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A. Waaler – One of the best experts on this subject based on the ideXlab platform.

  • The influence of Albunex on the pulmonary circulation in patients with pulmonary hypertension or left heart failure
    European heart journal, 1996
    Co-Authors: Zotz R, S. Genth, V. Mitrovic, A. Waaler, Raimund Erbel, Jürgen Meyer
    Abstract:

    To determine the safety of the ultrasound contrast agent Albunex, its influence on right and left heart haemodynamics in patients with pulmonary artery hypertension or left heart failure was assessed after intravenous injection. Patients with a left ventricular ejection fraction smaller than 40% or a systolic pulmonary artery pressure greater than 40 mmHg received 0.08 and 0.22 ml.kg -1 Albunex and 10 ml albumin in random order during right heart catheterization and transthoracic echocardiography. Right atrial, systolic and diastolic pulmonary artery and capillary wedge pressures were measured at 3 min and 5 min and cardiac output at 5 min after the intravenous injection of Albunex and control. The mean differences of pre- and postinjection values and their confidence intervals were tabulated and significance was anticipated if the confidence interval did not include 0. Significant changes to pre-injection values could be observed in diastolic pulmonary artery pressure 5 min after the injection of albumin and 0.08 ml.kg -1 Albunex, and in right atrial pressure 5 min after the injection of 0.22 ml. kg -1 Albunex only. Since intermediate opacification of the left ventricle was seen in only four patients with 0.22 ml.kg -1 Albunex, in the patients studied higher doses of Albunex and their safety need to be assessed.

  • Digital radiofrequency echocardiography in the detection of myocardial contrast following intravenous administration of Albunex.
    European heart journal, 1993
    Co-Authors: Mark J. Monaghan, A. Waaler, J. M. Metcalfe, S. Odunlami, David E. Jewitt
    Abstract:

    Conventional contrast echo techniques have proved inadequate for the detection of myocardial perfusion using intravenously injected echo contrast agents because of the limitations and relative insensitivity of standard echocardiographic equipment. In order to avoid these problems, we have obtained pure digital radiofrequency ultrasound data from the left ventricle and myocardium during i.v. contrast myocardial perfusion echo studies. In 30 patients, following coronary arteriography, i.v. injections of the echo contrast agent Albunex (sonicated human serum albumin) in two doses of 0.08 and 0.22ml . kg−1 were administered during digital radiofrequency echocardiography sampling of data from the myocardium and left ventricular cavity. Analysis of mean integrated backscatter (MIB, a measure of the total ultrasound energy) was performed before, during and after Albunex injection. The data were also analysed for a shift in frequency spectrum which could be caused by resonance of the Albunex contrast microspheres in the heart, a phenomenon which has been previously demonstrated in vitro. Digital radiofrequency ultrasound data were successfully obtained and analysed in 23 patients. In 31 segments where reasonable resting perfusion was expected, there was a significant increase in MIB from 0.644 to 1.245, P

  • digital radiofrequency echocardiography in the detection of myocardial contrast following intravenous administration of Albunex
    European Heart Journal, 1993
    Co-Authors: Mark J. Monaghan, A. Waaler, J. M. Metcalfe, S. Odunlami, David E. Jewitt
    Abstract:

    Conventional contrast echo techniques have proved inadequate for the detection of myocardial perfusion using intravenously injected echo contrast agents because of the limitations and relative insensitivity of standard echocardiographic equipment. In order to avoid these problems, we have obtained pure digital radiofrequency ultrasound data from the left ventricle and myocardium during i.v. contrast myocardial perfusion echo studies. In 30 patients, following coronary arteriography, i.v. injections of the echo contrast agent Albunex (sonicated human serum albumin) in two doses of 0.08 and 0.22ml . kg−1 were administered during digital radiofrequency echocardiography sampling of data from the myocardium and left ventricular cavity. Analysis of mean integrated backscatter (MIB, a measure of the total ultrasound energy) was performed before, during and after Albunex injection. The data were also analysed for a shift in frequency spectrum which could be caused by resonance of the Albunex contrast microspheres in the heart, a phenomenon which has been previously demonstrated in vitro. Digital radiofrequency ultrasound data were successfully obtained and analysed in 23 patients. In 31 segments where reasonable resting perfusion was expected, there was a significant increase in MIB from 0.644 to 1.245, P <0.001 and time intensity curves could be constructed showing wash-in and wash-out of contrast from the myocardium. In 10 segments supplied by significantly diseased vessels, MIB intensity increased from 1.044 to 1.874, P =0.054. In myocardial segments supplied by non-diseased vessels, microsphere resonance also caused a drop in mean frequency of 140 KHz, P <0.001 and permitted similar temporal analysis of myocardial perfusion. Frequency changes preceded intensity changes in both the LV and myocardium by 2.3 beats and may represent faster pulmonary transmit of smaller contrast microspheres. In conclusion, digital radiofrequency ultrasound echocardiographic analysis provides a method of detecting myocardial perfusion following i.v. Albunex. It should provide the basis for future methods enabling study of organ tissue perfperfusion by ultrasound following i.v. injection of ultrasonic contrast agents.

Michael H. Picard – One of the best experts on this subject based on the ideXlab platform.

  • Multicenter evaluation of SonoVue for improved endocardial border delineation.
    Echocardiography (Mount Kisco N.Y.), 2002
    Co-Authors: Navin C Nanda, Daniel C. Wistran, Ronald P. Karlsberg, Terrence C. Hack, William B. Smith, David A. Foley, Michael H. Picard, Bruno Cotter
    Abstract:

    Objectives: Two multicenter studies were conducted to evaluate the safety and efficacy of SonoVue as a contrast agent for enhanced left ventricular endocardial border delineation (LVEBD), and to compare the efficacy of SonoVue and Albunex in adult patients with a suboptimal, nonenhanced echocardiogram. Background: The use of contrast to enhance echocardiographic assessment of LVEBD is well-established. SonoVue is a new microbubble contrast agent that contains sulfur hexafluoride. Methods: Patients were randomized to receive four injections of SonoVue (0.5, 1, 2, and 4 ml), or two injections of Albunex and two injections of hand-agitated saline (0.08 and 0.22 ml/kg). Echocardiographic images were evaluated at the study centers and by four blinded, offsite reviewers for degree of left ventricle opacification (LVO), duration of contrast enhancement, and LVEBD. Results: LVO scores were significantly higher for all doses of SonoVue. Patients with complete LVO ranged from 34%–87% for SonoVue and from 0%–16% for Albunex. The mean duration of useful contrast effect ranged from 0.8–4.1 minutes for SonoVue and < 15 seconds for Albunex. Mean increases in LVEBD scores ranged from 3.8–18.2 for SonoVue and 0.1–4.3 for Albunex. SonoVue (cumulative 7.5 ml dose) was well-tolerated, with a safety profile similar to that observed in the control group. Conclusions: SonoVue is superior to Albunex for improving visualization of endocardial borders in patients with suboptimal noncontrast echocardiograms. Optimal increases in LVEBD, LVO, and duration of useful contrast effect were observed at the 2.0 ml dose of SonoVue.

  • Improvement of transthoracic pulmonary venous flow Doppler signal with intravenous injection of sonicated albumin.
    Journal of the American College of Cardiology, 1995
    Co-Authors: Michael J.a. Williams, Brian M. Mcclements, Michael H. Picard
    Abstract:

    Objectives. This study was performed to determine whether intravenous injection of a sonicated albumin echocardiographic contrast agent (Albunex) improved the quality of the transthoracic pulmonary venous flow Doppler signal. Background. Previous studies have shown that transesophageal echocardiography provides pulmonary venous flow Doppler signals superior in quality to those seen with transthoracic echocardiography, which are of limited quality in up to 25% of patients. Methods. Twenty-one patients underwent transthoracic pulsed wave Doppler examination of pulmonary venous flow before, during and after two doses of Albunex ranging from 0.08 ml/kg (low dose) to 0.22 ml/kg (high dose). In addition, five patients underwent transesophageal examination of pulmonary venous flow before and after a 0.08-ml/kg dose of Albunex. The efficacy of the contrast injection was determined using a score that graded the quality of the three components of the pulmonary venous Doppler signal from 0 to 3 (0 = no visible signal; 3 = optimal signal). Results. Albunex enhanced the quality of the pulmonary venous Doppler signal from baseline (score 3.9 ± 1.8 [mean ±SD]) and at both low (score 5.1 ± 2.2, p Conclusions. Albunex improves the quality of the transthoracic pulmonary venous Doppler signal, thus allowing improved accuracy of measurement. This approach appears to be effective for increasing the quality of data obtained from the transthoracic examination.

N. De Jong – One of the best experts on this subject based on the ideXlab platform.

  • Acoustic modeling of shell-encapsulated gas bubbles
    'Elsevier BV', 1998
    Co-Authors: Frinking P.j.a., N. De Jong
    Abstract:

    Existing theoretical models do not adequately describe the scatter and attenuation properties of the ultrasound contrast agents Quantison(TM) and Myomap(TM). An adapted version of the Rayleigh-Plesset equation, in which the shell is described by a viscoelastic solid, is proposed and validated for these agents and Albunex(®). The acoustic transmission and scattering are measured in the frequency band from 1-10 MHz. The measured transmission is used to estimate two parameters, the effective bulk modulus, K(eff) describing the elasticity, and the friction parameter, S(F), describing the viscosity of the shell. For the scattering, the difference between measurements and calculations is < 3 dB. For Quantison(TM), the effective bulk modulus is independent of the bubble diameter. For Albunex(®), it increases for decreasing bubble diameter. The nonlinear response of Quantison(TM) is minimal for acoustic pressures up to 200 kPa. For acoustic pressures above 200 kPa, the measured scattering abruptly increases. This increase reaches a level of 20 dB for an acoustic pressure of 1.8 MPa. This response cannot be predicted by the theoretical model developed in this article.Existing theoretical models do not adequately describe the scatter and attenuation properties of the ultrasound contrast agents QuantisonTM and MyomapTM. An adapted version of the Rayleigh-Plesset equation, in which the shell is described by a viscoelastic solid, is proposed and validated for these agents and Albunex. The acoustic transmission and scattering are measured in the frequency band from 1-10 MHz. The measured transmission is used to estimate two parameters, the effective bulk modulus, Keff, describing the elasticity, and the friction parameter, SF, describing the viscosity of the shell. For the scattering, the difference between measurements and calculations is

  • Higher harmonics of vibrating gas-filled microspheres. Part one: simulations
    Ultrasonics, 1994
    Co-Authors: N. De Jong, Ronald Cornet, Charles T. Lancée
    Abstract:

    Abstract The acoustic behaviour of an ideal gas bubble in water is considered and the equation of motion is extended to model an Albunex microsphere. Calculations reveal large differences in non-linear behaviour between ideal gas bubbles and Albunex microspheres, due to the additional restoring force of, and friction inside, the shell that surrounds the Albunex microsphere. Simulations with the Albunex contrast agent further reveal that the optimal driving frequency is 1 MHz, resulting in a second harmonic that is 20 dB below the first harmonic at an acoustic pressure of 50 kPa. The difference increases to 25 dB for a driving frequency of 2 MHz.

  • Higher harmonics of vibrating gas-filled microspheres. Part two: measurements
    Ultrasonics, 1994
    Co-Authors: N. De Jong, Ronald Cornet, Charles T. Lancée
    Abstract:

    Abstract Acoustic measurements on diluted Albunex at two driving frequencies (1 and 2 MHz) are reported which show that the level of the second-harmonic response is about 20 dB below the first harmonic at an acoustic pressure amplitude of 50 kPa. It is demonstrated that, under controlled conditions, it is possible to discriminate between Albunex and other scattering/reflecting objects using the non-linear behaviour of the microspheres.

Lars Hoff – One of the best experts on this subject based on the ideXlab platform.

  • Modelling of the Ultrasound Return from Albunex
    , 2007
    Co-Authors: Microspheres Sverre, Sverre Holm, Marte Myhrum, Lars Hoff
    Abstract:

    A mathematical model that predicts the changes to the ultrasound frequency spectrum after passing through human tissue and Albunex â (a registered trademark of Molecular Biosystems Inc., San Diego, CA) microspheres is proposed. Changes in backscattered intensity and mean frequency of the reflected signal can be estimated as a function of imaging geometry, ultrasound frequency, and microsphere concentration and size distribution. An important result is that the frequency shifts and the intensity variations are caused both by the microspheres in the path between the transducer and the region of interest, and by the reflection properties of the contrast agent in the region of interest. The model enables one to explain and predict clinically observed intensity effects such as the shadow effect in the right ventricle, and the fact that received intensity increases with concentration up to a certain point where it falls off. The effect of the removal of the larger microspheres in the lungs..

  • Albunex-a new ultrasound contrast agent
    , 1993
    Co-Authors: N. Sponheim, A. Waaler, N. De Jong, Lars Hoff, B. Muan, H. Morris, Sverre Holm, M. Myrum, T. Skotland
    Abstract:

    Albunex (Molecular Biosystems Inc (MBI), San Diego, USA and Nycomed Imaging AS, Oslo, Norway) is the first ultrasound contrast agent that is stable enough to show transpulmonary passage. This implies that the contrast agent can be injected intravenously and still give contrast in the left side of the heart. Albunex is made by sonication of a 5% solution of human albumin. This process generates air bubbles encapsulated by a shell of aggregated albumin. The air-filled microspheres have characteristics similar to those of air bubbles in water, with respect to both backscatter and attenuation of the ultrasound signal. Clinical studies have shown that Albunex is a safe product. We have documented the diagnostic efficacy of Albunex for the study of the anatomy and function of the heart, but more research needs to be done to document its diagnostic efficacy for the study of myocardial perfusion and Doppler enhancement. Acoustical properties of Albunex are discussed.

  • Ultrasound scattering properties of Albunex microspheres.
    Ultrasonics, 1993
    Co-Authors: N. De Jong, Lars Hoff
    Abstract:

    Albunex is an ultrasound contrast agent used in echocardiography and in other areas, it consists of microspheres of which more than 95% have a diameter in the range 1-10 microns. The scattering properties of this agent as functions of ultrasound frequency and microsphere diameter and concentration are investigated. A model of the Albunex microspheres has been previously described, considering the individual microspheres as air bubbles surrounded by a thin elastic shell. In the present study this model is extended by including into it the internal friction in the shell when the microsphere vibrates. Acoustic scattering and transmission are measured in the frequency range from 700 kHz to 12.5 MHz. The measured transmitted power is used to estimate the two parameters in the theoretical model: the shell elasticity parameter, Sp and the shell friction, Sf. Introduction of the shell friction into the model improves the agreement between theory and measurements. For the scattered power, differences between measured and calculated values lie within 3 dB. It is concluded that for the frequencies 2.5 and 5 MHz, microspheres with a diameter between 5 and 12 microns are preferred as these deliver the most significant contribution to the total scattered power and cause relatively little attenuation.

Michael J.a. Williams – One of the best experts on this subject based on the ideXlab platform.

  • Improvement of transthoracic pulmonary venous flow Doppler signal with intravenous injection of sonicated albumin.
    Journal of the American College of Cardiology, 1995
    Co-Authors: Michael J.a. Williams, Brian M. Mcclements, Michael H. Picard
    Abstract:

    Objectives. This study was performed to determine whether intravenous injection of a sonicated albumin echocardiographic contrast agent (Albunex) improved the quality of the transthoracic pulmonary venous flow Doppler signal. Background. Previous studies have shown that transesophageal echocardiography provides pulmonary venous flow Doppler signals superior in quality to those seen with transthoracic echocardiography, which are of limited quality in up to 25% of patients. Methods. Twenty-one patients underwent transthoracic pulsed wave Doppler examination of pulmonary venous flow before, during and after two doses of Albunex ranging from 0.08 ml/kg (low dose) to 0.22 ml/kg (high dose). In addition, five patients underwent transesophageal examination of pulmonary venous flow before and after a 0.08-ml/kg dose of Albunex. The efficacy of the contrast injection was determined using a score that graded the quality of the three components of the pulmonary venous Doppler signal from 0 to 3 (0 = no visible signal; 3 = optimal signal). Results. Albunex enhanced the quality of the pulmonary venous Doppler signal from baseline (score 3.9 ± 1.8 [mean ±SD]) and at both low (score 5.1 ± 2.2, p Conclusions. Albunex improves the quality of the transthoracic pulmonary venous Doppler signal, thus allowing improved accuracy of measurement. This approach appears to be effective for increasing the quality of data obtained from the transthoracic examination.