Flashcards in Principles of Radiology Deck (46)
Can xrays be focused on a single point?
What property of an xray allows it to penetrate
What produces an x ray?
Two electrodes in a glass vaccum tube
Which is the positive Electrode?
Anode, the TARGET of negative electrons
Which is the negative Electrode?
Cathode, the expeller of negative electrons
What does the cathode consist of
Tungsten filament wound in molybdenum cup
How does the cathode make electrons?
When the tungsten is heated it boils off electrons
What is the process of "boiling off" electrons that the cathode goes through when heated?
What is the anode made of
Copper for heat conduction and tungsten to produce radiation
What percent of the xray kinetic energy produced by the cathode is turned into heat?
What are the 3 ways an x ray can interact with a patient?
Why are scattered x rays bad?
They produce fog on a film
They are a source of exposure for patients
What happens when an x ray scatters?
It changes direction and has its energy lowered
What is another word to describe an absorbed xray?
What determines an xray's absorbtion?
What color does an absorbed x-ray produce on the film?
What measurement refers to the amount of x-rays being directed at the patient?
What measurement is the penetrating power of the x-ray beam?
What is meant by the term "dead man switch"
It means you have to depress the button to make x-rays....you can't leave the switch on passively
What is the formula for the inverse square law?
I = 1/d^2
What is the inverse square law?
The intensity of the radiation varies inversely with the square of the source-film distance
What is SFD?
According to the inverse square law, what happens to the intensity of the beam if the SFD is doubled?
Intensity decreases by 4x
Why does the intensity of the beam lessen as the SFD is increased?
There is more time for the x-rays to disperse which makes the beam less focused.
What happens that causes dark/black areas to develop on image?
Primary photons are transmitted through the tissue and are received by the film
Why are absorbed x-rays also called attenuated x-rays?
Because the intensity of the beam is reduced as it passed through tissues. Photons are absorbed by the tissue thereby removing them from the beam
What will result in full beam attenuation
What are the two most attenuating natural tissues
Enamel and Cortical bone
What is the letter designating the fastest speed film?