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PubMed2003

The pulse length-dependence of inertial cavitation dose and hemolysis.

Gas-based ultrasound (US) contrast agents increase erythrocyte sonolysis, presumably via enhancing inertial cavitation (IC) activity. The amount of IC activity (IC "dose") and hemolysis generated by exposure to 1.15 MHz US were examined with different US pulse lengths, but with the same delivered acoustic energy, for Optison and Albunex. The hypotheses were that 1. at longer pulse lengths, IC would generate more bubbles that could nucleate additional IC activity; 2. if the interval between pulse pairs were short enough for the next pulse to hit derivative bubbles before their dissolution, more IC could be induced; and 3. hemolysis would be proportional to IC activity. Two types of studies were performed. In the first, bubble generation after each burst of IC activity was quantified using an active cavitation detector (ACD), for different pulse lengths (5, 10, 20, 30, 50, 100 or 200 cycles), but the same pressure level (3 MPa) and total "on" time (173.16 ms). Low concentrations of either Optison or Albunex were added into the tank with high-intensity and interrogating transducers orthogonal to each other. For pulse lengths > 100 cycles, and pulse repetition intervals < 5 ms, a "cascade" effect (explosive bubble generation) was observed. In the second, IC was measured by passive detection methods. IC dose and hemolysis were determined in whole blood samples at a pressure level (3 MPa) and interpulse interval (5 ms) that induced the "cascade" effect. Each blood sample was mixed with the same number of contrast microbubbles (Optison approximately 0.3 v/v % and Albunex approximately 0.5 v/v %), but exposed to different pulse lengths (5, 10, 20, 30, 50, 100 or 200 cycles). With Optison, up to 60% hemolysis was produced with long pulses (100 and 200 cycles), compared with < 10% with short pulses (5 and 10 cycles). Albunex generated considerably less IC activity and hemolysis. The r(2) value was 0.99 for the correlation between hemolysis and IC dose. High pulse-repetition frequency (PRF) (500 Hz) generated more hemolysis than the low PRF (200 Hz) at 3 MPa. All experimental results could be explained by the dissolution times of IC-generated bubbles.

Albumins↗

PubMed2003

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

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

Animals↗

PubMed2003

Echoscintigraphy: a new imaging modality for the reduction of color blooming and acoustic shadowing in contrast sonography.

The purpose of this study was to develop and evaluate a new imaging modality (echoscintigraphy) to reduce color blooming and acoustic shadowing in contrast sonography. After injection of various amounts (700 to 40,000 bubbles/mL) of the echo contrast agent SH-U 563A into a flow phantom, artificial vessels were insonated in the intermittent harmonic-power Doppler imaging (H-PDI) mode. The receive gain was varied from 50% to 75%. The cross-sectional area (CSA) of the tube was assessed using a new summation algorithm (echoscintigraphy) and a conventional single-frame analysis (S-FA) of the H-PDI-signals. Echoscintigraphy is based on the recording and summation of low-intensity signals that are emitted during the ultrasound (US)-induced destruction of microbubbles. Application of the summation algorithm at low-contrast concentration allowed a gain-independent automatic calculation of the CSA at medium and high gain settings. Using the S-FA method, the assessment of the vessel diameter and the CSA was gain-dependent and allowed correct measurements only from 60% to 65% gain. At a high receive-gain and high contrast concentration, S-FA resulted in an overestimation of the CSA up to 35.5%. Echoscintigraphy allows correct display of contrast-filled vessels over a wide range of gain settings at low contrast concentrations, where S-FA does not adequately display echo contrast. Thus, echoscintigraphy minimizes artefacts resulting from color blooming and acoustic shadowing.

Algorithms↗

PubMed2003

Transfer function analysis of ultrasonic time-intensity measurements.

Time-intensity measurements of ultrasonic-contrast microbubbles based on the dilution theory have been used to assist blood flow estimation. The compartment model has been employed to describe the dilution process. Under the linear and time-invariant assumption, the time-intensity curve measured at the output of a compartment (i.e., blood mixing chamber) is the convolution of the input time-intensity curve with the compartment's transfer function. Thus, transfer function analysis is possible using deconvolution when the temporal variations in both the input and the output intensities are available. Note that the linear and time-invariant assumption requires a constant flow rate because, with flow pulsation, the flow rate changes with time and the mixing process becomes time varying. Thus, the purpose of this paper was to study the effects of flow pulsation on time-intensity measurements. In addition, a deconvolution technique based on a recursive least squares approach is used for transfer function analysis. Both simulations and experiments were performed; the results from which indicate that the pulsation generally does not affect the validity of time-intensity-based flow estimation. The proposed deconvolution technique is also effective for both constant and pulsatile flows; thus, permitting transfer function analysis in various flow conditions. One potential application of this transfer function analysis is to remove the effects of a noninstantaneous input function. The results from this paper lead to future work in brain-perfusion estimation based on extracranial time-intensity measurements.

Blood Flow Velocity↗

PubMed2003

Contrast agent bubble and erythrocyte behavior in a 1.5-MHz standing ultrasound wave.

Human erythrocytes and Optison contrast agent have been exposed to ultrasound, both alone and in combination, in a single-half-wavelength chamber driven at its resonance frequency (fo) of 1.5 MHz. Cell movements were recorded by video microscopy at speeds up to 500 frames/s. The hypothesis that cells near a standing wave pressure node might be stressed by the microbubble products of sonicated contrast agent was examined. In the absence of contrast agent, cells moved rapidly to form an aggregate in the standing wave pressure node plane. First subharmonic and second harmonic emissions were detected from cell-contrast agent suspensions immediately on exposure to a threshold peak pressure amplitude of 0.98 MPa. Emissions at 3fo/2 occurred at 1.47 MPa, whereas white noise and lower-order subharmonic emissions coincided with the appearance of visible bubbles at a threshold of approximately 1.96 MPa. Cells exposed together with contrast agent at a pressure of 0.98 MPa precessed very rapidly about the pressure node plane. This behavior was discussed in the context of a recent analysis predicting that, in contrast to the situation for lower-pressure amplitudes, subresonant size bubbles translate about pressure node plane if the driving pressure amplitude is sufficiently high. Many precessing erythrocytes were clearly spiculated and this morphology persisted after the cells had left the area of precession. Hemoglobin release was significant under conditions inducing precession with first subharmonic and first harmonic emissions. Protein release increased discontinuously near the pressure thresholds, where more complex categories of frequency emission were detected. The potential of this system, which induces erythrocyte morphology changes and some protein release at the first emission threshold, to provide some control on the membrane-permeabilizing stress experienced by cells in a cavitation field is discussed.

Albumins↗

PubMed1995

When can Doppler be used in place of integrated backscatter as a measure of scattered ultrasound intensity?

The purpose of this work was to determine under what circumstances the intensity of Doppler audio signals can be used as a substitute for the more direct and complex measure of ultrasonic backscatter (integrated backscatter) which requires radio-frequency ultrasound signals. Using a rotating rubber disk phantom and a microbubble echo-contrast flow phantom, we have shown that the intensity of audio Doppler signals is independent of the constraints typically associated with Doppler ultrasound (velocity and angle), but like integrated backscatter depends on the transmit intensity, gain of the ultrasound receiver, attenuation and the nature of the scatterers. Using Doppler ultrasound for backscatter measurements is ideally suited for the expected application of the technique: the assessment of echo contrast in cardiac chambers, blood vessels and tissue perfusion (i.e., any flow system). Compared to integrated backscatter, the Doppler audio method has the advantage of using standard clinical ultrasound machines, requires less sophisticated data storage and processing equipment and the positioning system for the region of interest (the Doppler sample volume) is built into all pulsed-wave Doppler machines. Further, the low-velocity filter removes all nonmoving scatterers (like the intense echoes from heart valves and the walls of blood vessels), thus allowing study of only those echoes originating from the blood pool. This combination of features is what attracted us to the Doppler method for quantitating ultrasonic backscatter in flow systems.

Blood Flow Velocity↗

PubMed1997

Direct effects of DC cardioversion on blood echogenicity: an in vitro study.

Exacerbation of left atrial spontaneous echo contrast (SEC) after cardioversion of atrial fibrillation has been attributed to left atrial mechanical dysfunction induced by the procedure ("atrial stunning"). An in vitro model was devised to determine whether electrically induced changes in blood properties might contribute to SEC formation after cardioversion. Human blood echogenicity was examined quantitatively by videodensitometry before and after shocks of 1, 2, 5, and 20 J. Changes in blood cell numbers, cell morphology, and erythrocyte sedimentation rate were determined by haematological analysis. Immediately following electrical discharges, transient and dose-related, highly echogenic microbubbles were noted, but shocks of increasing intensity did not induce SEC at high blood velocity or alter the severity of SEC at low blood velocity. No quantitative or qualitative changes in haematological parameters were observed. These results suggest that direct effects of electrical shock on blood do not contribute to SEC after cardioversion. Systemic haematological responses to electric shock that might indirectly promote red cell aggregation in vivo cannot be excluded by this in vitro study.

Adult↗

PubMed1997

Correlation of ultrasound-induced hemolysis with cavitation detector output in vitro.

A 20-MHz passive acoustic detector was used to quantify the amount of transient acoustic cavitation occurring in a sample exposed to intense pulsed ultrasound. A dilute suspension of human erythrocytes with and without a microbubble echo-contrast agent was exposed in vitro to 500 W/cm2 (SPPA) ultrasound of center frequency 1 MHz and tone burst duration 20, 100, 200, 500 and 1000 microseconds at a pulse repetition frequency of 20 Hz. Inertial cavitation occurring within the sample, as measured by the temporal average of the detector output, correlated well with hemolysis, suggesting that violent bubble collapse is responsible for cell damage. The result also raises the prospect of cavitation monitoring as a possible predictor of adverse bioeffects when echo-contrast agents are used clinically.

Albumins↗

PubMed1997

Insufficient and absent acoustic temporal bone window: potential and limitations of transcranial contrast-enhanced color-coded sonography and contrast-enhanced power-based sonography.

The aim of this study was to investigate the diagnostic potential of contrast-enhanced transcranial color-coded sonography (CE-TCCS) and contrast-enhanced transcranial power-based sonography (CE-TPS) in patients with insufficient or absent acoustic bone windows (IABW). Due to temporal bone thickness, the basal cerebral circulation could not be insonated in 21 of 172 patients using unenhanced transcranial color-coded real-time sonography (TCCS) and transcranial power-based sonography. Additional CE-TCCS and CE-TPS were performed after application of 400 mg/ml galactose microbubble suspension. In both modalities, the use of echo-contrast agents allowed visualisation of the first segment of the middle cerebral artery (MCA) in all patients. The A1 segment of the anterior cerebral artery (67% in CE-TCCS; 81% in CE-TPS), P1 segment of the posterior cerebral artery (71% in CE-TCCS; 76% in CE-TPS) and the basilar artery (48% in CE-TCCS; 67% in CE-TPS) were depictable in the majority of the examinations. The M3 (5% in CE-TCCS; 33% in CE-TPS; p < 0.05), P2 (24% in CE-TCCS; 71% in CE-TPS; p < 0.005), P3 segments (0% in CE-TCCS; 43% in CE-TPS; p < 0.005) and the posterior communicating artery (5% in CE-TCCS; 33% in CE-TPS; p < 0.05) were detected in a significantly greater proportion of subjects using power Doppler. In conclusion, CE-TCCS and CE-TPS appear to be sensitive ultrasonic tools that provide reliable data regarding the basal cerebral circulation in patients with IABW. Furthermore, CE-TPS offers advantages over CE-TSSC in the identification of small-caliber arteries and vessels that run at unfavorable angels to the ultrasound beam. Both methods can overcome hyperostosis of the skull that is a major hindrance in transcranial ultrasonography, and may be helpful in the diagnosis of occlusive diseases of intracranial vessels.

Adult↗

PubMed1997

Quantitative acoustic characterization of a new surfactant-based ultrasound contrast agent.

The acoustic properties of a new ultrasound contrast agent, ST68, have been investigated. ST68 is a sonicated mixture of nonionic surfactants (Span-type and Tween-type) consisting of stabilized microbubbles with a mean diameter of 3.8 microns and a concentrations of 7.1 x 10(8) bubbles/mL. A pulsatile flow system was used to acquire data in vitro. The acoustic properties of ST68, as a function of time, frequency and dose, were calculated. Enhancement changed nonlinearly with contrast agent dose; maximum was 13.1 dB +/- 1.0 dB for a dose of 0.30 microL/mL of suspending medium. Attenuation reached approximately 11 dB/cm for dosages above 0.27 microL/mL and for frequencies between 2.5 and 6.0 MHz. In vivo, i.v. injections of ST68 were given to 4 rabbits (doses from 0.01 to 0.23 mL/kg). A clear increase in flow signal intensity was observed for 1 to 2 min. An in vivo dose-response curve was calculated from audio Doppler signals obtained with a 10-MHz cuff transducer placed around the distal aorta. Maximum enhancement was 18.3 dB +/- 3.13 dB for a 0.13 mL/kg dose. Moreover, ST68 appears to follow a simple relationship between in vivo enhancement and dose. In conclusion, ST68 is capable of producing marked vascular enhancement. Its acoustic properties have been characterized in vitro and in vivo.

Acoustics↗

PubMed1997

Preliminary study in differential contrast echography.

Microbubble-based contrast agents have backscattering properties that differ greatly from those of soft tissues. These agents exhibit nonlinear scattering properties in response to incident acoustic energy, causing harmonic components in reflected energy. Even in linear scattering conditions, an important difference is observed in the frequency dependence of their backscatter coefficient, when compared to that of tissues. In this situation, any such differential behaviour can be exploited by imaging instrumentation to enhance the detection of agent-containing vessels against background tissue. The resulting B-mode image brightness (or pixel level) can thus be the representation of a local parameter computed from radio frequency (rf) signal processing of the raw echoes. The object of this article is to report on parametric imaging studies performed with Sonovue (formerly code named BR1, Bracco Research SA), aimed at assessing the contrast-enhancing potential of spectral rf signal processing. The technique used, termed here "differential contrast echography" (DCE), is applicable in real-time B-mode imaging. It is based on an on-line subtractive approach, using dual-channel signal processing to implement differential filtering and demodulation. In this preliminary work, DCE was implemented off-line, on rf echo signals digitised from commercial B-mode scanners. Data acquisition, DCE processing and complete B-mode image reconstruction were programmed on a personal computer. The images presented were produced from test phantoms as well as animal phased array scanning. The phantom included a flow channel, background scattering material, fixed echogenic targets and echo-free regions. Animal scanning was performed on rabbit liver. The results obtained from DCE show promising contrast-enhancing properties. The regions containing no contrast agent are significantly suppressed from the image, preferentially leaving the regions perfused by the contrast agent. This property was favourable to experimenting with image-overlay presentations, superimposing colour-coded DCE imaging with standard log-compressed grey-scale B-mode, in a way analogous to duplex imaging combining colour Doppler and B-mode.

Algorithms↗

PubMed1997

Ultrasound properties of liver tissue during heating.

The objective of this work was to determine changes in the ultrasound properties of heated tissues, with potential application to monitoring of minimally invasive thermal therapy (MITT). Changes in backscatter coefficients and frequency-dependent attenuation coefficients were measured over the frequency range 2.5 MHz to 5 MHz from heated samples of store-bought fresh bovine liver, which was used as a tissue model. Individual liver samples were heated from 37 degrees C to either 50 degrees C, 55 degrees C, 60 degrees C, 65 degrees C or 70 degrees C by warm water. The backscatter coefficient increased during the first 3 min by a factor of 1.09 and 1.11 before the tissue reached 50 degrees C and 55 degrees C, respectively. A decrease in backscatter coefficient followed at 50 degrees C by a factor of 1.12 below the initial level and, at 55 degrees C, the backscatter coefficient dropped below the initial level by a factor of 1.19. The backscatter coefficient decreased within the first 2 min by a factor of 1.22 before the tissue reached 60 degrees C, then increased gradually to a factor of 1.05 below the initial level. At 65 degrees C and 70 degrees C, the changes in backscatter coefficient were highly variable, which may have been due to production of gas microbubbles in the heated tissues. The ultrasound attenuation coefficient increased by as much as 1.48 dB cm-1 over a 30-min period at 70 degrees C. First-order rate parameters derived from the attenuation results revealed one rate process at 50 degrees C and 55 degrees C and two rate processes at 60 degrees C, 65 degrees C and 70 degrees C. An activation energy of 1.00 x 10(4) cal mol-1 was derived from the second rate constants at 60 degrees C, 65 degrees C and 70 degrees C, which indicates that changes in attenuation may be due to protein denaturation. In conclusion, ultrasound image monitoring of thermal therapy treatment in liver may be feasible; however, the backscatter coefficient changes during heating are small and are of the same order as the variation in these changes from point to point in the tissue.

Animals↗

PubMed1998

Diagnosis and monitoring of middle cerebral artery occlusion with contrast-enhanced transcranial color-coded real-time sonography in patients with inadequate acoustic bone windows.

Transcranial color-coded real-time sonography (TCCS) is an emerging diagnostic technique that allows noninvasive imaging of intracranial vessels within parenchymal structures. However, in some patients, transcranial ultrasound is particularly hindered by insufficient ultrasound penetration through the temporal bone. The present study evaluates whether or not application of an echo-contrast agent in ultrasound-refractory patients with middle cerebral artery (MCA) trunk occlusion enhances image acquisition enough to yield accurate diagnoses. Contrast-enhanced (CE) TCCS examinations, computed tomography scans and angiographic studies were performed in 20 patients with clinical symptoms suggestive of MCA occlusion within 12 h of the onset of symptoms. For comparison, 20 control persons without history or clinical signs for cerebrovascular diseases were examined using CE-TCCS. In none of the patients or control subjects did unenhanced TCCS investigations depict any color-coded vascular signal of an intracranial vessel. After application of 9 mL of 400 mg/mL galactose-based microbubbles, CE-TCCS was performed. In subjects with MCA occlusion, CE-TCCS examinations were repeated within 24 h, 48 h and 5 days after stroke. In stroke patients (n = 20), CE-TCCS showed an occluded MCA main stem in 11 patients, and this vessel was clearly demonstrable on the unaffected side. On the affected side, the posterior cerebral artery (PCA) and anterior cerebral artery (ACA) could be visualized in 8 of 11 subjects; in 3 patients, at least 1 of these vessels was detectable. Angiographic studies confirmed the diagnosis of MCA trunk occlusion in all 11 individuals. In follow-up investigations, 3 stroke patients had angiographic and CE-TCCS examinations consistent with vessel reperfusion. Nine stroke patients had a patent MCA shown in angiographic and CE-TCCS examinations. In the control group, the MCA trunk could be visualized in all subjects by CE-TCCS. CE-TCCS is a sensitive and specific ultrasound method for the diagnosis of MCA trunk occlusion that overcomes the anatomical hindrance of inadequate acoustic bone window. This technique may help to identify patients suitable for thrombolytic therapies and monitor their response.

Aged↗

PubMed1998

Contrast-enhanced sonography of tumor neovascularity in a rabbit model.

This project was designed to detect the development of tumor neovascularity and determine if intravenous microbubble contrast improves visualization of otherwise undetectable tumors in an animal model. VX-2 carcinoma was implanted into one thigh of 10 New Zealand white rabbits. Tumors were assessed without and with contrast at 1- to 4-day intervals from day 3-19 postimplantation, using gray scale, color flow, pulse Doppler and power Doppler imaging. Tumor vascularity was compared with the contralateral thigh muscle, so each animal was its own control. Contrast injection improved visualization of tumor neovascularity. Early tumors had homogeneous vasculature but, with time, the centers became less vascular, while the periphery increased. Following contrast injection, color gain was decreased by 40% without compromising color intensity. Neovascularity was detected by contrast injection before the tumor could be palpated or visualized by gray scale. Based on these data, we conclude that enhancement of neovascularity by intravenous contrast permits earlier detection and improved visualization of soft tissue tumors in rabbits.

Animals↗

PubMed1998

Quantification of the enhanced backscatter phenomenon from an intravenous and an intra-arterial contrast agent.

The phenomenon of enhanced backscatter from myocardial contrast agents was studied using two examples, a robust thicker-walled, intra-arterial agent (AIP 201) and a smaller thinner-walled, intravenous agent (Quantison). Both agents are composed of albumin-encapsulated microbubbles. Samples of the agents were inserted into an in vitro phantom and insonated under different scanning regimes. Upon insonation, Quantison exhibited a pronounced increase in mean backscatter at medium and low concentrations, which decreased dramatically with increasing number of frames of insonation. At high concentrations, no dramatic decrease or increase in mean backscatter was observed over the period of the experiment. AIP 201 exhibited an overall decrease in mean backscatter with increasing number of frames of insonation. These results suggest that the difference in size and wall thickness of the contrast microcapsules can significantly affect the behaviour of the contrast agents in an ultrasound field.

Contrast Media↗

PubMed1998

Echo contrast-enhanced three-dimensional power Doppler of intracranial arteries.

The purpose of this study was to evaluate the potential of contrast-enhanced three-dimensional (3-D) power Doppler (CE3DPD) in the assessment of intracranial vascular structures, and to compare the results with unenhanced 3-D power Doppler (3DPD) and magnetic resonance angiography (MRA) findings. We insonated 25 patients without cerebrovascular diseases through the temporal bone window using 3DPD and CE3DPD; for comparison, 13 patients underwent MRA. Identification rates of vascular segments and of small branches of intracranial vessels were evaluated by two independent investigators blinded to MRA results. In 21 patients with adequate insonation conditions, CE3DPD significantly improved identification rates compared to 3DPD for the complete visualization of the P1 segment (80.9 vs. 19.0%, p < 0.005, P2 segment (80.9 vs. 42.8%, p < 0.05 and A1 segment (85.7 vs. 38.1%, p < 0.005). Furthermore, CE3DPD depicted, in significantly more examinations, branches of the middle (MCA) and posterior cerebral artery (PCA). Interobserver agreement was higher than 95% for the main intracranial segments and branches of the MCA, but relatively low (80.1-85.7%) for branches of the PCA. In comparison to CE3DPD, MRA identified only parieto-occipital branches of the PCA, temporal branches of the MCA, frontal branches of the anterior cerebral artery and the MCA bifurcation more frequently and accurately. In 4 patients with inadequate acoustic temporal bone windows, the application of a galactose-based microbubble suspension allowed clear 3-D visualization of almost all major intracranial vascular segments and some branches of the large arteries. In conclusion, CE3DPD is a more sensitive ultrasonic tool compared to unenhanced 3-D reconstructions. It makes 3-D ultrasound imaging of the basal cerebral circulation easier to perform and interpret, by providing an improved spatially oriented display of image position. As such, this method may increase operator diagnostic confidence level under pathologic conditions.

Adult↗

PubMed1998

Sonochemicals increase the mutation frequency of V79 cells in vitro.

Phosphate buffered saline (PBS) was insonated or sham-insonated (1 MHz, 35 W/cm2, continuous wave, 30 min) in rotating (200 rpm) sterile polystyrene culture tubes. After treatment, the PBS was used immediately to suspend washed Chinese hamster V79 cells in vitro. Cells were incubated in the PBS at 37 degrees C for 15 min and then transferred to complete growth medium. Some insonation regimens also involved the inclusion of Albunex (ALX; an ultrasound microbubble contrast agent) to enhance ultrasound-induced inertial cavitation. Following exposure to the pretreated PBS and 6 d of subculture in complete medium, the cells were assayed for plating efficiencies and mutation frequencies (resistance to 6-thioguanine). X-rays (3 Gy) served as a positive control. Cells exposed to insonated PBS with or without ALX or x-rays had statistically significantly elevated mean mutation frequencies (4.37+/-0.97, 4.54+/-1.00, and 24.28+/-3.83 mutant colonies/10(6) viable cells, respectively) relative to corresponding control regimens (ultrasound sham, 2.44+/-0.56; x-ray sham, 2.96+/-0.88 mutant colonies/10(6) viable cells. The data supported the hypothesis that sonochemicals resulting from inertial cavitation have mutagenic potential.

Albumins↗

PubMed1998

Improved investigation of portal-hepatic veins by echo-enhanced Doppler sonography.

Microbubbles of air released from a galactose vehicle (Levovist) amplify the intensity of Doppler signals. They survive both pulmonary and systemic capillary passage, leading to echo enhancement in the entire vascular system. The aim of this study was to investigate this agent in patients with liver disease and insufficient Doppler signals. A total of 275 Doppler examinations were performed in 176 patients; 20 of these patients could not be studied conventionally due to bowel gas, obesity or noncompliance. They received Levovist to examine portal or hepatic veins or TIPS patency. Angiography, computed tomography (CT) scan or magnetic resonance tomographic angiography (MRTA) was performed subsequently as a control. After administration of Levovist, portal or hepatic veins and TIPS patency could be unequivocally assessed in 18 of the 20 patients. In two patients, suspected occlusion of the portal vein was disproved because the diagnosis was not confirmed later. Only minor adverse effects were encountered. Echo-enhanced Doppler sonography with Levovist is well tolerated. Further study of the value of Levovist for the assessment of portal-hepatic vessels not amenable to conventional Doppler sonography is justified.

Contrast Media↗