Contrast Flashcards
Low kVp and high mAs leads to what type of scale: short or long?
Short scale
Which presents with high contrast: short or long scale?
Short
High kVp and low mAs leads to what type of scale: short or long?
Long scale
Which presents with low contrast: short or long scale?
Long
Does a long or short scale appear very black and white?
Short
Does a long or short scale appear very dull and gray?
Long
How is density affected if kVp is increased by 15% aka 10 kVp (the 15% kVp rule)?
Density will double
How is density affected if kVp is decreased by 15% aka 10 kVp (the 15% kVp rule)?
Density will be cut in half
How can underexposure be fixed by altering kVp?
Increased kVp by 15%
How can overexposure be fixed by altering kVp?
Decreasing kVp by 15%
A 15% decrease in kVp has the same affect on density as what change of mAs?
50% decrease
What is the difference between recorded detail and visible detail?
Recorded - degree to which the BORDERS of an object are clearly defined
Visible - how clearly seen an object appears on film
What things can affect recorded detail?
Patient motion, FFD, OFD, focal spot size, tube-part-film alignment
How can patient motion be controlled?
1 patient stabilization
2 keeping exposure time short
How does patient motion affect the image?
Blurring
What kind of FFD results in less magnification distortion?
Longer tube distance (FFD)
What specific FFD yields better detail and less magnification?
72” (compared to 40”)
Does an object closer to or farther away from the film create more magnification distortion?
Farther away
How does magnification affect recorded detail?
Decreases it
What type of focal spot produces better detail: large or small?
Small
Regarding the tube/patient/film alignment, what must occur to avoid distortion and loss of detail?
Objects must be perpendicular to the central ray or parallel to the film
What structure must be parallel to the film to avoid true/angular distortion?
Object
What structure must be perpendicular to the object and film to avoid true/angular distortion?
Central ray
