Medical Ultrasound Imaging
Saturday, 4 May 2024
 Info Sheets  Out- side     | 'Molecule' Searchterm 'Molecule' found in 5 articles 5 definitions [ • ] Result Pages : •
(Hb) Hemoglobin is the major endogenous oxygen-binding molecule, responsible for binding oxygen in the lung and transporting it to the tissues by means of the circulation. Hemoglobin is contained in very high concentration in the red blood cells. Hemoglobin is a Fe chelate tightly binding one Fe ion in its II oxidation state where it carries the charge 2+. If an oxygen molecule is bound to Hb, Hb is called oxyhemoglobin, if no oxygen molecule is bound it is called deoxyhemoglobin. When hemoglobin is oxidized (i.e. in a hematoma), Fe2+ is transformed into Fe3+. The resulting hemoglobin is then called metoxyhemoglobin (Hb Fe3+). •
Targeted ultrasound contrast agents provide advantages compared with usual microbubble blood pool agents. The goal of targeted ultrasound contrast agents is to significantly and selectively enhance the detection of a targeted vascular site. Tissue-specific ultrasound contrast agents improve the image contrast resolution through differential uptake. Targeted drug delivery via contrast microbubbles is another contrast media concept and provides the potential for earlier detection and characterization of disease. Targeted contrast imaging provides a higher sensitivity and specificity than obtained with a nontargeted contrast agent. The detection of disease-indicative molecular signatures may allow early assessment of pathology on a molecular level. Molecular imaging should be an efficient and less invasive technique to obtain three-dimensional localization of pathology. Ultrasound agents typically remain within the vascular space, and therefore possible targets include molecular markers on thrombus, endothelial cells, and leukocytes. Targeted contrast agents permit noninvasive detection of thrombus, cancer, inflammation, or other sites where specific integrins or other adhesion molecules are expressed. Adhesion molecules such as monoclonal antibodies, peptides, asialoglycoproteins, or polysaccharides are incorporated into the shell of the microbubble or liposome. After injection into the bloodstream, the targeted agent accumulates via adhesion receptors at the affected site, enhancing detection with an ultrasound system. See also Acoustically Active Lipospheres, and Tissue-Specific Ultrasound Contrast Agent.  Further Reading: News & More:
•
(AALs) Acoustically active lipospheres and ultrasound are under development to deliver bioactive molecules to the vascular endothelium. The AALs are similar to both ultrasound contrast agents and drug-delivering liposomes. They can carry bioactive substances using biologically inert shells and deliver those substances when disrupted by ultrasound. The lipospheres consist of a small gas microbubble surrounded by a thick oil shell and are enclosed by an outermost lipid layer. The gas bubble contained in these vehicles makes them acoustically active, similar to ultrasound contrast agents. Acoustically active lipospheres can be nondestructively deflected using ultrasound radiation force, and fragmented with high intensity ultrasound pulses. Their lipid-oil complex can carry bioactive substances at high concentrations. An optimized sequence of ultrasound pulses can deflect the AALs toward a vessel wall then disrupt them, painting their contents across the vascular endothelium. See also Filling Gas, and MRX 115. Further Reading: Basics:
News & More:
•
Perfluorochemicals are used as microbubble filling gases because of their low solubility in blood and high vapor pressure. Various types of perfluorochemical gases like perfluorocarbon, perfluorobutane, perfluoropropane, and perfluorohexane are used to substitute the air in microbubbles to improve the stability and plasma longevity of the agents.
Perfluorocarbons are liquids at room temperature but gas at body temperature. The large molecules of perfluorocarbons have slow diffusion and solubility which increase the enhancement time of the ultrasound contrast agent as compared to air. See also Filling Gas, and PESDA. Further Reading: Basics:
•
Ultrasound physics is based on the fact that periodic motion emitted of a vibrating object causes pressure waves. Ultrasonic waves are made of high pressure and low pressure (rarefactional pressure) pulses traveling through a medium. Properties of sound waves: The speed of ultrasound depends on the mass and spacing of the tissue molecules and the attracting force between the particles of the medium. Ultrasonic waves travels faster in dense materials and slower in compressible materials. Ultrasound is reflected at interfaces between tissues of different acoustic impedance e.g., soft tissue - air, bone - air, or soft tissue - bone. The sound waves are produced and received by the piezoelectric crystal of the transducer. The fast Fourier transformation converts the signal into a gray scale ultrasound picture. The ultrasonic transmission and absorption is dependend on: See also Sonographic Features, Doppler Effect and Thermal Effect. Result Pages : | Share This Page     Look Ups |
(.pdf)Medical-Ultrasound-Imaging.com
former US-TIP.com
Member of SoftWays' Medical Imaging Group - MR-TIP • Radiology TIP • Medical-Ultrasound-Imaging
Copyright © 2008 - 2024 SoftWays. All rights reserved.
Terms of Use | Privacy Policy | Advertise With Us
former US-TIP.com
Member of SoftWays' Medical Imaging Group - MR-TIP • Radiology TIP • Medical-Ultrasound-Imaging
Copyright © 2008 - 2024 SoftWays. All rights reserved.
Terms of Use | Privacy Policy | Advertise With Us
[last update: 2023-11-06 01:42:00]