NMTCB Content Pertaining to CT
1. Pitch >1: reduces resolutiondata must be interpolated lowers radiation dose
2. Pitch = 1: usually preferredbalance dose to resolution
3. Pitch < 1: improved resolutionincreases radiation dose
4. Axial mode: tube moves collecting data 360 degrees
tube stops and table moves to next position continues euntil all slices of data have been
acquired
5. Multi - Slice spiral / helical CT (MSCT): multiple slices in a single rotationcovers greater
volume
increasing the detectors rows with fan beam xrays, reducing imaging time
6. Cone Beam CT: applying a cone beam where the xray tube and the detectorrotate on the
same axis
detector area is flat
used in dentistry and interventional radiology
7. Automatic Exposure Control: method - Automatic Tube Current Modulation(ATCM)
Image optimization + maintaining image quality
8. Automatic Tube Current Modulation: regulates optical density by adjusting mAto the xray
tube thus sustaining the same density (area) being scanned.
9. Angular Modulation: within the scanning field of view, automatic modulationoccurs by
mA adjustment in the x-y axis
reducing the amount of radiation exposure which is based on the level of attenuation
10. AEC application - automatic exposure control: variation fo mAs are noted asthe optical
density varies from the head to neck to chest
the scout film defines the appropriate adjustments
, technologist defines the image noise target value which should remain constant throughout the
variations in density with the patient's body
11. Fourier Transform: The projection -slice theorem, which states that the one-di- mensional
Fourier Transform of the projection of a two-dimensional signal is equal to the slice of its two
dimensional at the same angle
basis for filtered backprojection
12. CT Scatter Iso - Dose Map: Calculating the patient dose - kerma-area product(KAP) and
dose-length product (DLP)
usually applied to CT fluoroscopy procedures
Isodose curves in uGy define the scatter of radiation in air kerma for whole bodyscanning
13. Filtered Backprojection (FBP): round object in the center field of view is madeof higher
density and scanned
spatial domain reveals multiple arrays with a concentration of the higher u value atthe center
spatial domain is converted to a frequency, a high pass filter is applied, moving thestar shape
defect, eliminates the projected ray
conversion back to the spatial domain renders the reconstructed object
14. Iterative Reconstruction (IR): initial raw data - apply FBPforward project generated
data is then compared to raw
goal - add/subtract differences in u to attain closest estimatereturn to FBP and repeat
certain number of interations is needed to complete the process
15. Streaking defect is elimated with which filter: Interative reconstruction
16. Iterative reconstruction when appropriated applied: processes images withlower amount
of xrays, lowering patient dose
1. Pitch >1: reduces resolutiondata must be interpolated lowers radiation dose
2. Pitch = 1: usually preferredbalance dose to resolution
3. Pitch < 1: improved resolutionincreases radiation dose
4. Axial mode: tube moves collecting data 360 degrees
tube stops and table moves to next position continues euntil all slices of data have been
acquired
5. Multi - Slice spiral / helical CT (MSCT): multiple slices in a single rotationcovers greater
volume
increasing the detectors rows with fan beam xrays, reducing imaging time
6. Cone Beam CT: applying a cone beam where the xray tube and the detectorrotate on the
same axis
detector area is flat
used in dentistry and interventional radiology
7. Automatic Exposure Control: method - Automatic Tube Current Modulation(ATCM)
Image optimization + maintaining image quality
8. Automatic Tube Current Modulation: regulates optical density by adjusting mAto the xray
tube thus sustaining the same density (area) being scanned.
9. Angular Modulation: within the scanning field of view, automatic modulationoccurs by
mA adjustment in the x-y axis
reducing the amount of radiation exposure which is based on the level of attenuation
10. AEC application - automatic exposure control: variation fo mAs are noted asthe optical
density varies from the head to neck to chest
the scout film defines the appropriate adjustments
, technologist defines the image noise target value which should remain constant throughout the
variations in density with the patient's body
11. Fourier Transform: The projection -slice theorem, which states that the one-di- mensional
Fourier Transform of the projection of a two-dimensional signal is equal to the slice of its two
dimensional at the same angle
basis for filtered backprojection
12. CT Scatter Iso - Dose Map: Calculating the patient dose - kerma-area product(KAP) and
dose-length product (DLP)
usually applied to CT fluoroscopy procedures
Isodose curves in uGy define the scatter of radiation in air kerma for whole bodyscanning
13. Filtered Backprojection (FBP): round object in the center field of view is madeof higher
density and scanned
spatial domain reveals multiple arrays with a concentration of the higher u value atthe center
spatial domain is converted to a frequency, a high pass filter is applied, moving thestar shape
defect, eliminates the projected ray
conversion back to the spatial domain renders the reconstructed object
14. Iterative Reconstruction (IR): initial raw data - apply FBPforward project generated
data is then compared to raw
goal - add/subtract differences in u to attain closest estimatereturn to FBP and repeat
certain number of interations is needed to complete the process
15. Streaking defect is elimated with which filter: Interative reconstruction
16. Iterative reconstruction when appropriated applied: processes images withlower amount
of xrays, lowering patient dose
