Principles of CT

The WW controls the image contrast and the WL controls the image brightness. a. True b. False

a. True

A single ray in computed tomography (CT) is: a. a beam of X-rays emanating from the X-ray tube. b. a single straight line path of an X-ray beam. c. a collection of beams gathered by the detector. d. the total attenuation as measured by the detector.

b. a single straight line path of an X-ray beam.

Data acquisition in CT refers to: a. acquiring the information from the detectors. b. acquiring information from the patient by using special motions of the X-ray tube and detectors. c. processing the information from the patient. d. acquiring the information from the computer.

b. acquiring information from the patient by using special motions of the X-ray tube and detectors.

A scaling factor of 1000 in the Hounsfield scale (H scale) for K results in a: a. contrast scale of 0.8% per CT number. b. contrast scale of 0.1 % per CT number. c. contrast scale of 0.5% per CT number. d. contrast scale of 0.2% per CT number.

b. contrast scale of 0.1 % per CT number.

The computer system receives _________ data from the data acquisition system. a. manipulated b. digital c. analog d. hard copy

b. digital

Fourth-generation CT scanners are characterized by: a. fan-beam geometry and continuous rotation of X-ray tube and detectors b. fan-beam geometry and complete rotation of X-ray tube around a stationary ring of detectors c. rotate-translate motion and parallel beam geometry. d. rotate-translate motion and fan-beam geometry.

b. fan-beam geometry and complete rotation of X-ray tube around a stationary ring of detectors

The opening in the gantry in which the patient is positioned during scanning is called the: a. positioning hole. b. gantry aperture. c. rotating frame. d. isocenter.

b. gantry aperture.

An example of a local operation that causes image brightness to change slowly or at a constant rate is called: a. high spatial frequency. b. low spatial frequency. c. area processes. d. convolution.

b. low spatial frequency.

Visible images include all of the following except: a. photographs. b. mathematical images. c. paintings. d. drawings.

b. mathematical images.

The display FOV can ________________ the scan FOV (sFOV). a. be replaced by b. be greater than c. be less than d. be reversed by

c. be less than

A view in CT is: a. a specific way in which the patient is positioned with respect to the detectors. b. the total attenuation as measured by the detector. c. a single straight line path of an X-ray beam. d. a collection of rays for one translation across the object.

d. a collection of rays for one translation across the object.

Most scanners have a gantry aperture of about: a. 70 cm. b. 70 inches. c. 100 cm. d. 70 mm.

a. 70 cm.

Which of the following refers to the size, shape, motion, and path traced by the X-ray beam as it scans the patient? a. Beam geometry b. Projection profile c. Detector tracing d. Data acquisition

a. Beam geometry

In which of the following are numerical representations of objects subjected to a series of operations to produce a desired result? a. Digital image processing b. Digital to analog conversion c. Analog-to-digital conversion d. Pattern recognition

a. Digital image processing

Which type of high-speed CT scanner was first introduced to image the cardiovascular system without artifacts caused by motion of the heart? a. Electron-beam CT (EBCT) scanner b. EMI Mark I CT scanner c. Dual-source CT (DSCT) scanner d. Single-slice CT scanner

a. Electron-beam CT (EBCT) scanner

What method of image compression results in the loss of no information during the compression process? a. Lossless compression b. Irreversible compression c. Permanent compression d. Lossy compression

a. Lossless compression

The following developments in CT were introduced during the period between 1973 and 1983 except: a. Multislice CT (MSCT). b. quality control (QC). c. detectors. d. image quality improvements.

a. Multislice CT (MSCT).

What form of archiving has proven most popular among CT departments? a. Picture archiving and communication system b. Optical card c. Film-based recording d. Magnetic tapes

a. Picture archiving and communication system

Which of the following assigns integers to the brightness values measured by the PM? a. Quantization b. Scanning c. Analog-to-digital conversion d. Sampling

a. Quantization

In which of the following is the brightness level of each pixel in a picture measured by a photomultiplier tube (PM)? a. Sampling b. Digital to analog conversion c. Scanning d. Quantization

a. Sampling

Which scanner results in a volume of the patient being scanned during a single breath-hold (rather than a single slice of tissue)? a. Spiral/helical scanner b. Seventh-generation scanner c. Second-generation scanner d. First-generation scanner

a. Spiral/helical scanner

Which CT scanner is based on a fan-beam geometry and complete rotation of the X-ray tube and detectors? a. Third-generation scanner b. Fourth-generation scanner c. First-generation scanner d. Second-generation scanner

a. Third-generation scanner

The sine wave is an example of an analog signal. a. True b. False

a. True

All of the following media forms can be used to store CT images except: a. VHS tapes. b. digital videotape. c. magnetic disks. d. laser optical disks.

a. VHS tapes.

Compared with conventional CT scanners, slip-ring scanners offer all of the following advantages except: a. capacity for interrupted acquisition protocols. b. elimination of start-stop action. c. minimal interscan delays. d. removal of cable wraparound.

a. capacity for interrupted acquisition protocols.

Sectional images are obtained from all of the following except: a. conventional radiography b. tomography c. transverse axial tomography d. computed tomography (CT)

a. conventional radiography

The systematic method of collecting data from the patient is called: a. data acquisition. b. image processing. c. image display. d. image communication.

a. data acquisition.

All of the following are major systems in the basic equipment configuration for computed tomography (CT) except: a. dictation system b. computer system c. imaging system d. image display, recording, storage, and communication system

a. dictation system

A CT image of 12 bits per pixel means: a. each pixel can have a total of 4096 shades of gray. b. the matrix is 4096 x 4096. c. the pixel size is 12 mm. d. the voxel size is 12 mm.

a. each pixel can have a total of 4096 shades of gray.

All of the following are purposes of the image display, recording, storage, and communication system except: a. enables scanning procedures. b. displays the output digital image. c. facilitates storage. d. provides a hard copy.

a. enables scanning procedures.

The scanner that uses an electron gun to "shoot" electrons toward a target ring is the: a. fifth-generation scanner. b. spiral/helical scanner. c. third-generation scanner. d. fourth-generation scanner.

a. fifth-generation scanner.

The ideal couch top (table top) of a CT scanner table has all of the following features except: a. limited horizontal and vertical movements. b. excellent vibration-damping features. c. low radiation absorption characteristics. d. carbon fiber design.

a. limited horizontal and vertical movements.

Which term describes the systematic motion of the xray tube as it rotates around the patient to collect xray transmission readings? a. scanning b. generation c. data processing d. sampling

a. scanning

The limitations of conventional tomography include all of the following except: a. the presence of ghost images on the film. b. superimposition of structures above and below the focal plane. c. image blur from movement of the tube and film. d. contrast degradation from the open beam geometry.

a. the presence of ghost images on the film.

The range of CT numbers in an image is called the: a. window width (WW). b. dynamic range. c. region of interest (ROI). d. window level (WL).

a. window width (WW).

In general, the tilting range of a CT gantry is about: a. ±12 degrees to ±30 degrees. b. ±2 degrees to ±5 degrees. c. ±5 degrees to ±5 degrees. d. no tilting of the gantry is possible.

a. ±12 degrees to ±30 degrees.

The CT number for water is: a. 100. b. 0. c. -1000. d. -100.

b. 0.

An 8-bit analog to digital converter (ADC) will divide a signal into: a. 8 parts. b. 256 parts. c. 64 parts. d. 8 parts.

b. 256 parts.

How many pixels make up a CT image whose matrix size is 512 x 512? a. 1024 b. 262,144 c. 512 d. 100,000

b. 262,144

Which form of imaging primarily uses DSCT scanners? a. Biopsy procedures b. Cardiac imaging c. Pulmonary imaging d. Virtual colonoscopy

b. Cardiac imaging

A spiral or helical beam is used to scan the patient in slice-by-slice data acquisition. a. True b. False

b. False

CT numbers are established by referencing the linear attenuation coefficient of air. a. True b. False

b. False

Digitization consists of four steps: scanning, sampling, quantization, and digital to analog conversion. a. True b. False

b. False

The photoelectric effect occurs mainly in tissues with a low atomic number. a. True b. False

b. False

Which of the following is classified as a high-speed CT scanner? a. Spiral/helical CT scanner b. Fifth-generation CT scanner c. Fourth-generation scanner d. Third-generation scanner

b. Fifth-generation CT scanner

Which X-ray generator is used in modern CT scanners? a. Single-phase full-wave rectified b. High-frequency generator c. Three-phase, six-pulse generator d. Single-phase half-wave rectified

b. High-frequency generator

Who developed the first whole body scanner? a. Kuhl b. Ledly c. Cormack and Housfield d. Oldendorf

b. Ledly

Which of the following represents the logical order in digitizing an image? a. Quantization, scanning, and sampling b. Scanning, sampling, and quantization c. Sampling, scanning, and quantization d. Sampling, quantization, and scanning

b. Scanning, sampling, and quantization

Which scanner allows for continuous rotation of the X-ray tube while the patient moves simultaneously through the gantry aperture? a. Dynamic volume scanner b. Spiral/helical scanner c. Fourth-generation conventional scanner d. Third-generation conventional scanner

b. Spiral/helical scanner

The mathematical techniques used by the computer to reconstruct the CT image are known as: a. computer programs. b. image reconstruction algorithms. c. pattern recognition. d. manipulation of images.

b. image reconstruction algorithms.

What contribution did Cormack make to the development of clinical CT? a. Britain's first business computer b. mathematical solutions in CT c. practical reconstruction of an image of the sun d. programs to calculate doses to patients

b. mathematical solutions in CT

In one type of fourth-generation CT scanner, the tilting action of the detector ring is referred to as: a. slip-ring technology. b. nutating. c. helical scanning. d. spiral scanning.

b. nutating.

The total number of X-ray transmission measurements is equal to the: a. number of views in each scan. b. product of the number of views and the number of rays in each view. c. total number of detectors. d. the number of views divided by the number of rays in each view.

b. product of the number of views and the number of rays in each view.

The imaging system components are located in the: a. computer room. b. scanner room. c. operator room. d. radiologist viewing area.

b. scanner room.

The purpose of the imaging system is to perform all of the following except: a. produce X-rays. b. store images for retrieval. c. detect and measure the radiation passing through the cross-section. d. shape and filter the X-ray.

b. store images for retrieval.

Attenuation of a beam of radiation depends on each of the following except: a. the electrons per gram of tissue. b. the speed of the radiation. c. the atomic number of the tissue. d. the energy of the radiation.

b. the speed of the radiation.

If the FOV for an examination is 30 cm and the matrix size is 1024 ´ 1024, what is the approximate pixel size? a. 25 mm b. 0.05 mm c. 0.3 mm d. 0.5 mm

c. 0.3 mm

Which of the following obeys Lambert-Beer's law? a. A polyenergetic beam of radiation b. A heterogeneous beam of radiation c. A homogeneous beam of radiation d. A polychromatic beam of radiation

c. A homogeneous beam of radiation

Which of the following is used to calculate CT numbers? a. CT number = u water + u tissue u K b. CT number = u water - u tissue x K/u water c. CT number = u tissue - u water x K/u water d. CT number = u tissue - u water x K/u tissue

c. CT number = u tissue - u water x K/u water

Which company pioneered the development of the first clinically useful CT scanner? a. GE b. Elscint c. EMI d. Siemens

c. EMI

In which scanner is the apex of the fan beam located outside the detector? a. Sixth-generation scanner b. Fifth-generation scanner c. Fourth-generation scanner d. Third-generation scanner

c. Fourth-generation scanner

Who developed the first clinically useful CT scanner? a. Siemens b. Roentgen c. Hounsfield d. Cormack

c. Hounsfield

Which of the following is where images are stored in a filmless imaging department? a. Hospital information system b. Data acquisition system c. Picture archiving and communications system (PACS) d. Radiology information system

c. Picture archiving and communications system (PACS)

What classification of CT software builds the CT image from the raw data collected from the detectors? a. Image postprocessing software b. Reformation software c. Reconstruction software d. Preprocessing software

c. Reconstruction software

Which generation of scanners, also called dual-source CT scanners, consists of two X-ray tubes and two sets of detectors? a. Third generation b. Fifth generation c. Sixth generation d. Fourth generation

c. Sixth generation

Which of the following is part of the imaging system? a. The CT control console b. The central processing unit (CPU) c. The X-ray tube and detectors d. The cathode ray tube display device

c. The X-ray tube and detectors

In CT, a. a computer is not required because the physicist calculates the image, which the computer then prints out. b. special detectors are used to reconstruct sectional images. c. a computer is used to reconstruct images of sectional anatomy. d. a computer is used to calculate radiation dose to the patient.

c. a computer is used to reconstruct images of sectional anatomy.

The attenuation used by Hounsfield in his original experiments was: a. a heterogeneous beam. b. a hardened beam. c. a monoenergetic beam. d. a polychromatic beam.

c. a monoenergetic beam.

CT detectors generate a signal that represents the attenuation as the ray moves across the slice. This signal is called: a. a data sample. b. a view sample. c. a profile. d. an acquisition sample.

c. a profile.

The reduction of the intensity of a beam of X-rays as it passes through the patient is: a. the relative transmission value. b. the natural logarithm. c. attenuation. d. the linear attenuation coefficient.

c. attenuation.

All these elements can be used during data acquisition to reduce patient dose except: a. ultrafast ceramic (UFC) detectors. b. combined applications. c. decreased pitch. d. online dose modulation.

c. decreased pitch.

The computer system for CT includes all of the following except: a. input-output devices. b. array processors and back-projector. c. detector electronics. d. the CPU.

c. detector electronics.

The detectors convert the attenuation data into ____________ signals. a. light b. mechanical c. electrical d. digital

c. electrical

The X-ray generator for CT scanners is usually a: a. three-phase, 12-pulse generator. b. single-phase, half-wave rectified unit. c. high-frequency unit. d. three-phase, six-pulse generator.

c. high-frequency unit.

The total number of data samples per scan or per slice in CT is the: a. number of views. b. number of data samples per view plus the number of views. c. number of data samples per view times the number of views. d. number of detectors plus the number of data samples per detector.

c. number of data samples per view times the number of views.

The contraction for "picture element" is: a. voxel. b. matrix. c. pixel. d. address.

c. pixel.

The least complicated and most frequently used image processing technique is the: a. global operation. b. geometric operation. c. point operation. d. local operation.

c. point operation.

Electromechanical devices made up of rings and brushes to transmit electrical energy across a rotating interface are called: a. target rings. b. spiral rings. c. slip rings. d. helical rings.

c. slip rings.

The field of view (FOV) is: a. a digital processing technique. b. the ROI. c. the reconstruction circle. d. a mathematical technique.

c. the reconstruction circle.

The purpose of image enhancement is: a. to improve the quality of images that have distortions. b. to reduce the size of the image. c. to generate an image more pleasing to the observer. d. to allow measurements and statistics to be performed.

c. to generate an image more pleasing to the observer.

A 10 ´ 10 matrix consists of ______ pixels. a. 10 b. 20 c. 120 d. 100

d. 100

The typical matrix size of a typical CT image is: a. 128 x 128 x 8 bytes deep. b. 32 x 32 x 8 bytes deep. c. 56 x 256 x 10 bytes deep. d. 512 x 512 x 8 bytes deep.

d. 512 x 512 x 8 bytes deep.

Which of the following X-ray tubes is most likely used in spiral/helical CT scanners? a. A tungsten target fixed anode tube b. A molybdenum target rotating anode tube c. A tungsten target rotating anode tube d. A rotating anode tube with a rhenium tungsten disk

d. A rotating anode tube with a rhenium tungsten disk

Which acronym has been established by the Radiological Society of North America (RSNA) and the accepted term for use within the radiologic community and major American radiology journals? a. CAT b. CTAT c. RT d. CT

d. CT

Which of the following is best used to describe patient dose in CT? a. Collective doses b. Isometric curves c. Exposure doses d. CT dose index (CTDI) and multiple-scan average dose (MSAD)

d. CT dose index (CTDI) and multiple-scan average dose (MSAD)

Which of the following refers to a method by which the patient is systematically scanned by the X-ray tube and detectors to collect enough information for image reconstruction? a. Sampling b. Beam geometry c. Projection reconstruction d. Data acquisition

d. Data acquisition

Which of the following reduces the amount of data that makes up the image? a. Image restoration b. Image enhancement c. Image analysis d. Image compression

d. Image compression

Which of the following does the computer system perform? a. Provides a hard copy b. Display the output image c. Detects radiation d. Image manipulation

d. Image manipulation

Which scanner is based on slip-ring technology? a. Third-generation conventional scanner b. Fourth-generation conventional scanner c. Fifth-generation scanner d. Spiral/helical scanner

d. Spiral/helical scanner

Which of the following allows the technologist to alter picture contrast? a. Touch panel b. Floppy disk drive c. Floating keyboard alphanumerical keys d. Window controls

d. Window controls

Data acquisition refers to: a. subjecting data to computer processing. b. storing the data collected from the patient onto magnetic tapes or disks. c. changing the data before they are displayed on a monitor. d. collecting X-ray transmission readings from the patient.

d. collecting X-ray transmission readings from the patient.

Radiation used by Hounsfield in his original experiments was: a. electrons b. xrays c. beta particles d. gamma rays

d. gamma rays

Nonvisible physical images include all of the following except: a. elevation maps. b. temperature. c. pressure. d. holograms.

d. holograms.

Which of the following refers to modifying CT data to make the images more useful to the observer? a. pattern recognition b. data collection c. image reconstruction d. image manipulation

d. image manipulation

When a large set of transmission measurements is collected from the patient at different locations and is used to build up an image of internal anatomy, it is referred to as: a. pattern recognition. b. digital image processing. c. tomography. d. image reconstruction from projections.

d. image reconstruction from projections.

A digital image: a. is a continuous image. b. is a nonvisible physical image. c. cannot be processed by a digital computer. d. is a numerical representation of an object.

d. is a numerical representation of an object.

Contrast stretching is an example of a: a. geometric operation. b. local operation. c. global operation. d. point processing technique.

d. point processing technique.

The process of dividing a picture into small regions called pixels is referred to as: a. analog-to-digital conversion. b. sampling. c. quantization. d. scanning.

d. scanning.

The design that incorporates the high-voltage generator on the rotating frame of the CT gantry eliminates: a. the detectors from within the gantry. b. the need for any cables. c. the need for short high-tension cables. d. the need for long high-tension cables.

d. the need for long high-tension cables.

The origin of digital image processing stems from: a. the Mayo Clinic. b. Hounsfield. c. General Electric. d. the space program.

d. the space program.