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For what purposes was positron emission tomography first used?
GaleEncyofNeuroDis
Physicians first used PET to study brain activity in neurological diseases and disorders including stroke, epilepsy, Alzheimer's disease, Parkinson's disease , and Huntington's disease
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∙ 13y ago
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How does a pet scan employ elementary particles?
Elementary particles are defined by current physics as quarks, leptons and gauge bosons. A PET (positron emission tomography) scan uses positrons (antiparticles of electrons, which are a type of lepton) to generate a picture of the tissue in question. First, a radioactive isotope that decays by β+ decay (e.g. C11, N13, O15, F18) is incorporated in a organic compound that will localize to the desired tissue. When the compound arrives at the tissue, it can then under go decay and emit a positron. This positron will annihilate with the first electron it encounters, converting both their masses to energy. This energy is expressed as two gamma photons travelling in directly opposite directions so as to conserve momentum. These gamma photons are detected by the PET scanner and when a large number of the atoms are decaying, the computer can use the relative time differential (nanoseconds) between the arrival of the two photons to calculate the position of its origin and render a 3D image of the tissue.
What is a positron?
A positron is a positively charged electron. It's an antielectron - antimatter! The positron has a charge of +1 (just the opposite of the -1 of the electron), and a spin of 1/2 as an electron does. The mass of this elementary particle is about 9.103826 x 10-31 kg. The actual charge on this particle is about +1.602 x 10-19 coulombs. We write it as β+ or e+ in nuclear equations. It was Paul Dirac who first theorized that it may exist back in 1928, and in 1932, Carl D. Anderson discovered and named the positron. How was it done? By allowing cosmic rays to pass through a cloud chamber shielded with lead and set up in a magnetic field, the electron-positron pairs that were sometimes created could be observed. Once created, the particles moved (curved) in opposite directions within the magnetic field. Simple and clever! It should be noted that Caltech graduate student Chung-Yao Chao is credited with detecting the positron in 1930, but he was unable to explain it. We should also note that the positron is emitted (positron emission) in beta plus decay, which is a form of radioactive decay. Pair production, the "conversion" of electromagnetic energy into a positron and an electron, is also a source of positrons. Regardless of the source, the positron will always seek to "combine" with any nearby electron with the mass of both particles being converted into electromagnetic energy (a pair of gamma rays). A more detailed description and some of the other characteristics of the positron can be found in the Wikipedia article on that subject. A link is provided below to that post and also to some Related questions that will aid in understanding this critter.
Is there proof a positron exists?
Positrons were first suggested by Paul Dirac in 1928, and they were observed directly in a cloud chamber by Carl D. Anderson in 1932. It should be noted that Caltech graduate student Chung-Yao Chao is credited with detecting the positron in 1930, but he was unable to explain it. As regards Anderson's experiment, it was fairly simple. Highly energetic cosmic rays passing through the cloud chamber interacted with other atoms in a number of pair production events. These high energy gamma rays were actually "creating" matter from electromagnetic energy. A magnetic field set up in the chamber caused the particle pairs, which are an electron and a positron, to be deflected in opposite directions because of their opposite charges. There was only one explanation for the observed results, and this explanation included the existence of a positron, the antiparticle of the electron. Just as Dirac predicted. Positrons have been seen as products in numerous high energy physics experiments. In addition, they are actually used in medical imaging, and we see this in Positron Emission Tomography (PET scan). Without positrons, PET scans wouldn't be possible. Links are provided below for more information.
When was PET invented?
The concept of emission and transmission PET (positron emmision tomography) was introduced by David E. Kuhl and Roy Edwards in the late 1950s. However, in 1961, James Robertson and his associates at Brookhaven National Laboratory built the first single-plane PET scan, nicknamed the "head-shrinker. The PET compound was first administered to two normal human volunteers by Abbas Alawi in August 1976 at the University of Pennsylvania. The PET/CT scanner, attributed to Dr David Townsend and Dr Nutt was named by TIME Magazine as the medical invention of the year in 2000. source: wikipedia and others
What is the equation of a positron emission from silicon?
Silicon-26 is a synthetic isotope of silicon; it is a man-made isotope. Additionally, silicon-26 is pretty unstable, and it has a half life of only about 2.234 seconds. This unstable isotope of silicon undergoes beta plus decay, which is also called positron emission. The result is the creation of an atom of aluminum. In the positron emission of silicon-26, let's start with the equation. Here it is: 1426Si => 1326Al + e+ Here we see Si-26 become Al-26. Inside the silicon-26 nucleus, the weak interaction (weak force) mediates the conversion of a proton into a neutron. When that happens, the silicon atom changes into an aluminum atom because there is one less proton in that used-to-be silicon nucleus. The atom's atomic number goes down by one, and the silicon becomes aluminum. This is an example of nuclear transmutation; it is the conversion of one element into another. We also see a positron (e+) leave the nucleus in the event, and this is why we sometimes call this type of beta decay positron emission. The positron that leaves this decay event has a great deal of kinetic energy, and it's really flying when it is ejected from the nucleus. The Al-26 that results is itself unstable, and the excited nucleus is a gamma emitter. Eventually though, the Al-26 "settles down" a bit. It has a really long half-life - some 7.17 x 105 years. It, too, will eventually decay, but it might undergo beta plus decay, or it could undergo electron capture. In either case, it becomes magnesium-26, which is stable.
What is the difference between a proton and antiproton?
AnswerThe difference between a proton and a positron is threefold. First, the proton is much more massive (a bit over 1800 times) than a positron. Second, the positron is an elementary particle (though it is antimatter), while the proton is made up of three elementary particles called quarks (two up quarks and one downquark). Third, the positron is antimatter while the proton is "regular" matter. Protons are stable particles (they are hydrogen-1 nuclei), and positrons are produced in positron emission (a type of radioactive decay) or in pair production (where a high energy gamma ray "splits" into an electron and a positron when passing near an atomic nucleus). After a positron appears, it will eventually (and in a relatively short period) combine with an electron in an even called mutual annihilation, and both particles will be converted into energy.Both the proton and positron have a charge of +1, and you can review more information by using the links below to the related questions about the proton and the positron.AnswerA proton is a particle found in the nucleus. It has a positive charge of +1. (Depending on how versed you are, this is equivalent to + 1.60 x 10-19 C of charge). The proton actually is comprised of three smaller subatomic particles called quarks, two up quarks (+2/3) and one down quark (- 1/3). The electron on the other hand is a fundamental particle in that it is not made up of anything smaller (that we know of yet). It has a -1 charge (again - 1.60 x 10-19 C). A positron, however, is antimatter. It is the antimatter of an electron. For intents and purposes it is an electron with a positive charge. If an electron and a positron should interact, they would annihilate one another.
What was the first antiparticle discovered?
In 1932, Carl D. Anderson, while studying cosmic rays , discovered the predicted positron, the first known antiparticle.
What where the purposes of the first languages?
Communication.
What DR homi bhabha discovered?
In 1935, Indian nuclear physicist Homi J. Bhabha published a paper in the Proceedings of the Royal Society, Series A, in which he performed the first calculation to determine the cross section of electron-positron scattering.Electron-positron scattering was later named Bhabha scattering, in honor of his contributions in the field.
What decays first duriing radioactive decay?
No, radioactive decay is not a chemical reaction. Radioactive decay is a type of change in the nucleus of an atom that results from instability in that nucleus. And that is a nuclear reaction rather than a chemical one.
What is positron annihilation spectroscopy?
Positron annihilation spectroscopy is a research tool that is being investigated because it may provide a way to look at defects in a solid matrix. A positron source is set up to direct positrons at a material under investigation. Because of the way positrons behave while slowing down (they usually don't just combine with the first electron they encounter), they tend to find their way into defects in the material structure of the solid into which they have been directed. When the positron does finally hook up with an electron and the annihilation event occurs, the energy and directivity of the gamma rays produced can be used to learn something about the structure of the atomic matrix in which the event occurred.
1995 dodge caravan evaporative emission control system leak?
Replace the gas cap first.
