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Exam 4 Rad 102

Chapters 11, 13 & 14 - Prime Factors, Minimizing Pt Dose, Vision and Perception

What are the prime exposure factors? Distance, mAs, kVp
Prime exposure factors are variables controlled by ________________. the technologist
What is the product of tube current and exposure time? mAs
Quantity of the beam is measured in _____________. Roentgen
Which factor controls quantity? mAs
mAs, distance and filtration directly affect ________________. quantity
Which factor control quality? kVp
X-ray quality is numerically represented by ______________. Half-value layer (HVL)
Reducing x-ray beam intensity (Quantity) by half its original value is _________________. Half-value layer (HVL)
Milliamperage (mA) is the measurement of ______________________. tube current
What does X-ray tube current measure? # of electrons crossing the tube from cathode to anode per second.
As mA increase, the number of electrons that are able to cross the tube to reach the x-ray target __________________. Increase
The penetrating ability of the x-ray beam refers to ________________. quality
Which systems provide the highest beam quality and quantity? High-frequency
What are the quantitative factors affecting x-ray emission? (4) mAs, kV, Distance, filtration
What are the qualitative factors affecting x-ray emission? (2) kV, filtration
What is the focal spot size (range) of an x-ray tube? 0.5 - 1.0
Large focal spot size has a beam of high __________________, but unchanged _______________. quantity (more x-rays produced) quality (looks the same)
Focal spot size is associated with ________ of an x-ray. detail
What is the unit of current? ampere
1 ampere (A) equals? 1 coulomb (C)/sec
What happens to the number of electrons passing from the cathode to the anode by doubling the mA? Increase 2 fold
Exposure time is directly proportional to _______________________. intensity of the beam
Short exposure times help in reducing _____________________. motion artifacts
What is the shortest time by a single phase system? 8ms
What does mAs control? (5) Quantity, radiographic film density, patient dose, intensity, x-ray output
By doubling the mAs, the dose is ___________. doubled
Increase in mAs causes a(n) ___________________ in beam quantity. increase
What will increasing the kVp on the control panel cause? an increase in speed and energy of the electrons
What does the Reciprocity Law state? the density on an x-ray film should remain unchanged as long as intensity and duration of x-ray exposure remains unchanged
Which factor controls quality? kVp
Change in kVp affects ____________. contrast
As kVp double, the amount of x-ray photos will increase approximately? 4 times
Amount of silver deposited on hard copy film image density
Intensity and density increases as SID __________________. decreases
What does the Inverse Square Law state? The intensity of radiation at a given distance from a point source is inversely related to the square of the distance between the object and the source.
What is the Inverse Square Law formula?
What is the function of the human eye? Gather light, focus it, convert it to nerve impulses and transmit it to the brain for processing.
What are the 2 retinal cells that transform light into a nervous signal? Rods and Cones
What is the aspect of the visual anatomy that transmit nervous signals to the brain? Optic Nerve
What is the primary location of rods in the eye? Retina cells
What is the primary location of cones in the eye? Fovea centralis
What is another name for nearsightedness? Myopia
What is another name for farsightedness? hyperopia
What do rods and cones do when stimulated by light? emit neurologic impulses
Daylight vision, color, processed by cones photopic vision
Which color of light are cones most sensitive to? yellow
Part of the eye that improves contrast perception? cones
Name for night vision which is sensitive to low light levels Scotopic Vision
Term for the visual phenomenon associated with viewing extremely small objects Threshold Detection
What is boundary effect? Difficulty is perceiving contrast difference at a distance
Neurologic basis for boundary effect. Some situations prevent neurological impulses from being transmitted by retina. Mach Effect
When intense light from view box hits the eye directly, bright light scatters inside the eye (compton effect) and decreases contrast perception... Veil Glare
Rule for views to be made in radiography, in order to perceive depth Must have two (2) 90° opposing views
What radiographs produce the highest ESE? Lumbar spine, pelvis and hip
Which radiographs produce the lowest ESE? Extremities
Ways to reduce patient does? Positioning Communication Technical Factors Filtration Field Size Gonadal Shielding
How do we reduce pt dose with technical factors? high kVp, lowest possible mAs, increase SID and SOD, highest generator efficiency
What is entrance skin exposure (ESE)? Maximun exposure to body
What is roentgen (R) in SI units? air kerma
What is rem in SI units? sievert
What is rad is SI unit? gray