-generation ultrasound contrast agent consisting of phospholipid-stabilized microbubbles filled with sulfur hexafluoride, with outstanding stability and resistance to pressure. The efficacy of SonoVue (0.5, 1, 2, 4 mL) was compared with Albunex (doses 0.08 and 0.22 mL/kg) in patients with suspected ischemic disease and suboptimal endocardial-border delineation on unenhanced echocardiography at rest. All the doses resulted in significantly greater increases compared with Albunex in left-ventricular endocardial-border delineation score as well as in the duration of clinically useful contrast effect. The utility of SonoVue in diagnosing ischemic heart disease was also evaluated during pharmacologic stress (arbutamine or dobutamine). SonoVue produced significant increases from baseline in endocardial-border delineation score both at rest and during pharmacologic stress. The possibility of detecting myocardial perfusion defects using SonoVue-enhanced power Doppler and gray-scale harmonic contrast echocardiography associated with continuous and intermittent imaging was assessed in patients with coronary artery disease. The results obtained were comparable with corresponding 99mTc sestamibi single-photon emission computed tomography images. An effective cardiovascular assessment of a patient should also include the evaluation of carotid vessels, intracranial circulation, and renal arteries. SonoVue provided significant improvements in the evaluation of the Doppler signal in terms of diagnosis agreement with reference imaging modality especially for intracranial vessels. The safety profile of SonoVue was evaluated in 1,406 patients. The incidence of adverse events was 10.4%, the great majority of which were of mild intensity and resolved without consequences.

Design of an ultrasound contrast agent for myocardial perfusion

Myocardial contrast echography (MCE) has been a major research objective in cardiovascular ultrasound for almost two decades. The design of a contrast agent fulfilling the needs of MCE requires taking into consideration a number of points: a basic decision has to be made whether a deposit agent or a free-flowing agent would be more appropriate and whether an agent active at low/medium mechanical index (MI) is preferable to an agent active only at high MI; only a small percentage of the cardiac output enters the coronary microcirculation, which means that highly sensitive bubble detection methods, such as harmonic imaging or pulse inversion, are needed; the low velocity of blood in the microcirculation that leads to extensive bubble destruction during imaging means that intermittent imaging and/or an agent active at low MI is (are) required; the duration of the contrast effect must be sufficient to allow a complete examination and is affected by the rate of contrast administration; the performance of the contrast agent should not be equipment-dependent. The ultimate goal in MCE is to be able to quantify blood flow in the various segments to determine if adequate oxygenation is achieved. Ultrasound-mediated bubble destruction followed by the measurement of bubble replenishment kinetics opens new perspectives for quantification. SonoVue is a free-flowing ultrasound contrast agent made of sulphur hexafluoride microbubbles stabilized by a highly elastic phospholipid monolayer. SonoVue is able to produce myocardial opacification at a wide range of acoustic pressures and in particular at MIs as low as 0.1. Its performance is not equipment-dependent. Good results for myocardial opacification have been observed in all animal species tested (dogs, minipigs, rabbits), using continuous as well as intermittent imaging. Trials are in progress to demonstrate the clinical utility of SonoVue for rest and stress perfusion studies, in particular for the diagnosis of CAD, the detection of myocardial infarction, the assessment of the success of interventions and myocardial viability, and the detection of hibernating myocardium.

Clinical experience with SonoVue in myocardial perfusion imaging

Ultrasound-enhancing agents have the potential to evaluate myocardial perfusion, adding a new dimension to echocardiography. This article summarizes the clinical studies involving SonoVue, a new intravenous ultrasound contrast agent, in assessing myocardial perfusion. Safe and well tolerated, SonoVue coupled with echocardiography has the capability to identify perfusion abnormalities, as confirmed by scintigraphic imaging. While the optimal modalities for ultrasound perfusion assessment are not yet determined, numerous technical advances have been introduced: continuous infusion or slow intravenous administration of the agent, harmonic intermittent imaging, pulse inversion, background subtraction, color coding, and others. SonoVue is a promising new agent in the booming field of myocardial contrast echocardiography.