Why is Bremsstrahlung radiation absolutely essential for there to be any subject contrast to produce an image?
heterogenous energies
100
Every density within the anatomy on a radiographic image should be a shade of ____.
gray
100
Define contrast
difference between intensities of light
100
What are the three geometric functions?
Sharpness of recorded detail, magnification or size distortion, and shape distortion.
100
Does a dark background have a high or low density?
Dark background = high density. Light background = low density
200
What must you know about the orbital electron shells in an atom to be able to predict the energy of a characteristic x-ray photon produced there?
Subtract further shell from nearer shell
200
What are the two major components of the image?
Visibility functions and geometric (recognizability) functions
200
What is the prime factor that controls contrast and how does it work?
kVp
high kVp --> low contrast, long gray scale
low kVp --> high contrast, short gray scale
200
Define sharpness of recorded detail
abruptness with which the edges of a particular image stop
200
How much does a densitometer measure?
0-4
300
Why are tungsten and rhenium used to coat the anode?
They have high atomic numbers and increase the intensity of the x-ray. They also have high melting points and both have large atoms with many orbital electrons, which is very effective at stopping the electron beam emitted from the cathode.
300
What are the three visibility functions?
1. density or brightness 2. contrast 3. noise
300
define magnification or size distortion
Difference in size between a real object and it's projected image in the picture.
300
What do the densitometer measurements mean?
0=white
4=black
400
The average energy of a heterogenous x-ray beam is about what fraction of it's peak energy?
1/3
400
What is density?
Amount of blackening present at any given point on the film
400
Define noise
undesirable information that interferes with the subject of interest
400
Define shape distortion
Difference between the shape of the real object and the shape of it's projected image on a radiograph
400
What are the useful measurements of a densometer?
0.25-2.5
500
If the number of x-rays in a beam were doubled, how much would it change the appearance of a graph of the x-ray beam spectrum?
The amplitude would lower
500
What is the opposite of density?
Brightness/intensity
500
Would braces be an example of noise? If not, give an example of noise
No, braces are not removable; therefore, they are not noise. Oxygen tubing is an example of noise.
500
If the length is doubled, but the width stays the same, has the object undergone magnification or shape distortion?
Shape distortion. If an object undergoes magnification, the width and length need to be magnified by the same amount.