Card Set Information
Review for exam two
What are the geometric properties of radiographic image quality?
How does radiographic image detail compare to actual object detail?
All radiographs display less detail than the object being imaged
How is resolution affected by an increase in OID?
How is resolution affected by an increase in SID?
Why does motion reduce recorded detail?
Because it failt to permit enough time for a well defined image to form. The image is spread over a linear distance and appears blurred
What are the two types of distortion?
How is size distortion affected by an increase in SID?
as SID increases Magnification decreases
What is foreshortening and what causes it?
forshortening projects the object so it appears shorter than it really is. It occurs when the part is improperly aligned
What is elongation and what causes it?
Elongation projects the object so it appears to be longer than it really is. It occurs when the tube or the image receptor is improperly aligned
What is proper alignment?
When the CR is perpendicular toboth the anatomical part and the image receptor.
What is the first step in the film critique process?
Classification of the image
- is it within acceptance limits
- optimal or not optimal
When should a film be repeated?
when it is outside acceptance limits
If the image is within acceptance limits, why would the flim critique process continue?
To decided if the image is optimal or not optimal if not optimal what would you do to fix it in the future
If an image is not optimal should it always be repeated?
No! Evaluation should be done to figure out how to fix it for future exams
What is a photographic problem and what are some possible ways to correct it?
a technical factor problem with visibility of detail and can be further classified as denisity or contrast problems
What is quality control?
aspect of quality assurance that monitors technical equiptment to maintain quality standards
What is the process of sensitometry?
to monitor the processor DAILY to determine if its performing within limits
What is the acceptance limits for collimation and what adverse effects may occur if collimation is outside of acceptance limits?
+/- 3% of SID are the acceptance limits
If the light field is bigger than x-ray field you clip anatomy
if the light field is smaller than x-ray field you increase patient dose
What is the acceptance limits for SID and what adverse effects may occur if SID is outside of acceptance limits?
acceptance limits- calculated SID +/- 2% of actual SID
If calculated SID is too short magnification occurs resolution decreases and density too dark and patient dose increases
if calculated SID is too long less magnification increases resolution and density decreases
What is the difference between reproducibility and linearity?
What is the unit of measurement for resolution?
line pairs per millimeter
As film/screen speed increases, what happens to resolution?
As focal spot size decreases, what happens to penumbra?
As grey scale bit depth increases, what happens to resolution?
As spatial frequency increases, what generally happens to MTF?
Why is size distortion always magnification in film/screen rediography?
Because minification can only occur in digital radiography
What are the sources for resolution loss in CR technology?
What are the sources of resolution loss for direct and indirect digital radiography?
Direct- divergence of light and the dead spaces
Indirect- dead space btwn dector elements
What are the acceptance limits for exposure time settings?