Computed Tomography
A high variation in pixel values in a homogenous phantom is a measure of _____.
image noise
Filtered back projection in CT refers to _____.
image reconstruction
The first generation of computed tomography used ______ detector (s).
one
The time from the end of CT imaging to image appearance is called the ____ time.
reconstruction
The concentration of scintillation detectors affects the _____ of the CT image.
spatial resolution
The new development in the fourth generation CT scanner is the _____.
stationary detector array
Each CT projection is ____. 1. printed on film 2. stored on the computer 3. displayed on the monitor
stored on the computer
CT scanners operate on ____ voltage generation
high frequency
Each pixel of information in the CT image contains numerical information in ___ units.
Hounsfield
The cross-sectional anatomy is translated into ____ during CT reconstruction.
a matrix of values
The second-generation CT scanners had the disadvantage of increased _____.
beam scatter
CT imaging has excellent ______ because of the narrow beam collimation.
contrast resolution
Many CT x-ray tubes have the capacity for millions of _____ with each exam.
heat units
The principal drawback of the first-generation CT scanner was the ____.
long scanning time
Each CT projection records variations in ____.
mass density and effective atomic number
The pixel size is reduced when the ____ size is increased and the ______ size is fixed.
matrix; field of view
The degree of spatial resolution in any CT imaging system is limited to the size of the ______.
pixel
Image noise in CT scanning depends on _______ 1. pixel size 2. slice thickness 3. detector efficiency
pixel size, slice thickness, & detector efficiency
The patient dose in CT is determined by the ____ collimator. 1. pre-patient 2. post-patient 3. pre-detector
pre-patient
What is the principal disadvantage of third generation CT scanners?
ring artifacts
The reduction in ______ was the principal advantage of the second-generation CT scanners.
scanning time
The third generation of CT scanners allowed for further reduction in ____. 1. scanning time 2. fan-beam width 3. scattered radiation
scanning time & scattered radiation
The _____ generation of CT scanners was the first to have the fan beam transect the entire patient at all times.
third
Each sweep of the source-detector around the body during CT is called a _____.
translation
The CT scanner must be calibrated so that _____ is at CT number zero.
water
