Exam 1- Principles of Exposure Flashcards
2 branches of radiographic quality-
visibility & recognizability (sharpness) of detail
visibility of detail-
receptor exposure, contrast, & noise/artifacts
recognizability (sharpness) of detail-
spatial resolution & distortion (size & shape)
mAs only affects ____ of the image-
visibility
short scale contrast used to look at-
bony anatomy
noise-
any undesirable info. that interferes w: subject of interest in radiographic img.
artifact-
any extraneous obj./unwanted img. that obscures desired info. in radiograph
magnification (size distortion)-
diff. b/w size of object in img. vs actual size of obj.
shape distortion-
difference between shape of obj. in img. vs actual shape of obj.
elongation-
when object appears longer in img. than it actually is
foreshortening-
when object appears shorter in img. than it actually is
mA (milliamperage)-
measurement of flow rate of electrons through x-ray tube
time (s) (exposure time)-
amt. of time in seconds during exposure
mAs-
total exposure
kVp-
-energy level of electricity being forced across x-ray tube
-peak energy level
focal spot-
refers to specific target area on target surface of x-ray tube
AEC-
allows rad. to set kVp & the system determines when adequate exposure reached IR
density control-
each increment setting represents a 25% change in intensity
APR-
preset technical factors
2 sides of x-ray tube-
anode & cathode
4 things needed to produce x-ray-
1.) source of electrons
2.) focusing cup
3.) way to speed up electrons
4.) way to stop electrons abruptly
most of energy striking anode results in-
heat (only 1% results in x-ray photons)
SID-
distance of CR from focal spot to IR
Primary Radiation/Beam-
the beam from the focal spot that goes to the object being imaged (patient)
remnant beam-
sometimes called image forming radiation/exit radiation/beam; where it exits patient down to IR
amount of x-ray that passes through the body-
5% or less
amount of the beam that results in scatter-
15%
amount of the beam that is absorbed-
80%
attenuation-
partial absorption of x-ray beam as it passes through body
inherent filtration-
built into x-ray tube
3 parts of inherent filtration-
1.) glass envelope
2.) insulating oil
3.) exit window
added filtration-
added by the tech.
filtration purpose-
absorb low energy x-ray photons before they reach patient
beam restriction aka-
collimation
anode heel affect-
difference in beam intensity along longitudinal axis of x-ray tube
central ray-
center of x-ray beam & direction in which it travels
grids purpose-
absorbes scatter
grids job-
keep scatter from reaching IR
scatter produced-
inside the patient