199,441 research outputs found
Coronary CT Angiography: Evaluation of Stenosis and Occlusion
No full textOnce an atherosclerotic plaque has been identified and properly characterized by means of coronary CT angiography (CTA), the next step is to define the extent of atherosclerotic involvement, i.e., significant reduction of the lumen by stenosis or complete occlusion of the vessel. A reduction in the caliber of the vessel lumen is associated with a reduction in blood flow and may have significant hemodynamic consequences; however, an important and clearly evident parietal atherosclerotic plaque may be present without significantly reducing lumen caliber. Thus, an exact definition of the extent of lumen reduction by means of coronary CTA is very important from a clinical point of view. In most cases, this diagnostic procedure is employed in not highly symptomatic patients (in patients in whom there is strong clinical suspicion of coronary disease, catheter angiography is directly performed); then, depending on the results of the clinical examination, a decision is made as to whether a more invasive approach (catheter angiographsy) is required. This decision depends at least in part on the significance of the vessel stenosis. Both the aim and the key role of coronary CTA are to differentiate patients with normal coronary vessels from those with limited atherosclerotic involvement without evidence of stenosis (who may benefit from supportive drug therapy) and from those with significant stenosis. In this latter group, catheter coronary angiography may confirm the significance of the disease and define the therapeutic approach.
The direct evidence of arterial stenosis provided by coronary CTA yields additional information. For example, a stenosis > 70% causes a significant hemodynamic reduction of vascular flow. Completely asymptomatic patients, with negative treadmill tests, may present with important and significant stenosis of one or more coronary arteries but with an overall reduction in flow that is less than the 70% threshold.
In clinical practice, a stenosis is considered significant when the vessel caliber is reduced by > 50%. Thus, the goal is to interpret coronary CTA images such that the level of stenotic vascular involvement is precisely determined
Mario Alberto Pavone e Salerno: uno studioso, una città
No full textUn ricordo di Mario Alberto Pavone e del suo rapporto con la città di Salerno
Rapporto sulle nuove misure di CO2 nella galleria drenante Pavone di Vena (06 Settembre 2006)
No full textL’intervento è stato effettuato su segnalazione fatta il giorno 30 Agosto 2006 dal
Geometra Alletto a S. Giammanco. Secondo quanto riferito dal Geom. Alletto, a partire da
quella mattina si stava verificando un forte accumulo di gas all’interno della galleria
drenante Pavone ubicata in Contrada Rocca Campana di Vena, tanto da impedirne
l’accesso al personale operaio ivi presente quotidianamente. Tale fenomeno risultava
simile a quello segnalato nel Novembre 2005, a seguito del quale si era effettuato un
precedente intervento (vedasi rapporto interno UFVG2005/115).Istituto Nazionale di Geofisica e VulcanologiaUnpublishedope
X-Ray Exposure in Coronary CT Angiography
No full textIn coronary CT angiography (CTA), X-ray radiation is delivered through an X-ray tube from which the amount of radiation emitted can be carefully controlled. Recently, the use of X-rays for diagnostic purposes has been the subject of important and renewed attention, with the aim of limiting radiation exposure and thus its negative consequences on human health. The potential oncological impact of X-rays is well-known. Earlier generations of radiologists used diagnostic equipment often without the protection that has since become routine. Consequently, they often suffered dermatological problems on their hands as well as an increased frequency of tumors, mostly of the hematopoietic series. In the following, we focus on the unintentional exposure that occurs during a diagnostic evaluations, i.e., for coronary artery disease
On the solutions of the differential overland flow equation
No full textIn this paper we study the overland flow equation for an arbitrary positive value of the rating exponent m. We write the general solution of the equation and generalize the series solution given in [1] and [2]. Finally, we show how the five solutions presented in [5] are actually a special case of a general formula valid for any rational m≥1
The overland flow equation for constant rainfall excess: an evaluation of runoff volume and time to equilibrium
No full textIn this paper we study the runoff volume V(t) per unit area generated by the overland flow in the time interval [0,t], under a stationary rainfall r and initially dry conditions. For all positive values of the rating exponent m we express V(t) in closed form in terms of the solution q(t) of the overland flow equation. We define a simpler, approximated value of V(t) and show that, for m≥1, the error is smaller than a quantity of the form c e^{-pt}. Finally, for 1≤m≤3, we find an explicit upper bound for the time to equilibrium t_e, by showing that q(t) differs from the equilibrium outflow r by a quantity of the form c e^{-pt}
Rapporto sulle nuove misure di CO2 nella galleria drenante Pavone di Vena (06 Settembre 2006)
No full textL’intervento è stato effettuato su segnalazione fatta il giorno 30 Agosto 2006 dal
Geometra Alletto a S. Giammanco. Secondo quanto riferito dal Geom. Alletto, a partire da
quella mattina si stava verificando un forte accumulo di gas all’interno della galleria
drenante Pavone ubicata in Contrada Rocca Campana di Vena, tanto da impedirne
l’accesso al personale operaio ivi presente quotidianamente. Tale fenomeno risultava
simile a quello segnalato nel Novembre 2005, a seguito del quale si era effettuato un
precedente intervento (vedasi rapporto interno UFVG2005/115).Istituto Nazionale di Geofisica e VulcanologiaUnpublishedope
Identification and Characterization of the Atherosclerotic Plaque Using Coronary CT Angiography
No full textCoronary CT angiography (CTA) is the first diagnostic modality that allows simultaneous evaluation of the lumen and wall of these small, rapidly pulsating arteries. Catheter coronary angiography, by contrast, only evaluates the internal, patent lumen of these vessels, without providing direct information on the vessel wall or the extent of vascular parietal involvement by atherosclerosis. While it identifies areas of stenosis or obstruction, it does not show details of the plaque itself, unless heavy calcifications make the atherosclerotic plaque evident on the X-ray image. Intravascular ultrasonography (IVUS) is an excellent method to obtain high-resolution images of the vascular wall, with identification of the different layers and proper characterization of the atherosclerotic plaque; however, it is an invasive procedure, performed in the course of catheter coronary angiography, and does not simultaneously evaluate the vessel lumen. Coronary CTA is therefore the first non-invasive imaging technique that allows evaluation of the lumen and walls of the coronary arteries, a particular advantage in determining the atherosclerotic burden in these arteries. Since atherosclerosis is a disease of the vessel wall, obtaining proper and direct evidence of a coronary plaque is an important new diagnostic possibility. The technique provides morphological information and CT density measurements, with important prognostic and therapeutic implications
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