Computed Tomography

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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


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