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Result : Searchterm 'Pressure' found in 0 term [] and 11 definitions []
| previous 6 - 10 (of 11) nextResult Pages : [1 2 3] | | | | Searchterm 'Pressure' was also found in the following services: | | | | |
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(Pa) The SI unit of pressure.
Definition: 1 pascal is equal to 1 N/m2 = 1
J/m3 = 1 kg·m-1·s-2
1 kPa = 0.145 lbf/in2.
Air pressure is measured in hectopascal (hPa), with 1 hPa = 1 millibar.
The unit is named for Blaise Pascal (1623-1662), French philosopher and mathematician. | | | | | |
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A logarithmic measure of sound loudness closely related to the decibel. The unit decibel is used for objective measurements, that means, they measure the actual pressure of the sound waves as recorded using a microphone. The unit phon is used for subjective measurements, that means, measurements made using the ears of a human listener.
A sound has the loudness 'p' phon if it seems to the listener to be equal in loudness to the sound of a pure tone of the frequency 1 kilohertz and strength 'p' decibel. A measurement in phons will be similar to a measurement in decibel, but not identical, since the perceived loudness of a sound depends on the distribution of frequencies in the sound as well as the pressure of the sound waves. In the U.S., sound loudness is frequently measured in sones rather than phons: a sound of loudness 's' sones has loudness 10 log2 s + 40 phons.
See also Acoustic Noise. | | | | • View the DATABASE results for 'Phon' (48).
| | | • View the NEWS results for 'Phon' (2).
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A bolus is a rapid infusion of high dose contrast agent. Dynamic and accumulation phase imaging can be performed after bolus injection. Since the transit time of the bolus through the tissue is only a few seconds, high temporal resolution imaging can be required to obtain sequential images during the wash in and wash out of the contrast material and, therefore, resolve the first pass of the tracer.
For the same injected dose of contrast agent the injection rate (and, consequently, the total injected volume) modifies the bolus peak profile. Increasing the injection rate produces a sharpening of the peak
(Cmax increase, Tmax decrease, peak length decrease). At a
low injection rate, the first pass presents a plateau form.
Substantial changes in the gadolinium concentrations during signal acquisition induce artifacts. Furthermore, the haemodynamic
parameters ( cardiac output, blood pressure) influence
the bolus profile.
The characteristics of gadolinium agents are favorable in the early bolus
phase, whereas the advantages of large complexes (e.g. blood pool agents) and ultrasmall superparamagnetic iron oxide ( USPIO) are most evident in the distribution phase. | | | | | | • View the DATABASE results for 'Bolus Injection' (9).
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In the last years, cardiac MRI techniques have progressively improved. No other noninvasive imaging modality provides the same degree of contrast and temporal resolution for the assessment of cardiovascular anatomy and pathology. Contraindications MRI are the same as for other magnetic resonance techniques.
The primary advantage of MRI is extremely high contrast resolution between different tissue types, including blood. Moreover, MRI is a true 3 dimensional imaging modality and images can be obtained in any oblique plane along the true cardiac axes while preserving high temporal and spatial resolution with precise demonstration of cardiac anatomy without the administration of contrast media.
Due to these properties, MRI can precisely characterize cardiac function and quantify cavity volumes, ejection fraction, and left ventricular mass. In addition, cardiac MRI has the ability to quantify flow (see flow quantification), including bulk flow in vessels, pressure gradients across stenosis, regurgitant fractions and shunt fractions. Valve morphology and area can be determined and the severity of stenosis quantified. In certain disease states, such as myocardial infarction, the contrast resolution of MRI is further improved by the addition of extrinsic contrast agents (see myocardial late enhancement).
A dedicated cardiac coil, and a field strength higher than 1 Tesla is recommended to have sufficient signal. Cardiac MRI acquires ECG gating. Cardiac gating (ECGs) obtained within the MRI scanner, can be degraded by the superimposed electrical potential of flowing blood in the magnetic field. Therefore, excellent contact between the skin and ECG leads is necessary. For male patients, the skin at the lead sites can be shaved. A good cooperation of the patient is necessary because breath holding at the end of expiration is practiced during the most sequences.
See also Displacement Encoding with Stimulated Echoes.
For Ultrasound Imaging (USI) see Cardiac Ultrasound at Medical-Ultrasound-Imaging.com.
See also the related poll results: ' In 2010 your scanner will probably work with a field strength of' and ' MRI will have replaced 50% of x-ray exams by' | | | | | | • View the DATABASE results for 'Cardiac MRI' (15).
| | | • View the NEWS results for 'Cardiac MRI' (15).
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MRI technology visualizes heart metabolism in real time Friday, 18 November 2022 by medicalxpress.com | | |
Even early forms of liver disease affect heart health, Cedars-Sinai study finds Thursday, 8 December 2022 by www.eurekalert.org | | |
MRI sheds light on COVID vaccine-associated heart muscle injury Tuesday, 15 February 2022 by www.sciencedaily.com | | |
Radiologists must master cardiac CT, MRI to keep pace with demand: The heart is not a magical organ Monday, 1 March 2021 by www.radiologybusiness.com | | |
Diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) in the heart (myocardium) Sunday, 30 August 2020 by github.com | | |
Non-invasive diagnostic procedures for suspected CHD: Search reveals informative evidence Wednesday, 8 July 2020 by medicalxpress.co | | |
Cardiac MRI Becoming More Widely Available Thanks to AI and Reduced Exam Times Wednesday, 19 February 2020 by www.dicardiology.com | | |
Controlling patient's breathing makes cardiac MRI more accurate Friday, 13 May 2016 by www.upi.com | | |
Precise visualization of myocardial injury: World's first patient-based cardiac MRI study using 7T MRI Wednesday, 10 February 2016 by medicalxpress.com | | |
New technique could allow for safer, more accurate heart scans Thursday, 10 December 2015 by www.gizmag.com |
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The element helium (He) was discovered 1868 when P.J.C. Janssen and N. Lockyer detected a new line in the solar spectrum during the solar eclipse. Lockyer and E. Frankland suggested the name helium (Gr. Helios, the sun) for the new element. In 1895, helium was discovered in the uranium mineral cleveite and in 1907 it was found out that alpha particles are helium nuclei.
Properties: Helium belongs to the noble gases, is colorless, odorless, and occurs in two naturally isotopes, helium 3 and helium 4. As an inert gas, helium does not react chemically largely and don't burns. Helium 4 makes up over 99% of naturally occurring helium atoms. Helium is extracted from natural gas e.g. present in various radioactive minerals as a decay product. Deposits and sources are in the USA, Poland, the USSR, and a few in India. The rare deposits and increased consumption lead to a shortage of this gas.
K. Onnes worked for many years to liquefy helium, which persisted as a gas to the lowest temperature. Helium does not freeze at atmospheric pressure.
The density of helium vapor at his boiling point of 4.2 Kelvin is very high, with the vapor expanding greatly when heated to room temperature.
Nb, Tc, Pb, La, V, and Ta are superconductors at liquid helium temperature. Liquid helium is commonly used as a cryogen for superconducting magnets. A rapid evaporation of the cryogen is named Quench. See also Quenching.
Cryogenic liquids and their associated cold vapors can produce effects on the skin similar to a thermal burn and can cause frostbite. Prolonged breathing of extremely cold gases may damage the lungs and in absence of enough air or oxygen, asphyxiation and death can occur. Unprotected skin can stick to very cold metal (e.g. cooled by liquid helium) and then tear when pulled away. | | | | • View the DATABASE results for 'Helium' (43).
| | | • View the NEWS results for 'Helium' (2).
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News & More:
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Renergen surges after xceptional™ helium concentration reports Monday, 29 March 2021 by www.businesslive.co.za | | |
Not just balloons: Helium shortage may deflate MRIs, airbags and research Friday, 3 May 2019 by eu.usatoday.com | | |
Liquid helium, the lifeblood of MRI machines Tuesday, 5 March 2019 by www.gasworld.com | | |
Preclinical Imaging Systems Reduce Environmental Impact Monday, 4 November 2019 by www.itnonline.com | | |
Huge newfound deposit of helium will keep MRI scanners running Monday, 27 June 2016 by www.newscientist.com | | |
Philips launches Ingenia Ambition X 1.5T MR with industry-first fully sealed magnet for more productive, helium-free operations Tuesday, 11 September 2018 by www.philips.com | | |
Tech firms, medical research threatened by helium shortage Thursday, 19 September 2013 by www.livemint.com | | |
How 9/11 Made The Global Helium Shortage Worse Thursday, 3 July 2014 by www.popsci.com | | |
Cooling MRI magnets without a continuous supply of scarce helium Tuesday, 13 August 2013 by www.wired.co.uk |
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