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  • 1
    Keywords: Germany ; SYSTEM ; SYSTEMS ; ACCURACY ; SURGERY ; FIELD ; TRIAL ; TRIALS ; PROBES ; TRACKING ; ultrasound ; 2D ; RE ; GUIDANCE ; INTERFERENCE ; ABLATION ; TECHNOLOGY ; image-guided surgery ; ATRIAL-FIBRILLATION ; 3-D ULTRASOUND ; 3-DIMENSIONAL ECHOCARDIOGRAPHY ; 3D ultrasound ; electromagnetic tracking ; image-guided applications ; Live3D ; TEE ; TTE
    Abstract: In the last few years, 3D ultrasound probes have became readily available. New fields of image-guided surgery applications are opened by attaching small electromagnetic position sensors to 3D ultrasound probes. However, nothing is known about the distortions caused by 3D ultrasound probes regarding electromagnetic sensors. Several trials were performed to investigate error-proneness of state-of-the-art electromagnetic tracking systems when used in combination with 3D ultrasound probes. It was found that 3D ultrasound probes do distort electromagnetic sensors more than 2D probes do. When attaching electromagnetic sensors to 3D probes, maximum errors of 5 mm up to 119 rum occur. The distortion strongly depends on the electromagnetic technology as well on the probe technology used. Thus, for 3D ultrasound-guided applications using electromagnetic tracking technology, the interference of ultrasound probes and electromagnetic sensors have to be checked carefully
    Type of Publication: Journal article published
    PubMed ID: 16965976
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  • 2
    Keywords: APOPTOSIS ; CELLS ; EXPRESSION ; AGENTS ; Germany ; human ; EXPOSURE ; TISSUE ; REPERFUSION ; FLOW ; treatment ; PHAGOCYTOSIS ; STRESS ; SAFETY ; CONTRAST AGENTS ; ultrasound ; albumin ; INCREASE ; TRANSFECTION ; HEALTHY-VOLUNTEERS ; function ; LOSSES ; PLASMID ; ALBUMIN MICROBUBBLES ; MYOCARDIAL CONTRAST ECHOCARDIOGRAPHY ; neutrophil granulocytes ; ultrasound microbubbles
    Abstract: Activated polymorphonuclear neutrophil (PMN) granulocytes can bind and subsequently phagocytose microbubbles used as ultrasound (US) contrast agents. The purpose of the present study was to assess insonation effects on cell membrane integrity and metabolic activity of activated PMN. Furthermore, we investigated whether or not there is an acoustic threshold at which insonation of PMN results in increase of membrane permeability without causing complete cell destruction. PMN isolated from healthy volunteers were activated with phorbol myristate acetate (PMA) for 15 min to allow phagocytosis of albumin and lipid microbubbles and were subsequently exposed to US with a mechanical index between 0.15 and 1.8. Apoptosis, loss of membrane integrity and formation of cell fragments were evaluated by measurement of lactate dehydrogenase leakage and by double staining with annexin V and propidium iodide, using flow cytometry. Neutrophil superoxide anion generation was measured photometrically. Insonation of activated PMN in the presence of microbubbles amplified apoptosis and lactate dehydrogenase leakage and induced loss of membrane integrity and complete cell destruction with increasing acoustic pressures. The bioeffects observed by insonation with high mechanical indices (1.0 to 1.8), and particularly the formation of cell fragments, were significantly more pronounced in the presence of albumin microbubbles. Insonation in the presence of lipid microbubbles increased cell membrane permeability, but caused significantly less cell destruction and left the metabolic activity of activated PMN uninfluenced. Thus, both albumin and lipid microbubbles induce apoptosis and membrane injury during insonation of activated PMN. However, insonation in the presence of lipid microbubbles seems to influence cell viability to a smaller extent. This could be of advantage in the setting of US-guided local drug delivery. In this setting, increase of membrane permeability may allow bioactive substances to enter into cells, which survive the US treatment, and specifically modify their function. (E-mail: Grigorios_Korosoglou@med.uni-heidelberg.de) (C) 2006 World Federation for Ultrasound in Medicine & Biology
    Type of Publication: Journal article published
    PubMed ID: 16464675
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  • 3
    Keywords: Germany ; THERAPY ; imaging ; FREQUENCY ; FIELD ; FREQUENCIES ; WATER ; NO ; PARAMETERS ; ATTENUATION ; ultrasound ; ABSORPTION ; HYPERTHERMIA ; RE ; CAPACITY ; NUCLEAR ; USA ; phantom ; comparison ; acoustic properties ; coagulation ; CONDUCTIVITY ; egg white phantom ; HIFU ; POLYACRYLAMIDE-GEL ; thermal properties ; tissue-mimicking phantom
    Abstract: A polyacrylamide phantom containing egg white has been proposed previously as an adequate tissue-mimicking material for high intensity focused ultrasound (HIFU) application. In this work, we report on measurements of egg white phantom thermal conductivity and specific heat capacity. We measured changes in acoustical properties which occurred during the heating and the coagulation process. Using a thin thermocouple embedded in the phantom material, we recorded the temperature response in the focus of the ultrasound field during HIFU application and phantom coagulation. The measured values for the thermal conductivity (0.59 +/- 0.06 W/m/degrees C) and the specific heat capacity (4270 +/- 365 J/kg/degrees C) are similar to the values of water. The attenuation coefficient decreased in the temperature range between 26 degrees C and 50 degrees C and showed a nonlinear dependence on frequency with an exponent of 1.50 +/- 0.05 that was temperature-independent within the investigated temperature range. Below 65 degrees C, no irreversible changes in material absorption were observed. The coagulation process started at 67 degrees C and no adjacent rapid changes in temperature response were detected. In comparison with the noncoagulated phantom, the coagulated phantom material showed an enhanced absorption and a threefold higher attenuation coefficient at a frequency of 1 MHz
    Type of Publication: Journal article published
    PubMed ID: 17434665
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  • 4
    Keywords: tumor ; AGENTS ; BLOOD ; Germany ; IN-VIVO ; MODEL ; PERFUSION ; THERAPY ; VIVO ; imaging ; QUANTIFICATION ; VOLUME ; liver ; TISSUE ; TIME ; BLOOD-FLOW ; INDEX ; CONTRAST ; blood flow ; CONTRAST AGENT ; FLOW ; INJECTION ; BIOLOGY ; metastases ; US ; PARAMETERS ; tomography ; KINETICS ; LIVER METASTASES ; CONTRAST AGENTS ; POWER DOPPLER SONOGRAPHY ; INDUCED DESTRUCTION ; AGENT ; TRANSIT-TIME ; DESTRUCTION ; REAL-TIME ; tissue viability ; OCT ; ENHANCED SONOGRAPHY ; HEPATIC METASTASES ; HEPATIC PERFUSION ; low-MI ultrasound ; MATHEMATICAL-MODEL ; quantification of perfusion ; replenishment kinetics ; TUMOR PERFUSION ; ultrasound contrast agent
    Abstract: Low-MI (mechanical index) ultrasound allows real-time observation of replenishment kinetics after destruction ("flash") of ultrasound contrast agents (USCA). We developed an examination protocol and a mathematical model to quantify perfusion of liver tissue and hepatic metastases. Using a modified multivessel model, we attempted a consistent, physiological description of microbubble replenishment in liver tissue. Perfusion parameters were calculated, separately for the arterial and portal venous phase of liver perfusion, using an i.v. bolus injection of 2 x 2.4 mL SonoVue(R). The model was evaluated for 10 examinations of liver metastases using flash/low-MI imaging. In contrast to the established, exponential model, the new model consistently describes the sigmoid replenishment of USCA measured in vivo, using flash/low-MI imaging. Parameters for blood volume, blood velocity and blood flow in liver tissue and metastases can be calculated during the arterial and the portal venous phase after a CA bolus injection. The median arterial perfusion in the examined liver metastases was more than 2.5 times higher than in normal liver tissue, whereas the median perfusion during the portal venous phase was more than five times higher in the liver tissue than that in metastases. Microbubble replenishment measured with flash/low-MI US techniques can be consistently analyzed using the multivessel model, even after a bolus injection of USCA. This allows for the quantification of perfusion of liver tissue and hepatic metastases and provides promising parameters of tissue viability and tumor characterization. (C) 2004 World Federation for Ultrasound in Medicine Biology
    Type of Publication: Journal article published
    PubMed ID: 15582235
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  • 5
    Keywords: ANGIOGENESIS ; CELL LUNG-CANCER ; DOPPLER ; Germany ; IN-VIVO ; PERFUSION ; imaging ; QUANTIFICATION ; BLOOD-FLOW ; animals ; tumour ; CONTRAST ; NUDE-MICE ; US ; VASCULARIZATION ; COLOR DOPPLER ; intermittent sonography,ultrasound contrast agent,quantification,blood how,perfusion,tumour angiogen ; MYOCARDIAL PERFUSION ; ULTRASOUND-INDUCED DESTRUCTION
    Type of Publication: Journal article published
    PubMed ID: 12946512
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  • 6
    Keywords: IN-VITRO ; tumor ; BLOOD ; Germany ; IN-VIVO ; MODEL ; PERFUSION ; THERAPY ; VIVO ; QUANTIFICATION ; VOLUME ; NEW-YORK ; TISSUE ; TUMORS ; BLOOD-FLOW ; CONTRAST ; blood flow ; CONTRAST AGENT ; FLOW ; BIOLOGY ; ACQUISITION ; VARIABILITY ; PARAMETERS ; KINETICS ; TUMOR ANGIOGENESIS ; POWER DOPPLER SONOGRAPHY ; VASCULARIZATION ; INDUCED DESTRUCTION ; MICROBUBBLES ; replenishment kinetics,intermittent sonography,quantification,blood flow,tumor perfusion,ultrasound
    Abstract: To improve the quantification of tissue perfusion using intermittent sonography, a new model describing replenishment kinetics of microbubbles is proposed. The new approach takes into account the variability of blood flow velocities found in vivo, especially in tumors, and consistently describes the refilling process of microbubbles. Based upon this model, blood volume, blood velocity, blood flow and perfusion in 17 experimental tumors were calculated, and compared with the results obtained with the established, phenomenologically derived exponential kinetic model. In contrast to the existing model, our approach describes tissue vascularization more physiologically and allows deduction of a consistent new hyperbolic model for quantification of intermittent sonography. Blood volume and mean blood velocity did significantly correlate between both the new and the established model (k = 0.99; k = 0.94, both p 〈 0.001). However, mean tumor blood velocity was lower (-19%,p 〈 0.01) with the established model compared to the newly developed model. In addition, the range and distribution of blood flow velocities found in vivo can be estimated with the new model. Furthermore, it uses simpler mathematical fitting routines and allows easier data acquisition, which may allow a more practicable clinical application of intermittent sonography. In conclusion, a more valid, detailed and accurate calculation of perfusion parameters, especially of tumors, can be derived in vivo with the new multivessel model of intermittent sonography. (E-mail: m.krix@dkfz.de) (C) 2003 World Federation for Ultrasound in Medicine Biology
    Type of Publication: Journal article published
    PubMed ID: 14597339
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  • 7
    Abstract: We developed a real-time low-MI contrast-enhanced ultrasound method (CEUS), compared it with venous occlusion plethysmography (VOP) and evaluated its robustness in the quantification of skeletal muscle perfusion during exercise. Contrast pulse sequencing (7 MHz) during continuous intravenous infusion of SonoVue (4.8 mL/300 s) was used repeatedly in eight healthy volunteers to monitor changes of the muscle perfusion before, during and after isometric exercises (10 to 50% of individual maximum strength for 20 to 30 s) of the gastrocnemius muscle in real time. CEUS was correlated with VOP at different time points, and the exactness of several CEUS parameters obtained from ultrasound-signal-intensity-time curves was evaluated. Real-time CEUS depicted a large variability of the skeletal muscle blood volume at rest (mean, 3.48; range, 0.60 to 9.92 [approximately mL]), with a significant reproducibility (r=0.72, p〈0.05) and correlation with VOP (r=0.59, p〈0.001). Mean blood volume during exercise was 1.58(approximately mL), increased to a mean maximum after exercise of 8.88 (approximately mL), the mean change of the local blood volume during and directly after the exercise was -0.10 and +1.57(approximately mL/s). The average CEUS signal during exercise decreased (mean area under the curve, -50.4 [approximately mL.s]) and subsequently increased post exercise (mean 118.6 [approximately mL.s]). CEUS parameters could be calculated with mean relative errors between 6 and 36%. Continuous assessment of local muscle microcirculation during exercise is possible with real-time CEUS with an acceptable robustness. Its application may be of particular interest in a better understanding of the role of perfusion during muscle training, and the monitoring of pathological vascular response, such as in diabetic microvessel diseases
    Type of Publication: Journal article published
    PubMed ID: 19682788
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  • 8
    Keywords: ANGIOGENESIS ; CANCER ; LUNG ; SOLITARY PULMONARY NODULES ; DIFFERENTIATION ; TISSUE ; LESIONS ; sensitivity ; CONTRAST AGENTS ; SONOGRAPHY ; DIFFERENTIAL-DIAGNOSIS ; INITIAL-EXPERIENCE ; CT PERFUSION ; Perfusion kinetics ; Thoracic ultrasound
    Abstract: We proposed to assess the feasibility of low mechanical index (MI) contrast enhanced ultrasound (CEUS) in the characterisation of thoracic lesions. Fifty patients were prospectively examined by CEUS and images acquired on a low MI (0.17-0.24) setting following injection of SonoVue. From region-of-interest (ROI) generated signal intensity (SI) time curves, the maximum SI, bolus arrival time (BAT), time to peak intensity (TTP), wash-in slope and mean transit time (MTT) were calculated. Using the Wilcoxon rank test; parameters and threshold values for positive differentiation were determined. In addition, for the parameters that allowed positive differentiation between malignant and benign lesions receiver operator curves (ROC) were obtained. The wash-in slope, TTP and MTT (p = 0.0003, 〈0.0001, 0.02) allowed positive differentiation. The sensitivity and specificity was 93% and 78%, with 6.87 s(-1) threshold value for the wash-in slope, 78% and 89% with 11.84 s threshold for the TTP and 48% and 89% with 78.6 s threshold for the MTT. CEUS is a useful tool for differentiating malignant and benign thoracic lesions.
    Type of Publication: Journal article published
    PubMed ID: 21963035
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