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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Der Radiologe 36 (1996), S. 327-336 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Elektronenstrahltomographie ; Koronarkalzifikationen ; Koronare Herzkrankheit ; Kosteneffizienz ; Key words Electron beam tomography ; Coronary calcification ; Coronary artery disease ; Cost-efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Background: Electron beam CT (EBCT) can acquire rapid, multiple thin-section tomograms of the beating heart in synchrony with the electrocardiogram and quantify coronary calcification without intravenous contrast. Coronary calcification is an active process exclusively associated with atherosclerotic plaque formation and regulated in a manner similar to the calcification of bone. Clinical studies have demonstrated that EBCT coronary calcification (1) follows a pattern similar to the epidemiology of coronary artery disease (CAD), (2) has a high sensitivity (90–95 %) for coronary plaque and significant angiographic coronary stenoses, and (3) has the potential to assess the prognosis of patients with coronary atherosclerotic disease. Coronary calcium area or “score” correlates best with overall plaque burden within the coronary system. However, coronary calcium is of limited value in distinguishing coronary stenosis on a segment-by-segment basis. EBCT and CAD: Due to spiraling health care costs, there is a need for cost-efficient strategies in the diagnosis and stratification of patients with known or suspected CAD. There are two major patient groups in which EBCT calcium scanning has a potential for cost-efficient application: (1) in asymptomatic, high-risk patients, identification of significant plaque burden may direct judicious use of long-term drug therapy or further investigation to those individuals most likely to benefit from an aggressive risk factor modification and medical program; (2) in patients with chest pain syndromes but no prior CAD, EBCT calcium scanning compares favorably with conventional diagnostic methods. In particular, using receiver operating characteristic analysis, the sensitivity and specificity of an EBCT calcium score of 80 in detecting obstructive CAD are both about 85 %. Using a theoretical model, EBCT calcium scanning was found to be the most cost-effective approach to diagnosis in populations with a low-to-moderate likelihood of obstructive CAD when compared with treadmill exercise, stress thallium, and stress echocardiography. Conclusions: EBCT calcium scanning is not a substitute for coronary angiography, but it has clear advantages over other more traditional diagnostic methods for CAD. In particular, it can be performed conveniently and inexpensively in most patients. Additionally, the site and extent of calcification are intimately related to the atherosclerotic plaque burden. The analyses presented suggest that it may also provide a cost-effective clinical alternative in specific subsets of the population.
    Notes: Zusammenfassung Die koronare Kalzifizierung ist ein aktiver Prozeß während der Entwicklung von atherosklerotischen Plaques. Die Darstellung von koronarem Kalzium durch die Elektronenstrahltomographie (EBT) hat eine gute Sensitivität und Spezifität für die Voraussage oder den Ausschluß von signifikanten Koronarstenosen und korreliert gut mit der Prognose von Patienten mit koronarer Herzkrankheit (KHK). Besonders bei 2 Patientengruppen kann die EBT einen kosteneffizienten Ansatz für die Diagnostik und Beurteilung darstellen: 1. Bei asymptomatischen Patienten mit hohem koronarem Risiko kann die Quantifizierung von Kalzium Patienten mit hohem Plaquevolumen identifizieren und gestattet damit den gezielten Einsatz einer teuren Langzeittherapie bei einer Population, die mit der höchsten Wahrscheinlichkeit von der Modifikation von Risikofaktoren profitieren würde. Umgekehrt schließt ein negativer Scan (ohne koronare Kalzifizierungen) eine signifikante KHK mit hoher Wahrscheinlichkeit aus. 2. Bei Patienten mit Angina pectoris ohne etablierte KHK stellt die EBT in einem theoretischen Modell im Vergleich zu konventionellen Belastungstest bis zu einer Prävalenz der KHK von 70 % in der Bevölkerung den kosteneffektivsten diagnostischen Ansatz dar. Danach erweist sich die direkte Koronarangiographie am billigsten. EBT hat nur ein minimales Risiko für den Patienten und kann in ausgewählten Patientenkollektiven kostengünstige therapeutische und diagnostische Entscheidungen ermöglichen.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0649
    Keywords: 82.40.Py ; 35.80. + s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The reaction zone in the hostile combustion environment of a 100 kW oil-burning furnace has been imaged by laser-induced fluorescence using a broad-band XeCl-excimer laser. Upon excitation, the averaged images obtained by using an interference filter around 320 nm (FWHM of 10 nm) show three distinct areas along the direction of the gas flow. An intense emission spreads around the spray axis and is attributed to the fluorescence of large hydrocarbons in the unburned fuel. Approximately 12 cm downstream of the nozzle, a narrow dark region is displayed suggesting the preheat zone of the combustion process where large hydrocarbons are considerably degraded. The third distinct region is characterized by a strong onset of the fluorescence intensity localized downstream of the dark region. This feature is strongly suppressed by replacing the interference filter by a broad-band transmission filter passing light from 350 to 500 nm. Since OH strongly absorbs at the laser wavelength and its fluorescence is significantly lower above 345 nm, the findings imply that the major contribution to the observed intensity in this region originates from the OH radical. This molecule reaches its maximum concentration immediately downstream of the flame front. However, a contribution from other flame species fluorescing around 320 nm cannot be ruled out. Nevertheless, the combined spatial and spectral information obtained imply that the reaction zone of the combustion process can be localized accurately. The results are compared with simultaneously performed numerical simulations of the burner and are in reasonable agreement.
    Type of Medium: Electronic Resource
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