Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
30 Cards in this Set
- Front
- Back
|
Define CONTRAST RESOLUTION.
|
The ability to differentiate small differences in density on the image.
|
|
|
Define SPATIAL RESOLUTION.
|
The measure of the size of the smallest object that can be visualized in an image.
|
|
|
Define NOISE.
|
Appears in a CT image as a point-to-point fluctuation in the CT number within a uniform material.
|
|
|
Define DOSE.
|
The amount of ionizing radiation absorbed by the patient per unit mass.
|
|
|
Define ATTENUATION.
|
The progressive reduction of the intensity of the x-ray beam as it passes through the patients tissues.
|
|
|
CT number for water is always__, the CT number for air is always__.
|
0, -1000
|
|
|
The mA is the ____ _______.
mAs is the product of? |
Tube current.
mA and the rotation time. |
|
|
What does mAs not affect?
|
image contrast or resolution
|
|
|
kV is the ____ _______.
The tube voltage causes? kVp determines the? |
Tube voltage.
A current to flow. Energy of the x-ray photons. |
|
|
kVp controls what in a CT image?
|
The Contrast.
|
|
|
Define SLICE THICKNESS.
|
The number of millimeters of anatomy, intersected by the thickness of the x-ray beam.
|
|
|
On single row detector scanners the slice thickness is defined by?
|
The size of the focal spot and collimators.
|
|
|
The acquired slice thickness indicates?
|
Which rows of detectors are being used.
|
|
|
Reconstructed slice thickness, or effective slice thickness is?
|
The thickness of the final image.
|
|
|
Define PARTIAL VOLUME.
|
Mathematical averaging of several millimeters of varying density tissues, which is displayed on a single shade of gray on the resulting image.
|
|
|
Define PITCH on a single row detector scanner.
|
The pitch equals the movement of the patient table in one gantry rotation divided by the slice thickness.
|
|
|
Define PITCH on a multi-row detector scanner.
|
The movement of the pt table in 1 gantry rotation divided by the total slice volume -OR- The movement of the pt table in 1 gantry rotation divided by the thickness of a single slice.
|
|
|
If you reduce the pitch you are going to...
|
Improve resoltion along the slice direction and minimize the appearance of noise in the image.
|
|
|
Define RECONSTRUCTION INTERVAL.
|
How the helical slices are reconstructed, the amount of overlap between adjacent slices. If the reconstruction interval is equal to the slice thickness, the reconstructed slices will be contiguous, if less than the slice thickness, the reconstructed images will overlap
|
|
|
Define PIXEL.
|
A single picture element of the image matrix.
|
|
|
Define VOXEL.
|
A volume element.
|
|
|
The SCAN FOV determines?
|
The total area over which projection data is colected, determines the number of detectors collecting data for a particular scan.
|
|
|
The RECONSTRUCTIVE FOV or DISPLAY FOV is the?
|
Region of interest illustrated in the resulting images and the field-of-view reconstructed from the complete set of raw data. Always equal to or smaller than the scan FOV.
|
|
|
Small FOV
Larger FOV |
Optimized inplane/spatial resolution.
less noise. |
|
|
Define IN-PLANE SPATIAL RESOLUTION.
|
The reconstruction FOV divided by the number of pixels along each direction in the image matrix.
|
|
|
What is the image matrix?
|
The grid of pixels that form the image.
|
|
|
Matrix affects?
|
Spatial Resolution and the appearance of image noise.
|
|
|
Larger image matrix yields better resolution but it will...
|
Increase the appearance of image noise.
|
|
|
Magnification simply...
|
enlarges the individual pixels of the reconstructed image for display purposes.
|
|
|
What is the only way to enlarge the size of the image if the raw data is no longer available?
|
magnification.
|
