# CT Registry Review - Physics

54 Questions | Total Attempts: 9713  Settings  The CT Registry Review Program presents a detailed discussion of every concept outlined in the content specifications for the CT certification exam. It is designed to help technologists prepare effectively for the CT exam and enable them to accurately take and interpret CT scans of patients. Are you looking for one? The quiz below suits you perfectly, Give it a try and all the best.

Related Topics
• 1.
Partial volume averaging on the CT image may be decreased by:
• A.

Increasing matrix size

• B.

Decreasing matrix size

• C.

Increasing slice thickness

• D.

Decreasing slice thickness

• 2.
The loss of anatomic information between contiguous sections due to inconsistent patient breathing is called:
• A.

Cupping artifact

• B.

Misregistration

• C.

Overshoot artifact

• D.

Out of field artifact

• 3.
A CT image is formed in part by projecting back all of the attenuation values recorded during data acquisition onto a:
• A.

Pixel

• B.

Voxel

• C.

Matrix

• D.

Reformat

• 4.
What is the dimension of each pixel in an image with 512 x 512mm matrix and a DFOV equaling 25.6?
• A.

0.5 mm

• B.

0.5 cm

• C.

0.05 cm

• D.

Both A and C

• 5.
First generation CT scanners used a method of data acquisition based on a _______________ principle.
• A.

Multiplanar

• B.

Rotation only

• C.

Translate - rotate

• D.

Transaxial

• 6.
CT numbers are usually provided in the form of:
• A.

Hounsfield units

• B.

Electromagnetic interference numbers

• C.

Cormacks

• D.

U

• 7.
Which of the following may be used for the archival storage of CT images?1. magnetic tape2. VHS tape3. magnetic optical disk
• A.

1 only

• B.

1 and 3

• C.

2 and 3

• D.

1,2, and 3

• 8.
The reduction in intensity of an x-ray beam as it interacts with matter is termed:
• A.

Scatter

• B.

Attenuation

• C.

Transmission

• D.

Luminescence

• 9.
• A.

Increased transmission measurements

• B.

Increased patient dose

• C.

Decreased transmission measurements

• D.

Excess tube wear

• 10.
Which of the following is the most common type of noise found in the CT image?
• A.

Statistical noise

• B.

Electronic noise

• C.

Artifactual noise

• D.

Filter noise

• 11.
Scintillation crystals are used exclusively as detectors in __________________ CT scanners?
• A.

Electron beam

• B.

Third-generation

• C.

Fourth generation

• D.

Spiral

• 12.
A first generation CT Scanner consists of an x-ray tube and two detectors that translate across the patients's head while rotating in 1 degree increments for a total of:
• A.

45 degrees

• B.

90 degrees

• C.

180 degrees

• D.

360 degrees

• 13.
Which of the following factors doesn not affect the dimensions of a voxel?
• A.

Slice thickness

• B.

Matrix size

• C.

Kernel

• D.

DFOV

• 14.
Areas of a CT image that contain abrupt changes in tissue density are electronically represented by which of the following?
• A.

Positive CT numbers

• B.

High spatial frequencies

• C.

Negative CT numbers

• D.

Low spatial frequencies

• 15.
• A.

1 only

• B.

1 and 2 only

• C.

2 and 3 only

• D.

1, 2, and 3

• 16.
Which of the following archival media is capable of storing the largest number of CT images?
• A.

Floppy disk

• B.

Magnetic tape

• C.

VHS tape

• D.

Optical disk

• 17.
The term used to describe the relation between the linear attenuation coefficients of an object and the calculated CT numbers is:
• A.

Linearity

• B.

Mottle

• C.

Quantum noise

• D.

Spatial resolution

• 18.
• A.

Data acquisition system (DAS)

• B.

Analog-to-analog converter

• C.

Digital-to-analog converter

• D.

Array Processor

• 19.
• A.

The algorithm, matrix size, and DFOV may all be changed.

• B.

The slice thickness and SFOV may be changed

• C.

Scan (raw) data must be available

• D.

Retrospective image reconstuction may be used to adjust the center of the displayed image.

• 20.
Which of the following decreases the noise of the CT image?
• A.

Decrease in dose

• B.

Decrease in lice thickness

• C.

Increase in matrix size

• D.

Decrease in matrix size

• 21.
Increasing the pitch during a spiral CT examination adversely affects the spatial resolution along with which of the following?
• A.

Axial plane

• B.

X axis

• C.

Y axis

• D.

Z axis

• 22.
Which of the following statements regarding prepatient collimation is true?1. An increase in prepatient collimation increases Pt dose.2. Prepatient collimation is used to focus radiation through the section of interest.3. Prepatient collimation directly controls slice thickness.
• A.

2 only

• B.

3 only

• C.

1 and 2 only

• D.

2 and 3 only

• 23.
When an operator reduces the SFOV for a particular body part, which of the following technical changes occurs?
• A.

The displayed image appears larger

• B.

Spatial resolution increases

• C.

A smaller number of detectors are activated.

• D.

The displayed image appears smaller.

• 24.
An average CT number value for blood is:
• A.

-20 Hounsfield units

• B.

+10 Hounsfield units

• C.

+45 Hounsfield units

• D.

+100 Hounsfield units

• 25.
Which of the following types of gas is commonly used for gas ionization CT detectors?
• A.

Xenon

• B.

• C.

Helium

• D.

Nitrogen

• 26.
The mathematical manipulations required during the reconstruction of a CT image are accomplished using a(n):1.  algorithm2.  kernel3.  mathematical filter function
• A.

1 only

• B.

1 and 2 only

• C.

1 and 3 only

• D.

1,2, and 3

• 27.
Quality control measurements to test the accuracy of the calibration of the CT scanner should be performed?
• A.

Daily

• B.

Weekly

• C.

Monthly

• D.

Annually

• 28.
Which of the following technical parameters would greatly improve the quality of CT studies requiring multiplanar reformats?
• A.

Noncontiguous scans

• B.

Wide section thicknesses

• C.

Contiguous cans with wide section thickness

• D.

Overlapping scans with narrow section thickness

• 29.
Pixels whose average attenuation coefficients are less than that of water have which of the following types of CT number values?
• A.

Extremely large

• B.

High positive

• C.

Negative

• D.

None of the above

• 30.
Which of the following mathematical techniques is used exclusively for image reconstruction with spiral CT scanners?
• A.

Back-projection

• B.

Convolution

• C.

Interpolation

• D.

Iterative techniques

• 31.
Which of the following reduces scatter radiation reaching the detectors?
• A.

Postpatient collimation

• B.

Prepatient collimation

• C.

Predetector collimation

• D.

Both A and C

• 32.
A voxel may be defined as which of the following?
• A.

The portion of the CRT displaying the image

• B.

A miniature image

• C.

A volume element

• D.

An arrangement of pixels

• 33.
Which of the following would increase spatial resolution of a CT examination using the  following parameters: large focal spot size, 10 mm sections, 512 x 512 mm matrix.1. Change to small focal spot size2. Perform 5 mm sections3. Reconstruct images in a 320 x 320 mm matrix
• A.

1 only

• B.

1 and 2 only

• C.

1 and 3 only

• D.

1,2, and 3

• 34.
The portion of the primary beam interacting with a single detector is known as a:
• A.

Ray

• B.

View

• C.

Profile

• D.

Sample

• 35.
A pixel may be defined as:
• A.

athe portion of the CRT displaying the image

• B.

A volume element

• C.

A picture element

• D.

A miniature image

• 36.
The mathematical technique that involves the estimation of an unknown value from values on either side of it is known as:
• A.

Filtering

• B.

Interpolation

• C.

Convolution

• D.

Summation

• 37.
Pixels  representing tissues with average attenuation coeffients greater than that of water have which of the following types of values?
• A.

Extremely small

• B.

Positive

• C.

Negative

• D.

None of the above

• 38.
When compared with conventional radiography, CT produces diagnostic images with improved:
• A.

Low-contrast resolution

• B.

Spatial resolution

• C.

Minute detail

• D.

Patient dose reduction

• 39.
In 1917, the Austrian mathematian _____________________ proved that it was possible to reconstruct a three-dimentional object fromt he infinite set of all of its projections.
• A.

• B.

Tsien

• C.

Bracewell

• D.

Cormack

• 40.
Which of the following is not commonly used as a CT scintillation detector material?
• A.

Ceramic rare earth

• B.

Silver halide

• C.

Bismuth germinate

• D.

• 41.
Which of the following is the primary interaction between x-ray photons and tissue during  CT examinations?
• A.

Bremsstrahlung effect

• B.

Characteristic effect

• C.

Compton effect

• D.

Coherent scatter

• 42.
Areas of a CT image that contain minimal changes in tissue density are llectronically represented by:
• A.

Positive CT numbers

• B.

High spatial frequencies

• C.

Negative CT numbers

• D.

Low spatial frequencies

• 43.
Ring artifacts on the CT image are asociated with which of the following tube-detector geometric relationships?
• A.

Rotate-nutate

• B.

Rotate-stationary

• C.

Rotate-rotate

• D.

Translate-rotate

• 44.
In the binary number system, a byte is a series of ___________ bits of information.
• A.

2

• B.

4

• C.

8

• D.

16

• 45.
An accurate, modern CT scanner is capable of a spatial resolution of up to:
• A.

10 lp/mm

• B.

20 lp/mm

• C.

10 lp/cm

• D.

20 lp/cm

• 46.
Which of the following is the best method to reduce respiratory motion on the CT image?
• A.

Good patient - technologist communication

• B.

Reduced scan times

• C.

Use of immobilization devices

• D.

• 47.
Which of the following statements is correct regarding the radiographic film used to archive CT images?1. it is a double-emulsion film2. it is sensitive to UV light only3. it may be used in conjunction with a multiformat or laser camera
• A.

1 only

• B.

2 only

• C.

3 only

• D.

1 and 3 only

• 48.
Which of the following reconstruction methods is used by most modern CT Scanners?
• A.

Back projection

• B.

Iterative methods

• C.

Fourier transform

• D.

Filtered back-projection

• 49.
Fourth-generation  CT scanners use a _________________ tube-detector configuration.
• A.

Rotate - translate

• B.

Electron beam - stationary

• C.

Rotate - stationary

• D.

Rotate - rotate

• 50.
The fluctuation of CT numbers in an image of uniform, homogeneous material is known as:
• A.

Linearity

• B.

Noise

• C.

Artifact

• D.

Partial volume effect

• 51.
• A.

The decrease in average photon energy of a heterogeneous x-ray beam

• B.

The increase in average photon energy of a homogeneous x-ray beam

• C.

The increase in average photon energy of a heterogeneous x-ray beam

• D.

None of the above

• 52.
The process by which electrons are produced at the cathode of a CT x-ray tube is known as:
• A.

Rectification

• B.

Anode heel effect

• C.

Thermionic emission

• D.

Isotropic emission

• 53.
• A.

Decreased aperture size

• B.

Decreased miliampere-seconds (mAs)

• C.

Increased filtration

• D.

Increased aperture size

• 54.
A straight line appearing vertically on the scanogram (pilot) of a fourth-generation CT scanner is an artifact most likely caused by:
• A.