Questions and Answers
What is the ability to differentiate a structure that varies only slightly in density from its surroundings?
Low-contrast sensitivity
What is the term for any systematic discrepancy between the CT numbers in the reconstructed image and the true attenuation coefficients of the object?
Artifact
What is the cause of quantum mottle?
Insufficient number of x-ray photons detected
What is the result of decreasing the number of x-ray photons to create an image?
Signup and view all the answers
What type of artifact is caused by a temporary short circuit in the X-ray tube?
Signup and view all the answers
What is the term for the undesirable fluctuation of pixel values in an image of a homogeneous material?
Signup and view all the answers
What is the result of increasing the signal-to-noise ratio?
Signup and view all the answers
What type of artifact is also known as incomplete projection artifact?
Signup and view all the answers
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Study Notes
Contrast Resolution
- Ability to differentiate structures that vary slightly in density from their surroundings
- Also referred to as sensitivity of the system or low-contrast sensitivity
- Encompasses low-contrast detectability, which is the ability to distinguish an object nearly the same density as its background
CT Image Artifacts
- Defined as anything appearing on the image that is not present in the object scanned
- Systematic discrepancy between reconstructed image CT numbers and true attenuation coefficients of the object
- Divided into three categories
Noise
- Undesirable fluctuation of pixel values in an image of a homogeneous material
- Recognized as grainy appearance or "Salt and pepper" look on an underexposed image
- Can occur due to quantum mottle, which results from insufficient detected photons
- Signal-to-noise ratio (SNR) measures the number of x-ray photons detected per pixel
- Higher SNR indicates less obtrusive background noise
Other Artifacts
- Out of field artifacts (also known as incomplete projection artifact)
- Tube arcing artifacts caused by temporary short circuit in the X-ray tube, leading to momentary loss of X-ray output
