WORKING OF GAMMA CAMERA:
A gamma camera is an medical imaging device, most commonly used as a imaging device in nuclear medicine. It produces images of the distribution of gamma rays emitted by metastable radionuclides (isotopes), also called metastable nuclear isomers. A gamma ray comprises gamma photons, which are high energetic photons (at least 5000 times those of visible light). They are produced from sub-atomic particle interaction, such as electron-positron annihilation and radioactive decay. (Annihilation is the collision of a positron with an electron, followed by vanishing of both. Two (sometimes more) (gamma) photons are produced moving in almost opposite directions.) A radionuclide can also produce subatomic particles (which give ionization). Excited metastable isomers de-excite with sending a gamma photon mostly within much les than one picosecond, but some isomers are far much slower. These are for example the Technetium isomers 99mTc (here indicated without atom number; m indicates metastable; half-life 6.01 hours) and 95mTc (half-life of 61 days) are used in medical and industrial applications.
A gamma camera is a complex device consisting of one or more detectors mounted on a gantry. It is connected to an acquisition system for operating the camera and for storing the images. The system counts gamma photons that are absorbed by a crystal in the camera, usually a large flat crystal of NaI with thallium doping in a light-sealed housing. The crystal scintillates in response to incident gamma radiation: when a gamma photon knocks an electron loose from an iodine atom in the crystal, a faint flash of light is produced when the electron again finds a minimal energy state. The initial phenomenon of the excited electron is similar to the photoelectric effect (an electron hitting an atom, with as a result the emission of another electron and back-scatter of the electron with a lower speed) and (particularly with gamma rays) the Compton effect. This is generally an electron hitting an atom, with as a result the emission of a photon and back-scatter of the electron with a lower speed. So actual it is fluorescence, but here for impinging gamma rays. The flash of light must be detected. Photomultiplier tubes (extremely sensitive detectors of UV, near-IR and visible light) behind the crystal detect the fluorescent flashes and a computer sums the fluorescent counts. The computer in turn constructs and displays a two dimensional image of the relative spatial count density on a monitor. This image then reflects the distribution and relative concentration of radioactive tracer elements present in the organs and tissues imaged.
A gamma camera is an medical imaging device, most commonly used as a imaging device in nuclear medicine. It produces images of the distribution of gamma rays emitted by metastable radionuclides (isotopes), also called metastable nuclear isomers. A gamma ray comprises gamma photons, which are high energetic photons (at least 5000 times those of visible light). They are produced from sub-atomic particle interaction, such as electron-positron annihilation and radioactive decay. (Annihilation is the collision of a positron with an electron, followed by vanishing of both. Two (sometimes more) (gamma) photons are produced moving in almost opposite directions.) A radionuclide can also produce subatomic particles (which give ionization). Excited metastable isomers de-excite with sending a gamma photon mostly within much les than one picosecond, but some isomers are far much slower. These are for example the Technetium isomers 99mTc (here indicated without atom number; m indicates metastable; half-life 6.01 hours) and 95mTc (half-life of 61 days) are used in medical and industrial applications.
A gamma camera is a complex device consisting of one or more detectors mounted on a gantry. It is connected to an acquisition system for operating the camera and for storing the images. The system counts gamma photons that are absorbed by a crystal in the camera, usually a large flat crystal of NaI with thallium doping in a light-sealed housing. The crystal scintillates in response to incident gamma radiation: when a gamma photon knocks an electron loose from an iodine atom in the crystal, a faint flash of light is produced when the electron again finds a minimal energy state. The initial phenomenon of the excited electron is similar to the photoelectric effect (an electron hitting an atom, with as a result the emission of another electron and back-scatter of the electron with a lower speed) and (particularly with gamma rays) the Compton effect. This is generally an electron hitting an atom, with as a result the emission of a photon and back-scatter of the electron with a lower speed. So actual it is fluorescence, but here for impinging gamma rays. The flash of light must be detected. Photomultiplier tubes (extremely sensitive detectors of UV, near-IR and visible light) behind the crystal detect the fluorescent flashes and a computer sums the fluorescent counts. The computer in turn constructs and displays a two dimensional image of the relative spatial count density on a monitor. This image then reflects the distribution and relative concentration of radioactive tracer elements present in the organs and tissues imaged.
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