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3.Computed Tomography Certification - Image Quality fully solved
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3.Computed Tomography Certification - Image Quality fully solved
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3.Computed Tomography Certification -Image Quality
which of the following determinants of CT image quality is responsible for how grainy or speckled a CT
image appears?
- resolution
- linearity
- noise
- contrast - correct answer ✔✔noise
when a CT image appears grainy or speckled it is referred to as a "noisy" image
an increase in _________ will result in hardening of the beam
- tissue density
- tissue thickness
- kVp - correct answer ✔✔all of them
which of the following are possible results of partial voluming?
- decreased sharpness of edges
- misleading CT numbers
- improvement in resolution - correct answer ✔✔- decreased sharpness of edges
- misleading CT numbers
partial voluming occurs when more than one tissue is contained within a voxel. as a result, the
attenuation values of the tissues are averaged together to determine the final CT number assigned to
represent the pixel in the image. the resultant pixel value may not accurately represent any of the
specific tissues, in addition partial voluming can blur edges between tissues if the edges fall within the
voxel
which of the following is FALSE about the spatial resolution of an image?
, - resolution is dependent on matrix size
- resolution is dependent on reconstruction FOV
- resolution is dependent on scanned FOV - correct answer ✔✔- resolution is dependent on matrix size
- resolution is dependent on reconstruction FOV
which of the following is NOT directly proportional to mAS?
- the mean energy of the xray photons leaving the tube
- the number of xray photons leaving the xray tube
- xray tube heating
- dose to the patient - correct answer ✔✔the mean energy of the xray photons leaving the tube
which of the following has the highest patient dose assuming all other parameters are the same?
- mA=200, rotation time =2 seconds
- mA=200, rotation time =1 second
- mA= 150, rotation time = 3 seconds
- mA= 400, rotation time = 1 second - correct answer ✔✔- mA= 150, rotation time = 3 seconds
150mA x 3 seconds = 450mAs > all other options
which of the following will result in an increased voxel size?
- decreased reconstruction FOV
- increased slice thickness
- increased matrix - correct answer ✔✔increased slice thickness
increasing matrix and decreased reconstruction FOV will result in smaller voxels
what is the conversion equation from CT number to hounsfield unit? - correct answer ✔✔CT number =
hounsfield unit
if the radiologist requires 2mm thick contiguous slices through the pituitary, and 2.4cm of coverage,
________ slices are necessary? - correct answer ✔✔12
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