UNIT 1: Quality Factors Review Flashcards
What are the 4 quality factors of X-Ray?
-Photographic: IR Exposure, Contrast
-Geometric: Spatial Resolution(detail), Distortion(Magnification & Foreshortening/Elongation)
IR exposure is a measurement of
-Total amount of signal received by the Image Receptor
-Measurement of beam INTENSITY
Sensitivity Number (S#)
Exposure Index (El)
Log Median Exposure (LgM)
Describe the relationship that the following factors have on IR exposure: mAs, kVp, Grids, Distance
-mAs: direct and proportional relationship
-kVp: direct relationship (uses 15% rule)
-Grid: indirect relationship (uses GCF), manipulate mAs to maintain IR exposure
-Distance: indirect relationship (uses Inverse Square Law)
What are 3 additional influencing factors that affect IR exposure?
- Patient Factors
-OID
-Screen Speed
If S number is too high, is the image over or underexposed?
Underexposed
If S number is too low, is the image over or underexposed?
Overexposed
Image vs Subject Contrast
-Image Contrast: difference in IR exposure between two adjacent areas on an image
-Subject Contrast: difference in x-ray intensities that are transmitted through the subject(patient) and recorded on the IR
Long Scale vs Short Scale Contrast
-Long Scale: many shades of gray (more information)
-Short Scale: few shades of gray yet more “appealing” to the eye
Describe the relationship that the following factors have on Subject Contrast: kVp, Grid, OID, Collimation
-kVp: indirect relationship
-Grid: direct relationship
-OID: direct relationship
-Collimation: direct relationship
What are 3 additional influencing factors that affect Subject Contrast?
-Patient factors
-Contrast media
-Filtration(?)
What is the purpose of the Look Up Table?
-Determine a preset grayscale for display based on the selection of the Radiographer
-Applied to the data that has standard contrast for that exam to give the desired image contrast for display
Define Spatial Resolution
Degree of sharpness, or accuracy of the structural lines recorded on the image
Describe the relationship that the following factors have on Spatial Resolution: FSS, SID, OID, Pixel Size
-FSS: indirect relationship
-SID: direct relationship
-OID: indirect relationship
-Pixel Size: indirect relationship
What are 3 additional influencing factors that affect Spatial Resolution?
-Quantum mottle
-Motion
-Scatter(only impacts visibility, NOT recorded detail)
What tool is used to measure spatial resolution?
Line pair test
*more lines= better resolution
Define Distortion and its types
The misrepresentation of the size or shape of a structure being examined
-Magnification
-Foreshortening
-Elongation
What are the two types of shape distortion and what causes them?
-Foreshortening: Part and IR alignment
-Elongation: Tube and IR alignment
How does size distortion happen?
-Big OID
-Small SID
Formulas
Factors affecting image quality chart
Frequency
cycles per unit of time
Wavelength
Distance between two waves
Amplitude
Height of the wave
mAs
-Total current sent to the Cathode during exposure
-Controls the number of electrons in the thermionic cloud
-Controls Beam Intensity/quantity
kVp
-Controls the Voltage sent to the anode
-Controls the attraction between the electrons and the anode
-Affects both quality (but can also affect quantity)
Low kVp = ______ frequency
Low
High kVp = _______ frequency
High
A 15% increase in kVp means a _________ exposure to the IR
Double
A 15% decrease in kVp means _________ exposure to the IR
Half
Beam quantity is known as
-mAs
-beam intensity
-amplitude
Beam quality is known as
-kVp
-beam penetrability
-energy
-frequency
T or F: wavelength and frequency are inversely proportional
True
Cathode serves as a
source of electrons
Anode serves as
a target, it is the source of the x-ray beams
If we doubled the distance, the intensity would decrease by a factor of
4
If we tripled the distance, the intensity would decrease by a factor of
9
Quantum mottle
Inconsistent or uneven distribution of x-ray photons on the surface of the IR resulting in insufficient exposure
T or F: exposure and brightness are directly related
False
CR vs DR
Is quantum mottle over or under exposure
Under exposure
X-ray tube labeled
