Image Acq. Unit 4 Quality Factors Radiographic Distortion
no magnification -not possible, will always have a little magnification no matter what.
magnification factor of 1.0 = ______ ______________
False -Doesn't have anything to do with shape distortion, only size
*True/False:*If there is an increase in SID, there is a decrease in shape distortion.
True
*True/False:*Sometimes shape distortion is used to angle the CR to better demonstrate certain structures.
Foreshortening
This is when the image looks smaller than what the actual size is.
SOD
This represents source to object distance
Shape distortion
This results from improper alignment of the CR (tube), anatomical part, and/or image receptor
LAO
To get the right lung without any superimposition, what projection would you do?
decease it
Any factor that increases distortion, will do what to detail?
It increases
As OID increases, what happens to distortion?
It decreases
As SID increases, what happens to distortion?
It increases
As angulation increases, what happens to distortion?
SID - OID
How can you find SOD if its not given in a problem?
Size distortion
The increase in an object's image size as compared to its actual size; image size can NEVER be smaller than the actual size. -Also known as "magnification"
True
*True/False:* As OID increases, size distortion/magnification increases, and resolution decreases.
True
*True/False:* As SID increases, size distortion/magnification decreases, and resolution increases.
True
*True/False:* As angulation of the tube part increases, the IR = an increase in shape distortion, and a decrease in resolution.
True
*True/False:* If there is a decrease in SID, there will be an increase in size distortion and and increase in magnification.
False
*True/False:* OID is directly related to resolution/detail.
True
*True/False:* SID is directly related to resolution/detail.
True
*True/False:* SID is inversely proportional to distortion.
True
*True/False:* The OID is directly proportional to magnification.
False
*True/False:*Focal spot size, film/screen speed, and all types of motion impact resolution and distortion.
NO
Does motion affect distortion?
Yes
Do patient factors affect distortion?
Distortion
Misrepresentation of either the size or shape of an object being imaged.
Magnification factor
This indicates how much size distortion or magnification is shown on a radiograph.
Size and shape
What are the two types of distortion?
Elongation and foreshortening
What are the two types of shape distortion?
Place the part to be imaged closest to the IR.
What can the technologist do to use the shortest OID?
OID
What has the greatest impact on size distortion?
decrease OID
What is the best way to reduce magnification?
Increase OID and decrease SID
What is the best way to reduce resolution?
MF = SID/SOD = Image width/Object width
What is the equation for magnification factor?
Magnification
What is the type of size distortion?
Increase the SID to prevent magnification
What might the technologist do to compensate for an unwanted, longer OID?
Use the shortest or smallest OID
What should the technologist always do to prevent magnification of structures?
OID and SID
What two things play a big role in controlling size distortion?
Increase
When OID increases, size distortion or magnification do what?
decrease
When SID increases, size distortion or magnification will _________.
Spatial resolution
When distortion occurs there is also a reduction in what? -This is true for both size and shape distortion.
