Review Flashcards
Radiation is defined as:
energy in the form of waves sent out over a distance
When a neutral atom gains or loses an electron, the atom is said to be:
ionized
What is defined as a charged particle?
An ion
Which of the following is an ionizing radiation?
x-ray
X-rays are what form of ionizing radiation?
Electromagnetic
X-ray wavelength is ___ proportional to frequency
inversely
X-rays are considered ___: photons of many different energies
heterogeneous
X-ray energies are ______ related to their wavelength.
inversely
Which of the following is a characteristic of x-rays?
-capable of producing harmful effects
-capable of penetrating matter
-electrically neutral
-have no mass
-all of the above
all of the above
The property of x-rays that accounts for their effect on biological systems is that they:
cause ionization in matter
What is the primary beam made of?
Photons
What is remnant radiation?
X rays that pass through the patient and interact with image receptor
What is electromagnetic energy attenuation?
It is the reduction in intensity that is the result of absorption and scattering
Energy of a photon is directly proportional to what other characteristic of a sine wave?
The photon’s frequency
Which type of atom, bone or soft tissue, is more likely to have a photoelectric interaction with the incident photons? Why?
Bone: incident photons are more likely to be absorbed
What do the effects of photoelectric events look like on a diagnostic image?
Photoelectric events correspond to a light or white shade on the image
T/.F: Photoelectric events are important because they contribute to the contrast of our images.
True
What are the most important characteristics of image quality?
Spatial resolution
Contrast resolution
The ability to image similar tissue and be able to distinguish between them; variation in grayscale. Best measures the visibility of image detail
Contrast resolution
Imaging small objects with high subject contrast; best measures the sharpness of image detail
Spatial resolution
Spatial resolution can also be called what?
Image detail/Recorded detail
If you want to get sharpness of image detail you should do what 3 things?
-Smallest focal spot
-Longest SID
-Anatomy as close to the IR as possible
A random fluctuation in the OD of the image.
Noise
Quantum mottle is a form of what?
Noise
What is most detrimental to recorded detail?
Motion
What are some ways to reduce motion blur?
-use shortest exposure time
-provide clear instructions
If you have increased image blur (or noise) you have reduced ___________?
Spatial resolution
What type of relationship does focal spot size and focal spot blur have?
Direct
As focal spot size increases what happens to recorded detail?
Decreases (inverse relationship)
To produce a change of OD you must adjust which controlling factor?
mAs
What does mAS control inside the x-ray tube?
Quantity; # of electrons boiled off of the filament
This law states that density is proportional to the total energy imparted onto the IR.Or, as long as mAs stays the same, a change in mA or time will not effect the OD.
Reciprocity law
Why is kVp a secondary or influencing factor of OD?
kVp = the amount of electron kinetic energy
What is the controlling factor for radiographic contrast?
kVp
Which kVp setting (high/low) will produce long scale, low contrast?
High kVp
What type of distortion is magnification?
Size distortion
How is size distortion (aka magnification) best reduced?
Increasing the SID and decreasing OID
How does SID and OID affect recorded detail?
The longer the SID and the shorter the OID = sharper image detail
Which will increase radiographic magnification more: Increasing OID or decreasing SID?
Increasing OID
Improper alignment of the patient, x-ray tube and IR results in ______?
Shape distortion
If there is an issue with alignment of the body part and IR, size distortion is classified as either _____ or _____.
Foreshortening or elongation
What can be used to assist the radiologic technologist in limiting superimposition?
Oblique positions and axial projections
Brightness in digital imaging is the equivalent of describing ________ in analog (screen film) imaging.
Optical density
What is collimation? And why is collimation important?
The action of narrowing the x-ray beam; reduces patient radiation dose and increases image quality
Which imaging technique factor corresponds with patient dose?
mAs
