Unit 1: Introduction and History of
Computed Tomography
tomography - correct answer ✔✔derived from the Greek word tomos meaning section
In 1937, transverse axial tomography was the term used to refer to the - correct answer ✔✔imaging
ability of cross-sectional images to be acquired
bone shade color= - correct answer ✔✔white
soft tissue shade color= - correct answer ✔✔grey
air shade color= - correct answer ✔✔black
Hounsfield Unit (HU) - correct answer ✔✔represents the attenuating properties or density of each tissue
The number is the Hounsfield number or CT number and has a range of _________. ( The number
identifies the structure it passed trough) - correct answer ✔✔2000 , (-1000 to 1,000)
Water's HU? - correct answer ✔✔0
Air's HU? - correct answer ✔✔-1,000
Bone HU? - correct answer ✔✔+1,000
•His research resulted in the first clinically useful CT scanner for imaging the brain when in 1972 the first
patient was scanned by his machine - correct answer ✔✔Godfrey Newbold Hounsfield
, University medical physicist that developed the mathematical solutions to reconstruct images in
Computed tomography - correct answer ✔✔Allan MacLeod Cormack
CT Components - correct answer ✔✔1.High frequency Generator
2.X-ray Tube
3.Detectors
4.Photodiode
5.Filters
6.Collimators
7.Cooling system
High Frequency Generator - correct answer ✔✔located in the gantry and produce the high voltage
supply to the x-ray tube. The power capacity of the generator is listed in Kilowatts (kW). In short it
supplies the kV to the tube with a max. of 120-140 kVp, which allows for lower mA settings and lower
heat load to x-ray tube.
Filtration - correct answer ✔✔Compensating filtration filters are used to reduce the patient radiation
dose by removing lower energy x-rays (soft x-rays) and harden the beam
Bow tie filters - correct answer ✔✔*compensate for uneven filtration
reduce scatter
reduce noise
*reduce the beam intensity at the periphery of the patient body where the anatomy is less dense.
Collimation - correct answer ✔✔•restricts the beam to improve image quality by reducing scatter as in
routine x-ray. Often two types of collimation are used: Pre-patient (source) and Post-patient collimation.
Pre-patient collimation takes place at the x-ray source and helps to restrict and shape the beam. Post
collimation works like a grid to remove scatter from the patient before it reaches the detector.
Pre-patient collimaton - correct answer ✔✔-Mounted on the xray tube
-Limits the area of the patient that intercepts the useful beam.
-helps restrict and shape the beam
Computed Tomography
tomography - correct answer ✔✔derived from the Greek word tomos meaning section
In 1937, transverse axial tomography was the term used to refer to the - correct answer ✔✔imaging
ability of cross-sectional images to be acquired
bone shade color= - correct answer ✔✔white
soft tissue shade color= - correct answer ✔✔grey
air shade color= - correct answer ✔✔black
Hounsfield Unit (HU) - correct answer ✔✔represents the attenuating properties or density of each tissue
The number is the Hounsfield number or CT number and has a range of _________. ( The number
identifies the structure it passed trough) - correct answer ✔✔2000 , (-1000 to 1,000)
Water's HU? - correct answer ✔✔0
Air's HU? - correct answer ✔✔-1,000
Bone HU? - correct answer ✔✔+1,000
•His research resulted in the first clinically useful CT scanner for imaging the brain when in 1972 the first
patient was scanned by his machine - correct answer ✔✔Godfrey Newbold Hounsfield
, University medical physicist that developed the mathematical solutions to reconstruct images in
Computed tomography - correct answer ✔✔Allan MacLeod Cormack
CT Components - correct answer ✔✔1.High frequency Generator
2.X-ray Tube
3.Detectors
4.Photodiode
5.Filters
6.Collimators
7.Cooling system
High Frequency Generator - correct answer ✔✔located in the gantry and produce the high voltage
supply to the x-ray tube. The power capacity of the generator is listed in Kilowatts (kW). In short it
supplies the kV to the tube with a max. of 120-140 kVp, which allows for lower mA settings and lower
heat load to x-ray tube.
Filtration - correct answer ✔✔Compensating filtration filters are used to reduce the patient radiation
dose by removing lower energy x-rays (soft x-rays) and harden the beam
Bow tie filters - correct answer ✔✔*compensate for uneven filtration
reduce scatter
reduce noise
*reduce the beam intensity at the periphery of the patient body where the anatomy is less dense.
Collimation - correct answer ✔✔•restricts the beam to improve image quality by reducing scatter as in
routine x-ray. Often two types of collimation are used: Pre-patient (source) and Post-patient collimation.
Pre-patient collimation takes place at the x-ray source and helps to restrict and shape the beam. Post
collimation works like a grid to remove scatter from the patient before it reaches the detector.
Pre-patient collimaton - correct answer ✔✔-Mounted on the xray tube
-Limits the area of the patient that intercepts the useful beam.
-helps restrict and shape the beam
