CT Questions
If the CT table is moving at 10 mm/sec., and a section thickness of 8 mm is being acquired, what is the pitch? Answer to the second digit beyond the decimal point.
1.25 TEST QUESTION
Detector alignment is not critical in CT. Select one: True False
False
The primary advantage to the helical scanner is that a full 360-degree set of data is acquired for each section. Select one: True False
False
The HU of water is always 1. Select one: True False
False TEST QUESTION
CT radiation beams are double collimated. Select one: True False
True
CT tubes commonly fail after several months. Select one: True False
True
A CT imaging system produces which type of image? Select one: a. Axial b. Biaxial c. Fulcrum plane d. Longitudinal e. Transverse
a. Axial
A series of tissue density values that evolved for CT measurements is called _____ units. Select one: a. Hounsfield b. SI c. Attenuation d. All of the above
a. Hounsfield
Which of the following terms is equivalent to spiral? Select one: a. Elliptical b. Helical c. Interpolation d. Paraboloid e. Trispiral
b. Helical
Noise on a CT image increases with an increase in: Select one: a. kVp b. mA c. Matrix size d. Pixel size e. Slice thickness
c. Matrix size
What range of beam pitch is recommended for multislice spiral CT? Select one: a. 0.5 to 1 b. 0.5 to 2.0 c. 0.5 to 4 d. 1 e. 1 to 2
d. 1
Spatial resolution for CT imaging systems is approximately: Select one: a. 1 cm b. 10 cm c. 100 cm d. 1 mm e. 10 mm
d. 1 mm
Which of the following is one advantage of spiral CT over conventional CT? Select one: a. Better patient dose utilization b. Improved contrast resolution c. Improved spatial resolution d. Lack of motion artifact e. Large matrix reconstruction
d. Lack of motion artifact
The thickness of section in CT depends primarily on: Select one: a. kVp b. mAs c. Matrix size d. Predetector collimation e. Prepatient collimation
d. Predetector collimation
Which advanced function allows the user to remove all tissue above and below a certain threshold and to show the object in three-dimensions for better visualization? Select one: a. MPR b. MIP c. MinIP d. SSD
d. SSD
When a shaded surface display reformation is implemented, the image will appear: Select one: a. As CT angiography b. As z-axis reformation c. Isometric d. Surface-rendered e. Volume-rendered
d. Surface-rendered
The resolution of the CT image depends on the: Select one: a. pixel b. voxel c. matrix d. all of the above
d. all of the above
Streak artifacts on a CT image are usually due to: Select one: a. Beam Hardening b. Bone/soft tissue interface c. Bowel gas d. Detector imbalance e. Metal clips
e. Metal clips TEST QUESTION
A comparison of scintillation and gas-filled detectors shows that: Select one: a. Both have approximately the same total detection efficiency. b. Both rely heavily on Compton interaction. c. Only scintillation detectors require prepatient collimation. d. The gas-filled detectors have higher intrinsic efficiency. e. The scintillation detectors have higher geometric efficiency.
e. The scintillation detectors have higher geometric efficiency. TEST QUESTION
The largest number of individual detectors in a multislice CT imager is approximately: Select one: a. Two b. Four c. Ten d. Hundreds e. Thousands
e. Thousands
Motion on a CT image is a function of exposure time. Select one: True False
True
Factors that affect image quality in CT consist of: 1. spatial resolution 2. noise 3. contrast media
a. 1 and 2
Which advanced workstation function can reconstruct images into another plane? Select one: a. MPR b. MIP c. VRT d. SSD
a. MPR
Sensitivity profile in CT is determined principally by the: Select one: a. Bow-tie filter b. Predetector collimator c. Prepatient collimator d. Reconstruction algorithm e. Ramp function
b. Predetector collimator
The ____ is how well the detectors convert incoming photons. Select one: a. capture efficiency b. absoprtion efficiency c. conversion efficiency d. response time
b. absoprtion efficiency
Each translation of a source detector assembly produces which of the following? Select one: a. A matrix b. A pixel c. A projection d. A voxel e. An image
c. A projection
CT is preformed at high kVp principally to: Select one: a. Improve image contrast. b. Minimize beam hardening. c. Reduce patient dose. d. Reduce scatter radiation. e. Reduce x-ray tube loading
c. Reduce patient dose.
Which of the following technique developments made spiral CT possible? Select one: a. Dose-efficiency detectors b. High-frequency generators c. Interpolation algorithms d. Slip rings e. Volume imaging
d. Slip rings
Why is it recommended that beam pitch should not exceed 2.0? Select one: a. Increased noise b. Poor contrast resolution c. Poor patient dose utilization d. Poor spatial resolution e. Poor z-axis resolution
e. Poor z-axis resolution
Which of the following is a constituent of a CT imager? 1. A computer 2. A television monitor 3. An algorithm 4. An image intensifier
1, 2, and 3 are correct
If the table is moving at 12 mm/sec., and a section thickness of 10 mm is being acquired, what is the pitch? Answer to the second digit beyond the decimal point.
1.20 TEST QUESTION
If the table is moving at 5 mm/sec., and a pitch of 1.5 is being used, what is the section thickness? Answer: ____ mm
3.33 TEST QUESTION
The CT number for gray matter is 43. Given that information and knowledge of the formula for the calculation for the CT number. The linear attenuation coefficient for gray matter is.
44.849
If the pitch of 0.5 is being used with a section thickness of 10 mm, what is the proper CT table speed? Answer: ____ mm/sec
5 TEST QUESTION
If the table is moving at 5 mm/sec., and a pitch of 0.8 is being used, what is the section thickness for this CT scan in mm? Answer: ____ mm Answer to the second digit beyond the decimal point. Just type the number.
6.25 TEST QUESTION
If a pitch of 1.0 is being used with a section thickness of 8 mm, what is the proper table speed? Answer: ____ mm/sec
8 TEST QUESTION
Because of their simplistic nature, first-generation CT scanners were much smaller than those used today. Select one: True False
False
CT x-ray tubes produce a massive amount of heat as compared to conventional radiographic tubes. Select one: True False
True
Patient dose during CT is measured according to the CTDI. Select one: True False
True
The amount of noise controls the low-contrast resolving ability of the CT unit. Select one: True False
True
The operating console of a CT imager will normally have controls for which of the following? 1. kVp 2. Exposure time 3. Slice thickness 4. SID indicator
a. 1, 2, and 3 are correct
Which of the following reconstruction techniques exhibits the most image noise? Select one: a. 180-degree interpolation b. 360-degree interpolation c. Back-projected conventional CT d. Filtered back projection conventional CT e. High-dose CT
a. 180-degree interpolation TEST QUESTION
How much z-axis tissue will be imaged during a 20 s procedure if the slice width is 5 mm at a pitch of 1 and the gantry rotation time of 2 s? a. 5 cm b. 10 cm c. 100 cm d. 5 mm e. 10 mm
a. 5 cm TEST QUESTION
In its simplest configuration, the CT imaging system consists of an x-ray source and which of the following? Select one: a. A detector b. A selenium plate c. A video display terminal d. An image intensifier e. An x-ray beam collimator
a. A detector TEST QUESTION
Which of the following is characteristic of first-generation CT imaging systems? Select one: a. A pencil x-ray beam b. A selenium or film image receptor c. Multiple sources and multiple detectors d. Rotate-only geometry e. Slip rings
a. A pencil x-ray beam
During CT imaging, beam hardening artifacts: Select one: a. Are due to the polyenergetic beam. b. Can be corrected by preprocessing. c. Produce CT numbers higher in the periphery. d. Result in brighter pixels in the center of the patient. e. Result in higher attenuation in the center of the patient.
a. Are due to the polyenergetic beam.
Fourth-generation CT imaging systems: Select one: a. Are faster than third-generation CT imaging systems. b. Have rotate-rotate geometry. c. Incorporate area-beam geometry. d. May use selenium or film as the image receptor. e. Require prepatient collimation.
a. Are faster than third-generation CT imaging systems.
A principal advantage of multislice spiral CT compared with step-and-shoot CT is all of the following except: Select one: a. Better spatial resolution b. Faster imaging c. Larger tissue volume d. Lower patient dose e. Three-dimensional image reconstruction
a. Better spatial resolution
Which of the following has been used as a detector in a CT imaging system? Select one: a. Bismuth germanate b. CaWO4 c. High-pressure air d. Selenium e. Silver halide
a. Bismuth germanate
The ability to reconstruct an image at any z-axis position is due to: Select one: a. Extrapolation b. Filtered back projection c. Fourier transformation d. Interpolation e. Linear estimation
a. Extrapolation
Which of the following characteristics is specific to a spiral CT x-ray tube? Select one: a. High anode heat capacity b. High rotation speed c. Large effective focal spots d. Large target angle e. Small effective focal spots
a. High anode heat capacity TEST QUESTION
In computed tomography, how does the x-ray tube move? Select one: a. In a full circle around the patient. b. Back and forth in a half-circle under and around the patient. c. Side to side in a horizontal plane over the patient. d. None of these.
a. In a full circle around the patient.
A ____ artifact is caused by attenuation of the beam as it passes through the patient. Select one: a. beam-hardening b. ring c. star d. streak
a. beam-hardening TEST QUESTION
The ______ is how well the detectors receive photons from the patient. Select one: a. capture efficiency b. absorption efficiency c. conversion efficiency d. response time
a. capture efficiency
A grid pattern is not added to the CT image to: Select one: a. clean up scatter b. confirm centering c. aid in patient positioning d. describe precise location
a. clean up scatter
The process of modifying pixel values by a mathematical formula is called: Select one: a. convolution b. deconvolution c. calculus d. all of the above
a. convolution TEST QUESTION
The CT radiographer usually varies the ____ to control the primary beam. Select one: a. mA b. time c. kVp d. detail
a. mA
Contrast is adjusted by windowing, changing window width and window level. Window width determines the: Select one: a. number of gray levels displays b. determines the midpoint of the gray range c. size of the field of view d. slice thickness
a. number of gray levels displays
In the CT detector, the x-ray photon is absorbed by: Select one: a. sodium iodide crystals b. photostimulable fluorohalides c. polyester d. none of the above
a. sodium iodide crystals
If a 20-second spiral CT examination is acquired at a pitch of 1.5 with collimation of 10 mm, what volume of tissue was imaged? Select one: a. 3 cm b. 30 cm c. 300 cm d. 3 mm e. 30 mm
b. 30 cm TEST QUESTION
Which of the following is characteristic of a CT image but not of a conventional radiograph? Select one: a. Anatomic structures are superimposed. b. Better contrast resolution is obtained. c. Better spatial resolution is obtained. d. More scatter radiation reaches the image receptor. e. Overlying and underlying tissues are blurred.
b. Better contrast resolution is obtained.
Which of the following is specifically characteristic of spiral CT? Select one: a. Continuous bidirectional rotation of the x-ray tube. b. Continuous x-ray tube rotation in one direction. c. Rotating detector array. d. Stationary patient couch. e. Step-like motion of the patient couch.
b. Continuous x-ray tube rotation in one direction.
The translate-rotate mode: Select one: a. Collects data only during the rotate portion. b. Describes both first- and second-generation CT imaging systems. c. Requires higher heat capacity x-ray tubes. d. Requires only solid-state detectors. e. Results in imaging times as short as 1 second.
b. Describes both first- and second-generation CT imaging systems.
Who was the first to incorporate digital imaging with the CT scanner? Select one: a. Paul Lauterbor b. Godfrey Hounsfield c. Sol Nudleman d. M. Paul Capp
b. Godfrey Hounsfield
The first commercial CT scanner could image the ________ . Select one: a. Abdomen only b. Head only c. Head and abdomen d. Total body
b. Head only
The single most important advantage of spiral CT is which of the following? Select one: a. Imaging of a large volume of anatomy at low patient dose. b. Imaging of a large volume of anatomy in one breath-hold. c. Improved contrast resolution. d. Improved spatial resolution.I e. Improved z-axis resolution.
b. Imaging of a large volume of anatomy in one breath-hold. TEST QUESTION
Noise on a CT image can be reduced by: Select one: a. Increasing kVp b. Increasing mAs c. Increasing matrix size d. Reducing image time e. Reducing pixel size
b. Increasing mAs TEST QUESTION
When a CT image is described, contrast resolution: Select one: a. Is limited by the MTF of the system. b. Is limited by the noise of the system. c. Is not as good as in conventional radiography. d. Is the same as spatial resolution. e. Means that contrast material was injected.
b. Is limited by the noise of the system.
CT angiography relies on a reconstruction process that is called: Select one: a. Longitudinal reformation b. Maximum intensity projection c. Shaded surface display d. Surface-rendered e. Volume-rendered
b. Maximum intensity projection
The simplest form of three-dimensional imaging is: Select one: a. Isometric b. Maximum-intensity projection c. Shaded surface display d. Shaded volume display e. Slip-ring technology
b. Maximum-intensity projection
The invention of computed tomography is heralded as ________ . Select one: a. The advanced use of three-dimensional computation in medical imaging. b. One of the greatest milestones in medical imaging. c. The stepping stone for the development of MRI. d. The first modality to use PACS.
b. One of the greatest milestones in medical imaging. TEST QUESTION
Third-generation CT imaging systems have which of the following? Select one: a. Multiple-detector, area-beam geometry b. Rotate-rotate geometry c. Rotate-translate geometry d. Single-detector, fan-beam geometry e. Translate-translate geometry
b. Rotate-rotate geometry
Spatial resolution refers to which of the following? Select one: a. The ability to classify large low-contrast objects. b. The ability to identify small high-contrast objects. c. The ability to identify tissues of varying composition. d. The binary number system. e. The constancy of the imaging system over time.
b. The ability to identify small high-contrast objects.
Which of the following subsystems would normally be associated with the CT gantry assembly? Select one: a. Image postprocessing b. The detector array c. The algorithm d. The physicians viewing console
b. The detector array
Contrast is adjusted by windowing, changing window width and window level. Window level determines the: Select one: a. number of gray levels displays b. determines the midpoint of the gray range c. size of the field of view d. slice thickness
b. determines the midpoint of the gray range
Images created with Computed Tomography and Magnetic Resonance Imaging can be manipulated to control the contrast, density, or even projected in a different plane. This is possible because the images that are created are: Select one: a. not made with x-rays b. digital c. made with magnetic fields d. not placed on film
b. digital
The most recent generation CT scanners use a ____ motion. Select one: a. spiral b. helical c. linear d. elliptical
b. helical
The _____ artifact is caused by detector error when performing CT. Select one: a. beam-hardening b. ring c. star d. streak
b. ring
Dose in CT is considered to be: Select one: a. independent of size b. size dependent c. related to the CT numbers d. similar to a chest examination
b. size dependent
In reference material for CT is ________ and is related to the _______ of the tissue. Select one: a. water, field of view b. water, linear attenuation coefficient c. muscle, gray level d. bone, mass attenuation
b. water, linear attenuation coefficient
A CT imaging system has a limiting resolution of 7 lp/cm. An object of what size can be resolved? Select one: a. 0.35 mm b. 0.5 mm c. 0.7 mm d. 1.4 mm e. 3.5 mm
c. 0.7 mm TEST QUESTION
What is the pixel size of an image reconstructed from a 24 cm diameter region of interest (ROI) in a 320 x 320 matrix? Select one: a. 0.25 mm b. 0.5 mm c. 0.75 mm d. 1.3 mm e. 1.5 mm
c. 0.75 mm TEST QUESTION
A CT image is made with a 5 mm slice thickness and a 0.5 mm pixel size. What is the size of the voxel? Select one: a. 0.75 mm3 b. 1.00 mm3 c. 1.25 mm3 d. 1.5 mm3 e. 2.5 mm3
c. 1.25 mm3 TEST QUESTION
During a 360-degree x-ray rotation, the patient couch moves 15 mm during each revolution. Slice thickness is 10 mm. What is the slice pitch? Select one: a. 0.66 b. 1.25 c. 1.5 d. 1.66 e. 2.0
c. 1.5 TEST QUESTION
Thirty centimeters of tissue along the z-axis is to be imaged with a 5 mm slice thickness at a pitch of 2.0. What imaging time is required? Select one: a. 20 s b. 25 s c. 30 s d. 35 s e. 40 s
c. 30 s TEST QUESTION
The image produced by CT scanning is which of the following? Select one: a. An anteroposterior view b. Dynamic (moving) c. A cross section d. All of the above
c. A cross section
Early reconstruction of raw compute tomography data took a few ______ to form a recognizable image. Select one: a. Minutes b. Hours c. Days d. Weeks
c. Days TEST QUESTION
The most common reporting method of dose reporting on the present CT scanners is: Select one: a. Multiple Scan Average Dose (MSAD) b. Computed Tomography Dose Index (CTDI) c. Dose-length product (DLP) d. Computed Tomography Dose Index Volume (CTDIvol)
c. Dose-length product (DLP)
A Hounsfield unit: Select one: a. Has a value from -100 to +100. b. Has a value from -500 to +500. c. Is the numerical value of a pixel. d. Is the numerical value of anode heat generated. e. Is the volume of a voxel expressed in mm3.
c. Is the numerical value of a pixel.
A CT image matrix contains which of the following? Select one: a. Algorithms b. Equations of information c. Picture elements d. Silver halide information units e. Slice sensitivity 1.00
c. Picture elements
Spatial resolution in CT imaging depends principally on: Select one: a. Focal spot size. b. kVp. c. Pixel size. d. Postpatient collimation. e. Slice thickness.
c. Pixel size.
Which of the following subsystems would normally be associated with the gantry assembly? Select one: a. Image postprocessing. b. The algorithms. c. The detector array. d. The physician's viewing console. e. The software.
c. The detector array.
Which advanced function uses a histogram-type graph to differentiate various structures using different colors that represent each of the intensities in the image? Select one: a. MPR b. MIP c. VRT d. SSD
c. VRT
The ____ is determined by how well the detector converts the absorbed photon information to a digital signal for the computer. Select one: a. capture efficiency b. absorption efficiency c. conversion efficiency d. response time
c. conversion efficiency
CT is able to differentiate between tissues with similar densities compared with conventional radiography due to: Select one: a. digital magnification b. the use of a computer for data processing c. improved contrast resolution d. axial slices
c. improved contrast resolution TEST QUESTION
Oral contrast for CT should be mixed so it is: Select one: a. the same as for general diagnostic examinations b. more concentrated than for general examinations c. less concentrated than for general examinations d. contrast media is not necessary
c. less concentrated than for general examinations
An array of numbers arranged in a grid of rows and columns is called a: Select one: a. pixel b. voxel c. matrix d. scan profile
c. matrix
To achieve coronal or sagittal sections with computed tomography: Select one: a. the gantry is repositioned b. the patient is repositioned c. reconfiguration software is implemented d. none of the above
c. reconfiguration software is implemented TEST QUESTION
The locilization image produced by the CT scanner is called: Select one: a. fluoroscopy b. scout film c. scanogram d. all of the above
c. scanogram TEST QUESTION
A _____ artifact is caused by the presence of metal in the patient when performing CT. Select one: a. beam-hardening b. ring c. star d. streak
c. star
The gantry of the CT unit contains the: Select one: a. film b. menu c. x-ray tube d. all of the above
c. x-ray tube TEST QUESTION
Which of the following Hounsfield unit (HU) values most closely represents the value for blood? Select one: a. -80 HU b. -40 HU c. -2 HU d. 20 HU e. 100 HU
d. 20 HU
In a CT imaging system, prepatient collimation: Select one: a. Controls pixel size b. Controls scatter radiation that reaches the detector c. Determines image noise d. Determines patient dose e. Determines slice thickness
d. Determines patient dose TEST QUESTION
The primary mathematical method used in the creation of computerize medical images is the ______ transformation. Select one: a. Pythagorean b. Bohr c. Einstein d. Fourier
d. Fourier
During spiral CT examination of a supine patient, the z-axis: Select one: a. Is the anterior-posterior axis. b. Is the lateral axis, left to right. c. Is the lateral axis, right to left. d. Is the long axis of the body. e. Varies with the examination.
d. Is the long axis of the body.
Which of the following is another term for slice thickness? Select one: a. Dose profile b. Interpolation profile c. Reconstruction index d. Section sensitivity profile e. Z-axis profile
d. Section sensitivity profile
Slice thickness can also be expressed as which of the following? Select one: a. Dose profile b. Low-contrast resolution c. Resolution profile d. Sensitivity profile e. Spatial profile
d. Sensitivity profile
The precise pixel value in HU depends on which of the following? Select one: a. 32 shades of gray. b. Light field, x-ray beam coincidnce. c. Pixel size. d. The x-ray attenuation coefficient. e. X-ray beam size.
d. The x-ray attenuation coefficient.
Partial volume artifacts are more likely with: Select one: a. Higher kVp b. Higher mA c. Larger pixel size d. Thicker slices e. Thinner slices
d. Thicker slices
Computed tomography sections are available as: Select one: a. coronal b. transverse c. sagittal d. all of the above
d. all of the above
Modern pulsed CT scanners operate at: Select one: a. 120 kVp b. 1 to 5 msec pulses c. up to 1,000 mA d. all of the above
d. all of the above
The CT console provides the radiographer access to: Select one: a. the software program b. data acquisition c. data display d. all of the above
d. all of the above
The CT radiation beam is collimated: Select one: a. at the tube exit b. at the detector entrance c. twice d. all of the above
d. all of the above
The CT table is Select one: a. made of carbon graphite b. rated for maximum weight c. motor-driven d. all of the above
d. all of the above
The smaller the scan field size in CT, the: Select one: a. better the resolution b. faster the scan time c. less risk of motion d. all of the above
d. all of the above
Fourth-generation CT scanners use the following configuration: Select one: a. translate tube and rotating detectors b. rotating tube and detectors c. only rotating detectors d. only rotating tube
d. only rotating tube
A _____ artifact is caused by motion when performing CT examinations. Select one: a. beam-hardening b. ring c. star d. streak
d. streak
Approximately what is the minimum power requirement for the high-voltage generator and x-ray tube for spiral CT? Select one: a. 10 kW b. 20 kW c. 30 kW d. 40 kW e. 50 kW
e. 50 kW TEST QUESTION
Which of the following is an advantage of spiral CT over conventional CT? Select one: a. Better patient dose utilization. b. Improved contrast resolution. c. Improved spatial resolution. d. Large matrix reconstruction. e. Reduced scanning time.
e. Reduced scanning time.
A principal advantage of reconstruction in any z-axis position is: Select one: a. Image acquisition during a single breath-hold. b. Improved contrast resolution. c. Improved spatial resolution. d. Larger volume of tissue imaged. e. Reduction of partial volume.
e. Reduction of partial volume.
CT imaging systems incorporate: Select one: a. Charged electrostatic plates b. High-frequency radiographic grids c. Light-localizing, variable-aperture collimators d. Multiple reconstruction algorithms e. Single-focus x-ray tubes
e. Single-focus x-ray tubes
With increasing slice pitch: Select one: a. Image noise is reduced. b. Patient dose is increased. c. Sagittal/coronal reconstruction is improved. d. The section sensitivity profile decreases. e. The section sensitivity profile increases.
e. The section sensitivity profile increases.
Which of the following statements about multislice CT is true? Select one: a. Higher-resolution multislice spiral CT results in low patient radiation dose. b. Larger detector size results in better spatial resolution. c. Narrower slice scanning results in better contrast resolution at the same mA. d. The simplest approach to multislice scanning is the use of eight detector arrays, each of equal width. e. Wider multislices allow imaging of a greater tissue volume.
e. Wider multislices allow imaging of a greater tissue volume.