Spatial Resolution
Contrast Resolution
Noise in CT
Artifacts
More Artifacts and Miscellaneous
100
In-Plane Spatial Resolution is expressed using this measurement.
What is "line pairs per cm or mm"
100
Decreasing kVp in CT has this effect on contrast resolution.
What is increases contrast resolution? (increases the ability to see structures of similar density/CT #)
100
"Sharp" or high resolution algorithms will have this effect on noise on a CT image.
Increased Noise
100
A ring artifact is an issue with this generation of CT scanner
What is 3rd Generation? (Rotate-Rotate)
100
This correction was made between the acquisition of Image A and Image B.
What is bringing the patients arms out of the scan field of view (likely over their heads)
200
Spatial Frequency plotted as a function of image fidelity is know as this.
What is MTF (Modular Transfer Function)
200
If a technologist wishes to decrease contrast resolution on a CT image, they will do this to the Window Width (WW)
What is increase/widen WW?
(Wider WW decreases contrast, which decreases the ability to distinguish structures of similar density/CT #)
200
Decreasing tube current in CT has this effect on noise.
What is increased noise?
200
This is the cause of the artifact seen here.
What is Contrast Streak? Extreme differences in CT#s ﴾Air and Barium﴿ can be a combination motion and partial volume averaging issue
200
This is one of three ways to increase temporal resolution on CT images
What is one of the following:
Increase Scan Speed‐ reduces motion,therefore increasing/improving temporal rez.
Special Algorithms: Half scan algorithm
Gating scans: proactively or retroactively)
300
Increasing Slice Thickness has this effect on spatial resolution.
What is Decreases Spatial Resolution?
300
Increasing tube current in CT has this effect on contrast resolution
What is Increases contrast resolution
(as less noise will be present due to more photons)
300
Thinner Slices have this effect on noise
What is increased noise?
300
Patient Movement during a CT scan results in this category of artifact.
What is streaking?
300
This is the correction for a Ring Artifact
Calibrate scanner, if that fails, contact service/biomed.
400
A smaller Field of View (FOV) has this effect on spatial resolution.
What is increases spatial resolution?
400
These types of reconstruction algorithms will increase
contrast resolution on CT images
What are "smooth algorithms"
Improve/increase contrast (ability to distinguish structures/tissues of similar density)
400
Decreasing noise by adjusting CT parameters usually this effect on patient dose.
Increases patient dose
400
This is the correction for non removable metallic artifacts
What is MAR (Metallic artifact reduction) algorithm
400
Increasing the Scan FOV will have this affect on pixel size.
Increased/Larger pixels (which also decreases spatial resolution)
500
Unlike radiography, images in CT can have both high spatial resolution/detail and this seen on the same image.
What is increased noise?
500
Radiography can discriminate a density difference of 10% while CT can detect density differences of this percentage range
What is 0.25-.05%
500
Increased patient size results in increased noise because more of this is produced in a large patient.
What is Scatter Radiation?
500
The artifact seen here occurs when voxels contain multiple tissues that have significantly different linear attenuation coefficients.
What is partial volume averaging artifact?
500
This is how a cone beam/windmill artifact is corrected.
Use of cone beam algorithm and use recommended pitch selections.