Medical Ultrasound Imaging
Tuesday, 3 December 2024
 Info Sheets  Out- side     | 'Perfusion Imaging' p2 Searchterm 'Perfusion Imaging' found in 20 articles 5 definitions [ • ] - 15 booleans [• ]Result Pages : •
(CHI) Contrast harmonic imaging is an ultrasound technique to improve the measurement of blood perfusion or capillary blood flow. Based on the nonlinear properties of contrast agents, CHI transmits at the fundamental frequency but receives at the second harmonic. Contrast enhanced echo signals contain significant energy components at higher harmonics (bubbles acts as harmonic oscillators), while tissue echoes do not. Caused by that contrast signal can be separated from tissue echoes by the characteristic signal. In combination with the pulse inversion technique, CHI promises very high contrast agent sensitivity with high spatial resolution. See also Ultrasound Contrast Agent Safety and Hemoglobin.  Further Reading: Basics:
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Harmonic B-mode imaging takes advantage of the non-linear oscillation
of microbubbles. During harmonic imaging, the sound signal is transmitted at a frequency of around 1.5 to 2.0 MHz and received at twice this frequency. The microbubbles also reflect waves with wavelengths different from the transmitted one, the detectors can be set to receive only the latter ones and create only images of the contrast agent. Using bandpass filters the transmitted frequency is separated from the received signal to get improved visualization of vessels containing ultrasound contrast agents (USCAs). The signal to noise ratio during the presence of microbubbles in tissue is four- to fivefold higher at the harmonic compared with the basic frequency. Using harmonic B-mode imaging, harmonic frequencies produced by the ultrasound propagation through tissue have to be taken into account. The tissue reflection produces only a small amount harmonic energy compared to USCAs, but has to be removed by background subtraction for quantitative evaluation of myocardial perfusion. See also Non-linear Propagation. •
Quantison, consisting of air-filled microbubbles with stiff and rigid human serum albumin shells, is an investigational ultrasound contrast agent for the assessment of coronary artery disease. The stiff shell inhibits the bubbles from oscillating and decrease non-linear scattering. Quantison is capable of long lasting cavity contrast and myocardial opacification using intermittent imaging.
Drug Information and Specification
RESEARCH NAME
AIP101
DEVELOPER
Andaris Ltd. (acquired by Quadrant)
INDICATION -
DEVELOPMENT STAGE APPLICATION
Intravenous injection
TYPE
Microbubble
Human serum albumin
CHARGE
-
Air
MICROBUBBLE SIZE
-
PREPARATION
Reconstitute with water
DO NOT RELY ON THE INFORMATION PROVIDED HERE, THEY ARE
NOT A SUBSTITUTE FOR THE ACCOMPANYING PACKAGE INSERT! •
Selective detection of the microbubble contrast medium can be enhanced by Doppler processing that removes signals with zero Doppler frequency shifts. This will remove tissue harmonics.
By detecting overlong bursts of inverted pulses and using Doppler detection methods, very high sensitivity to microbubbles can be achieved. The bubbles can be detected at sufficiently low incident power levels to avoid destroying them. Pulse inversion Doppler has demonstrated the first real-time images of myocardial perfusion using perfluorocarbon gas agents. See also Pulse Inversion Imaging, Myocardial Contrast Echocardiography, and Perfluorochemicals. Further Reading: Basics:
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The thermal effect of ultrasound is caused by absorption of the ultrasound beam energy. As the ultrasound waves are absorbed, their energy is converted into heat. The higher the frequency, the greater the absorbed dose, converted to heat according the equation: f = 1/T where T is the period as in simple harmonic motion. Ultrasound is a mechanical energy in which a pressure wave travels through tissue. Heat is produced at the transducer surface and also tissue in the depth can be heated as ultrasound is absorbed. The thermal effect is highest in tissue with a high absorption coefficient, particularly in bone, and is low where there is little absorption. The temperature rise is also dependent on the thermal characteristics of the tissue (conduction of heat and perfusion), the ultrasound intensity and the length of examination time. The intensity is also dependent on the power output and the position of the tissue in the beam profile. The intensity at a particular point can be changed by many of the operator controls, for example power output, mode (B-mode, color flow, spectral Doppler), scan depth, focus, zoom and area of color flow imaging. The transducer face and tissue in contact with the transducer can be heated. See also Thermal Units Per Hour and Ultrasound Radiation Force. Result Pages : | Share This Page     Look Ups |
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Copyright © 2008 - 2024 SoftWays. All rights reserved.
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[last update: 2023-11-06 01:42:00]