Computed tomography
CT Vs Radiography - correct answer ✔✔CT forms cross sectional images eliminating the superimposition
of structures that occurs in plane film imaging because of compression of 3D body systems onto the 2D
recording system.
Sensitivity of CT to subtle differences in x-ray attenuation is at least a factor 10 higher than normally
achieved by screen film recording systems because of the virtual elimination of scatter
Radiation exposure - correct answer ✔✔Multiple x-ray images being taken so the amount of radiation
exposure is higher than that of x-rays.
Production of images - correct answer ✔✔Motorized x-ray source which rotates around the bore of the
gantry. Couch moves through the gantry, narrow x-ray beams shot at the body. Within the gantry- x-ray
detectors located directly opposite the source so beams shot directly through the body. Detected beams
transmitted to a computer. After completing a full rotation the computer generates a 2D slice of the
patient and the couch is moved further into the boar. Slices can be stacked together to make a 3D image.
1970's - correct answer ✔✔CT scanner invented by Godfrey Houndsfield, took several hours to acquire
an the raw data for a single slice and took days to reconstruct a single image. Used existing x-ray
technology, first to combine the x-ray machine with a computer. Could only take pictures of the brain
(first scan taken in 1971)
First CT scanner - correct answer ✔✔Single pencil beam configuration, moved one degree for 180
degrees. Attenuation that occurred was picked up by a single detector. One the beam had passed all the
way through, the objects were rotated one degree and the beams would pass through again. Around 9
days to obtain a full image- transferred to a supercomputer which would take around 2.5 hours to
reconstruct the image
First generation scanner - correct answer ✔✔Single pencil beam configuration, moved one degree for
180 degrees. Only for imaging the brain. Around 20 minutes to obtain a full image. Beam went through
the brain and then rotated one degree. Info sent of site to a computer to be reconstructed.
CT Vs Radiography - correct answer ✔✔CT forms cross sectional images eliminating the superimposition
of structures that occurs in plane film imaging because of compression of 3D body systems onto the 2D
recording system.
Sensitivity of CT to subtle differences in x-ray attenuation is at least a factor 10 higher than normally
achieved by screen film recording systems because of the virtual elimination of scatter
Radiation exposure - correct answer ✔✔Multiple x-ray images being taken so the amount of radiation
exposure is higher than that of x-rays.
Production of images - correct answer ✔✔Motorized x-ray source which rotates around the bore of the
gantry. Couch moves through the gantry, narrow x-ray beams shot at the body. Within the gantry- x-ray
detectors located directly opposite the source so beams shot directly through the body. Detected beams
transmitted to a computer. After completing a full rotation the computer generates a 2D slice of the
patient and the couch is moved further into the boar. Slices can be stacked together to make a 3D image.
1970's - correct answer ✔✔CT scanner invented by Godfrey Houndsfield, took several hours to acquire
an the raw data for a single slice and took days to reconstruct a single image. Used existing x-ray
technology, first to combine the x-ray machine with a computer. Could only take pictures of the brain
(first scan taken in 1971)
First CT scanner - correct answer ✔✔Single pencil beam configuration, moved one degree for 180
degrees. Attenuation that occurred was picked up by a single detector. One the beam had passed all the
way through, the objects were rotated one degree and the beams would pass through again. Around 9
days to obtain a full image- transferred to a supercomputer which would take around 2.5 hours to
reconstruct the image
First generation scanner - correct answer ✔✔Single pencil beam configuration, moved one degree for
180 degrees. Only for imaging the brain. Around 20 minutes to obtain a full image. Beam went through
the brain and then rotated one degree. Info sent of site to a computer to be reconstructed.
