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At least 811 records · Page 45Linked to original sources

PubMed2002

The magnitude of radiation force on ultrasound contrast agents.

High-speed photography of insonified bubbles with a time resolution of 10 ns allows observations of translation due to radiation force, in addition to the visualization of radial oscillations. A modified version of the Rayleigh-Plesset equation is used to estimate the radius-time behavior of insonified microbubbles, and the accuracy of this model is verified experimentally. The translation of insonified microbubbles is calculated using a differential equation relating the acceleration of the bubble to the forces due to acoustic radiation and the drag imposed by the fluid. Simulations and experiments indicate that microbubbles translate significant distances with clinically relevant parameters. A 1.5 micron radius contrast agent can translate over 5 microns during a single 20-cycle, 2.25 MHz, 380 kPa acoustic pulse, achieving velocities over 0.5 m/s. Therefore, radiation force should be considered during an ultrasonic examination because of the possibility of influencing the position and flow velocity of the contrast agents with the interrogating acoustic beam.

Contrast Media↗

PubMed1998

Variables controlling contrast generation in a urinary bladder model.

An ultrasound system has been developed to generate microbubbles in vivo for use as ultrasound contrast agent. Possible application include diagnosis of reflux in the urinary tract. In experiments designed to elucidate the contrast microbubble generation process, acoustic bursts (at 1.8 MHz, 125 ms) were propagated through a latex rubber balloon, modeled after a rabbit urinary bladder, containing fluids of various air and carbon dioxide saturations and concentrations of cavitation nuclei (0.198-micron-diam polystyrene particles). The peak rarefactional pressure threshold for contrast microbubble generation, as visualized with a diagnostic ultrasound system, decreased approximately a factor of 2 for increasing particle concentration from 10(8) to 10(10) particles/cc, with the lowest threshold of 5.24 MPa. For samples with gas saturations below 50% and 10(10) particles/cc, the average thresholds were at least twice as high as those of more saturated fluids (with mean threshold for saturated fluids of 6.45 MPa), and samples containing CO2 had considerably lower thresholds than respective under-saturations in air. At a fixed pressure amplitude, echogenicity tended to increase with both increasing particle concentration and gas saturation; this was more favorable for samples containing CO2. Even in a restricted-nuclei environment such as the urinary bladder, generation of vaporous cavitation should be possible; however, subsequently, abundant gas is needed to grow vaporous bubbles to persistent and imageable sizes, to assist in the diagnosis of urinary reflux.

Animals↗

PubMed2000

Modeling of high-intensity focused ultrasound-induced lesions in the presence of cavitation bubbles

The classical "Bio Heat Transfer Equation (BHTE)" model is adapted to take into account the effects of oscillating microbubbles that occur naturally in the tissue during high-intensity focused ultrasound (HIFU) treatment. First, the Gilmore-Akulichev model is used to quantify the acoustic pressure scattered by microbubbles submitted to HIFU. Because this scattered pressure is not monochromatic, the concept of harmonic attenuation is introduced and a global attenuation coefficient is estimated for bubble-filled tissues. The first results show that this global attenuation coefficient varies significantly with respect to several parameters such as the frequency and the density of microbubbles in the medium, but also with respect to the incident acoustic pressure which thus becomes a transcendental function. Under these conditions, a layer-by-layer modeling, in the direction of propagation, is proposed to calculate the ultrasonic beam. Finally, the BHTE is solved and the HIFU-induced lesions are estimated by the calculation of the thermal dose. Using this model, it can be observed first that, when the firing power increases, the lesion develops clearly in the direction of the transducer, with a shape agreeing with in vivo experimentation. Next, it is observed that the lesion can be significantly modified in size and position, if an interface (skin or inner wall) is simulated as a zone with multiple cavitation nuclei. With a firing power increase, it is also shown how a secondary lesion can appear at the interface and how, beyond a certain threshold, this lesion develops at the main lesion expense. Finally, a better in-depth homogeneity of lesions is observed when the acoustic frequency of HIFU is increased.

Journal Article↗

PubMed2003

Kinetics of a US contrast agent in benign and malignant adnexal tumors.

PURPOSE: To evaluate the effects of a microbubble contrast agent on the power Doppler ultrasonographic (US) examination of adnexal tumors, with a special focus on the timing of the transit of the microbubble bolus. MATERIALS AND METHODS: Seventy patients who were suspected of having ovarian tumors were examined preoperatively with contrast material-enhanced US. Images obtained during a 5-minute examination were stored digitally, and the behavior of the contrast agent was evaluated objectively with measurement of the time-dependent image intensity at the region of interest with a computer program. A time-intensity curve in each case was derived and analyzed. The Mann-Whitney U test was used to compare intensity changes and tumor parameters in benign and malignant adnexal tumors. RESULTS: Both the baseline and maximum power Doppler intensities, as well as the absolute and relative (percent) rise in intensity, were significantly higher (P <.001) in malignant as compared with benign tumors. The arrival time was shorter (17.5 vs 22.5 seconds; P =.005) and the duration of contrast agent effect was longer (190.4 vs 103.6 seconds; P <.001) in malignant tumors than they were in benign tumors. The area under the time-intensity curve was significantly greater in malignant tumors compared with that in benign tumors (P <.001). CONCLUSION: After microbubble contrast agent injection, malignant and benign adnexal lesions behave differently in degree, onset, and duration of Doppler US enhancement.

Adnexal Diseases↗

PubMed2005

Heating and coagulation volume obtained with high-intensity focused ultrasound therapy: comparison of perflutren protein-type A microspheres and MRX-133 in rabbits.

PURPOSE: To compare the efficiency of different microbubble contrast agents in the heating and coagulation of rabbit liver tissue by using high-intensity focused ultrasound therapy. MATERIALS AND METHODS: The use of and protocols for Japan white rabbits were approved by the University of Tokyo Committee on Animal Resources. In vitro experiments were conducted in a 1-mL cylindric space of polyacrylamide gel, which contained different microbubble contrast agents (MRX-133 or perflutren protein-type A microspheres). In vivo experiments were performed in six Japan white rabbits (two for the perflutren protein-type A microsphere group, two for the MRX-133 group, and two for the control group). In each rabbit, the liver was directly subjected to high-intensity focused ultrasound after intravenous injection of different microbubble contrast agents. Natural saline was used as a control. High-intensity focused ultrasound was applied for 30 seconds by using a 2.18-MHz transducer, and the temperature increase and volume of coagulation necrosis were evaluated. Statistical analysis was performed by using an analysis of variance test, which was followed by a Student-Newman-Keuls test; a P value of <.05 was considered to indicate a statistically significant difference. RESULTS: In the MRX-133 group, the mean temperature increase was significantly greater and faster than that in the control group (P < .01) or in the perflutren protein-type A microsphere group (P < .05). In the perflutren protein-type A microsphere group, the mean temperature increase was greater and faster than that of the control group (P < .01) for both in vitro and in vivo experiments. The mean volume of the coagulation necrosis lesion was 117.9 mm3 +/- 48.4 (+/-standard deviation) for the MRX-133 group, 45.4 mm3 +/- 24.9 for the perflutren protein-type A microsphere group, and 17.7 mm3 +/- 9.0 for the control group. In the MRX-133 group, the mean volume of coagulation necrosis was significantly greater than that of the control or the perflutren protein-type A microsphere group (P < .01), and in the perflutren protein-type A microsphere group, the volume of coagulation necrosis was greater than that of the control group (P < .05). CONCLUSION: MRX-133 had greater efficiency than perflutren protein-type A microspheres in high-intensity focused ultrasound-induced heating and coagulation of rabbit liver tissue.

Animals↗

PubMed2000

Hepatic tumors: contrast agent-enhancement patterns with pulse-inversion harmonic US.

PURPOSE: To evaluate contrast agent-enhancement patterns in hepatic hemangiomas, hepatic metastases, and hepatocellular carcinomas (HCCs) at pulse-inversion harmonic ultrasonography (US) with a microbubble contrast agent. MATERIALS AND METHODS: Twenty hepatic hemangiomas in 20 patients and 41 malignant hepatic tumors in 23 patients (33 metastases and eight HCCs) were evaluated with pulse-inversion harmonic US. US images were obtained before injection and every 10-15 seconds after injection of a 4-g bolus (300 mg/mL) of SH U 508A (a microbubble contrast agent) for 5 minutes. The contrast-enhancement patterns of 61 hepatic lesions were assessed. RESULTS: Of 20 hemangiomas, 19 revealed peripheral enhancement, which was globular in 14 (70%) and rimlike in five (25%), with centripetal fill-in; the remaining one (5%) showed homogeneous enhancement. In 33 metastases, the enhancement was rimlike in 16 (48%), homogeneous in seven (21%), and stippled in two (6%); in the remaining eight metastases (24%), no enhancement was seen. Of eight HCCs, four (50%) showed homogeneous enhancement and the remaining four (50%) showed heterogeneous enhancement. Centripetal fill-in of lesions with intratumoral enhancement was not seen in any malignancy. CONCLUSION: Pulse-inversion harmonic US with a microbubble contrast agent is potentially useful for the specific diagnosis of hemangiomas that demonstrate characteristic enhancement features.

Adult↗

PubMed2002

Noninvasive imaging of myocardial reperfusion injury using leukocyte-targeted contrast echocardiography.

BACKGROUND: We hypothesized that myocardial contrast echocardiography (MCE) with leukocyte-targeted microbubbles could temporally and spatially characterize the severity of postischemic myocardial inflammation. METHODS AND RESULTS: In 9 open-chest dogs, either the left anterior descending or left circumflex coronary artery was occluded for 90 minutes (n=6), while the remaining dogs served as non-ischemic controls. During occlusion, MCE was performed to determine the risk area (RA) and regions supplied by collateral flow. Myocardial inflammation was assessed 5, 60, and 120 minutes after reflow by MCE imaging of leukocyte-targeted (phosphatidylserine-containing) lipid microbubbles. The spatial extent and severity of inflammation were also assessed by radionuclide imaging of the neutrophil-avid tracer 99mTcRP517 and tissue myeloperoxidase activity. Early after reflow, MCE detected inflammation throughout the entire risk area, the extent of which decreased over time due to reduced signal in collateral-supplied regions. The spatial extent of inflammation late after reflow was similar for MCE and radionuclide imaging. The severity of inflammation in the infarct zone, the noninfarcted risk area, and collateral-supplied territories determined by quantitative MCE correlated well with myeloperoxidase activity (r=0.81). CONCLUSIONS: MCE with leukocyte-targeted microbubbles can temporally assess the severity and extent of postischemic myocardial inflammation and could be used to evaluate new treatment strategies designed to limit inflammation in acute coronary syndromes.

Animals↗

PubMed1993

A transpulmonary contrast medium enhances the transcranial Doppler signal in humans.

BACKGROUND AND PURPOSE: Transtemporal insonation in transcranial Doppler sonography is often impaired by an insufficient signal-to-noise ratio, especially in elderly patients. A transpulmonary stable air microbubble suspension was injected intravenously in humans as an intracranial ultrasonic contrast agent. METHODS: In a clinical phase II study, 20 patients (15 women, 5 men; mean age, 65.5 +/- 11.5 years) presenting with clinical indications for transcranial Doppler investigation were examined. A total of 97 intravenous injections with different concentrations (200, 300, and 400 mg/mL of suspension) of air microbubbles bound to galactose microparticles as a carrier were performed. The signal enhancement of color-coded pulse curves of basal cerebral arteries was evaluated off-line in comparison to an integrated color-coded decibel scale, considering quality, quantity, and time course of enhancement requiring a 3-dB level above the native signal. The overall diagnostic information was assessed according to a reliability score. RESULTS: The first acoustic signal increase was registered after an average of 21 seconds. Time intervals for a dose-dependent peak intensity and maximal duration were 41.3 +/- 17.1 seconds and 118.0 +/- 69.8 seconds (200 mg/mL); 55.5 +/- 27.7 seconds and 237.0 +/- 112.3 seconds (300 mg/mL); and 66.1 +/- 31.8 seconds and 293.0 +/- 122.0 seconds (400 mg/mL), respectively. Duration of signal enhancement increased significantly (P < .05) with higher concentrations. The extent of signal enhancement during the whole pulse curve reached an average of 9.1 +/- 5.0 dB for 200 mg/mL, 12.0 +/- 5.4 dB for 300 mg/mL (significant on P < .05 level), and 13.1 +/- 5.6 dB for 400 mg/mL concentration (P = NS). Respective maximal intensity spots reached 17.5 +/- 6.0, 20.7 +/- 5.5, and 22.7 +/- 5.9 dB for increasing concentrations, respectively. Overall visual assessment of enhanced pulse curves for diagnostic reliability showed a sufficient result in 38.1% of all injections with 200 mg/mL, in 88.6% with 300 mg/mL, and in 84.2% with 400 mg/mL concentration. Minimal side effects occurring in 12.4% of all injections were all reversible. CONCLUSIONS: Transpulmonary stable air microbubbles bound to a galactose carrier represent a useful and safe contrast agent in case of an insufficient native signal in transcranial Doppler investigation.

Adult↗

PubMed1996

Patent foramen ovale and transcranial Doppler. Comparison of different procedures.

BACKGROUND AND PURPOSE: The capability of transcranial Doppler sonography (TCD) to detect a patent foramen ovale (PFO) has been established. However, which provocative maneuver and what timing of contrast injection are most effective to induce a right-to-left shunt has not yet been determined. METHODS: We selected 38 cerebrovascular patients (21 men, 17 women) with positive contrast study for PFO on transesophageal echocardiography. Patients underwent a TCD with bilateral monitoring of the middle cerebral arteries (MCAs) and injection of a contrast solution. The injection was repeated (1) during normal breathing (basal conditions); (2) before Valsalva maneuver (VM); (3) during VM; (4) immediately after VM; and (5) during cough. The latency time and the total number of microbubbles for each side were recorded. RESULTS: TCD found positive results for PFO in 30 patients. Twenty were positive even during basal conditions. The number of positive cases varied according to the timing of the VM in relation to the contrast injection: 28, 25, and 27 cases were positive when the injection was performed before, during, and after VM, respectively, while 26 were positive during cough. There were significant differences in the number of microbubbles in the MCAs between the procedures (P < .001, ANOVA): the highest number was detected in the injection before VM and the lowest number during basal conditions (P < .001, Wilcoxon's test with Bonferroni's correction). The latency time was significantly shorter when the injection followed VM. CONCLUSIONS: The injection performed before VM appeared to be the most effective TCD procedure in determining the transit of microbubbles through a PFO and subsequently in the MCAs.

Adult↗

PubMed2005

Assessment of temperature, proximity, and course of the esophagus during radiofrequency ablation within the left atrium.

BACKGROUND: Left atrioesophageal fistula is a devastating complication of atrial fibrillation ablation. There is no standard approach for avoiding this complication, which is caused by thermal injury during ablation. The objectives of this study were to evaluate the course of the esophagus and the temperature within the esophagus during pulmonary vein antrum isolation (PVAI) and correlate these data with esophagus tissue damage. METHODS AND RESULTS: Eight-one patients presenting for PVAI underwent esophagus evaluation that included temperature probe placement. Esophagus course was obtained with computed tomography, 3D imaging (NAVX), or intracardiac echocardiography. For each lesion, the power, catheter and esophagus temperature, location, and presence of microbubbles were recorded. Lesion location and esophagus course were defined with 6 predetermined left atrial anatomic segments. Endoscopy evaluated tissue changes during and after PVAI. Of 81 patients, the esophagus coursed near the right pulmonary veins in 23 (28.4%), left pulmonary veins in 31 (38.3%), and mid-posterior wall in 27 (33%). Esophagus temperature was significantly higher during left atrial lesions along its course than with lesions elsewhere (38.9+/-1.4 degrees C, 36.8+/-0.5 degrees C, P<0.01). Lesions that generated microbubbles had higher esophagus temperatures than those without (39.3+/-1.5 degrees C, 38.5+/-0.9 degrees C, P<0.01). Power was not predictive of esophagus temperatures. Distance between the esophagus and left atrium was 4.4+/-1.2 mm. CONCLUSIONS: Lesions near the course of the esophagus that generated microbubbles significantly increased esophagus temperature compared with lesions that did not. Power did not correlate with esophagus temperatures. Esophagus variability makes the avoidance of lesions along its course difficult. Rather than avoiding posterior lesions, emphasis could be placed on better esophagus monitoring for creation of safer lesions.

Adult↗

PubMed2000

Influence of the ultrasound contrast agent Levovist on human nailfold capillary microcirculation.

Little is known about the behavior of ultrasound contrast microbubbles in human capillaries. The evaluation of circulatory effects of echo contrast media may bring valuable information for the interpretation of echo contrast phenomena in the human myocardium. In 12 healthy volunteers (aged 31 +/- 6.7 years; five women), nailfold capillaries were examined by means of TV microscopy. The authors investigated acral microcirculation at rest and after local cold application with and without saccharide-based microbubbles (10 mL Levovist 300 mg/mL IV). The mean blood flow velocity at rest was 1.18 +/- 0.18 mm/s (mean value +/-1 SD) and 1.11 +/- 0.11 mm/s (mean value +/- 1 SD) after the injection of Levovist (ns). One minute after local cold exposure a decrease of the blood flow velocity by 61% before and by 75% after intravenous Levovist was found. In both groups the cold-induced decrease of blood flow velocity was statistically significant (p<0.01), whereas there was no significant difference in flow reaction between the two groups. No wall adhesion of blood cells or extravasation of contrast into the surrounding tissue was detected. After intravenous injection of a regular dose of saccharide-based microbubbles Levovist, no change of blood cell flow velocity and no wall adhesion or extravasation could be found at rest and after cold application in human nailfold capillaries. Since microcirculatory flow characteristics in the finger nailfold capillaries are not influenced by Levovist, it might be assumed also that myocardial blood flow behavior remains unchanged, so that this contrast agent may be used as a flow tracer for cardiac investigation.

Adult↗

PubMed2004

Clinical utility of echocontrast agents in neurosonology.

INTRODUCTION: Neurosonological investigations of the extracranial and intracranial brain supplying arteries are helpful in the assessment of stroke and stroke-prone patients. METHODS: In this paper we review the indications, application and advantages of second-generation (gas-filled) microbubble contrast agents such as SonoVue. RESULTS: Gas-filled microbubbles have a strong echo enhancing effect and produce enhancement for several minutes, enabling the sonographer to perform the investigation with a single injection or two or three repeated injections without the need for continuous administration. Echocontrast agents provide better delineation of normal blood flow, occlusions, pseudo-occlusions, stenoses, and collaterals in the extracranial and intracranial vascular beds. They are of particular value during transcranial color-coded transcranial duplex investigations via the temporal and occipital window. CONCLUSIONS: Echocontrast agents give additional information on the patient's vascular situation that is often crucial to planning further diagnostic and therapeutic steps. The use of second-generation gas-filled microbubbles, such as SonoVue in transcranial neurosonology, may help to avoid unnecessary, expensive and potentially harmful additional investigations such as intra-arterial DSA. Future applications include the visualization of brain tissue perfusion.

Cerebrovascular Disorders↗

PubMed2002

A new method for evaluation of split renal cortical blood flow with contrast echography.

The recent development of contrast echography has made renal enhancement possible through an intravenous injection of microbubble-based contrast. In animal models, tissue perfusion can be quantified using contrast echography by measurement of the rate at which microbubbles replenish tissue after their ultrasound-induced destruction. Our purpose in this study was to evaluate renal blood flow with contrast echography in humans. To increase the sensitivity for microbubbles, we used a combination of power Doppler harmonic and intermittent imaging. The pulsing interval (PI) was changed from 10 cardiac cycles to 1 cardiac cycle during an intravenous infusion of the contrast agent, and alterations in the intensity of the renal cortex were represented as a decline ratio (DR). In 24 patients with various renal diseases, we were able to observe all 48 kidneys with adequate enhancement of the renal cortex. At PI of 10 cardiac cycles, the enhancement was homogeneous and strong, while, obviously, changing PI from 10 to 1 cardiac cycles caused a decline of enhancement. An excellent correlation was found between DR using contrast echography and renal plasma flow determined by clearance and radionuclide measurements. An excellent correlation was found between the DR values determined by contrast echography and the renal plasma flow values determined using clearance and radionuclide measurements. These results suggest that DR may be useful for evaluation of both total and split renal blood flow. Thus the contrast echographic method presented here could succeed in assessing renal cortical blood flow less invasively than conventional methods in humans.

Adolescent↗

PubMed2004

Ultrasound evaluation of valsartan therapy for renal cortical perfusion.

An increase in renal blood flow with a concomitant decrease in filtration fraction at the onset of angiotensin II receptor blocker treatment has been shown to predict a long-term renoprotective effect. However, no studies are available regarding angiotensin receptor blocker-induced changes in renal cortical perfusion observed in the clinical setting. We have recently developed a convenient method of evaluating human renal cortical blood flow with contrast-enhanced harmonic ultrasonography. The goal of this study was to use this method to examine the effect of valsartan, an angiotensin II receptor blocker, on renal cortical perfusion. We performed intermittent second harmonic imaging with venous infusion of a microbubble contrast agent in 7 healthy volunteers. Contrast-enhanced harmonic ultrasonography performed after oral administration of valsartan (80mg) showed a significant increase in microbubble velocity, which correlated well with the increase in total renal blood flow determined by p-aminohippurate clearance (r=0.950, p < 0.001). Although fractional vascular volume was not significantly increased, alterations in renal cortical blood flow calculated by the product of microbubble velocity and fractional volume were also correlated with the change in total renal blood flow (r=0.756, p < 0.05). These results indicate that valsartan increases the renal cortical blood flow in normal kidneys, mainly by increasing blood flow velocity. Contrast-enhanced harmonic ultrasonography is a promising technique for evaluating the precise effect on renal cortical perfusion and optimal dose of valsartan in diseased kidneys.

Adult↗

PubMed1994

Perfluorocarbon-enhanced sonography: value in detecting acute venous thrombosis in rabbits.

OBJECTIVE: We have previously shown that perfluorocarbon emulsions administered i.v. act as contrast material during sonography by creating moving echoes in veins. Accordingly, we performed a study on rabbits designed to establish the value of perfluorocarbon-enhanced sonography in detecting acute venous thrombi. MATERIALS AND METHODS: Constriction of the inferior vena cava (IVC) just above the renal veins was established surgically in 15 rabbits. Thrombus was induced in the IVC in 10 of these; the other five served as controls. Gray-scale and color Doppler sonography were performed before and after the i.v. infusion of 3 ml/kg of perflubron emulsion (formulation AF0102, Alliance Pharmaceutical, San Diego, CA). Sonograms were evaluated for the presence and extent of thrombus. Three additional rabbits with percutaneously induced IVC thrombosis were studied before and after the i.v. administration of 0.2 ml of a preparation of microbubbles of perfluorocarbon gas (formulation PRD002, Alliance Pharmaceutical). In these animals thrombi were confirmed at autopsy. RESULTS: Unenhanced sonograms allowed detection of thrombi in the IVC in nine of the 10 animals with surgically induced thrombus but were inaccurate in determining clot extent. Filling the lumen of the IVC with moving echoes created by administration of perflubron emulsion allowed more complete delineation of the size and extent of thrombus and permitted detection of residual venous flow not observed on unenhanced scans. The perfluorocarbon gas microbubbles provided similar benefits. CONCLUSION: Our results show that i.v. administration of perflubron emulsion or perfluorocarbon gas microbubbles improves imaging of veins on sonography and may aid in the assessment of thrombi.

Acute Disease↗

PubMed1985

Comparison of bubble release from various types of oxygenators.

A comparative study of microbubble release from various types of oxygenators was performed using ultrasonic Doppler techniques. Bubble count versus amplitude histograms were calculated to derive the statistical distribution of the relative microbubble sizes. To compare the different oxygenators with respect to differences in microbubble releases, several key parameters as, temperature, liquid flow rate, gas to flow relationship, liquid level within the oxygenator, were altered one at a time to indicate different and oxygenator related sensitivities with respect to variations of the key parameters.

Extracorporeal Circulation↗

PubMed2003

Characterization of focal hepatic lesions with contrast-enhanced C-cube gray scale ultrasonography.

AIM: To characterize enhancement patterns of focal hepatic lesions using C-cube gray scale sonography with a microbubble contrast agent and to evaluate its usefulness in differential diagnosis of hepatic lesions. METHODS: Fifty-four patients with 58 focal hepatic lesions were examined with Levovist-enhanced C-cube gray scale sonography. The final diagnosis of hepatic lesions was 29 primary liver cancers, 4 metastases, 8 hemangiomas, 12 focal nodular hyperplasias, 2 inflammatory pseudotumors of the liver and 3 angiomyolipomas. The initiation time of enhancement in various lesions and enhancement duration after administration of contrast agent were compared. Vascular findings in lesions were classified as peripheral enhancement, homogenous enhancement, mosaic enhancement and no enhancement depending on microbubble signals in the lesion relative to the liver parenchyma. RESULTS: The initiation time of enhancement in hemangioma (48+/-12 s) was significantly later compared to other lesions (P<0.05). The enhancement duration of malignancies (69+/-33 s in primary liver cancer, 61+/-23 s in metastasis) was significantly shorter compared to benign lesions (P<0.05). Intranodular enhancement appearing at arterial phase and decreasing at portal venous phase was considered characteristic for malignancy. Intranodular enhancement did not appear earlier than the liver parenchyma, and peripheral enhancement pattern was regarded as positive findings for hemangioma. Intranodular enhancement appeared in the arterial phase, and homogenous enhancement pattern sustained in the whole portal venous phase were regarded as positive findings for focal nodular hyperplasia. No microbubble signals appeared in two inflammatory pseudotumors of the liver. CONCLUSION: C-cube gray scale sonography can demonstrate dynamic intranodular enhancement in various focal hepatic lesions. The information provided by this methodology may be useful in the differential diagnosis of hepatic lesions.

Adult↗

PubMed2003

Renal blood flow measurement with contrast-enhanced harmonic ultrasonography: evaluation of dopamine-induced changes in renal cortical perfusion in humans.

BACKGROUND: An accessible non-invasive method for evaluating renal regional blood flow in real time is highly desirable in the clinical setting. Recent progress in ultrasonography with microbubble contrast has allowed quantification of regional blood flow in animal models. AIMS: Goal ofthis study was to establish a convenient contrast--enhanced harmonic ultrasonography (CEHU) method for evaluating renal cortical blood flow in humans. METHODS: We carried out intermittent second harmonic imaging in 9 healthy volunteers. Pulse interval was progressively decreased from 4 s - 0.2 s during continuous venous infusion of the microbubble contrast agent. RESULTS: Pulse interval versus CEHU-derived acoustic intensity plots provided microbubble velocity (MV) and fractional vascular volume (FVV) during renal cortical perfusion in humans. Low-dose dopamine infusion (2 microg/min/kg) resulted in a significant increase in MV which correlated well with the increase in total renal blood flow (RBF) determined by a conventional study of p-aminohippurate clearance (C(PAH)) (r = 0.956, p < 0.0001). Although FVV was not significantly increased, alterations in CEHU-derived renal cortical blood flow calculated by the products of MV and FVV were also correlated with alterations in total RBF (r = 0.969, p < 0.0001). Thus, low-dose dopamine infusion increases renal cortical blood flow observed in CEHU, mainly by increasing MV. CONCLUSIONS: The present study shows that renal cortical blood flow in humans can be measured non-invasively by CEHU and that CEHU can be used for quantitatively evaluating changes induced by a therapeutic agent such as dopamine in flow velocity and in FVV.

Adult↗