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Magnetocardiography
Magnetocardiography (MCG) is a technique to measure the magnetic fields produced by electrical currents in the heart using extremely sensitive devices such as the superconducting quantum interference device (SQUID). If the magnetic field is measured using a multichannel device, a map of the magnetic field is obtained over the chest; from such a map, using mathematical algorithms that take into account the conductivity structure of the torso, it is possible to locate the source of the activity. For example, sources of abnormal rhythms or arrhythmia may be located using MCG. History The first MCG measurements were made by Baule and McFee using two large coils placed over the chest, connected in opposition to cancel out the relatively large magnetic background. Heart signals were indeed seen, but were very noisy. The next development was by David Cohen, who used a magnetically shielded room to reduce the background, and a smaller coil with better electronics; the heart signals we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Field Imaging
Magnetic Field Imaging (MFI) is a non-invasive and side-effect-free cardiac diagnostic method. In more recent technology, magnetocardiography (MCG) has become the clinically predominant application for recording the heart's magnetic signals. that detects and records the electromagnetic signals that are associated with the heartbeat using a multi-channel magnetic sensor array. The electric signals are known from the ECG. In the 1990s and beyond, more recent technology has supplanted the MFI, particularly MCG (xref. Cardiomag Imaging, Inc.). Through clinical research in Europe, Asia, and the U.S. (see publications in footnotes), MCG has been proven to have practical application for diagnosis of cardiac disease, and has become the clinically predominant application for recording the heart's magnetic signals. In comparison to MCG, MFI, among others, records the whole relevant area above the chest of the person. Background The general principal of MFI is based on two facts: *Cell ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biomagnetism
Biomagnetism is the phenomenon of magnetic fields ''produced'' by living organisms; it is a subset of bioelectromagnetism. In contrast, organisms' use of magnetism in navigation is magnetoception and the study of the magnetic fields' ''effects'' on organisms is ''magnetobiology''. (The word biomagnetism has also been used loosely to include magnetobiology, further encompassing almost any combination of the words magnetism, cosmology, and biology, such as "magnetoastrobiology".) The origin of the word biomagnetism is unclear, but seems to have appeared several hundred years ago, linked to the expression "animal magnetism". The present scientific definition took form in the 1970s, when an increasing number of researchers began to measure the magnetic fields produced by the human body. The first valid measurement was actually made in 1963, but the field of research began to expand only after a low-noise technique was developed in 1970.{{cite journal , last1=Cohen , first1=David , la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetoencephalography
Magnetoencephalography (MEG) is a functional neuroimaging technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers. Arrays of SQUIDs (superconducting quantum interference devices) are currently the most common magnetometer, while the SERF (spin exchange relaxation-free) magnetometer is being investigated for future machines. Applications of MEG include basic research into perceptual and cognitive brain processes, localizing regions affected by pathology before surgical removal, determining the function of various parts of the brain, and neurofeedback. This can be applied in a clinical setting to find locations of abnormalities as well as in an experimental setting to simply measure brain activity. History MEG signals were first measured by University of Illinois physicist David Cohen in 1968, before the availability of the SQUID, using a copper induction coil as the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David Cohen (physicist)
David Cohen made many of the first pioneering measurements in the area of biomagnetism (magnetic fields produced by the body), although he was initially trained as a nuclear physicist. Early life and education Cohen was born of immigrant parents in Winnipeg, Manitoba, Canada. He was raised there and earned a B.A. degree at the University of Manitoba. Then, he attended graduate school at the University of California, Berkeley, where he gained a Ph.D. in experimental nuclear physics. Career Working in this area, and using large magnets, he became interested in the other extreme; this was the measurement of very weak magnetic fields, which for example might be produced by the weak natural currents in the human body. In 1963, he proposed a method using a magnetically shielded room to keep out external magnetic disturbances, as in radiation shielding in nuclear experiments. At that time others reported the first biomagnetic measurement, where the MCG (''magnetocardiogram'', the magneti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biomagnetism
Biomagnetism is the phenomenon of magnetic fields ''produced'' by living organisms; it is a subset of bioelectromagnetism. In contrast, organisms' use of magnetism in navigation is magnetoception and the study of the magnetic fields' ''effects'' on organisms is ''magnetobiology''. (The word biomagnetism has also been used loosely to include magnetobiology, further encompassing almost any combination of the words magnetism, cosmology, and biology, such as "magnetoastrobiology".) The origin of the word biomagnetism is unclear, but seems to have appeared several hundred years ago, linked to the expression "animal magnetism". The present scientific definition took form in the 1970s, when an increasing number of researchers began to measure the magnetic fields produced by the human body. The first valid measurement was actually made in 1963, but the field of research began to expand only after a low-noise technique was developed in 1970.{{cite journal , last1=Cohen , first1=David , la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bioelectromagnetics
Bioelectromagnetics, also known as bioelectromagnetism, is the study of the interaction between electromagnetic fields and biological entities. Areas of study include electromagnetic fields produced by living cells, tissues or organisms, the effects of man-made sources of electromagnetic fields like mobile phones, and the application of electromagnetic radiation toward therapies for the treatment of various conditions. Biological phenomena Bioelectromagnetism is studied primarily through the techniques of electrophysiology. In the late eighteenth century, the Italian physician and physicist Luigi Galvani first recorded the phenomenon while dissecting a frog at a table where he had been conducting experiments with static electricity. Galvani coined the term ''animal electricity'' to describe the phenomenon, while contemporaries labeled it galvanism. Galvani and contemporaries regarded muscle activation as resulting from an electrical fluid or substance in the nerves. Short-liv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Edward Zimmerman
James Edward Zimmerman (February 19, 1923 – August 4, 1999) was born in Lantry, South Dakota. He was coinventorof the radio-frequency superconducting quantum interference device (SQUID) and he is credited with coining the term. Career * Westinghouse Research Laboratory, Pittsburgh Pennsylvania - 1943 – ?? * Smithsonian Institution, 1953 – 1955 * Ford Motor Company, Scientific Laboratory in Dearborn, Michigan, 1955 – 1969 * SHE (later BTi, then 4-D Neuroimaging), Founder 1969 – 1970 * National Bureau of Standards, 1970 – 1985 While at NIST, Zimmerman introduced two important innovations in SQUID magnetometry: * Fractional-turn SQUID, improving the coupling efficiency * SQUID gradiometer, improving sensitivity to nearby fields In addition, in the late 1970s and early 1980s, he also gave a major contribution to the development of low-power closed-cycle Stirling refrigerators, to reach temperatures in the range 4K - 8K with the purpose of cooling ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetogastrography
Magnetogastrography is the science of recording magnetogastrograms (MGGs). Magnetogastrograms are recordings of magnetic fields resulting from electrical currents in the stomach. The magnetic fields are typically recorded using SQUIDs. See also * Electrogastrogram * Magnetoencephalography Magnetoencephalography (MEG) is a functional neuroimaging technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers. Arrays of SQUIDs (s ... External links Gastrointestinal SQUID Technology Laboratory at Vanderbilt University Medical imaging {{treatment-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field. A permanent magnet's magnetic field pulls on ferromagnetic materials such as iron, and attracts or repels other magnets. In addition, a nonuniform magnetic field exerts minuscule forces on "nonmagnetic" materials by three other magnetic effects: paramagnetism, diamagnetism, and antiferromagnetism, although these forces are usually so small they can only be detected by laboratory equipment. Magnetic fields surround magnetized materials, and are created by electric currents such as those used in electromagnets, and by electric fields varying in time. Since both strength and direction of a magnetic field may vary with location, it is described mathematically by a function assigning a vector to each point of space, cal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clinical Diagnosis
Medical diagnosis (abbreviated Dx, Dx, or Ds) is the process of determining which disease or condition explains a person's symptoms and signs. It is most often referred to as diagnosis with the medical context being implicit. The information required for diagnosis is typically collected from a history and physical examination of the person seeking medical care. Often, one or more diagnostic procedures, such as medical tests, are also done during the process. Sometimes posthumous diagnosis is considered a kind of medical diagnosis. Diagnosis is often challenging because many signs and symptoms are nonspecific. For example, redness of the skin (erythema), by itself, is a sign of many disorders and thus does not tell the healthcare professional what is wrong. Thus differential diagnosis, in which several possible explanations are compared and contrasted, must be performed. This involves the correlation of various pieces of information followed by the recognition and differentiation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heart
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to the lungs. In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the chest. In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. Fish, in contrast, have two chambers, an atrium and a ventricle, while most reptiles have three chambers. In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow. The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
