Midterm Flashcards
What does the mid-sagittal plan divide?
Left and right sides of body
What does the mid-coronal plane divide?
Anterior and posterior sides of body
What does the horizontal or transverse plane divide?
Superior and inferior parts of body
Define the term “position”
side of the body nearest film; should be marked as such. ie: RAO
Define the term “projection”
path of the x-ray beam: AP/PA/oblique
Define the term “view”
side of anatomy best visuallized, usually side nearest film
Which body substance has the least subject density? the greatest? And how would they appear radiologically?
Least attenuation: Air, looks DARK = “radiolucent
Very attenuated: Bone, looks LIGHTER
Most attenuated: Metal, looks WHITE = “radiopaque”
What is “attenuation”?
Attenuation: a quantity that characterizes how easily a material or medium can be penetrated by a beam of light, sound, particles or other energy or matter
How does pathology affect attenuation? Specifics?
Disease process may affect the way tissue attenuates x-rays. Additive condition (blastic): Increased attenuation (LIGHTER) Destructive condition (lytic): Decreased attenuation (DARKER)
What body parts attenuate most and least?
look up
How are attenuation and radiographic blackness related?
Less attenuation = greater radiographic blackness; mAs controls it (milliamps x seconds = mAs)
What is radiographic density?
radiographic density = radiographic blackness (amount of blackness on film) Controlled by mAs
When you double or halve mA and leave everything else as is, what happens to your film? To your patient?
Doubling mAs doubles Radiographic Blackness and patient exposure. Cutting mAs by half makes half the blackness and halves patient exposure
What happens to your film when you double or halve exposure time and leave everything else as is?
??
What reduces blur?
Greater mAs = greater radiographic blackness, which results in less blur
What is the minimum change that can be made to mAs in order to see a visible change in radiographic density?
25-30% change in mAs is necessary for a visible change in blackness
What x-ray factor is primarily responsible for controlling contrast (variety of gray shades from darkest to lightest)?
kVp which controls penetration. Higher kVp lowers dosage, decreased mAs (?)
What is generally meant by improving contrast?
Increasing the number of shades of gray
How might you improve contrast?
Grids absorb scatter radiation as it exits, which reduces radiation fog = improved contrast
What is beam restriction?
Beam restriction reduces scatter, improves image quality and greatly reduces patient exposure. Beam must always be restricted
What is scatter? Good or bad?
Scatter is dependent on kVp, amount and type of irradiated tissue (soft tissue scatters more than bone). Scatter is bad.
How is scatter minimized?
Aperture diaphragm, cones/cylinders, collimaters (double check this)