Spatial Resolution Flashcards
Define resolution
The accuracy & clarity in which anatomical lines are seen(sharpness of an image)
What is resolution also referred to as
Sharpness
Detail
Definition
What is an objective evaluation of sharpness
Measuring the amount of sharpness on the image
How is spatial resolution measured
Line pairs / millimeter
More line pairs = good resolution or bad resolution
Good resolution
What is the test tool range
0.5 - 5.0 line pairs per millimeter
What is the maximum line pairs per millimeter for Digital radiography
4 line pairs per millimeter
What is the maximum line pairs per millimeter for computed radiography
6 line pairs per millimeter
What are line pairs in a given length referred to as
Spatial frequency
What creates one wave length?
One line and one space
Define spatial frequency
Number of waves passing a fixed point per second
What is spatial frequency measured in
Cycles per unit of length
(Ex: 6 cycles / millimeter)
Are spatial frequency and spatial resolution the same?
Yes
Spatial resolution uses line pairs per millimeter
Spatial frequency uses cycles per length
What is spatial resolution measured on
The sharpness of an image
How is spatial frequency measured
Represent the structural complexity of anatomical organs
What is the relationship between spatial frequency and anatomy size
Inverse relationship
Define modulation transfer function ( MTF)
Ability for imaging system to display small objects on the image
What is the relationship between MTF & spatial frequency
Inverse relationship
As spatial frequency increases, MTF decreases
( the more detail required to see anatomy, the more difficult it is to see so…the less MTF is needed)
What are the 3 types of resolution sharpness from the chart?
Geometric
Digital
Motion
Define geometric sharpness
Factors that relates to the primary beam itself
- focal spot size & Distance (SID)
Define motion unsharpness
Due to patient or equipment motion
Define digital sharpness
Factors that inherent in digital systems that affect sharpness
In geometric sharpness, if you increase SID to hat happens to resolution and why
Resolution increases because as SID increases the beam diverges LESS
In geometric sharpness, if you increase OID what happens to resolution and why?
Resolution decreases because as OID increases the remnant X-rays diverge more
In geometric sharpness if you increase FSS what happens to resolution and why
Resolution will decrease because as FSS increases, x rays will originate from larger surface area( more divergence)
In digital resolution , smaller pixels make for what….which make what?
Smaller pixels means more pixels in the image & more pixels is better spatial resolution
In digital resolution, what is the matrix
Layout (grid) of the total number of pixels
( 5x5 matrix = 25 pixels)
Define pixel pitch
As pixels per mm increase the distance between them decreases
If the size of each pixel decreases how would it effect
Matrix size
# of pixel/ mm
Pixel pitch
Spatial resolution
Matrix size increases
# of pixels /mm increase
Pixel pitch will decrease
Spatial resolution will increase
How it matrix size determined
By detector elements
Smaller Detector Elements produce what
More pixels , which makes larger matrix size, and a smaller DEL pitch for better resolution
How will high fill factors effect spatial resolution
Better spatial resolution
What’s the best way to help reduce motion
Lower exposure time
Communication
Immobilization
What are the reasons we use immobilization
For pt safety
Reduce repeats
Personal safety
Which factors have NO effect of spatial resolution
Contrast
Kvp
mAs
Grid
Tube filtration
Collimation
