Computed Tomography (CT)
What is CT and what is it used for? – answer CT uses diagnostic x-rays to create cross-
sectional images of the human body. It uses mathematical algorithms to combine these
images together. It's helpful in obtaining of volume of information so we can see
structures in 3 dimensions. It's extremely helpful with cancers to be able to detect the
size and shape of a mass.
What are the components of the equipment? - answer Gantry: Gantry includes the
couch (table) and support, scanner housing, x ray tube, and detectors.
Computer: displays images
Operating console: CT can have up to three operating consoles.
How does the equipment work? – answer The x-ray tube is pulsed and has a fan
shaped/ narrow beam. It has a rotating tube that is opposite of the detector. The tube
has a small focal spot. The detector sends data to the computer and measures the
attenuation coefficient. The computer receives, process, displays and stores data. It
also displays the technique, and allows for post processing.
What are housefield units? - answertissue density values and measure the thickness of
tissue that can be used for contrast, and detection of diseases.
What are the limitations of CT? - answer-While the machine is helical, 360 data is not
required
- Motion can cause streaking of the image
- Metal objects attenuate 100% of the beam
- Beam hardening causes broad dark bands/streaks
- Partial volume effect (smaller structures get hidden)
- ring artifacts
- higher dose
- high cost
What are the advantages of CT? - answer-acquire more images fast
- higher detail
- more diagnostic information than other modalities
- reduces the need for exploratory surgeries
- ability to get view of large part of body
- reduced scatter radiation
What are the safety concerns associated with CT? - answer- higher patient dose
- pregnancy (contrast and breast feeding)
- contrast allergy
What is CT and what is it used for? – answer CT uses diagnostic x-rays to create cross-
sectional images of the human body. It uses mathematical algorithms to combine these
images together. It's helpful in obtaining of volume of information so we can see
structures in 3 dimensions. It's extremely helpful with cancers to be able to detect the
size and shape of a mass.
What are the components of the equipment? - answer Gantry: Gantry includes the
couch (table) and support, scanner housing, x ray tube, and detectors.
Computer: displays images
Operating console: CT can have up to three operating consoles.
How does the equipment work? – answer The x-ray tube is pulsed and has a fan
shaped/ narrow beam. It has a rotating tube that is opposite of the detector. The tube
has a small focal spot. The detector sends data to the computer and measures the
attenuation coefficient. The computer receives, process, displays and stores data. It
also displays the technique, and allows for post processing.
What are housefield units? - answertissue density values and measure the thickness of
tissue that can be used for contrast, and detection of diseases.
What are the limitations of CT? - answer-While the machine is helical, 360 data is not
required
- Motion can cause streaking of the image
- Metal objects attenuate 100% of the beam
- Beam hardening causes broad dark bands/streaks
- Partial volume effect (smaller structures get hidden)
- ring artifacts
- higher dose
- high cost
What are the advantages of CT? - answer-acquire more images fast
- higher detail
- more diagnostic information than other modalities
- reduces the need for exploratory surgeries
- ability to get view of large part of body
- reduced scatter radiation
What are the safety concerns associated with CT? - answer- higher patient dose
- pregnancy (contrast and breast feeding)
- contrast allergy
