2. Radiographic Contrast II Flashcards
It is the range of differences in the intensity of the x-ray beam after it has been attenuated by the subject
Subject Contrast
is the primary controller of subject contrast
Kilovoltage (kVp or kilovoltage peak)
The \_\_\_\_\_ the range of photon energies, the \_\_\_\_\_ the ability of the photons to penetrate the body tissues
wider,
greater
SID
Source to Image Receptor Distance
As long as the kVp
is adequate to penetrate the part being examined,
___ kVp will produce ___ subject contrast
low,
high
It produces higher subject contrast because most of these low energy photons
are absorbed by thicker parts while more penetrate the thin
part.
Low kVP
\_\_\_\_\_ causes density differences that were previously undetectable to become visible, resulting in an increase in the diagnostic information provided by the image
Increasing kVp
In \_\_\_\_\_\_\_\_ – low kVps are used to enhance the differences between the air-filled lungs and the overlying bony structures
rib radiography
In addition to kVp, _______ has a significant effect on
contrast
radiation fog
Radiation fog is a result of x-ray interactions with matter, primarily _____
Compton scatter
These changes cause the lightest film densities to be “\_\_\_\_\_\_” so they can no longer be distinguished from one another
fogged over
Fog can be caused by factors other than scatter radiation and includes :
subjecting film to heat, low level ionizing radiation, or
chemical fumes
may also
cause objectionable fog levels.
Developer temperature, replenishment,
and developer contamination
depends on the
thickness of the body
part and the field size
Amount of Irradiated Material
Factors affecting scatter radiation
Field size
most important factor in the production of scatter radiation
Field size
a small x-ray field usually called ______ irradiate less tissue and generates fewer scattered photons
Narrow beam
As body part thickness decreases so does ______
absorption
When the difference between adjacent thicknesses of
various body parts is great, subject contrast is _______
increased
When little difference exists in the thickness of
adjacent body parts, subject contrast is ______
decreased
When the overall thickness of a body part increases when a
field size increases, the amount of scatter created will
______
increased
A decrease in overall body part thickness or field size results in ______ subject contrast
increased
Controlling factors:
kVp,
Amount of Irradiated Material,
Type of Irradiated Material
is influenced by the atomic number of the material and its tissue density
Type of Irradiated Material