Photons: Discrete concentrations of energy, apparently massless elementary particles, that move at the speed of light. They are the unit or quantum of electromagnetic radiation. Photons are emitted when electrons move from one energy state to another. (From Hawley's Condensed Chemical Dictionary, 11th ed)Tomography, Emission-Computed, Single-Photon: A method of computed tomography that uses radionuclides which emit a single photon of a given energy. The camera is rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer is then used to reconstruct the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the organ. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as size and volume of the organ. The disadvantage is that, unlike positron-emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of many available photons and hence degrades the image.Elementary Particles: Individual components of atoms, usually subatomic; subnuclear particles are usually detected only when the atomic nucleus decays and then only transiently, as most of them are unstable, often yielding pure energy without substance, i.e., radiation.Scattering, Radiation: The diversion of RADIATION (thermal, electromagnetic, or nuclear) from its original path as a result of interactions or collisions with atoms, molecules, or larger particles in the atmosphere or other media. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Radiometry: The measurement of radiation by photography, as in x-ray film and film badge, by Geiger-Mueller tube, and by SCINTILLATION COUNTING.Phantoms, Imaging: Devices or objects in various imaging techniques used to visualize or enhance visualization by simulating conditions encountered in the procedure. Phantoms are used very often in procedures employing or measuring x-irradiation or radioactive material to evaluate performance. Phantoms often have properties similar to human tissue. Water demonstrates absorbing properties similar to normal tissue, hence water-filled phantoms are used to map radiation levels. Phantoms are used also as teaching aids to simulate real conditions with x-ray or ultrasonic machines. (From Iturralde, Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990)Light: That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.Monte Carlo Method: In statistics, a technique for numerically approximating the solution of a mathematical problem by studying the distribution of some random variable, often generated by a computer. The name alludes to the randomness characteristic of the games of chance played at the gambling casinos in Monte Carlo. (From Random House Unabridged Dictionary, 2d ed, 1993)Scintillation Counting: Detection and counting of scintillations produced in a fluorescent material by ionizing radiation.Microscopy, Fluorescence, Multiphoton: Fluorescence microscopy utilizing multiple low-energy photons to produce the excitation event of the fluorophore. Multiphoton microscopes have a simplified optical path in the emission side due to the lack of an emission pinhole, which is necessary with normal confocal microscopes. Ultimately this allows spatial isolation of the excitation event, enabling deeper imaging into optically thick tissue, while restricting photobleaching and phototoxicity to the area being imaged.Organotechnetium Compounds: Organic compounds that contain technetium as an integral part of the molecule. These compounds are often used as radionuclide imaging agents.Particle Accelerators: Devices which accelerate electrically charged atomic or subatomic particles, such as electrons, protons or ions, to high velocities so they have high kinetic energy.Radiation Dosage: The amount of radiation energy that is deposited in a unit mass of material, such as tissues of plants or animal. In RADIOTHERAPY, radiation dosage is expressed in gray units (Gy). In RADIOLOGIC HEALTH, the dosage is expressed by the product of absorbed dose (Gy) and quality factor (a function of linear energy transfer), and is called radiation dose equivalent in sievert units (Sv).Radiopharmaceuticals: Compounds that are used in medicine as sources of radiation for radiotherapy and for diagnostic purposes. They have numerous uses in research and industry. (Martindale, The Extra Pharmacopoeia, 30th ed, p1161)Technetium Tc 99m Exametazime: A gamma-emitting RADIONUCLIDE IMAGING agent used in the evaluation of regional cerebral blood flow and in non-invasive dynamic biodistribution studies and MYOCARDIAL PERFUSION IMAGING. It has also been used to label leukocytes in the investigation of INFLAMMATORY BOWEL DISEASES.Thallium Radioisotopes: Unstable isotopes of thallium that decay or disintegrate emitting radiation. Tl atoms with atomic weights 198-202, 204, and 206-210 are thallium radioisotopes.Technetium: The first artificially produced element and a radioactive fission product of URANIUM. Technetium has the atomic symbol Tc, atomic number 43, and atomic weight 98.91. All technetium isotopes are radioactive. Technetium 99m (m=metastable) which is the decay product of Molybdenum 99, has a half-life of about 6 hours and is used diagnostically as a radioactive imaging agent. Technetium 99 which is a decay product of technetium 99m, has a half-life of 210,000 years.Tomography, Emission-Computed: Tomography using radioactive emissions from injected RADIONUCLIDES and computer ALGORITHMS to reconstruct an image.Oximes: Compounds that contain the radical R2C=N.OH derived from condensation of ALDEHYDES or KETONES with HYDROXYLAMINE. Members of this group are CHOLINESTERASE REACTIVATORS.Equipment Failure Analysis: The evaluation of incidents involving the loss of function of a device. These evaluations are used for a variety of purposes such as to determine the failure rates, the causes of failures, costs of failures, and the reliability and maintainability of devices.Radiotherapy Planning, Computer-Assisted: Computer-assisted mathematical calculations of beam angles, intensities of radiation, and duration of irradiation in radiotherapy.Relative Biological Effectiveness: The ratio of radiation dosages required to produce identical change based on a formula comparing other types of radiation with that of gamma or roentgen rays.Equipment Design: Methods of creating machines and devices.Tellurium: Tellurium. An element that is a member of the chalcogen family. It has the atomic symbol Te, atomic number 52, and atomic weight 127.60. It has been used as a coloring agent and in the manufacture of electrical equipment. Exposure may cause nausea, vomiting, and CNS depression.Radiotherapy, High-Energy: Radiotherapy using high-energy (megavolt or higher) ionizing radiation. Types of radiation include gamma rays, produced by a radioisotope within a teletherapy unit; x-rays, electrons, protons, alpha particles (helium ions) and heavy charged ions, produced by particle acceleration; and neutrons and pi-mesons (pions), produced as secondary particles following bombardment of a target with a primary particle.Radiotherapy Dosage: The total amount of radiation absorbed by tissues as a result of radiotherapy.Iodine Radioisotopes: Unstable isotopes of iodine that decay or disintegrate emitting radiation. I atoms with atomic weights 117-139, except I 127, are radioactive iodine isotopes.Tomography, Optical: Projection of near-IR light (INFRARED RAYS), in the 700-1000 nm region, across an object in parallel beams to an array of sensitive photodetectors. This is repeated at various angles and a mathematical reconstruction provides three dimensional MEDICAL IMAGING of tissues. Based on the relative transparency of tissues to this spectra, it has been used to monitor local oxygenation, brain and joints.Proton Therapy: The use of an external beam of PROTONS as radiotherapy.Semiconductors: Materials that have a limited and usually variable electrical conductivity. They are particularly useful for the production of solid-state electronic devices.Optical Processes: Behavior of LIGHT and its interactions with itself and materials.Optics and Photonics: A specialized field of physics and engineering involved in studying the behavior and properties of light and the technology of analyzing, generating, transmitting, and manipulating ELECTROMAGNETIC RADIATION in the visible, infrared, and ultraviolet range.Gamma Cameras: Electronic instruments that produce photographs or cathode-ray tube images of the gamma-ray emissions from organs containing radionuclide tracers.Lasers: An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the infrared, visible, ultraviolet, or X-ray regions of the spectrum.Photometry: Measurement of the various properties of light.Radioisotopes: Isotopes that exhibit radioactivity and undergo radioactive decay. (From Grant & Hackh's Chemical Dictionary, 5th ed & McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Iofetamine: An amphetamine analog that is rapidly taken up by the lungs and from there redistributed primarily to the brain and liver. It is used in brain radionuclide scanning with I-123.Radiation: Emission or propagation of acoustic waves (SOUND), ELECTROMAGNETIC ENERGY waves (such as LIGHT; RADIO WAVES; GAMMA RAYS; or X-RAYS), or a stream of subatomic particles (such as ELECTRONS; NEUTRONS; PROTONS; or ALPHA PARTICLES).Dose-Response Relationship, Radiation: The relationship between the dose of administered radiation and the response of the organism or tissue to the radiation.Electrons: Stable elementary particles having the smallest known negative charge, present in all elements; also called negatrons. Positively charged electrons are called positrons. The numbers, energies and arrangement of electrons around atomic nuclei determine the chemical identities of elements. Beams of electrons are called CATHODE RAYS.Spectrometry, Gamma: Determination of the energy distribution of gamma rays emitted by nuclei. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Luminescent Measurements: Techniques used for determining the values of photometric parameters of light resulting from LUMINESCENCE.Lutetium: Lutetium. An element of the rare earth family of metals. It has the atomic symbol Lu, atomic number 71, and atomic weight 175.Cadmium Compounds: Inorganic compounds that contain cadmium as an integral part of the molecule.Synchrotrons: Devices for accelerating protons or electrons in closed orbits where the accelerating voltage and magnetic field strength varies (the accelerating voltage is held constant for electrons) in order to keep the orbit radius constant.Diagnostic Imaging: Any visual display of structural or functional patterns of organs or tissues for diagnostic evaluation. It includes measuring physiologic and metabolic responses to physical and chemical stimuli, as well as ultramicroscopy.Retinal Rod Photoreceptor Cells: Photosensitive afferent neurons located in the peripheral retina, with their density increases radially away from the FOVEA CENTRALIS. Being much more sensitive to light than the RETINAL CONE CELLS, the rod cells are responsible for twilight vision (at scotopic intensities) as well as peripheral vision, but provide no color discrimination.Heavy Ion Radiotherapy: The use of a heavy ion particle beam for radiotherapy, such as the HEAVY IONS of CARBON.Quantum Theory: The theory that the radiation and absorption of energy take place in definite quantities called quanta (E) which vary in size and are defined by the equation E=hv in which h is Planck's constant and v is the frequency of the radiation.Positron-Emission Tomography: An imaging technique using compounds labelled with short-lived positron-emitting radionuclides (such as carbon-11, nitrogen-13, oxygen-15 and fluorine-18) to measure cell metabolism. It has been useful in study of soft tissues such as CANCER; CARDIOVASCULAR SYSTEM; and brain. SINGLE-PHOTON EMISSION-COMPUTED TOMOGRAPHY is closely related to positron emission tomography, but uses isotopes with longer half-lives and resolution is lower.Rhodopsin: A purplish-red, light-sensitive pigment found in RETINAL ROD CELLS of most vertebrates. It is a complex consisting of a molecule of ROD OPSIN and a molecule of 11-cis retinal (RETINALDEHYDE). Rhodopsin exhibits peak absorption wavelength at about 500 nm.Radionuclide Imaging: The production of an image obtained by cameras that detect the radioactive emissions of an injected radionuclide as it has distributed differentially throughout tissues in the body. The image obtained from a moving detector is called a scan, while the image obtained from a stationary camera device is called a scintiphotograph.Thallium: A heavy, bluish white metal, atomic number 81, atomic weight [204.382; 204.385], symbol Tl.Luminescence: Emission of LIGHT when ELECTRONS return to the electronic ground state from an excited state and lose the energy as PHOTONS. It is sometimes called cool light in contrast to INCANDESCENCE. LUMINESCENT MEASUREMENTS take advantage of this type of light emitted from LUMINESCENT AGENTS.Computer Simulation: Computer-based representation of physical systems and phenomena such as chemical processes.Xenon Radioisotopes: Unstable isotopes of xenon that decay or disintegrate emitting radiation. Xe atoms with atomic weights 121-123, 125, 127, 133, 135, 137-145 are radioactive xenon isotopes.Linear Energy Transfer: Rate of energy dissipation along the path of charged particles. In radiobiology and health physics, exposure is measured in kiloelectron volts per micrometer of tissue (keV/micrometer T).X-Rays: Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard X-rays are the higher energy, shorter wavelength X-rays. Soft x-rays or Grenz rays are less energetic and longer in wavelength. The short wavelength end of the X-ray spectrum overlaps the GAMMA RAYS wavelength range. The distinction between gamma rays and X-rays is based on their radiation source.Spectrum Analysis: The measurement of the amplitude of the components of a complex waveform throughout the frequency range of the waveform. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Technetium Tc 99m Sestamibi: A technetium imaging agent used to reveal blood-starved cardiac tissue during a heart attack.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Radiotherapy, Intensity-Modulated: CONFORMAL RADIOTHERAPY that combines several intensity-modulated beams to provide improved dose homogeneity and highly conformal dose distributions.Vision, Ocular: The process in which light signals are transformed by the PHOTORECEPTOR CELLS into electrical signals which can then be transmitted to the brain.Technetium Tc 99m Pyrophosphate: A radionuclide imaging agent used primarily in scintigraphy or tomography of the heart to evaluate the extent of the necrotic myocardial process. It has also been used in noninvasive tests for the distribution of organ involvement in different types of amyloidosis and for the evaluation of muscle necrosis in the extremities.Photoreceptor Cells: Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade.Photosynthesis: The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide using energy obtained from light rather than from the oxidation of chemical compounds. Photosynthesis comprises two separate processes: the light reactions and the dark reactions. In higher plants; GREEN ALGAE; and CYANOBACTERIA; NADPH and ATP formed by the light reactions drive the dark reactions which result in the fixation of carbon dioxide. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001)IodobenzenesNeutrons: Electrically neutral elementary particles found in all atomic nuclei except light hydrogen; the mass is equal to that of the proton and electron combined and they are unstable when isolated from the nucleus, undergoing beta decay. Slow, thermal, epithermal, and fast neutrons refer to the energy levels with which the neutrons are ejected from heavier nuclei during their decay.Fluorescence: The property of emitting radiation while being irradiated. The radiation emitted is usually of longer wavelength than that incident or absorbed, e.g., a substance can be irradiated with invisible radiation and emit visible light. X-ray fluorescence is used in diagnosis.X-Ray Therapy: Medical treatment involving the use of controlled amounts of X-Rays.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Computer-Aided Design: The use of computers for designing and/or manufacturing of anything, including drugs, surgical procedures, orthotics, and prosthetics.Cerebrovascular Circulation: The circulation of blood through the BLOOD VESSELS of the BRAIN.Radiotherapy, Conformal: Radiotherapy where there is improved dose homogeneity within the tumor and reduced dosage to uninvolved structures. The precise shaping of dose distribution is achieved via the use of computer-controlled multileaf collimators.Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Models, Theoretical: Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Protons: Stable elementary particles having the smallest known positive charge, found in the nuclei of all elements. The proton mass is less than that of a neutron. A proton is the nucleus of the light hydrogen atom, i.e., the hydrogen ion.Astronomical Objects: Aggregates of matter in outer space.Spectrometry, Fluorescence: Measurement of the intensity and quality of fluorescence.Tomography: Imaging methods that result in sharp images of objects located on a chosen plane and blurred images located above or below the plane.Radius: The outer shorter of the two bones of the FOREARM, lying parallel to the ULNA and partially revolving around it.PhotochemistryFast Neutrons: Neutrons, the energy of which exceeds some arbitrary level, usually around one million electron volts.Heavy Ions: Positively-charged atomic nuclei that have been stripped of their electrons. These particles have one or more units of electric charge and a mass exceeding that of the Helium-4 nucleus (alpha particle).Darkness: The absence of light.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Organs at Risk: Organs which might be damaged during exposure to a toxin or to some form of therapy. It most frequently refers to healthy organs located in the radiation field during radiation therapy.Models, Structural: A representation, generally small in scale, to show the structure, construction, or appearance of something. (From Random House Unabridged Dictionary, 2d ed)Molecular Imaging: The use of molecularly targeted imaging probes to localize and/or monitor biochemical and cellular processes via various imaging modalities that include RADIONUCLIDE IMAGING; ULTRASONOGRAPHY; MAGNETIC RESONANCE IMAGING; FLUORESCENCE IMAGING; and MICROSCOPY.Image Enhancement: Improvement of the quality of a picture by various techniques, including computer processing, digital filtering, echocardiographic techniques, light and ultrastructural MICROSCOPY, fluorescence spectrometry and microscopy, scintigraphy, and in vitro image processing at the molecular level.Minerals: Native, inorganic or fossilized organic substances having a definite chemical composition and formed by inorganic reactions. They may occur as individual crystals or may be disseminated in some other mineral or rock. (Grant & Hackh's Chemical Dictionary, 5th ed; McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Tropanes: N-methyl-8-azabicyclo[3.2.1]octanes best known for the ones found in PLANTS.Dark Adaptation: Adjustment of the eyes under conditions of low light. The sensitivity of the eye to light is increased during dark adaptation.
VLPC stands for visible-light photon counter and refers to a new high quantum efficiency multi-photon counting detector, which operates at visible wavelengths. The ability to be capable of counting the exact number of photons that are detected is extremely important for QKD. The device is being used extensively in the central tracking detector of the D0 experiment, and for muon cooling studies for a muon collider (MICE). ...
Time-correlated single-photon counting (TCSPC) is usually employed because it compensates for variations in source intensity and single photon pulse amplitudes. Using commercial TCSPC equipment a fluorescence decay curve can be recorded with a time resolution down to 405 fs.[6] The recorded fluorescence decay histogram obeys Poisson statistics which is considered in determining goodness of fit during fitting. More specifically, TCSPC records times at which individual photons are detected by a fast single-photon detector (typically a photo-multiplier tube (PMT) or a single photon avalanche photo diode (SPAD)) with respect to the excitation laser pulse. The recordings are repeated for multiple laser pulses and after enough recorded events, one is able to build a histogram of the number of events across all of these recorded time points. This histogram can then be fit to an exponential function that contains the exponential ...
The near-infrared (NIR) window (also known as optical window or therapeutic window) defines the range of wavelengths from 650 to 1350 nm where light has its maximum depth of penetration in tissue. Within the NIR window, scattering is the most dominant light-tissue interaction, and therefore the propagating light becomes diffused rapidly. Since scattering increases the distance travelled by photons within tissue, the probability of photon absorption also increases. Because scattering has weak dependence on wavelength, the NIR window is primarily limited by the light absorption of blood at short wavelengths and water at long wavelengths. The technique using this window is called NIRS. Medical imaging techniques such as fluorescence image-guided surgery often make use of the NIR window to detect deep structures. The absorption coefficient ( μ a {\displaystyle \mu _{a}} ) is defined as the probability of photon absorption in tissue per unit path length. ...
and a second-order process with respect to light intensity. For this reason it is a non-linear process several orders of magnitude weaker than linear absorption, thus very high light intensities are required to increase the number of such rare events. For example, tightly-focused laser beams provide the needed intensities. Here, pulsed laser sources are preferred as they deliver high-intensity pulses while depositing a relatively low average energy. To enable 3D structuring, the light source must be adequately adapted to the photoresist in that single-photon absorption is highly suppressed while two-photon absorption is favoured. This condition is met if and only if the resist is highly transparent for the laser light's output wavelength λ and, simultaneously, absorbing at λ/2. As a result, a given sample relative to the focused laser beam can be scanned while changing the resist's solubility only in a confined volume. The geometry of the latter mainly depends on the ...
is the refractive index of the medium) by looking at whether this particle does or does not emit Cherenkov light in a certain medium. Knowing particle momentum, one can separate particles lighter than a certain threshold from those heavier than the threshold. The most advanced type of a detector is the RICH, or Ring-imaging Cherenkov detector, developed in the 1980s. In a RICH detector, a cone of Cherenkov light is produced when a high speed charged particle traverses a suitable medium, often called radiator. This light cone is detected on a position sensitive planar photon detector, which allows reconstructing a ring or disc, the radius of which is a measure for the Cherenkov emission angle. Both focusing and proximity-focusing detectors are in use. In a focusing RICH detector, the photons are collected by a spherical mirror and focused onto the photon detector placed at the focal plane. The result is a circle with a radius independent of the emission point ...
Raman scattering is another phenomenon that involves inelastic scattering of light caused by the vibrational properties of matter. The detected range of frequency shifts and other effects are very different compared to Brillouin scattering. In Raman scattering, photons are scattered by the effect of vibrational and rotational transitions in the bonds between first-order neighboring atoms, while Brillouin scattering results from the scattering of photons caused by large scale, low-frequency phonons. The effects of the two phenomena provide very different information about the sample: Raman spectroscopy can be used to determine the transmitting medium's chemical composition and molecular structure, while Brillouin scattering can be used to measure the material's properties on a larger scale - such as its elastic behavior. The frequency shifts from Brillouin scattering, a technique known as Brillouin spectroscopy, are detected with an interferometer while Raman scattering uses ...
... (DLS) is a technique in physics that can be used to determine the size distribution profile of small particles in suspension or polymers in solution. In the scope of DLS, temporal fluctuations are usually analyzed by means of the intensity or photon auto-correlation function (also known as photon correlation spectroscopy or quasi-elastic light scattering). In the time domain analysis, the autocorrelation function (ACF) usually decays starting from zero delay time, and faster dynamics due to smaller particles lead to faster decorrelation of scattered intensity trace. It has been shown that the intensity ACF is the Fourier transformation of the power spectrum, and therefore the DLS measurements can be equally well performed in the spectral domain. DLS can also be used to probe the behavior of complex fluids such as concentrated polymer solutions. A monochromatic light source, usually a laser, is shot through a polarizer and into a sample. The scattered light then goes ...
... or mirrors are important to the survival of many kinds of animal, and, in some cases, have been mimicked by engineers developing photonic crystals. Examples are the scales of silvery fish, and the tapetum lucidum that causes the eyeshine of dogs and cats. All these reflectors work by interference of light in multilayer structures with dimensions less than a wavelength, so can be classed as photonic crystals. Other animal photonic crystals have evolved to reflect narrow spectra, producing animal coloration. The scales of silvery fish, by reflecting light from the flank make detection by a predator difficult because the reflected light is similar to the incident light in the absence of the prey (Fig. 1). The eyes of some bivalve mollusks, such as the scallop (Pecten) use a concave mirror, the argentea, at the back of the eye, to create an image on the retina. The deep-sea ostracod Gigantocypris has eyes with parabolic reflectors. The compound eyes of ...
When two particles interact, their mutual cross section is the area transverse to their relative motion within which they must meet in order to scatter from each other. If the particles are hard inelastic spheres that interact only upon contact, their scattering cross section is related to their geometric size. If the particles interact through some action-at-a-distance force, such as electromagnetism or gravity, their scattering cross section is generally larger than their geometric size. When a cross section is specified as a function of some final-state variable, such as particle angle or energy, it is called a differential cross section. When a cross section is integrated over all scattering angles (and possibly other variables), it is called a total cross section. Cross sections are typically denoted σ (sigma) and measured in units of area. Scattering cross sections may be defined in nuclear, atomic, and particle physics for collisions of accelerated beams of one type of particle with ...
Radiological materials emit gamma photons, which gamma radiation detectors, also called radiation portal monitors (RPM), are good at detecting. Systems currently used in US ports (and steel mills) use several (usually 4) large PVT panels as scintillators and can be used on vehicles moving up to 16 km/h.[19] They provide very little information on energy of detected photons, and as a result, they were criticized for their inability to distinguish gammas originating from nuclear sources from gammas originating from a large variety of benign cargo types that naturally emit radioactivity, including bananas, cat litter, granite, porcelain, stoneware, etc.[4] Those naturally occurring radioactive materials, called NORMs account for 99% of nuisance alarms.[20] Some radiation, like in the case of large loads of bananas is due to potassium and its rarely occurring (0.0117%) radioactive isotope potassium-40, other is due to radium or uranium that occur naturally in earth and rock, and ...
இயற்பியலில், ஒளியணு,ஒளிமம், சக்திச்சொட்டு அல்லது ஒளியன் (photon, ஃபோட்டான் அல்லது ஃபோட்டோன்) என்பது எடையில்லாததாகக் கருதப்படும், ஆனால் ஆற்றலின் திரட்சி என்று கருதப்படும் ஓர் அடிப்படைத் துகளாகும். இது கண்களுக்குப் புலனாகும் ஒளிக்கதிரினதும், பிற பல்வகை மின்காந்தக் கதிர்வீச்சுகளினதும் அடிப்படையான அலகளவாகக் கொள்ளப்படுகிறது. இது மின்காந்த விசையின் விசைக்கடத்தி ஆகும். இந்த ...
A collision cascade (also known as a displacement cascade or a displacement spike) is a set of nearby adjacent energetic (much higher than ordinary thermal energies) collisions of atoms induced by an energetic particle in a solid or liquid. If the maximum atom or ion energies in a collision cascade are higher than the threshold displacement energy of the material (tens of eVs or more), the collisions can permanently displace atoms from their lattice sites and produce defects. The initial energetic atom can be, e.g., an ion from a particle accelerator, an atomic recoil produced by a passing high-energy neutron, electron or photon, or be produced when a radioactive nucleus decays and gives the atom a recoil energy. The nature of collision cascades can vary strongly depending on the energy and mass of the recoil/incoming ion and density of the material (stopping power). When the initial recoil/ion mass is low, and the material where the cascade occurs has a low density (i.e. the recoil-material ...
இயற்பியலில், ஒளியணு,ஒளிமம், சக்திச்சொட்டு அல்லது ஒளியன் (photon, ஃபோட்டான் அல்லது ஃபோட்டோன்) என்பது எடையில்லாததாகக் கருதப்படும், ஆனால் ஆற்றலின் திரட்சி என்று கருதப்படும் ஓர் அடிப்படைத் துகளாகும். இது கண்களுக்குப் புலனாகும் ஒளிக்கதிரினதும், பிற பல்வகை மின்காந்தக் கதிர்வீச்சுகளினதும் அடிப்படையான அலகளவாகக் கொள்ளப்படுகிறது. இது மின்காந்த விசையின் விசைக்கடத்தி ஆகும். இந்த ...
Penn researchers compare overall adverse events of proton and photon therapies and found that proton therapy reduces side ... Proton therapy has a few key differences from traditional photon radiation. Photon radiation typically uses multiple x-ray ... Cancer patients receiving proton therapy instead of traditional photon radiation are at a significantly lower risk of ... 391 of whom received proton therapy and 1,092 who underwent photon treatment. All patients had non-metastatic cancer and were ...
Learn more about Pinnacle Proton-photon planning with Intensity-Modulated Proton Therapy (IMPT). View specifications, download ... Proton-photon planning with Intensity-Modulated Proton Therapy (IMPT) NOCTN167 Find similar products ...
Comparing Photon Therapy To Proton Therapy To Treat Patients With Lung Cancer. The safety and scientific validity of this study ... Radiation: Photon Beam Radiation Therapy Undergo photon beam radiation therapy. Other: Quality-of-Life Assessment Ancillary ... Active Comparator: Arm I (photon beam radiation therapy and chemotherapy) Patients undergo photon beam radiation therapy 5 days ... ARM I: Patients undergo photon beam radiation therapy 5 days per week for a total of 35 fractions and receive either paclitaxel ...
Comparing Photon Therapy To Proton Therapy To Treat Patients With Lung Cancer. This study is currently recruiting participants ... Active Comparator: Arm I (photon beam radiation therapy and chemotherapy) Patients undergo photon beam radiation therapy 5 days ... Radiation: photon beam radiation therapy Radiation: proton beam radiation therapy Drug: paclitaxel Drug: carboplatin Drug: ... ARM I: Patients undergo photon beam radiation therapy 5 days per week for a total of 35 fractions and receive either paclitaxel ...
RADIATION PROTECTION MEASUREMENTS WITH THE VARIANCE-COVARIANCE METHOD IN THE STRAY RADIATION FIELDS FROM PHOTON AND PROTON THERAPY ... In the photon beam the stray absorbed dose ranged between 0.3 and 2.4 μGy per monitor unit, and the dose equivalent between 0.4 ... study the stray radiation fields from the photon therapy facility at the Technical University of Denmark and the scanned proton therapy ...
Proton therapy versus photon radiation therapy for the management of a recurrent desmoid tumor of the right flank: a cas.... ... p Proton therapy versus photon radiation therapy for the management of a recurrent desmoid tumor of the right flank: a case ... Proton therapy versus photon radiation therapy for the management of a recurrent desmoid tumor of the right flank: a case ... epdcx:valueString Proton therapy versus photon radiation therapy for the management of a recurrent desmoid tumor of the right ...
Läs mer om Pinnacle Proton-photon planning with Intensity-Modulated Proton Therapy (IMPT). Visa specifikationer, ladda ner ... Proton-photon planning with Intensity-Modulated Proton Therapy (IMPT) Hitta liknande produkter Pinnacle Proton Planning is ...
Proton Therapy vs. Photon Therapy. 21. Christie Kang. Cellular. Sr. $75 280. Adlai E. Stevenson High School. 6. Effect of ...
Kil, W.J., Nichols, R.C., Kilkenny, J.W. et al. Proton therapy versus photon radiation therapy for the management of a ... Proton therapy versus photon radiation therapy for the management of a recurrent desmoid tumor of the right flank: a case ... Proton therapy has been demonstrated to reduce gastrointestinal exposure compared to photon-based radiotherapy in the treatment ... Milby AB, Both S, Ingram M, Lin LL: Dosimetric comparison of combined intensity-modulated radiotherapy (IMRT) and proton therapy ...
Proton therapy versus photon radiation therapy for the management of a recurrent desmoid tumor of the right flank: a case ... Proton therapy has been demonstrated to reduce gastrointestinal exposure compared to photon-based radiotherapy in the treatment ... Proton therapyIntensity-modulated radiotherapyBenign tumorsCase report. Background. Desmoid tumor (DT) is a deep-seated ... Proton therapy (PT) has the potential to improve the therapeutic index in such a setting compared to conventional x-ray-based ...
How does it differ from traditional (photon) therapy?. Proton therapy is different from traditional X-ray or photon therapy ... What is proton therapy?. Proton therapy is an advanced form of radiation therapy that uses protons, which are charged particles ... Is proton therapy recommended for other pediatric cancers?. Proton therapy has been used for several different pediatric ... The advantage of proton therapy over traditional forms of radiation treatment is its ability to deliver a pencil-thin beam of ...
Proton Therapy for Skull Base Chordomas and Chondrosarcomas. 33. Photon Irradiation for Spinal Chordomas and Chondrosarcomas. ... Fractionated Photon Radiation Therapy for Skull Base Chordomas and Chondrosarcomas. 31. Stereotactic Radiosurgery for Skull ... Proton Therapy for Spinal Chordomas and Chondrosarcomas. 35. Heavy Ion Radiation for Chordomas and Chondrosarcomas ...
For physicians who are interested in knowing whether there will be potential benefit in prescribing proton therapy over photon ... If requested, a photon plan can be generated as well.. *The Princess Margaret team will provide a written report and electronic ... How to Request Proton Therapy Consultation Services. *Referring physicians should write a referral letter or fill out the ... Proton therapy is an advanced form of precision cancer treatment, which may reduce unnecessary radiation dose to normal tissues ...
... instead of traditional photon radiation, and it will result in similar outcomes with less impact on quality of life. ... CHOP cancer patients who need radiation therapy are treated at Penn, including proton therapy through the Roberts Proton ... Those numbers are still well below what is typically associated with photon radiation. In rhabdomyosarcoma, for example, 46 ... Proton Therapy Lowers Treatment Side Effects in Pediatric Head and Neck Cancer Patients Penn, CHOP study finds treatment is ...
Pediatric patients with head and neck cancer can be treated with proton beam therapy instead of traditional photon radiation, ... CHOP cancer patients who need radiation therapy are treated at Penn, including proton therapy through the Roberts Proton ... Pediatric patients with head and neck cancer can be treated with proton beam therapy (PBT) instead of traditional photon ... Proton Therapy Lowers Treatment Side Effects in Pediatric Head and Neck Cancer Patients. Penn, CHOP study finds treatment is ...
penn-medicine-virtua-strategic-alliance-brings-first-proton-therapy-to-south-jersey More in Medicine & Health. * No substantial ... Traditional therapy uses x-rays, which are a form of photon radiation. The rays go into the body from one side and come out the ... "Penn has established itself as a global leader in proton therapy both for the treatment of patients and the training of other ... The new $35 million center, which will allow cancer patients to undergo cutting edge proton therapy in single-room treatments, ...
Differences Between Proton Therapy and Traditional Radiation. Photons (Traditional Radiation). Protons. Deposit much of their ... Proton Therapy for Mesothelioma. The main barriers to proton therapy are the high cost of the equipment and the high level of ... Proton therapy is not an option for many patients.. To be eligible to receive proton therapy as part of an aggressive ... Proton Therapy for Mesothelioma Treatment. Fact Checked Proton therapy is an alternative to traditional radiation therapy. It ...
Photons/therapeutic use. *Proton Therapy/adverse effects*. *Radiation Pneumonitis/etiology. *Radiodermatitis/etiology* ... Proton therapy for breast cancer after mastectomy: early outcomes of a prospective clinical trial.. MacDonald SM1, Patel SA, ... No photon or electron component was used. The maximum skin toxicity during radiation was grade 2, according to the Common ... Proton therapy for breast cancer after mastectomy: early outcomes of a prospective clinical trial. In regard to MacDonald et al ...
Proton therapy Proton Therapy uses energy from protons instead of photons. Protons deliver their maximum amount of energy to ... Proton Therapy Center. The Proton Therapy Center uses a beam of protons to deliver radiation directly to the tumor. ... MD Andersons Proton Therapy Center treats several types of cancer. Read more about proton therapy ... The electrons collide with a metal barrier, creating powerful X-rays called photons. The photons are shaped into beams and ...
Comparing Proton Therapy to Photon Radiation Therapy for Esophageal Cancer This trial studies how well proton beam radiation ... Intensity modulated photon radiotherapy uses high-energy x-rays to deliver radiation directly to the tumor without damaging ...
Cancer: Proton therapy has fewer side effects than X-ray radiation. Is proton therapy a better alternative for photon therapy ...
Passive Scattering Proton Therapy vs Intensity-Modulated Photon Radiotherapy for Locally Advanced NSCLC. In a study reported in ... improved heart-but not lung-radiation dose-volume indices vs intensity-modulated photon radiotherapy (IMRT) in patients with ...
Proton therapy in paediatric oncology: an Irish perspective. Proton therapy in paediatric oncology: an Irish perspective Lee, K ... photons. PT is often used in paediatric oncology due to its Methods A retrospective review of all children referred for ... Proton therapy in paediatric oncology: an Irish perspective. Lee, K.; OSullivan, C.; Daly, P.; Pears, J.; Owens, C.; ... Proton therapy for pediatric hodgkin lymphoma. Wray, J; Flampouri, S; Slayton, W; Joyce, M; Sandler, E; Morris, CG; Li, Z; ...
... then Im sure well do a much better job with proton therapy, far beyond the current practice of using photon beams," Cao said. ... Cao observed that for some cancer patients proton therapy was only 5 percent more effective than standard photon therapy, while ... "With proton therapy, precision is key," said Cao. "If the protons arent delivered to the exact site [of cancer] every single ... If the proton therapy is delivered with precision to the tumor site, no damage is caused to surrounding healthy tissues and ...
  • Also, the relative risk of a severe toxicity was two-thirds lower for proton patients compared to photon patients. (medindia.net)
  • A weighted analysis of both patient groups, which controlled for other factors that may have led to differences between the patient groups, found that the relative risk of a severe toxicity was two-thirds lower for proton patients compared to photon patients. (medindia.net)
  • Researchers from the Perelman School of Medicine at the University of Pennsylvania as well as Children's Hospital of Philadelphia analyzed cases of pediatric head and neck cancer treated with PBT between 2010 and 2016 and found similar rates of tumor control and lower rates of toxicity than what is historically expected from photon radiation. (pennmedicine.org)
  • Detailed analysis of photon and proton dose distributions will be performed, and the correlation between dose-volume parameters and clinical and dosimetric outcome will be established and tested. (helse-bergen.no)
  • In the photon beam the stray absorbed dose ranged between 0.3 and 2.4 μGy per monitor unit, and the dose equivalent between 0.4 and 9 μSv per monitor unit, depending on beam energy and measurement position. (diva-portal.org)
  • This randomized phase III trial studies proton chemoradiotherapy to see how well it works compared to photon chemoradiotherapy in treating patients with stage II-IIIB non-small cell lung cancer that cannot be removed by surgery. (clinicaltrials.gov)
  • It is not yet known whether proton chemoradiotherapy is more effective than photon chemoradiotherapy in treating non-small cell lung cancer. (clinicaltrials.gov)
  • UH is one of the only cancer centers in the country to offer such a broad range of advanced photon-based radiation technology under one roof. (medindia.net)