CT REGISTRY EQUATIONS &
QUESTIONS AND ANSWERS WITH
SOLUTIONS 2024
To determine how many pixels are being used? - ANSWER 1. Multiply # of rows x the # of columns in the
matrix
2. Divide the field of view by the matrix size; Make sure you are using the same units for both.
To determine the number of slices needed? - ANSWER Divide the coverage area by the slice thickness.
Pt dose is equal to? - ANSWER mA aka tube current x Rotation time
The number of samples of attenuation profiles present in the raw data is determined by? - ANSWER
Multiplying the number of detectors by the # of projections
Usual full rotation is? - ANSWER 360 degrees
To determine how many projections were obtained per degree? - ANSWER Divide the number of
projections by 360 degrees.
3 ways to compensate for increased noise associated with thin slices? - ANSWER 1. Increase
reconstruction field of view
2. Decrease matrix size
3. Increase mA
Spatial Resolution depends on? - ANSWER Reconstruction Field of View-the smaller the field of view the
greater the resolution
Image Matrix- Greater the matrix size the greater the resolution
Decrease in FOV does what to pixel size? - ANSWER Decreases it.
, Increase in matrix size does what to pixel size? - ANSWER Decreases pixel and voxel size.
To determine the pitch on a single row detector? - ANSWER Divide the movement of the table by the
slice thickness
To determine the pitch on a multi row detector? - ANSWER Divide the movement of the table by the
total slice volume or the thickness of a single slice
Name the 5 imaging parameters? - ANSWER 1. Contrast Resolution
2. Spatial Resolution
3. Temporal Resolution
4. Noise
5. Patient dose
Typical slice thickness for a CT of the HEAD? - ANSWER 5-10 mm
CT findings are described as? - ANSWER Isodense, hypodense, and hyperdense
What is considered the reference density - ANSWER Brain
The more dense a structure is .... - ANSWER The brighter it appears such as skull=white
The less dense a structure is ... - ANSWER The darker the appearance such as CSF and air appear black
Typical amount of contrast used for a CT of the Chest? - ANSWER 50-100 mL
Imaging protocol for CT of the Chest? - ANSWER 10 mm slices from the lung apex to the C/P angles
Prep for contrast? - ANSWER NPO 4-6 hours
QUESTIONS AND ANSWERS WITH
SOLUTIONS 2024
To determine how many pixels are being used? - ANSWER 1. Multiply # of rows x the # of columns in the
matrix
2. Divide the field of view by the matrix size; Make sure you are using the same units for both.
To determine the number of slices needed? - ANSWER Divide the coverage area by the slice thickness.
Pt dose is equal to? - ANSWER mA aka tube current x Rotation time
The number of samples of attenuation profiles present in the raw data is determined by? - ANSWER
Multiplying the number of detectors by the # of projections
Usual full rotation is? - ANSWER 360 degrees
To determine how many projections were obtained per degree? - ANSWER Divide the number of
projections by 360 degrees.
3 ways to compensate for increased noise associated with thin slices? - ANSWER 1. Increase
reconstruction field of view
2. Decrease matrix size
3. Increase mA
Spatial Resolution depends on? - ANSWER Reconstruction Field of View-the smaller the field of view the
greater the resolution
Image Matrix- Greater the matrix size the greater the resolution
Decrease in FOV does what to pixel size? - ANSWER Decreases it.
, Increase in matrix size does what to pixel size? - ANSWER Decreases pixel and voxel size.
To determine the pitch on a single row detector? - ANSWER Divide the movement of the table by the
slice thickness
To determine the pitch on a multi row detector? - ANSWER Divide the movement of the table by the
total slice volume or the thickness of a single slice
Name the 5 imaging parameters? - ANSWER 1. Contrast Resolution
2. Spatial Resolution
3. Temporal Resolution
4. Noise
5. Patient dose
Typical slice thickness for a CT of the HEAD? - ANSWER 5-10 mm
CT findings are described as? - ANSWER Isodense, hypodense, and hyperdense
What is considered the reference density - ANSWER Brain
The more dense a structure is .... - ANSWER The brighter it appears such as skull=white
The less dense a structure is ... - ANSWER The darker the appearance such as CSF and air appear black
Typical amount of contrast used for a CT of the Chest? - ANSWER 50-100 mL
Imaging protocol for CT of the Chest? - ANSWER 10 mm slices from the lung apex to the C/P angles
Prep for contrast? - ANSWER NPO 4-6 hours
