Quiz 4
An undesired surge of electrical current within the x-ray tube causes tube arcing. A) True B) False
A
How is noise measured? A) By finding the standard deviation of the CT numbers within the region of interest. B) By finding the standard median of the CT numbers within the region of interest. C) By finding the variance of the CT numbers within the region of interest. D) By finding the mean of the CT numbers within the region of interest.
A
How often should noise and uniformity testing be done? A) weekly B) monthly C) semiannually D) annually
A
Reconstructing raw data to create new images is done from the operator's console. A) True B) False
A
Surface rendering is useful for examining tubular structures. A) True B) False
A
The American College of Radiology CT accreditation phantom is a solid phantom that contains four modules, and is constructed primarily from a water-equivalent material. A) True B) False
A
What is interactive reformation? A) Reformation that allows the operator to use a mouse or other device to manually change the image plane while the software continually updates the image. B) Reformation that is specifically designed to look inside the lumen of a structure C) Another name for three-dimensional reformation
A
What is the maximum variation from the intended slice thickness for a slice thickness of 5 mm or less? A) ±0.5 mm B) ±1 mm C) ±0.5 cm D) ±1 cm
A
What percent of the data available does surface rendering typically use? A) 10% B) 25% C) 50% D) 100%
A
When voxels are isotropic, any oblique plane can be created with virtually no loss of image quality. A) True B) False
A
Which American College of Radiology (ACR) CT accreditation phantom module is used to asses positioning and alignment? A) Module 1 B) Module 2 C) Module 3 D) Module 4
A
Which is not true about image reformation? A) Raw data are used B) It generates images in a different plane or orientation C) It is used to better display relationships D) It may be either 2D or 3D
A
Which type of artifacts can occur when voxels are not isotropic? A) Stair-step B) Motion C) Ring D) Streak
A
Which type of imaging visualizes a structure as if it were hollow and the viewer were inside of it? A) Endoluminal imaging B) Projection displays C) Surface rendering D) Volume rendering
A
Who often shares the responsibility for performing and documenting quality control tests? A) CT technologists and medical physicists B) CT technologists and physicians C) Medical physicists and scanner manufacturers D) Physicians and medical physicists
A
A voxel is isotropic when the z direction is equal to the slice thickness. A) True B) False
B
Multiplanar reformations (MPRs) are 3D image displays. A) True B) False
B
Ring artifacts appear only on MDCT helical systems. A) True B) False
B
There is always the same specific pattern in the appearance of tube arc artifacts. A) True B) False
B
Tube arcing is patient-induced artifact. A) True B) False
B
What causes the edge gradient effect? A) More than one type of tissue is contained within a voxel. B) Irregularly shaped objects that have a pronounced difference in density from surrounding structures. C) Anatomy that extends out-side of the selected SFOV D) Patient motion
B
What is another name for region-of-interest editing? A) Minimum-intensity projection B) Segmentation C) Overlapping reconstruction D) Surface rendering
B
What is another name for surface rendering? A) Projection display B) Shaded-surface display C) Volume rendering D) Endoluminal imaging
B
What is region-of-interest editing? A) Creating images by comparing the intensity of each voxel in the data set to some predetermined threshold B) The process of selectively removing or isolating information from the data set C) The method of examining each voxel along a line from the viewer's eye through the data set and selecting only the voxel with the highest value for inclusion in the displayed image D) A form of value rendering that is designed to look inside the lumen of a structure
B
What is the goal of using a thin slice for scanning and reconstruction and thicker slices for viewing and storing? A) To generate scans that are generated with isotropic, or near isotropic voxels B) To maintain the advantage of high-resolution imaging but also create image files that are manageable and more easily reviewed by radiologists C) To create reformatted images that better display anatomic relationship
B
What is the maximum variation from the intended slice thickness for a slice thickness of 5 mm or greater? A) ±0.5 mm B) ±1 mm C) ±0.5 mm D) ±1 cm
B
Which describes a cupping artifact? A) When there is an appearance of dark bands or streaks between dense objects in the image. B) When the periphery of the image is lighter. C) When fine stripes appear to be radiating from a dense structure. D) When the object appears in only a small number of views collected from the tube's 360° path?
B
Which is a major drawback of workstation-created MPRs? A) If oblique or curved images are needed, the technologist must create them manually B) Data contain hundreds of images potentially slowing down the PACS network C) Operators cannot use trial and error to obtain the ideal image plane D) There is significant loss of image quality
B
Which is not a manifestation of patient motion? A) streaking B) concentric rings C) blurring D) ghosting
B
How often is direct spatial resolution testing using a line pairs phantom performed in most quality assurance programs? A) daily B) weekly C) monthly D) annually
C
How often is slice thickness accuracy testing performed in most quality assurance programs? A) weekly B) monthly C) semiannually D) annually
C
Where are laser lights located? A) Inside the gantry B) Outside the gantry C) Both inside and outside the gantry
C
Which classification of image artifacts causes ring artifacts? A) Patient-based B) Physics-based C) Equipment-based
C
Which is a drawback of manual segmentation? A) Image complexity and the variety of image types and clinical indications make it impractical B) Low contrast between structures can cause otherwise robust automatic algorithms to fail C) It can be very hard to separate the object from the image background
C
Which is another name for image reformation? A) Projection display B) Surface rendering C) Image rendering D) Segmentation
C
Which is not a feature CT systems use to minimize beam hardening? A) Filtration B) Beam-hardening correction software C) Slowing gantry rotation speed D) Calibration correction
C
Which is not a type of segmentation? A) Manual B) Semiautomatic C) Workstation-created D) Fully automated
C
Which of the following does not have to be identical to reformat a CT study? A) DFOV B) Gantry tilt C) Beam pitch D) Image center
C
According to the ACR reference CTDI, what is the recommended radiation dose for an adult head? A) 20 mGy B) 25 mGy C) 50 mGy D) 75 mGy
D
In which 3D technique does the image appear flat? A) Shaded-surface display B) Surface rendering C) Volume rendering D) Maximum-intensity projections
D
What cause spiral interpolation artifacts? A) Patient motion B) The x-ray beams are composed of different energies C) Too few samples D) Images are created from views not in the same plane
D
What is ghosting? A) Another name for tube arcing B) Another name for the edge gradient effect C) A type of filter used to eliminate beam hardening D) A type of image artifact where objects appear to have a shadow
D
What is the best way to reduce metallic artifact? A) Give the patient clear breathing instructions B) Recalibrate the scanner C) Select a SFOV that is larger than the patient. D) Minimize the metal present in the SFOV
D
Which is not a typical classification for the causes of artifacts? A) Physics-based B) Equipment-based C) Patient-based D) Technologist-based
D
Which statement is true about overlapping reconstructions? A) The more the pixel size exceeds slice thickness, the greater the benefit of overlapping reconstructions for source data in multiplanar reformation (MPR) and 3D reformation. B) The more the pixel size exceeds slice thickness, the less the benefit of overlapping reconstructions for source data in multiplanar reformation (MPR) and 3D reformation. C) The more the slice thickness exceeds pixel size, the less the benefit of overlapping reconstructions for source data in multiplanar reformation (MPR) and 3D reformation. D) The more the slice thickness exceeds pixel size, the greater the benefit of overlapping reconstructions for source data in multiplanar reformation (MPR) and 3D reformation.
D
A 3D semitransparent representation of the imaged structure is known as___. (use the abbreviation)
VR
Any object seen on the image that is not present in the object scanned is considered an ___
artifact
The range of x-ray intensity values to which the scanner can accurately respond is called the ___
dynamic range
A form of volume rendering known as___is designed to reveal the inside of the lumen of a structure.
endoluminal
____refers to the relationship between CT numbers and the linear attenuation values of the scanned object at a designated kVp value.
linearity
Manipulating raw data and image data after scanning has taken place is called___processing.
post
Assembling data to produce images in different planes, or to produce 3D images is called ____
reformation
Creating a MIP from only a portion of the data set is called the variable___lab method.
sliding
Insufficient projection data is called ____
undersampling
___refers to the ability of the scanner to yield the same CT number regardless of the location of an ROI within a homogenous object.
uniformity