SEARCH · PubMed Health

Results for “Microbubbles”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,711 records · Page 95Linked to original sources

PubMed1994

Ultrasound contrast agents in radiological diagnosis.

Contrast enhancement is widely applied to vascular imaging and has become a routine part of diagnostic X-ray, CT, MR and radionuclide methods for vascular diagnosis. Colour Doppler imaging, although offering a unique method for non-invasive vascular imaging, suffers limitations determined by the low velocity of blood in small vessels and the weakness of backscattered ultrasound from blood deep in the body. While the low velocity of blood in small vessels remains a fundamental obstacle, there is clear clinical potential for a method capable of enhancing the acoustic backscatter from blood itself, especially in the systemic arterial system, by means of an ultrasound contrast agent. In this paper, studies are made on a stabilized microbubble contrast agent capable of undergoing resonant oscillation in the ultrasound field used to create an image. The effect on this resonant behaviour is that very small quantities of the contrast agent in the systemic arterial circulation can produce outstanding enhancement of Doppler ultrasound signals from major and peripheral arteries. In addition, nonlinear oscillation of these bubbles makes possible an entirely new form of imaging, referred to here as harmonic imaging. It is felt that the use of these contrast agents will enable detection of smaller vessels in the arterial and venous circulation than is currently possible, of neovascular flow associated with malignant tumours, wound healing and possibly the measurement of blood flow rates in such tissues as the myocardium. Harmonic imaging adds to this capability by effectively subtracting Doppler signals from moving solid tissue, thus lowering the threshold of detectable velocity in the vascular system.

Animals↗

PubMed1993

[Anterograde and retrograde cardioplegia in myocardial revascularization. An intraoperative contrast echographic study].

The aim of this study was to assess the distribution of antegrade and retrograde cardioplegia with intraoperative contrast echocardiography in patients undergoing coronary artery bypass grafting. Fifteen patients with chronic stable angina pectoris and severe coronary artery disease were studied. The severity of coronary artery disease was assessed at coronary angiography, using the Jeopardy Score System. The presence and the extent of collateral circulation was evaluated on the basis of preoperative coronary angiography and graded as: absent or poor; good or excellent. Coronary revascularization was carried out during extracorporeal circulation and myocardial protection was performed with antegrade (aortic root) and retrograde (right atrial) cardioplegia. The echo contrast agent was sterilely prepared 1 hour prior to surgery and consisted of a solution of sonicated 5% human albumin microbubbles. Two ml of sonicated albumin were injected along with antegrade cardioplegia and 4 ml with retrograde cardioplegia. The echocardiographic images were obtained with transesophageal echocardiography in the transgastric left ventricular short-axis view. Images were recorded on videotape for off-line planimetric measurement of percent myocardial opacification. Data were analyzed with the analysis of variance. Multiple comparisons were made with Student's paired t test and using Bonferroni's correction. Myocardial opacification was 58.9 +/- 12.9% during antegrade cardioplegia and 77.5 +/- 16.4% during retrograde cardioplegia (p = 0.003). This overall difference was mainly due to the impact of collateral circulation in the distribution of antegrade cardioplegia. Patients with absent or poor collateral circulation showed a lower degree of myocardial opacification than patients with good or excellent myocardial opacification (44.3 +/- 12.0% versus 64.2 +/- 8.6%; p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1993

[CO2US via an implantable port--drug distribution in intraarterial chemotherapy for hepatic tumors and evaluation of effect].

The distribution of blood flow was determined from the distribution of CO2 by US performed during the infusion of CO2 microbubbles via an implantable port (IP-CO2US) in intraarterial chemotherapy for hepatic tumor, and the usefulness of this method in determining tumor vascularity and evaluating the effects of therapy was investigated. A total of 16 patients, 12 of whom had metastatic liver tumor, two hepatocellular carcinoma, one gall bladder carcinoma, and one cholangiocellular carcinoma were studied. The enhanced areas in the liver in 16 patients in whom IP-CO2US was performed a total of 24 times were consistent in all cases with the enhanced areas demonstrated by IP-RI angiography performed a total of 10 times within 10 days, and were also consistent with one exception with the enhanced areas demonstrated by IP-CTA performed 14 times. The tumor detection rate was markedly higher with IP-CO2US than with plain US or IP-DSA, and was similar to that of IP-CTA. Evaluation of the vascularity of individual nodules by IP-CO2US surpassed that by IP-DSA, and was similar to that of IP-CTA. It was demonstrated that blood flow distribution (intrahepatic drug distribution) can be equally well grasped with IP-CO2US, which is a simple and convenient method, as with IP-RI angiography. It was also suggested that IP-CO2US is useful in the evaluation of tumor vascularity and the effect of therapy.

Antineoplastic Agents↗

PubMed1993

Myocardial distribution of cardioplegic solution after retrograde delivery in patients undergoing cardiac surgical procedures.

The myocardial distribution of both antegrade and retrograde cardioplegia for cardiac surgical intervention, after induction of cardioplegia via the aortic root, was directly assessed and compared in 19 patients by means of contrast echocardiography. Two-dimensional transesophageal echocardiographic images of the short axis of the left ventricle at the level of the papillary muscles were obtained after sonicated Renografin-76 microbubbles were injected into an aortic root and/or transatrial coronary sinus catheter during delivery of cardioplegic solution. Segmental distribution of cardioplegic solution was immediately noted in the myocardium at the time of contrast injections. In 11 of 18 patients (61%) cardioplegic solution was dispersed to all left ventricular myocardial segments after antegrade delivery. In 17 of 19 patients (90%) retrogradely delivered cardioplegic solution (after antegrade induction of cardioplegia in 18 of the 19 patients) was dispersed to all the left ventricular myocardial segments, including the septum. In 2 of the patients, initial lack of retrograde distribution of cardioplegic solution was remedied when the coronary sinus catheter was repositioned and contrast cardioplegic solution was reinjected. Imaging of the right ventricle was possible in only 4 of the 19 patients and revealed that after retrograde delivery, cardioplegic solution had been at least partially distributed to the right ventricle as well. We performed off-line videodensitometric analysis in 9 patients after retrograde delivery of cardioplegic solution. Mean peak pixel-intensity ratio of flow from the endocardium to the epicardium in the left ventricular free wall was 1.46 +/- 0.27, and mean peak pixel-intensity ratio of flow from the left to the right intraventricular septal endocardium was 1.39 +/- 0.33 (p < or = 0.05).

Aged↗

PubMed1995

A novel variable-gravity simulation method: potential for astronaut training.

Zero gravity conditions for astronaut training have traditionally used neutral buoyancy tanks, and with such tanks hypogravity conditions are produced by the use of supplemental weights. This technique does not allow for the influence of water viscosity on any reduced gravity exercise regime. With a water-foam fluid produced by using a microbubble air flow together with surface active agents to prevent bubble agglomeration, it has been found possible to simulate a range of gravity conditions without the need for supplemental weights and additionally with a substantial reduction in the resulting fluid viscosity. This new technique appears to have application in improving the simulation environment for astronaut training under the reduced gravity conditions to be found on the moon or on Mars, and may have terrestrial applications in patient rehabilitation and exercise as well.

Astronauts↗

PubMed1996

Non-invasive screening for renal artery stenosis with ultrasound contrast enhancement.

OBJECTIVE: Our aim was to evaluate duplex ultrasound imaging in the identification of renal artery stenosis using a new technique to enhance the recorded Doppler signal. DESIGN: Colour Doppler studies of interlobar renal arteries were performed before and after enhancement using an intravenous contrast of galactose microparticle suspension containing microbubbles (Levovist, Schering) in patients with angiographically confirmed renal artery stenosis. SETTING: Blood Pressure Unit, St. George's Hospital Medical School, and Department of Radiology. The Middlesex Hospital, London, UK. PARTICIPANTS: Twenty-one consecutive hypertensive patients in whom the diagnosis of renal artery stenosis was made on digital subtraction angiography. MAIN OUTCOME MEASURES: The diagnosis of haemodynamically significant renal artery stenosis (> or = 60% on angiography). RESULTS: With Levovist, there was a 20 db increase in the Doppler intensity and, as a result, intrarenal signals were much more clearly delineated and distinct spectral waveforms were obtained from all but one kidney, which was occluded. Significant associations were found between the degree of stenosis (as assessed by angiography) and the following Doppler parameters: diastolic velocity (F = 7.6; P < 0.01), acceleration time (F = 33.5, < 0.0001), peak systolic velocity (F = 37.7, P < 0.0001) and acceleration (F = 60.0; P < 0.0001). Without enhancement, there were five false-positive and two false-negative examinations (sensitivity 85%; specificity 79%) using the acceleration cut-off value of 3.5 m/s2 to identify haemodynamically significant renal artery stenosis (> or = 60% on angiography). After contrast enhancement, there were only three false-positive and one false-negative examinations (sensitivity 94% and specificity of 88%) using the acceleration cut-off value of 3.75 m/s2 and the examination time was reduced by approximately half (sensitivity and specificity of 90% using the acceleration cut-off value of 3.5 m/s2). CONCLUSIONS: Our results suggest that renal duplex scanning using contrast enhancement is a promising new non-invasive technique in screening patients with suspected renal artery stenosis. Contrast enhancement produces more reproducible spectral waveforms, improves accuracy and halves the examination time.

Adult↗

PubMed1996

Acute ventilatory response to simulated altitude, normobaric hypoxia, and hypobaria.

BACKGROUND: Some reports claim that ventilation (VE) is greater in human subjects in normobaric hypoxia than at altitude following an equivalent drop in inspired PO2 (PIO2). It has been suggested that reduced barometric pressure (PB) may decrease chemoreceptor sensitivity and account for these results. In this pilot study we tested the hypothesis that VE and hypoxic chemoresponsiveness would not be different after 30 min of normobaric hypoxia and altitude. METHODS: We exposed three male and three female subjects to four conditions in an environmental chamber, varying the order. The four conditions were: air (PB = 640, FIO2 = 0.204), hypobaria (434, 0.298), hypoxia (640, 0.141) and altitude (434, 0.203). We measured VE, end-tidal O2 and CO2 and arterial O2 saturation (SpO2) after 30 min in each environment, and while breathing 100% O2 for 1 min immediately thereafter. RESULTS: The mean increase in VE relative to air was 14%, 20% and 26% for hypobaria, hypoxia and altitude, respectively, with corresponding reductions in PETCO2 in the three conditions. The reduction in VE with 100% O2 was inversely proportional to the rise in SpO2 in all cases, indicating that chemoresponsiveness was unchanged by PB. When hypobaria preceded altitude, the VE at altitude increased less, relative to air, than when altitude was given first (not significant). CONCLUSIONS: The VE and chemosensitivity are about the same after 30 min of altitude and equivalent hypoxia. However, when the drop in PIO2 is not synchronous with the drop in PB, like at altitude, the VE values may be altered. Air density, hypoxic pulmonary vasoconstriction and circulating microbubbles may interact to account for the observed findings.

Adult↗

PubMed1996

Two-dimensional and Doppler echocardiographic abnormalities in idiopathic dilatation of the pulmonary artery.

Although idiopathic dilatation of the pulmonary artery is uncommon, it requires to be distinguished from other important congenital heart diseases for which it may be confused clinically. We describe the two-dimensional (2D) and Doppler echocardiographic findings in two patients with this condition. Enlargement of the main pulmonary artery and right ventricle was demonstrated in both patients using 2D echocardiography. Pulmonary regurgitation was confirmed in Case 1 by both pulsed-Doppler echocardiographic and Doppler colour flow imaging studies and in Case 2 by microbubbles (which were generated from saline-injection into a peripheral vein) oscillating up and down across the pulmonary valve in systole and diastole respectively.

Adult↗

PubMed1996

[The membrane oxygenator].

Researches in blood oxygenation through a membrane, in an extracorporal circuit, with the physiological flow of an adult and an oxygen saturation have led up, by experimental way, to use dissolved oxygen. The membrane is a plastic microporous film coating a strong textile support which constitutes a cylindrical rotor. The rotor micropores are crossed through by a pH 7.4 phosphate buffer aerosol which conveys the oxygen. This aerosol is dropped in the revolving rotor. Venous blood which spreads out on the external surface of the rotor is immediately hematosed in contact with the atmospheric pressure with free release of carbon dioxide without microbubbles formation. The low pressure which prevails in the rotor is maintained only when the membrane is hydrated by the aerosol. To do that, it is enough to maintain the hydratation by a buffer drip: one drop per second can be enough. During the high flow open-heart operation of an adult patient, the curves of physiological constants remain normal. The membrane is perfectly stable during the period it is used. In France, according to François de Gaudard d'Allaines, this equipment has allowed "the adult first open-heart operation with extracorporal circulation" (1958). About sixty operations have been realized under the responsibility of François de Gaudard d'Allaines and myself.

Extracorporeal Circulation↗

PubMed1997

[Doppler color ultrasonography with contrast media in the study of eye and orbit neoplasms].

We investigated the diagnostic efficacy of the i.v. administration of a sonography (US) contrast agent to study eye and orbit tumors at different stages. We administered Levovist (Schering), an air microbubble stabilized by fatty acid, which is specific for angiographic indications. Baseline color Doppler US was performed on 24 selected patients and tumor vascularization patterns were classified into three classes. Color Doppler signal enhancement was assessed after contrast agent administration and the signal-to-noise ratio (SNR) was improved in 70% of cases, which helped identify vascular patterns and improved flowmetric accuracy. The Doppler effect was also improved and vascular signal was always enhanced. The SNR was improved also by the postcontrast detection of small vessels missed on baseline scans. Doppler signal enhancement was proportional to precontrast vascularization and depended on tumor size, with poor results in lesions < 5 mm. In contrast, vascular signal spots with increased postcontrast echogenicity sometimes caused excessive noise affecting the results. No correlation was found between signal enhancement and lesion histotype or between signal and lesion site. Treated lesions exhibited poorer contrast agent enhancement. The examination technique must be accurate and the various parameters set optimally, especially the velocity scale, gain and filtration; the unit must feature adequate recording capabilities (mm/s). To conclude, we believe that the routine use of i.v. US contrast agents will play a major role in improving diagnostic imaging in oculistics also thanks to the lack of untoward reactions and to the ease of contrast agent preparation.

Adult↗

PubMed1997

[Multiple fistulae in coronary artery of left ventricle].

A 51 year-old man was admitted to the coronary care unit due an episode of retroestenal pain with ischaemic alterations in electrocardiogram. It was made the diagnosis of unstable angina. Cinecoronariography showed dilated coronary arteries without obstructions and multiples coronary fistulas draining into left ventricular cavity. Transesophagic echocardiogram with microbubbles injection into coronary arteries showed an important coronary steal phenomena. It is discussed the diagnosis and the treatment. This is one of the rare cases of coronary fistulas draining into the left ventricular cavity and the first one with alterations in the rest ECG.

Cineangiography↗

PubMed1998

[Levovist].

SH/TA-508 (Levovist) is agglomerates of microparticles consisting of galactose (99.9%) and palmitic acid (0.1%), and the active entity is the microbubbles stabilized by palmitic acid which covers the bubbles. SH/TA-508 micro-bubbles are stable under high-pressure condition and they circulate the whole body for several minutes along with blood flow after the intravenous injection. The left sided cardiac cavities and arteries are clearly opacified by using this contrast agent and the Doppler signals from the mitral, aortic and pulmonic vein are also enhanced significantly. Also microcirculating flow image of the liver, kidney and other organs are well enhanced in the clinical studies. SH/TA-508 improves the capability of ultrasound diagnosis.

Contrast Media↗

PubMed1998

[Flash echo imaging].

Ultrasound transmission sometimes limits the lifetime of microbubble-based contrast agents. At this time, a very large echo signal (like a flash) is obtained for the initial transmission of the ultrasound after several seconds' suspension. Flash Echo Imaging (FEI) is a new technique which uses the signals of the bubble's collapse. This paper explains a principle of FEI and functions of the FEI's application for ultrasound diagnostic system. It is also shown that perfusion of the tissue can be visualized by using FEI methods.

Animals↗

PubMed1998

[Myocardial contrast echocardiography as a potential diagnostic tool for the assessment of myocardial perfusion].

Myocardial contrast echocardiography (MCE) visualizes the spatial distribution of myocardial blood flow with the injection of microbubbles into the coronary artery. With MCE, we can easily assess the perfusion territory of the coronary artery and collateral circulation as positive contrast area and the risk area as contrast defects. In patients with acute myocardial infarction (AMI), we can assess the success of coronary reperfusion at the microcirculation level. Some patients with AMI manifest sizable contrast defects after reperfusion, called no-reflow phenomenon. This phenomenon identifies patients with poor functional and clinical outcomes among reperfused patients. Thus, MCE provided an useful method of assessing myocardial perfusion dynamics as well as myocardial viability in clinical setting.

Collateral Circulation↗

PubMed1998

[Transarterial enhanced ultrasonography examination of hepatocellular carcinoma using CO2].

The findings of enhanced ultrasonography under the injection of microbubbles of carbon dioxide into a hepatic artery (CO2-US) were evaluated in the patients with hepatocellular carcinoma (HCC). They were as follows. Most nodules showed early (within 3 seconds) stronger enhancement compared to the surrounding hepatic parenchyma, remaining the enhancing effects more longer than the surround. A few nodule showed isoenhance or nonenhancement. However, metastatic cancer of the liver often showed the early enhancement only at the edge of tumor. In hepatic hemangioma, only the spotty enhancement in the tumor and or the later (later than 4 seconds) enhancement at the edge of tumor was showed. The hyperenhanced mass was detected more often in a larger HCC and revealed to be a relatively poorly differentiated HCC with the capsule formation.

Carbon Dioxide↗

PubMed1998

[The diagnosis of the early stage of hepatocellular carcinoma by US-angiography with intraarterial Albunex (sonicated serum albumin) infusion].

Contrast-enhanced ultrasonography (arterial infusion) has been clinically established as a qualitative diagnosis imaging tool for hepatocellular carcinoma (HCC). Contrast-enhanced ultrasonography (CEUS) was performed after of Albunex (sonicated serum albumin) or Carbon Dioxide (CO2) microbubble by hand, into the hepatic artery as a diagnostic modality for the early HCC. Here, we discussed the diagnosis of the early HCC by CEUS using Albunex as a contrast medium. Briefly, a diagnosis of the early HCC was made CEUS examination of the hemodynamics of the arteries showed a hypovascular pattern. And tumor size was under 20 mm in diameter, the histopathologic examination was essential to reach a final diagnosis, well-differentiated HCC.

Albumins↗

PubMed1998

[Contrast-enhanced power Doppler imaging of the liver--preliminary animal study].

PURPOSE: To evaluate efficacy of contrast-enhanced power Doppler imaging of the liver. MATERIALS AND METHODS: We administered two kinds of contrast agents, SHU-508 (Schering AG, Germany) and FS069 (MBI, USA), intravenously to woodchucks with hepatocellular carcinomas. Power Doppler imaging of the liver was performed. To obtain minute hemodynamic information of the liver, we tried continuous infusion of contrast agents and flash echo mode (intermittent scanning) on power Doppler imaging. RESULTS: When we administered continuously contrast agents, the enhancement increased gradually and lasted until the end of the infusion. To compare with bolus injection, we were able to detect blood flow of the liver more clearly and easily without saturation artifacts. On power Doppler flash echo imaging of three or five seconds suspension, signals from only arterial flow were obtained. In comparison on seven seconds suspension imaging, signals from both arterial and portal flow were obtained. With flash echo mode, we could acquire the information of blood perfusion to depict the signals from eliminated microbubbles. CONCLUSION: With continuous infusion and flash echo mode on contrast-enhanced power Doppler imaging, we could get more detailed information of blood flow and perfusion of the liver. This method is expected to be useful for the diagnosis of liver tumor in clinical settings.

Albumins↗

PubMed1998

[Enhanced ultrasonography in the diagnosis of renal tumors].

At present, we have two methods of enhanced ultrasonography in the diagnosis of renal tumors. One is the ultrasound B-mode imaging enhancement under renal arterial infusion of carbon dioxide microbubbles, a contrast agent for US, and the other is the color Doppler signal enhancement under intra-venous injection of galactose-based echo contrast agent, SH/TA-508. Renal cell carcinoma were imaged from the very beginning of the injection of CO2 through the time complete washout from the kidney. On the other, intra-tumor color Doppler signals were remakedly emphasized after SH/TA-508 administration. Enhanced ultrasonography is useful in the detection of small renal cell carcinoma and differential diagnosis of renal masses.

Aged↗