CT Image Quality

8

A CT tube anode angle of ______ degrees would result in the smallest effective focal spot size.

Multislice

Cone-beam artifacts only appear in ______ scanners. Third generation Second generation First generation Multislice

Uniformity

Cupping artifacts are most closely related to which image quality? Uniformity Linearity Temporal resolution Contrast resolution

Streak

Edge gradient artifacts appear as a: Streak White circles Ring Band of noise across the image

Motion

Ghosting refers to _____ artifacts. Cupping Static Ring Motion

Scanning with thinner slices

How can partial volume averaging be reduced? Scanning with thinner slices Scanning with thicker slices All of these Using a half-scan algorithm

Increasing slice thickness

Image noise can be reduced by: Decreasing mAs Decreasing pixel size Increasing slice thickness All of these

0.5

Modern CT scanners are able to differentiate tissue with density differences of less than ____%

Cone-beam

Modern multislice CT scanners use _____ geometry. Pencil-thin beam Fan-beam Parallel-beam Cone-beam

Similar tissue types share the same voxel

Partial volume averaging occurs when: Detector elements fail Metal objects are present within the patient of the patient's clothing Similar tissue types share the same voxel Cardiac studies are performed

Third generation

Ring artifacts only appear in ______ scanners. First generation Third generation Multislice Second generation

Thin slice thicknesses, small detector sizes

Spatial resolution can be improved by using (may select more than one): Thin slice thicknesses Small detector sizes A matrix with large pixel sizes None of these

Temporal resolution

The half-scan algorithm technique is used to improve: Linearity Temporal resolution Spatial resolution Uniformity

Band of increased noise across the image

Tube arcing appears as a: Ring artifact Cone-beam artifact Streak artifact Band of increased noise across the image

Outside the x-ray tube, inside the x-ray tube

Tube arcing occurs (may select more than one): Outside the x-ray tube All of these Inside the x-ray tube Because of fluctuations in line voltage

Decreased contrast resolution

What is the effect of increased image noise? Decreased contrast resolution Improved image quality None of these Increased contrast resolution

Assignment of CT numbers to known linear attenuation coefficients

What is the linearity phantom used to test? Assignment of CT numbers to known linear attenuation coefficients Temporal resolution Contrast resolution Spatial resolution

Standard deviation of the CT number in water, CT number calibration

Which of the following QC tests should be done daily (may select more than one)? Standard deviation of the CT number in water CT number calibration CT couch indexing None of these

Scintillation

Which of the following detector types produces higher quality images? Gas None of these Scintillation Linear

Smaller pixel size

Which of the following factors decreases contrast resolution: Higher mAs Smaller pixel size Smaller field of view Smaller matrix size

Scanning with thinner slices

Which of the following techniques reduces edge gradient artifacts? Using detectors with large apertures Scanning with thicker slices Scanning with thinner slices Decreasing data sampling rates

Retrospective gating

Which of the following techniques would be used for a patient who has trouble holding his or her breath or has an irregular heart beat? Half-scan algorithm Smoothing Prospective gating Retrospective gating

CT table backlash

Which of the following tests determines the ability of the patient table to return to its original position after the scan? CT table indexing CT table backlash Localization device accuracy Slice width

CT number flatness

Which of the following tests determines the uniformity of CT numbers without the image? CT number flatness High-contrast resolution Low-contrast, standard deviation of CT numbers in water

Localization device accuracy

Which of the following tests uses a solid plastic phantom with two holes drilled into it at 90 degrees angles to form an "X"? Localization device accuracy Low-contrast resolution CT numbers calibration High-contrast resolution

128-slice, 64-slice

Which of the following types of CT scanners are capable of effectively imaging a beating heart? None of these 16-slice 128-slice 64-slice

Cone Beam

Which of the following types of beam geometry results in increased scatter? Parallel beam Fan beam Pencil beam Cone beam