Review Flashcards
Which of the following is a short coming in radiography?
Superimposition of structures
CT overcomes the limitations of radiography and tomography by?
-reducing the problem of superimposition
-improving the contrast of the image
-using quantitative detectors
In CT, what does data acquisition refer to?
Acquiring data from the patient through systematic motion of the xray tube and detectors
Attenuation of the beam of radiation depends on which of the following?
-atomic number
-density and electrons/gm of tissue
-the energy of radiation
What refers to the range of CT numbers?
Window width
Which of the following is used to calculate relative transmission or penetration measurements?
Log of the ratio of intensity of X-rays at the xray tube (Io) to the intensity of the detector (I)
An object has a slightly less density than water. What is the expected HU measurement?
-10
Which of the following is a low attenuation structure?
Trachea
An imaging nodalith that uses mathematical construct of image reconstruction from projections to produce sharp, clear images of cross sectional anatomy
CT
T/F
Conpared to conventional radiography, CT has poorer spatial resolution
True
Improved by thinner slices
CT image quality is typically evaluated using:
-spatial resolution
-low contrast resolution
-temporal resolution
Is CT qualitative or quantitative?
Quantitative, xray is qualitative
The fraction of scintillation light still present for a certain time after the xray excitation stops
Afterglow
What is the detector quantum efficiency of xenon gas detectors?
Low : 50-60%
