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  • 1
    Keywords: measurement ; ANGIOGENESIS ; Germany ; PERFUSION ; CLASSIFICATION ; CT ; imaging ; INFORMATION ; QUANTIFICATION ; liver ; TISSUE ; TUMORS ; computed tomography ; PATIENT ; BLOOD-FLOW ; INDEX ; primary ; INJECTION ; SIGNAL ; LESIONS ; PATTERNS ; DIFFERENCE ; metastases ; US ; tomography ; COMPUTED-TOMOGRAPHY ; LIVER METASTASES ; POWER DOPPLER SONOGRAPHY ; VASCULARIZATION ; contrast-enhanced ultrasound,liver metastases,arterial perfusion,low-MI imaging,SonoVue ; MICROBUBBLE CONTRAST ; SHU 508A
    Abstract: Rationale and Objectives: We investigated whether observing the arterial vascularization of liver metastases by contrast-enhanced ultrasound with low mechanical index (low-MI) imaging offers additional diagnostic information for the characterization of the liver lesions.Methods: Twenty nine patients with untreated liver metastases of different primaries were examined. Measurements were performed using a low frame rate, low-MI pulse inversion technique after injection of 2.4 mL SonoVue. The relative maximum signal intensity of the liver lesions related to the normal liver tissue was quantified. Ultrasound findings were compared with contrast-enhanced, dual-phase computed tomography (CT) using a pattern-based classification scheme.Results: Compared with contrast-enhanced CT, this modality better detects arterial perfusion. Metastases, even those usually considered hypovascularized, often showed homogeneous enhancement (66%) and higher arterial vascularization than normal liver tissue. CT did not show a comparable vascularization pattern (P 〈 0.001) or any similarly early signal intensity (P 〈 0.001).Conclusions: Contrast-enhanced CT may not be able to visualize short-lasting but large differences of the arterial perfusion of liver metastases, as does contrast-enhanced low-MI ultrasound. This offers new methods for their characterization and for monitoring of therapeutic effects
    Type of Publication: Journal article published
    PubMed ID: 15021325
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  • 2
    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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  • 3
    Publication Date: 2018-11-29
    Description: We report on the implementation of ultracold atoms as a source in a state of the art atom gravimeter. We perform gravity measurements with 10 nm s −2 statistical uncertainties in a so-far largely unexplored temperature range for such a high accuracy sensor, down to 50 nK. This allows for an improved characterization of the most limiting systematic effect, related to wavefront aberrations of light beamsplitters. A thorough model of the impact of this effect onto the measurement is developed and a method is proposed to correct for this bias based on the extrapolation of the measurements down to zero temperature. Finally, an uncertainty of 13 nm s −2 is obtained in the evaluation of this systematic effect, which can be improved further by performing measurements at even lower temperatures. Our results clearly demonstrate the benefit brought by ultracold atoms to the metrological study of free falling atom interferometers. By tackling their main limitation, the m...
    Electronic ISSN: 1367-2630
    Topics: Physics
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