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Exposure I Final
Radiology Exposure I Final
|If a lower mA is activated on the generator panel, AEC will
|use a longer time of exposure
|AEC devices provide a diagnostic quality radiograph when the
|part is positioned directly over the chamber
|When an AEC detector sets over an area of increased fluid, exposure to the IR will
|US Public law requires automatic termination of AEC exposure at _____mAs above 50kVp.
|With an ionization chamber device, the electrical charge produced is in proportion to the amount of radiation received. True or False?
|What will result in more exposure to the image receptor, but not alter the dynamic range when using AEC?
|changing the density control to +2
|AEC devices operate by measuring
|radiation transmitted through the patient
|The purpose of the back-up timer is to
|Set the maximum exposure time possible
|The dectectors, cells or sensors can differentiate between secondary and scatter radiation
|Your next KUB patient has Hyperstenic body habitus. Acknowledging that fact, you increase the density control to +2. How will the length of exposure change, as compared to density control at N?
|Exposure time will remain the same
|You are using AEC with the center sensor activated. If the centering point for an AP lumbar spine is set incorrectly over the liver, the radiograph will
|be lighter in film density or show underexposure
|Which one of these would assist in the control of motion in the AEC mode?
|Increase the mA
|Nsme four considerations with any AEC exposure
|Patient position kVp level Focal spot size Sensor selector
|Which statement is false concerning scattering radiation?
|Scattering radiation does not contribute to image density
|When kVp increases from 70 to 80
|more photons undergo interaction with matter
|As the beam size of radiation changes from 10x12 to 14x17 inches, scatter production
|Identigy the beam restriction device composed of a flat sheet of lead with a circular opening
|A collimator device has how many sets of lead shutters?
|You have produced a scout AP KUB (14x17 IR) using AEC mode. After fluorscopy, the radiologist requests an image of only the RUQ which requires only a 10x12 IR. The second image will
|produce a higher mAs readout
|Components of a collimator device are
|light source, mirror and shutters
|What collimator components must be an equal distance from the mirror?
|Light source and focal spot
|The collimator mirror is mounted at an angle of
|A visible sign of collimation to the necessary anatomical region is evidenced by the _____ around the radiographic image
|A radiograph produced with AEC exhibits increased exposure/film density due to excess scattering radiation. A second image is produced, but with increased collimation. The second image will show what level of contrast?
|No change in contrast scale occurs
|If an uneven beam field is projected onto the patient's anatomy, it is due to
|lead shutter(s) being misaligned
|What happens to exposure time when kVp is decreased to reduce scattering radiation when in the AEC mode?
|Exposure time increases
|The source of off-focus radiation is
|any point other than the focal spot
|What would NOT be classified as a beam restriction device?
|What feature do secondary radiation and scattering radiation have in common?
|Decrease in intensity of the beam
|The principal factors that affect the amount of scatter produced are mAs and the type of irradiated material
|A lead blocker or leaded rubber may serve as a beam restrictor
|If the primary beam is collimated from an activated AEC sensor, the result would be a
|change in exposure quantity to the IR
|Automatic collimators are known as positive beam limitation devices.
|Back up time of most AECs is set
|longer than the anticipated manual exposure time
|When mAs is reduced, the Photoelectric to Compton ratio will
|remain the same
|As more photons pass through the irradiated material unaffected, the resulting image receptor exposure has
|greater level of exposure to the IR
|Volume of the irradiated tissue increases as
|radiation field size increases patient thickness increases
|The shutters of a collimator will
|Reduce field size Reduce penumbra Reduce off-focus radiation
|As collimation increases,patient dose _____ and image contrast ______
|Exposure factors used for an AP KUB with a 14x17 cassette will not be sufficient for a bladder image on an 8x10 cassette. Exposure factors must be changed to compensate for the reduction in field size by
|increasing mAs 20-50%
|Increased collimation refers to a smaller radiation field
|Scattered photons will strike an area of he cassette unrelated to the anatomical area from which they were produced/created
|The most common phosphor used for CR imaging plates is
|barium flurohalide bromides
|The latent image in CR imaging is created by energy transfer involving
|When the CR imaging plate is scanned by the laser the phosphors release energy in the form of
|A photostimulable imaging plate includes
|A phosphor layer, a conductor layer and a protective layer
|During CR imaging plate processing, the laser frees trapped electrons,allowing them to return to a lower energy state. This process is known as
|During image acquisition, laser light scans the IP in a raster pattern which means
|line by line
|As increased collimation is used with a digital image, the image contrast will
|Which phosphor shape produces more light diffusion, thereby reducing spatial resolution of the digital image?
|Turbid or powder phosphor
|Translation refers to
|the laser scan across the imaging plate multiple times
|Erasure light bulbs diminish in the level of output over time
|What is NOT a determining factor of spatial resolution?
|Conductive layer thickness
|Spatial resolution is associated with contrast of the image. Another name for contrast resolution is
|Which form of digital data is classified as "noise"
|Speed class of an imaging plate is determined by the amount of photostimulable luminescence or PSL during the laser scan
|Upon laser beam scanning of the imaging plate, the emitted light is detected by the _______device that amplifies the light.
|It takes longer for the AEC to shut of the exposure on a thicker body part because the
|quantity of radiation is reduced
|During an AEC exposure, the sensors activated should be covered by the ______ anatomy
|It is acceptable to override an automatic collimator (PBL) in order to
|collimate tighter to reduce patient dose
|You have produced an incorrect level of exposure to the IR while in AEC mode. Name two reasons why this could result
|Used all of the energy available Panel not set correctly
|Define averaging in relation to AEC exposure technique
|averaging has to do with the 3 sensors and the energy produced from each one that is converted into a digital image
|Using kVp as the correction factor, increase image density/level of exposure by 100%. Use original factors of 10mAs @75kVp
|5 mAs @ 85kVp
|Maintain image density/level of exposure. INcrease kVp by 15% and state the new factors. Use the original factors of 40 mAs @ 80kVp
|20mAs at 90 kVp
|Maintain image density/level of exposure. Double the mAs value and state the new factors. Use the original factors of 30mAs at 70kVp
|60mAs @ 60kVp
|xray quality is numerically represented by
|Which one of these would display the most subject contrast?
|A muscular patient
|How many half-value layers must be added to the primary beam to reduce the intensity to less than 20 percent of its original value?
|Aluminum has an atomic number of
|What results when longer wavelength photons interact with anatomy
|Short or high scale contrast
|As kVp is increased, the primary beam is composed of
|higher frequency and shorter wavelengths
|What will approximately double the exposure to the IR/film density?
|Increasing kVp by 15%
|An adjustment from 70 to 80 kVp wil produce
|Wider exposure latitude, less patient absorption, shorter wavelengths
|If the original radiograph shows good quality and kVp is increased by 15%
|Density/exposure to the IR increases, contrast decreases
|Which interaction involves the production of secondary radiation?
|If the original radiograph shows good quality and the mAs is increased by a factor of 2
|density/exposure to IR remains the same, contrast increases
|Increasing the kVp on the control panel will cause an ______across the xray tube
|increase in the speed of the electrons
|How does high kVp, such as used with upright chest exams, affect radiographic contrast?
|Produces longer or low scale contrast
|As kVp increases, ______ mAs will be needed to produce an image of equal exposure
|In lower kVp range, a 15% change has a greater impact on xray emission than at higher kVp values. Consider the example 50kVp vs 100kVp.
|What is NOT TRUE about optimal kVp?
|It determines total quantity of primary radiation
|Higher kVp correlates with wider exposure latitude?
|Which patient would produce the most scattered radiation?
|Increased scatter radiation in the exit or remnant beam will cause an increase in
|What happens to patient absorption of energy, as kVp increases?
|The initial rad image exhibits underexposure. If kVp is increased as the correction it will affect
|more than one but not all
|Long scale contrast is defined as
|black to many gray shades to white
|Secondary radiation continues in a diverging direction, scatter is changed in direction of travel.
|Secondary radiation is lowered in intensity from the primary beam, as is scatter
|What is NOT TRUE concerning the relationship between image density and contrast?
|mAs is a quality factor and affects image density
|Which set of factors produces a rad with the highest scale of contrast?
|The 15% rule states that
|Density may be halved by decreasing kVp by 15% Density may be doubled by increasing kVp by 15%
|Name 3 true statements about scattered radiation
|It has less energy than primary It contributes to density on the image It travels in a different direction than primary
|Increasing energy of an incident electron results in the production of an xray photon with
|As kVp _____ a ______ range of photon energies is produced
|High contrast is directly related to
|number of photoelectric interactions
|The 10kvp guideline for kilovoltage is true in the range of
|An image contrast decreases, the number of densities in the image
|increase with more gray tones/densities
|Wide exposure latitude shows long scale of contrast, creating a greater margin for error
|the relationship between kVp and density is described as
|direct, but not proportional
|The original technique is 30mA @ 80kVp. What will produce a rad with twice the IR exposure/film density.
|30mas @90 kvp 60mas @ 80kvp
|How does kvp influence rad density?
|Sets penetrability of the photons in the beam
|Low kvp creates ____ contrast
|Low kvp creates ____ shades of gray
|Name a set of exposure factors that would provide an image with higher contrast than that produced by 12mas @92kvp but maintains the original density/level of exposure?
|The usage of high kVp techniques would result in
|lower patient dose, decreased contrast and less scatter fog
|What effect does beam penetration have on rad contrast?
|Increased kvp will decrease contrast
|Image density is a product of intensity x duration of exposure is a definition of
|The relationship of mA and time to maintain image density is directly proportional
|A disadvantage or limitation of high mA exposure is
|usage of a large focal spot
|mAs affects visibility of detail
|What happens to patient doseage as the mAs increases?
|The relationship between kVp and contrast is
|What interaction produces a longer scale of contrast due to a high level of scatter from increased beam penetration?
|What definition describes body habitus?
|Variations in the shape of the human body
|The relationship of mAs and kVp to maintain the level of exposure/film density is
|Low kVp results in ____ kinetic energy of electrons
|The NCRP recommends a minimum total filtration value of ______ mm Al/Eq for imaging at 70kVp or greater
|What influences the production of scattering radiation?
|Level of kvp, tissue thickness, field size of radiation
|Compton becomes the dominant interaction at ____kvp
|Which cast material of normal thickness requires only a doubling of mAs?
|An increase in kilovoltage applied to the xray tube increases the
|Name an example of a compensating filter
|Identify the purpose of a compensating filter
|Creates uniform image density
|The standard protective filter material used in diagnostic radiology is
|A long leg exam is ordered and the wedge filter is routinely used. The thin portion is placed at the
|proximal or hip end
|What effect does the addition of protective filtering have on the average energy of photons in the primary beam
|Increases the average energy
|Photons emerging from a properly filtered diagnostic unit are homogenous since they have the same energy level
|Which material requires a 2 times increase in mAs and an increase in kVp?
|Whether a fiberglass or plaster cast is applied, image contrast
|Filtration is the process of filtering undesirable _______by the insertion of absorbing material into the primary beam
|low energy xray photons
|Filtration at the required diagnostic (>70kVp) minimum removes a portion of the useful beam
|Which is the following is affected by half-value layer?
|total filtration is equal to the sum of _______filtration
|inherent and added
|Name one factor which would require the technologist to change AEC sensor selection
|Digitizing the light signal from the photomultiplier tube means assigning a numerical value to each light photon
|In CR imaging, images have increased contrast resolution along with increased spatial resolution
|Grid ratio determines the maximum angle by which a scattered photon can pass through the lead strips
|What artifact may be prevented by substituting a multi-hole grid for the standard linear grid when digital imaging is utilized?
|A low ratio grid compared to a high ratio grid will
|absorb less scatter radiation, produce a longer scale of contrast, require less exposure for a given density
|the efficiency of a grid is its ability to remove scattered radiation which is based on
|grid ration and grid frequency
|Using an out of range SId with a linear focused grid results in
|a loss of image density on the outer edges
|Angulation of the beam with a linear, focused grid may be done
|with the long axis
|Grid movement during the exposure serves what purpose?
|blurs grid lines
|If an image taken with a 12:1 linear focused grid with 100 lpi exhibits a loss of density at the internal edges. It is because the
|grid is upside down
|the majority of scattering energy is produced in the
|the patient has an imapact on all the properties that affect a balanced image, such as IR exposure/density, contrast/dynamic range, resolution and distortion
|The ____ the body part, the _____ the primary beams attenuation