Chapter One Lecture
Clinical Application Tip #1
A new patient arrives and you greet and seat him in your chair. You ask if he has current x-rays, and he replies, “I do not like x-rays. I had the ones sent over from my previous dentist, but I do not want anymore taken.” You look on the computer under his name, and there are four bitewings dated five years ago in his chart. The next step you take is important in how to handle this situation. Without any emotion in your voice, and showing a calm, kind, smile, reply, “Our dentists’ licenses are regulated by The Oregon Board of Dentistry. In order to treat a patient in Oregon, a dentist must possess either a current panographic radiograph combined with bitewings or a full mouth series of x-rays.
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Binding Energy: The energy (expressed in electron volts) that binds orbiting electrons around the nucleus inside an atom.
Bremsstrahlung: The slowing down and veering off course of the entering high-speed electron. The loss of its energy will be expressed as heat and X-rays.
Electromagnetic Spectrum: A grouping of energy waves that has the weightlessness of the waves and the speed of travel in common (186,000 miles per second).
Energy Wave: An energy wave travels in the same way as a ripple across a body of water.
Frequency: The number of oscillations that an energy wave makes per second is the frequency.
Hittoft-Crookes tube: A vacuum tube in which an electric current from a battery flows through it.
Ionization: When an orbiting electron is ejected from its shell in an electrically stable (neutral)
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Bremsstrahlung radiation produces the most x-rays, and characteristic x-rays follow.
The thermionic emission effect takes places at the tungsten filament at the cathode when the x-ray machine is turned on in the morning.
The person accredited with the initial discovery of x-rays is Wilhelm Conrad Roentgen on November 8, 1895 in Germany. However, Dr. Otto Walkhoff, a dentist in Germany took the first dental radiograph, and Dr. C. Edmund Kells from New Orleans took the first intraoral radiographs in the United States in April 1896.
When you turn on the x-ray machine, you activate the filament circuit.
The greatest binding energy is found in the K-shell electrons.
X-rays are generated when a stream of electrons traveling from one side of a vacuum tube is stopped on impact at the tungsten target of the anode.
When the high voltage circuit is activated, the x-ray machine beeps, the electrons travel from the filament to the target, heat is produced, and the electrons at the cathode fire across the tube and hit the target at the anode.
Electromagnetic radiation includes x-rays, gamma rays, microwaves and light waves.
X-rays result from electron and atomic interactions in an x-ray tube.
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The above figure is a representation of the thermionic emission, where V – applied forward bias, EF is the Fermi level.
Zondy, David . "Tesla's Death Ray." davidszondy. 23 March 2011. Web. 10 Sept. 2011. .
on the primary beam is that it limits the x-ray beam field size. The beam restricting device alters
In Dentistry, Radiography (the making of radiographs by exposing an image receptor) is very common. “Radiographs and other imaging modalities are used to diagnose and monitor oral diseases, as well as monitor dentofacial development and the progress or prognosis of therapy.” (Association, 2012). Even though radiation exposure from the dental radiographs is low, the patients and the ADA (American Dental Association) believes that there are some safety tips that must be followed in order for the patient to feel comfortable with getting the radiograph every six months to a year. Modern x-ray equipment is programmed to reduce the amount of radiation. X-rays in dentistry can be performed by using digital imaging or conventional film. Digital imaging continues to develop and is being more commonly used. In this paper I am going to explain how x-rays have became safer over time, what steps dental assistants use to prevent exposure on the patient as well as the office staff, and some safety tips.
Light is both part particle and part wave. Light is “the electromagnetic radiation that may be perceived by the human eye”. It consists of photons, which are massless bundles of concentrated electromagnetic energy. Light’s lower frequency is red, and the higher frequency is blue. Like sound, light has frequencies humans can’t detect. Ultraviolet light is at a frequency higher than violet, and infrared is at the frequency lower than the red of visible light. We get UV (ultraviolet) rays from the sun, and infrared is used in night vision to see better.
an initial energy of about 1 MeV will induce fission is rather low, but can be
Davisson and Germer found that by varying the applied voltage to the electron gun, the maximum intensity of electrons diffracted by the atomic surface was found at different angles. The highest intensity was found to be at an angle θ = 50° with a voltage of 54 V, giving the electrons a kinetic energy of 54 eV.
You can see this experiment going on in many different places, except they tend to use different atoms. The most common would be neon signs. The main color emitted when a free electron hits a neon atom is red, and with the high voltage, there will be many collisions that produce red light. Also since the voltage is variable, the origin of the multiple red lights shifts very quickly making it seem as if the whole thing is constantly emitting red light.
Spring, K. R., & Davidson, M. W. (2016, 05 17). Light: Particle or a Wave? Retrieved from Physics of Light and Color: http://micro.magnet.fsu.edu/primer/lightandcolor/particleorwave.html
"What is a particle accelerator?." HEPHY: Particle Accelerators. N.p., n.d. Web. 28 Apr. 2014. .
As x-rays exit the patient, they interact with a cesium iodide input phosphor which converts the x-ray energy into visible light. Cesium iodide crystals are a tightly packed layer of linear needles which help improve spatial resolution by allowing little light dispersion. Attached to the input phosphor is the photocathode. Bushong describes the photocathode as, “a thin metal layer usually composed of cesium and antinomy compounds that respond to stimulation of input phosphor light by the emission of electrons.” (Bushong, 2013, p. 405). This phenomenon of electron emission following light stimulation is called photoemission. The emission of just one electron through photoemission is dependent upon numerous light photons. The amount of electrons produced by the photocathode is directly proportional to how much light reaches it from the input phosphor, which is directly proportional to the intensity of the initial x-ray beam. These electrons will be accelerated to the anode where they will pass through a small hole to the output phosphor. The output phosphor, made of zinc cadmium sulfide, is where the electrons produced through photoemission will interact and produce light. It is extremely
Electromagnetic energy is a dynamic form of energy that is caused by the acceleration or oscillation of a charged particle. All substances above absolute zero (0 Kelvin) emit a range of electromagnetic energy. The sun emits electromagnetic energy and practically all of the natural electromagnetic energy injected into the earth is produced by the sun (Prakush, 2002).
waves are further divided into two groups or bands such as very low frequency (
The production of x-rays by relativistic electrons in accelerators is about 60 years old. The accelerator facilities used as synchrotron radiation sources have advanced significantly over the years, growing in utility to become a premier research tool for the study of materials. The evolution of these facilities is typically described as a sequence of generations of synchrotron radiation sources.