Module 3 Flashcards
Describe the effect of kVp on the quality of the x-ray beam
When kVp is increased, the speed of the electrons is increased making them hit the tungsten target with greater force and energy creating a more penetrating x-ray with shorter wavelengths = higher quality x-ray
Describe the effect kVp on the x-ray image (density and contrast)
Increasing kVp results in an increased overall density (darkness) on the image
Low kVp = high contrast (black/white)
High kVp = low contrast (gray)
Describe the effects of mA on the quantity of the x-ray beam
As mA is increased more electrons are produced increasing the number of x-rays produced
Describe the effect of mA on the x-ray image (density)
Increasing mA increases the overall density of the x-ray giving you a darker image; lowering the mA reduces the overall density of the image
Describe the relation of exposure time with kVp and mA
If you increase kVP, mA increases, and you will decrease the exposure time
Describe how distance affects the intensity of the x-ray beam
As an x-ray travels from the tungsten target the intensity of the beam lessens
List the distances that need to be considered when taking an x-ray
Target-surface distance
Target-object distance
Target-film/receptor distance
Define target-surface distance
The distance from the source of radiation to the pt’s skin
Define target-object distance
The distance from the source of radiation to the tooth
Define target-receptor distance
The distance from the source of radiation to the receptor/film
Define the inverse square law
The intensity of radiation is inversely proportional to the square of the distance from the source of the radiation
Describe how the inverse square law informs whether an 8 inch PID or 16 inch PID has more intense x-ray beams
When you change an 8 inch PID to a 16 inch PID, the source of film distance is now doubled so the beam is now 1/4 the intensity
Original intensity/new intensity = new distance^2/original distance ^2
Describe what is meant by half-value layer
The thickness of the tube filter (aluminum filters), which is placed in the path of the beam inside the x-ray tube head, removes low-energy, less penetrating longer wavelength x-rays
How is the half-value layer related to the intensity of the x-ray beam?
Decreases the intensity of the x-ray beam by half
