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H P Weskott

Publications and source records attributed to H P Weskott.

11 recordsLinked to original sources
PubMed2007

New perspectives for the use of contrast-enhanced liver ultrasound in clinical practice.

The introduction of second-generation microbubble ultrasound contrast agents and the development of contrast specific ultrasound techniques have improved the ability of contrast enhanced ultrasound in detecting and characterising liver lesions, offering new perspectives for its exploitation in clinical hepatology. Indeed, several studies have demonstrated a high diagnostic accuracy in focal lesion characterisation (85-96%) in patients either with or without underlying chronic liver disease. This review article describes the basic principles of contrast enhanced ultrasound, defines the different vascular features of benign and malignant liver lesions, and assesses its clinical impact in different clinical scenarios, according to the guidelines of the European Federation of Societies for Ultrasound in Medicine and Biology, contrast enhanced ultrasound enables the characterisation of focal liver lesions, regardless of the presence or absence of underlying chronic liver disease. Contrast enhanced ultrasound is also useful in staging and follow-up of cancer patients and in monitoring local ablative treatment. Contrast enhanced ultrasound is expected to be considerably increased and replace many computed tomography and magnetic resonance imaging examinations in near future, according to the European Federation of Societies for Ultrasound in Medicine and Biology guidelines. Therefore, it is necessary to take measures in order to meet the demand for an increasing number of these procedures.

Contrast Media↗
PubMed2000

[B-flow--a new method for detecting blood flow].

A new ultrasound-based blood flow detection method, B-Flow is introduced. The amplitude of scatterers in flowing blood is imaged by a subtraction mode of two to four vectors along one line. Noise reduction is gained by using digital encoded US pulses. Signal enhancement is performed by using a pulse compression method (coded excitation). Compared to Color Doppler (CDI) Imaging B-Flow has a higher time (frame rate) and better spatial resolution. Typical CDI artifacts like color blooming or aliasing are missed. B-Flow does not allow velocity measurements. B-Flow has its clinical value in imaging perfused arterial vessels, simultaneous imaging of high and low velocities and delineating plaque morphology with high resolution.

Arteries↗
PubMed2000

[Malignant hepatobiliary tumors. Surgical requirements concerning preoperative diagnosis].

Depending on the results of the diagnostic work-up of a hepatobiliary tumour, the further therapeutic strategy may vary appreciably. The data needed to decide whether a malignant growth is resectable or not include information on the nature, size and location of the tumour, the number of lesions presenting, extrahepatic tumour-related manifestations, the individual hepatic anatomy and additional liver diseases. Despite the recent technical advances, the various diagnostic imaging procedures all have their limitations; used in combination, however, they can provide adequate information in 90-100% of the cases. The most important of these procedures are ultrasonography and spiral CT--including the use of contrast agents--and in some cases also MRT. Thanks to the topographic information they provide, the three-dimensional methods are gaining popularity. While angiography, scintigraphy and ERCP are useful supplementary methods, they do not suffice for the primary diagnosis. In some cases, intra-operative diagnosis may make necessary a change in the planned therapeutic procedure. The limitations and possibilities of the diagnostic strategy--which in no small part is also codetermined by the patient's prehistory and the experience of the examiner--are discussed.

Adult↗
PubMed1999

Angiomyolipoma of the kidney and lymph nodes.

Angiomyolipoma (AML) is a benign mesenchymal tumor predominantly occurring in the kidney. Despite its low incidence of 0.07-0.03% in an unselected population, this tumor is well known, because the typical AML can be diagnosed without histological confirmation by a combination of ultrasound (US) and computerized tomography (CT) imaging in up to 95% of cases. In contrast, simultaneous involvement of the kidney and the regional lymph nodes is less known and might be confused with metastasizing malignant tumor. We report a case of the very uncommon simultaneous involvement of the kidney and the lymph nodes in AML.

Adult↗
PubMed1997

The sensitivity of new color systems in blood-flow diagnosis. The maximum entropy method and angio-color-comparative in vitro flow measurements to determine sensitivity.

BACKGROUND: Two new blood-flow-diagnosis techniques have recently been developed as supplements to the established color techniques: the MEM (maximum entropy method) technique and color flow amplitude (power Doppler). These are capable of representing blood flow in distinctly more slowly flowing areas than is possible with the conventional Doppler technique. METHODS: Both methods make use of the Doppler technique in part, yet analyze the reflected signal in a different manner, in so doing optimizing the relation between the noise and the signal. Measurements were obtained on two anatomic flow models to test the sensitivity of both techniques under slow flow conditions. RESULTS: The slowest flow the MEM technique was capable of recording was 0.5 mm/s, albeit utilizing a 5-MHz transducer for the MEM technique and a 10-MHz transducer for the angio technique. One may thus assume that the MEM technique would be still more sensitive when utilizing a 10-MHz transducer. The advantage of the MEM technique is its real-time flow representation: The angio technique requires a few seconds of acquisition time. This could have serious consequences during clinical utilization. Doppler sonography was merely capable of detecting a minimum flow velocity of 15 mm/s. The angio technique is less dependent on the angle during flow representation than the MEM technique. CONCLUSIONS: The distinctly higher sensitivity of these two new color techniques offers new possibilities in the clinical sector as far as the perfusion diagnosis of organs and tumors is concerned.

Angiography↗
PubMed1997

Amplitude Doppler US: slow blood flow detection tested with a flow phantom.

PURPOSE: To evaluate the in vitro sensitivity for the detection of slow blood flow in tiny tubes with an amplitude Doppler ultrasound (US) technique at different angles and pulse repetition frequencies. MATERIALS AND METHODS: Human blood treated with heparin was pumped through silicone tubes (flow phantoms made by the author) with lumina of 3.00 mm, 0.30 mm, and 0.05 mm. Slow flow was imaged by using amplitude and color Doppler US techniques with two US devices at different pulse repetition frequencies and angles and in different sound propagation media. RESULTS: Under ideal conditions, the lowest detectable velocity was 0.04-0.06 cm/sec in the 3.00-mm tube. Detection was about three to four times less sensitive in the 0.30-mm and 0.05-mm tubes. Amplitude Doppler US sensitivity is only slightly dependent on the angle of incidence and propagation medium. CONCLUSION: The fractional volume flow determined the sensitivity of the amplitude Doppler technique for detecting low flow. Amplitude Doppler US is nearly angle independent; thus, it is superior to color Doppler US. Amplitude Doppler US is three to four times more sensitive when tube have very tiny lumina and when probes of a lower frequency are used.

Blood Flow Velocity↗
PubMed1997

US-based evaluation of hemodynamic parameters in the common carotid artery: a nomogram trial.

PURPOSE: To evaluate hemodynamic data of the common carotid artery (CCA) with an ultrasound (US)-based technique in an age- and sex-matched healthy population. MATERIALS AND METHODS: Measurements from a color M-mode tracing of each CCA in 205 healthy subjects (age range, 20-87 years) were performed with a time domain processing system. Lumen change of the color M-mode tracing, flow velocity, volume flow rate, and diastolic volume index (DVI) were calculated five times. Blood pressure was measured after the US examination. Fifteen subjects were excluded from the nomogram trial because of hypertension, and 12 and four subjects were excluded because of an asymptomatic carotid artery stenosis or atrial fibrillation, respectively. RESULTS: Mean volume flow rate in the CCA of the remaining 174 healthy volunteers was 415.0 mL/min +/- 87.0 (men [n = 84], 441.0 mL/min +/- 95.5; women [n = 90], 390.2 mL/min +/- 70.5). The following statistically significant associations were noted: between vessel lumen and sex and blood pressure; between peak systolic velocity and sex and age; between volume flow rate and sex, age, and systolic blood pressure; and between DVI and age, heart rate, and systolic and diastolic blood pressure. CONCLUSION: Time domain processing is an intrasessionally well-reproducible US method for measuring velocities and volume flow in the CCA.

Adult↗
PubMed1996

[Sensitivity of new color systems: "maximum entropy method" and angio-color. Comparative in vitro flow measurements].

AIM: The sensitivity of the two procedures for slow blood flow velocities in two flow phantoms examined and compared to conventional colour Doppler. METHOD: In two phantoms with vessels between 0.3 and 6 mm diameter the slowest measurable blood flow with the different techniques was determined. The influence of various application angles was also studied. RESULTS: The slowest blood flow velocity detected with the MEM technique was 0.6 mm/s and with the angio-technique 0.4 mm/s. Two different scan-heads were used; a 5 MHz probe for the MEM procedures and a 10 MHz probe for ultrasound angiography. Using a 10 MHz scan-head will most likely lead to increased sensitivity of MEM. Blood flow representation with the MEM technique is real-time, while several seconds of acquisition time are required for the angio-technique, which is a disadvantage during clinical use. Conventional Doppler was merely able to represent 15 mm/s blood flow. The angio-technique was less dependent on the application angle than the MEM procedure. CONCLUSION: The definitely increased sensitivity of the two colour methods open up new areas in the diagnosis of organ and tumour perfusion.

Blood Flow Velocity↗
PubMed1995

[Ultrasound angiography: phantom measurements of slow blood flow].

Power Doppler ultrasound is a color-coded Doppler ultrasound method based on the strength of the Doppler shift signal. The sensitivity for slow flow was tested with different flow phantoms. The lowest detectable velocity was 0.04 cm/s in a water- or oil-filled tank at an angle of 45 degrees and 0.24 cm/s in an oil medium at an angle of 86 degrees. The pulse repetition frequency (PRF) was 100 kHz at the lowest detectable velocities, the acquisition time depended mostly on the attenuation of the medium. The new method depended very little on the angle of insonation. Under ideal conditions detectable flow velocities are within the range of mean capillary flow velocity.

Blood Flow Velocity↗
PubMed1993

Rapid and selective inhibition of platelet aggregation and thromboxane formation by intravenous low dose aspirin in man.

1. One of the major problems in the clinical use of low dose aspirin for the prevention of vascular occlusion is that it takes about 3-5 days to become effective, a time too long for patients with unstable angina or coronary thrombolysis. Intravenous aspirin may be expected to exert a more rapid effect, but its influence on endothelial prostacyclin synthesis is uncertain. 2. In a single-blind, randomized, prospective study, we compared the effects of a single intravenous low dose (50 mg) or high dose (500 mg) of aspirin or placebo infused over a 60 min period on platelet aggregation, platelet thromboxane A2 production and whole-body prostanoid synthesis in 10 healthy male subjects by gas chromatography-tandem mass spectrometry. 3. Before the study, blood flow rates in the basilic and subclavian veins were determined by sonographic colour velocity imaging; the infusion rate for low dose aspirin was calculated to avoid biologically effective plasma levels of aspirin in the systemic circulation. 4. Platelet aggregation induced by 1 mmol/l arachidonic acid was similarly inhibited by > 85% within 30 min after the start of the infusion of high dose or low dose aspirin, respectively, and remained suppressed for 24 h. Platelet thromboxane A2 release declined gradually after low dose aspirin, reaching a minimum of 93% inhibition after 60 min. High dose aspirin suppressed platelet thromboxane A2 release to below the detection limit after 10 min. 5. Urinary excretion of the major urinary metabolite of thromboxane A2 (2,3-dinor-thromboxane B2) was equally suppressed by both dosages of aspirin [no significant difference between high dose (-83.2%) and low dose (-67.4%)].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗