CTMR 403- Computed
Tomography Fundamentals
Exam Study Guide
Computed Tomography (CT) - Answer The Radiological Society of North America's
established term for the radiographic technique discovered by Hounsfield that
produces an image of a detailed cross-section of tissue.
Tomography - Answer An image of a patient's section oriented parallel to the film,
derived from the Greek word "tomos" meaning section.
Transverse Axial Tomography - Answer The technique term developed in 1937 referring
to the imaging ability of cross-sectional image acquisition.
Superimposition - Answer The major shortcoming of radiography where all structures
are overlapped, making it difficult to distinguish specific details.
Homogenous Tissues - Answer Tissues with slight density changes that are difficult to
distinguish using conventional radiography.
Computed Tomography (CT) vs. Radiography - Answer CT shows cross-sectional views
and 3D images, aims to minimize superimposition, improve image contrast, and record
small differences in subject contrast.
X-ray Beam Methodology in CT - Answer The x-ray beam transmits through a specific
cross-section, is tightly collimated to minimize scatter, and strikes electronic detectors
to measure small differences in tissue contrast.
Godfrey Newbold Hounsfield - Answer The individual born in 1919 in England who
discovered that x-rays passing through an object from all directions could be formed
into a three-dimensional image.
Allan MacLeod Cormack - Answer The individual who developed solutions to the
mathematical problems in early CT development.
Dr. Robert Ledley - Answer Employed as a professor at Georgetown University, he
developed the first whole-body CT scanner in 1974.
Dynamic Spatial Reconstructor (DSR) - Answer Installed in 1975 for dynamic volume
scanning at Mayo Clinic.
Electron Beam CT (EBCT) Scanner - Answer Approved by the U.S. FDA in 1983.
,Spiral CT Scanner - Answer Practical spiral CT scanner was first reported in 1989 at the
RSNA meeting in Chicago.
Multi-Slice CT (MSCT) - Answer Introduced in 1998 at the RSNA meeting.
Generations in CT - Answer Term used to refer to the method of scanning in computed
tomography.
Generation - Answer Refers to x-ray beam geometry and method of scanning, with
variations from first to seventh generation
Data Acquisition - Answer Involves collecting x-ray transmission measurements from
the patient using special electronic detectors
Volume Scanning - Answer Technique developed to reduce acquisition time by scanning
a volume of tissue in a spiral or helical path
Fourier Transform - Answer Analytic tool converting a signal from spatial domain to
frequency domain, crucial for reconstructing CT and MRI images
Digital Image Processing - Answer Involves using a digital computer to manipulate
digital images for enhanced diagnostic interpretation
Radiation Attenuation - Answer Reduction of radiation beam intensity passing through
an object, dependent on atomic density, atomic number, and photon energy
Lambert-Beer's Law - Answer Exponential relationship describing photon behavior as
they pass through tissues, used to calculate linear attenuation coefficient
CT Numbers - Answer Assigned to each pixel in a CT image, related to linear attenuation
coefficients of tissues, based on Hounsfield scale
Windowing - Answer Process of adjusting CT image grayscale through window width
(WW) and window level (WL) settings
Pixel - Answer Picture element in a digital image, with size determined by field of view
(FOV) and matrix size
Voxel - Answer Three-dimensional pixel, with size dependent on pixel size and slice
thickness
Bit Depth - Answer Number of bits per pixel, affecting the number of shades of gray used
per pixel
Data Flow - Answer Sequence of events in a CT scanner involving subsystems, scan
parameter setting, data acquisition, preprocessing, and image reconstruction
Imaging System - Answer Component of CT scanner producing x-rays, detecting
radiation, and converting transmitted photons into digital information
, Computer System - Answer Receives digital data, processes it for image reconstruction,
and performs postprocessing operations in a CT scanner
Image Display System - Answer Facilitates displaying, storing, and communicating
digital images, reports, and patient data in a CT scanner
CT Advantages - Answer Include excellent low-contrast resolution, versatile scanning
options, and image modification through digital processing
CT Limitations - Answer Compared to conventional radiography, limitations include
poorer spatial resolution, higher radiation dose, and difficulty imaging soft tissue
surrounded by bone
Adaptive Array Detector - Answer Arrangement of multirow detectors with different
values in design, enhancing data collection in CT systems
Linear Attenuation Coefficient - Answer Indicates the amount of attenuation that has
occurred, forming the basis of CT numbers (Hounsfield Units)
Pixel Size - Answer Size of a pixel in a digital image, influencing the spatial resolution
Data Processing - Answer Mathematical principles involving preprocessing,
corrections, and reformatting of raw data in CT imaging
Image Display, Storage, and Communication - Answer Involves converting
reconstructed CT images for viewing, storing, and electronic transmission
CT System - Answer Includes imaging system, computer system, and image display,
recording, storage, and communication system
Angular Modulation - Answer Automatic control of tube current in the x-y axis during CT
scanning
angular modulation - Answer The automatic control of the tube current (mA) in the x-y
axis (in-plane).
attenuation - Answer The reduction of the intensity of a beam of radiation as it passes
through an object—some photons are absorbed, but others are scattered.
automatic exposure control (AEC) - Answer Concept used to provide a level of image
quality in which there is consistent optical density for any examination regardless of the
thickness of the patient; image quality is controlled by varying the duration of the
exposure based on the size of the patient being imaged.
Tomography Fundamentals
Exam Study Guide
Computed Tomography (CT) - Answer The Radiological Society of North America's
established term for the radiographic technique discovered by Hounsfield that
produces an image of a detailed cross-section of tissue.
Tomography - Answer An image of a patient's section oriented parallel to the film,
derived from the Greek word "tomos" meaning section.
Transverse Axial Tomography - Answer The technique term developed in 1937 referring
to the imaging ability of cross-sectional image acquisition.
Superimposition - Answer The major shortcoming of radiography where all structures
are overlapped, making it difficult to distinguish specific details.
Homogenous Tissues - Answer Tissues with slight density changes that are difficult to
distinguish using conventional radiography.
Computed Tomography (CT) vs. Radiography - Answer CT shows cross-sectional views
and 3D images, aims to minimize superimposition, improve image contrast, and record
small differences in subject contrast.
X-ray Beam Methodology in CT - Answer The x-ray beam transmits through a specific
cross-section, is tightly collimated to minimize scatter, and strikes electronic detectors
to measure small differences in tissue contrast.
Godfrey Newbold Hounsfield - Answer The individual born in 1919 in England who
discovered that x-rays passing through an object from all directions could be formed
into a three-dimensional image.
Allan MacLeod Cormack - Answer The individual who developed solutions to the
mathematical problems in early CT development.
Dr. Robert Ledley - Answer Employed as a professor at Georgetown University, he
developed the first whole-body CT scanner in 1974.
Dynamic Spatial Reconstructor (DSR) - Answer Installed in 1975 for dynamic volume
scanning at Mayo Clinic.
Electron Beam CT (EBCT) Scanner - Answer Approved by the U.S. FDA in 1983.
,Spiral CT Scanner - Answer Practical spiral CT scanner was first reported in 1989 at the
RSNA meeting in Chicago.
Multi-Slice CT (MSCT) - Answer Introduced in 1998 at the RSNA meeting.
Generations in CT - Answer Term used to refer to the method of scanning in computed
tomography.
Generation - Answer Refers to x-ray beam geometry and method of scanning, with
variations from first to seventh generation
Data Acquisition - Answer Involves collecting x-ray transmission measurements from
the patient using special electronic detectors
Volume Scanning - Answer Technique developed to reduce acquisition time by scanning
a volume of tissue in a spiral or helical path
Fourier Transform - Answer Analytic tool converting a signal from spatial domain to
frequency domain, crucial for reconstructing CT and MRI images
Digital Image Processing - Answer Involves using a digital computer to manipulate
digital images for enhanced diagnostic interpretation
Radiation Attenuation - Answer Reduction of radiation beam intensity passing through
an object, dependent on atomic density, atomic number, and photon energy
Lambert-Beer's Law - Answer Exponential relationship describing photon behavior as
they pass through tissues, used to calculate linear attenuation coefficient
CT Numbers - Answer Assigned to each pixel in a CT image, related to linear attenuation
coefficients of tissues, based on Hounsfield scale
Windowing - Answer Process of adjusting CT image grayscale through window width
(WW) and window level (WL) settings
Pixel - Answer Picture element in a digital image, with size determined by field of view
(FOV) and matrix size
Voxel - Answer Three-dimensional pixel, with size dependent on pixel size and slice
thickness
Bit Depth - Answer Number of bits per pixel, affecting the number of shades of gray used
per pixel
Data Flow - Answer Sequence of events in a CT scanner involving subsystems, scan
parameter setting, data acquisition, preprocessing, and image reconstruction
Imaging System - Answer Component of CT scanner producing x-rays, detecting
radiation, and converting transmitted photons into digital information
, Computer System - Answer Receives digital data, processes it for image reconstruction,
and performs postprocessing operations in a CT scanner
Image Display System - Answer Facilitates displaying, storing, and communicating
digital images, reports, and patient data in a CT scanner
CT Advantages - Answer Include excellent low-contrast resolution, versatile scanning
options, and image modification through digital processing
CT Limitations - Answer Compared to conventional radiography, limitations include
poorer spatial resolution, higher radiation dose, and difficulty imaging soft tissue
surrounded by bone
Adaptive Array Detector - Answer Arrangement of multirow detectors with different
values in design, enhancing data collection in CT systems
Linear Attenuation Coefficient - Answer Indicates the amount of attenuation that has
occurred, forming the basis of CT numbers (Hounsfield Units)
Pixel Size - Answer Size of a pixel in a digital image, influencing the spatial resolution
Data Processing - Answer Mathematical principles involving preprocessing,
corrections, and reformatting of raw data in CT imaging
Image Display, Storage, and Communication - Answer Involves converting
reconstructed CT images for viewing, storing, and electronic transmission
CT System - Answer Includes imaging system, computer system, and image display,
recording, storage, and communication system
Angular Modulation - Answer Automatic control of tube current in the x-y axis during CT
scanning
angular modulation - Answer The automatic control of the tube current (mA) in the x-y
axis (in-plane).
attenuation - Answer The reduction of the intensity of a beam of radiation as it passes
through an object—some photons are absorbed, but others are scattered.
automatic exposure control (AEC) - Answer Concept used to provide a level of image
quality in which there is consistent optical density for any examination regardless of the
thickness of the patient; image quality is controlled by varying the duration of the
exposure based on the size of the patient being imaged.
