COMPUTED TOMOGRAPHY EXAMINATION
QUESTIONS AND 100% VERIFIED ANSWERS
CT was developed in - 1970s
Pioneer of CT and also Nobel Prize winner? - Godfrey Hounsfield
A collimated x-ray beam is directed on the patient and it detected by a - Solid state image
receptor
3 possible Types of image planes shown on the CT monitors? - Transverse, Sagittal,
Coronal
Conventional Tomography is also called? and why? - Axial Tomography: the plane of the
image is parallel with the long axis of the body
Type of image planes done with conventional tomography? - Sagittal and coronal plane
Types of image planes done on CT? - Transaxial (through Axial) and transverse
In CT, the internal structures of the body attenuate the x-ray according to - mass density
of tissues and effective atomic number
Projection formation - the detector makes a single sweep across the patient
Translation - a single complete rotation of source-detector assembly
1st Generation CT - Single Detector, A pencil beam x-ray, 5 min to image time
2nd Generation CT - translate-rotate system, multiple detectors, a fan shaped X-ray
beam, bow-tie filter reduce and conform to patient's body, 30 seconds to image time
3rd Generation CT - source-detector unit rotates around the patient, rotate only system,
less than 1 second image time, curvilinear detector array for better image quality, ring artifacts
caused by false detector bank
4th Generation CT - increased patient dose due to many detectors, rotate-stationary
system, Slip-Ring Technology, fixed circular detector with unto 4000 individual elements, varying
slice thickness, no ring artifacts
5th Generation CT - Helical Scanner, increased speed, reduced patient dose, currently
used system
CTDI - CT Dose Index
, CT System Components - Computer, Gantry, Ops Console
CT Gantry Components - X-ray Tube, Detector Arrays, Patient Support Couch, HV
Generator, All mechanical supports
System Component of the gantry - Scintillation detector, gas detector, collimator, hv
generator, patient positioning and support couch
Scintillation Detector - Measures glow or light
Gas Detector - filled with O2 or Xenon.
Computer in CT system - uses array processor for the image reconstruction, higher
computing power required for faster reconstruction of images
Reconstruction Time - The time from the end of the x-ray imaging to the appearance of
the actual image on the CT screen
PACS - Picture Archiving and Communications System: Automatic archiving system for
digital CT images
FOV - Field of View: in CT this represents volume of image slice which contains 262,144
pixels
Pixel - Each cell which contains specific CT number, hounsfield unit.
Voxel - Includes the height of the pixel, tissue volume.
Hounsfield Number - Also called CT number, ranges from -1000 to 1000, each cell has a
given CT number, CT number relates to the x-ray attenuation coefficient of the tissue
Filtered Back Projection - The acquired projections by each detector are stored in
memory of computer and then reconstructed by filtered back projection; a mathematical
reconstruction
Reconstructed image quality in CT is expressed in terms of - spatial resolution, contrast
resolution and noise
Range of CT number and CT number of water and what does it mean? - -1000 to 1000.
Water = 0. This is same as Hounsfield Unit. Higher the number the dense the tissue
Design limitation of the x-ray tube in CT? - Focal spot size and heat dissipation
Helical CT detector array design is important in terms of? - Reducing patient dose,
improving image quality, faster imaging time
QUESTIONS AND 100% VERIFIED ANSWERS
CT was developed in - 1970s
Pioneer of CT and also Nobel Prize winner? - Godfrey Hounsfield
A collimated x-ray beam is directed on the patient and it detected by a - Solid state image
receptor
3 possible Types of image planes shown on the CT monitors? - Transverse, Sagittal,
Coronal
Conventional Tomography is also called? and why? - Axial Tomography: the plane of the
image is parallel with the long axis of the body
Type of image planes done with conventional tomography? - Sagittal and coronal plane
Types of image planes done on CT? - Transaxial (through Axial) and transverse
In CT, the internal structures of the body attenuate the x-ray according to - mass density
of tissues and effective atomic number
Projection formation - the detector makes a single sweep across the patient
Translation - a single complete rotation of source-detector assembly
1st Generation CT - Single Detector, A pencil beam x-ray, 5 min to image time
2nd Generation CT - translate-rotate system, multiple detectors, a fan shaped X-ray
beam, bow-tie filter reduce and conform to patient's body, 30 seconds to image time
3rd Generation CT - source-detector unit rotates around the patient, rotate only system,
less than 1 second image time, curvilinear detector array for better image quality, ring artifacts
caused by false detector bank
4th Generation CT - increased patient dose due to many detectors, rotate-stationary
system, Slip-Ring Technology, fixed circular detector with unto 4000 individual elements, varying
slice thickness, no ring artifacts
5th Generation CT - Helical Scanner, increased speed, reduced patient dose, currently
used system
CTDI - CT Dose Index
, CT System Components - Computer, Gantry, Ops Console
CT Gantry Components - X-ray Tube, Detector Arrays, Patient Support Couch, HV
Generator, All mechanical supports
System Component of the gantry - Scintillation detector, gas detector, collimator, hv
generator, patient positioning and support couch
Scintillation Detector - Measures glow or light
Gas Detector - filled with O2 or Xenon.
Computer in CT system - uses array processor for the image reconstruction, higher
computing power required for faster reconstruction of images
Reconstruction Time - The time from the end of the x-ray imaging to the appearance of
the actual image on the CT screen
PACS - Picture Archiving and Communications System: Automatic archiving system for
digital CT images
FOV - Field of View: in CT this represents volume of image slice which contains 262,144
pixels
Pixel - Each cell which contains specific CT number, hounsfield unit.
Voxel - Includes the height of the pixel, tissue volume.
Hounsfield Number - Also called CT number, ranges from -1000 to 1000, each cell has a
given CT number, CT number relates to the x-ray attenuation coefficient of the tissue
Filtered Back Projection - The acquired projections by each detector are stored in
memory of computer and then reconstructed by filtered back projection; a mathematical
reconstruction
Reconstructed image quality in CT is expressed in terms of - spatial resolution, contrast
resolution and noise
Range of CT number and CT number of water and what does it mean? - -1000 to 1000.
Water = 0. This is same as Hounsfield Unit. Higher the number the dense the tissue
Design limitation of the x-ray tube in CT? - Focal spot size and heat dissipation
Helical CT detector array design is important in terms of? - Reducing patient dose,
improving image quality, faster imaging time
