111- Recorded Detail And Distortion Test Flashcards
Define recorded detail and provide other terms used to express recorded detail
Degree of geometric sharpness/ accuracy of structural lines Definition Sharpness Resolution Spatial resolution
What is the unit of resolution
Line pairs per mm
Define umbra and penumbra
Umbra- sharp area
Penumbra- unsnarl area
Define distortion and list the types of distortion
Misrepresentation of size or shape of part
Magnification, foreshortening, elongation
What factors affect size distortion
OID and SID
Explain how size distortion happens
Increased OID
How does patient thickness affect distortion
Pt thickness adds inherent OID which can magnify structures
What factors affect shape distortion
CR, IR, body part
Explain how shape distortion happens
Poor alignment if CR, IR, Ir body part
How will FSS, motion, OID and SID impact recorded detail
Decrease FSS increase detail
Decrease motion increase detail
Decrease OID increase detail
Increase SID increase detail
What are the two photographic properties of radiography and the two geometric properties
Photographic- contrast and density
Geometric- detail and distortion
List factors that affect visibility of detail
FSS, OID/SID, motion, kvp, mas
How will changing from a small to large focal spot affect density
No effect
How will changing from a small to large focal spot affect contrast
No effect
How will changing from a small to large focal spot affect detail
Decrease detail
How will changing from a small to large focal spot affect distortion
No effect
What factors affect spatial resolution in digital imaging?
Matrix size, pixel size, grayscale bit depth
In digital imaging, which axis represents height, width, and depth
Height - y
Width- x
Depth- z
What is the difference between system noise and quantum noise
System- background frequency interference
Quantum- lack of Xray photons
Describe how noise appears on an image
Grainy
If an image displays quantum noise, what caused this
Underexposure
How will you fix quantum noise on a digital image
Increase mas
Which is best for demonstrating increased spatial resolution, a high or low SNR
High SNR
As FSS decreases, what happens to umbra
Increases
As FSS decreases, what happens to penumbra
Decreases
As FSS decreases, what happens to resolution
Increases
As FSS decreases, what happens to recorded detail
Increases
How does FSS affect penumbra
Decrease FSS, decrease penumbra
How does OID affect penumbra
Decrease OID decrease penumbra
How does SID affect penumbra
Increase SID decrease penumbra
How does size distortion affect resolution
Decreases resolution
What is the best method for controlling involuntary motion
Short exposure time
What is the best way for controlling voluntary motion
Clear instructions
What is the last resort for controlling patient motion
Immobilization
Which distance is most associated with pt skin dose and why
SOD, the closer the source is to pt, more radiation is absorbed
Explain the relationship between a larger patient and entrance skin exposure
Bigger the patient, more ESE
How does the shape of the body part affect penumbra
Shapes in the body that match beam divergence create the least penumbra
What are two different formulas that can be used to calculate MF
SID/SOD
Image/object size
Magnification occurs when the body part is moved closer to or farther away from the central ray
Closer
Proper alignment is achieved when the central ray is ___ to the part and ____ to the image receptor
Perpendicular, perpendicular
