Chapter 16 & 17 Flashcards
The reduction in the total number of X-ray photons remaining in the beam after passing through a given thickness of material
Attenuation
The result of either photoelectric absorption or Compton scattering is called
Attenuation
How is the amount of attenuation determined?
By the amount and type of irradiated material
If the body part being X-rayed is thicker, the ______ the attenuation will be.
Greater
Lead and Barium have _____ atomic numbers
High
Hydrogen, carbon, and oxygen have ______ atomic numbers
Low
Higher atomic number materials attenuate a _______ percentage of the beam than lower atomic number materials.
Greater
What are the basic substances comprising the human body?
Air
Fat
Water
Muscle
Bone
Which body substance absorbs the least amount of photons?
Air
Because air absorbs the least amount of photons, the IR exposure is
Greater
Where can air be found in the body?
Lungs
Sinuses
In small amounts in the GI tract
Which two body substances are very similar?
Fat and Muscle
Fat and Muscle are both considered a _________ in the body
Soft tissue structure
The atomic number or tissue density of fat makes it very similar to ______
Water
Since muscle has a greater density than fat, then muscle is a ______ attenuator of the beam.
Greater
An abdomen X-ray will show _____ on each side of the spine due to absorption of radiation by these muscles
Psoas muscle
Which basic substance of the body has the highest effective atomic number?
Bone
Absorption by bone means fewer photons reaching the IR so less
IR exposure
The amount of radiation that strikes the IR is
IR Exposure
What is our subject?
The patient
The subject density is going to impact the
IR exposure
Thicker/denser parts absorb _____ radiation producing ____ IR exposure.
More
Less
The impact the subject has on the resultant radiographic IR exposure is
Subject density
The Degree of differential absorption resulting from the differing absorption characteristics of the tissues in the body
Subject contrast
Spatial resolution of the structures depends on the position within the body and also the body’s placement to the IR
Subject detail
Subject detail is also known as
OID
The patient has to be positioned specifically to demonstrate a particular structure because of the way certain structures lie within the body
Subject distortion
Subject distortion is our
Positioning
To get good detail, your part needs to be
As close to the IR as possible
Medical science concerned with all aspects of disease, including the structural and functional changes caused by as diseases process
Pathology
These diseases cause the body tissue to increase in thickness, atomic number, and tissue density
Additive conditions
A greater attenuation of the beam will exist in which conditions?
Additive
Additive conditions require _______ technical factors.
Increasing
Are additive conditions easier or harder to penetrate?
Harder
These diseases cause the body tissue to decrease in thickness, atomic number, and tissue density.
Destructive conditions
Destructive Conditions require _______ technical factors.
Decreasing
Are destructive conditions easier or harder to penetrate?
Easier
Which technical factor should be adjusted for additive conditions, and should you increase or decrease that factor?
Increase kVp
15% increase in kVp will double the IR exposure
15% rule
__% to __% kVp increase will compensate for most additive conditions.
5 to 15
_____ will adjust/compensate exposures for pathological change’s automatically
AEC systems
Destructive conditions require a ______ in which technical factor?
Decrease in mAs
A ____ % decrease in ______ will reduce the IR exposure by half.
50
mAs
A decrease of ____% to ____% in ____ will compensate for most destructive conditions.
25 to 50
mAs
White to black very quickly
Short scale
Many shades of grey
Long scale
The time necessary for the human eye to acquire information is
0.2 seconds
Which parts of the eye gather light?
Aqueous humor, cornea, iris, and lens
The eyes perceive the image and _______s it to the _______.
Transmits
Brain
The human eye is anatomically designed to _______, _______, __________, and transmit it to the brain for processing.
Gather light
Focus it
Convert it to nervous impulses
What parts of the retina is responsible for converting the image to nervous impulses?
Specialized cells, especially the fovea centralis (or macula lutea)
What transmits the impulses to the brain for processing?
Optic nerve
Where does human image conversion occur?
Rod and cone cells
The rod and cone cells are located in the
Retina
If corrective lens are required its because of
Cornea issues
Another name for retina is
Fovea centralis
The retina (fovea centralis) coverts light to
Nervous impulses
Rods are considered what type of vision
Scotopic (night)
What type of light are rods sensitive to?
Low light
Rods cannot function in
Bright light
Cones are considered what type of vision?
Photopic (daylight)
What type of light are cones sensitive to?
Bright light
Lack of cones is the cause of
Color blindness
Cones are responsible for
Contrast perception (greater recognition of grayscale differences)
Created when the eye perceives a boundary
Mach effect
Occurs when intensely bright light floods the eye directly.
Veil Glare
Veil glare occurs in _____ areas of the image and between images
Unexposed
Unwanted artifacts such as necklaces, buttons, zipper, and rings cause visual ____ while viewing radiographic images.
Noise
Radiographers should see the body as
Three dimensional
Radiographers should see radiographs as
2 dimensional
Radiographs are two dimensional because they are
Missing depth
To compensate for missing depth on a radiograph;
Never settle for a single view of any structure
