H I X-RAY INTERACTIONS WITH MATTER & FILM
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| will lose all of its kinetic energy and deposit in a shell on an atom | COMPTON EFFECT
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| classical scattering | COHERENT SCATTERING
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| general graying of the radiograph which reduces contrast | FOG
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| Incident x-ray photon interacts with target atom | COHERENT SCATTERING
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| Occurs with x-rays of moderate energy | COMPTON EFFECT
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| Occurs with photons less than 10 keV | COHERENT SCATTERING
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| Coherent scattering contributes to | Fog
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| No ionization occurs | COHERENT SCATTERING
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| Thompson scattering | COHERENT SCATTERING
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| Also known as Compton scattering | COMPTON EFFECT
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| occur most common | Compton and Photoelectric effects
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| This is an absorptive phenomena | PHOTOELECTRIC EFFECT
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| Electron that is removed from the atom is termed a | photoelectron
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| X-ray photon is not scattered but is absorbed | PHOTOELECTRIC EFFECT
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| X-ray photons undergo an ionizing interaction with inner shell electrons | PHOTOELECTRIC EFFECT
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| They are more tightly bound | PHOTOELECTRIC EFFECT
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| an absorption phenomenon | PHOTOELECTRIC EFFECT
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| The photoelectron escapes with kinetic energy equal to the difference between the energy of the incident x-ray photon and the binding energy of the electron | PHOTOELECTRIC EFFECT
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| atom is excited and releases the excess energy as a scattered x-ray | COHERENT SCATTERING
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| Xray photon of the same energy but in a different directionà | scatter photon
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| Causes the target atom to get excited and go to a higher state | COHERENT SCATTERING
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| approximately 5% of photons undergo coherent scattering | At 70 kVp
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| Incident x-ray and scattered x-ray have the same wavelength and the same energy | COHERENT SCATTERING
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| Incident x-ray photon interacts with an outer shell electron of the target atom and ejects the electron | ionization
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| ionization | COMPTON EFFECT
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| Scattered photon can be scattered in any direction including 180 degrees backwards | backscatter radiation
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| Usually scattered x-ray photon retains most of the energy of the incident x-ray | COMPTON EFFECT
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| looses the outer shell electron | COMPTON EFFECT
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| Backscatter radiation can come from | the patient, the cassette, or the tray
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| causes radiographs to look duller and flatter | Compton effect
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| electron has some kinetic energy after it is ejected | COMPTON EFFECT
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| hazardous to x-ray technicians and doctors | backscatter
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| the material in which x-ray photons or light photons emitted from the screens form the radiographic image | Emulsion
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| homogenous mixture of gelatin and silver halide crystals | Emulsion
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| foundation of the film | FILM BASE
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| Provides rigid structure but is flexible and fracture resistant | FILM BASE
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| Film base is made of | polyester
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| added to the base to tint the film | Blue dye
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| reduces eyestrain | Tinting
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| Original base | glass plates
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| In the mid 1920’s a safety base film began to be used | cellulose triacetate
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| The photon is directly absorbed by the nucleus | PHOTODISINTEGRATION
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| The nucleus is excited and instantaneously releases a nucleon or other nuclear fragment | PHOTODISINTEGRATION
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| The electron produced falls into a vacant shello | PHOTODISINTEGRATION
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| the quantity of matter per unit volume | MASS DENSITY
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| When the mass density is doubled | x-ray interaction is doubled
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| The radiographic image results from approximately | 1% of the x-rays
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| x-ray incident on the patient that reach the film | Less than 5%
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| The positron combines with another electron and energy is produced | annihilation radiation
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| X-ray photon goes close to the nuclear field of the an atom and disappears | PAIR PRODUCTION
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| Occurs with high energy x-ray photons – not diagnostic x-rays | PAIR PRODUCTION
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| Photon reduction is done exponentially | ATTENUATION
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| The reduction of the number of electrons in a beam | ATTENUATION
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| The half value layer for soft tissue is | 5 cm
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| x-rays that remain after the useful beam exits the patient | Remnant beam
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| Image forming x-rays interact with | image receptor
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| The thickness of radiographic film is between | 150-300 micrometers
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| Usually the emulsion is on both sides of the base | double emulsion
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| Two basic parts of film | film base and emulsion
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| protective covering made of gelatin | supercoat
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| binds the emulsion to the base | adhesive
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| chemical contaminant added to the crystal | silver-gold sulfide
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| silver-gold sulfide is called | sensitivity speck
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| determined by the process of how the silver halide crystals are formed | Film speed, contrast(gray scale), and resolution(clearness)
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| During the exposure, photoelectrons and silver ions are attracted to the sensitivity center and these form | silver metal (the latent image)
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| The blackness on the Xray film is due to | Silver metal
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| image after the exposure | latent image
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| image during chemical processing | manifest image
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| Only two interactions are important to radiology | Compton effect and the photoelectric effect
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| X-rays that undergo the photoelectric effect produce | diagnostic information
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| X-rays that do not reach the film give an | opaque area
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| In an optimally exposed film ________ are collected at the sensitivity center | 4-10 silver atoms
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| During processing, more silver atoms collect at the latent image center to form the | radiographic image (manifest image)
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| The collection of silver atoms is a | black grain
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| the functional part of the Xray emulsion | Silver halide crystals
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| the support medium for the silver halide crystals | gelatin
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| x-rays emerging from the tube that will be incident on the patient | Useful beam
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| Remnant beam consists of | x-rays and scattered x-rays
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| produced after a photoelectric interaction | characteristic xray
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| Ejection of a k shell electron from an incident x-ray causes an electron from an outer shell (usually the l shell) to drop in and fill the closer shell | PHOTOELECTRIC EFFECT
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| Interactions with low atomic number atoms (low binding energy) results in the photoelectron having | large amount of kinetic energy
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| As x-ray photon energy increases | the photoelectric effect decreases
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| As atomic number increases | the photoelectric effect increases
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| can only occur if the incident photon has enough energy to cause ionization | photoelectric effect
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