NMTCB-CT EXAM 2024-2025
Where are x-rays created? - ANSWER in the electron shell structure of an atom
What is Bremsstrahlung radiation? - ANSWER energetic electrons pass very near the
nucleus of an atom. The strong forces of th positive charged atom causes the negatively
charged electron to decelerate; the path of the electron is changed, and some of the
kinetic energy of the electron is lost, and converted into x-rays
what is characteristic x-ray radiation? - ANSWER produced following the ionization of an
atom that leaves an inner shell, outer shell electrons fall down to re-fill the inner shell. In
falling down, the electrons lose energy that is released as x-rays.
What does pre-collimation do? - ANSWER ELO (used before x-rays enter the patient)
defines the shape and width of the beam-usually fan or cone shaped-and protects the
patient from excess radiation
What does post-collimation do? - ANSWER ELO (used to reduce scatter after leaving the
patient) is used prior to the radiation striking the detectors
What are advantages of thinner collimation? - ANSWER A: less volume averaging
B: increased spatial resolution
A: decreased slice collimation
B: increased matrix
C: decreased spatial resolution
D: less artifacts
E: all the above
F: a,b,d **
, True or False: True or False: During CT, the gantry rotates continuously in one direction
on a slip ring system - ANSWER true
What is a scout imaged used for? - ANSWER Positioning /localization
Pitch - ANSWER the ratio of patient's movements through the gantry during one 360
degree beam rotation relative to the beam collimation (in single slice CT)
The table distance traveled in 1 gantry rotation of 360o divided by the total thickness of
all acquired slices—in multi detector CT
How is pitch calculated? - ANSWER pitch = table movement per rotation (mm)/ (number
of slices)(slices width in mm)
What happen if the pitch is decreased? - ANSWER --the number of views per linear scan
distance increases,
--spatial resolution is increased
--noise decreases
--exposure is also increased
Diagnostic CT-Change in pitch may be useful when: -ANSWER when there is need for
faster imaging time (during trauma, inability of the patient to comply/cooperate/tolerate
scanning, CTA)
What does the kilovolt potential (kvP) determine? -ANSWER determines the kinetic
energy given to the emitted electrons produced from the potential difference between
the cathode and the anode-- designates the maximum x-ray energy
What happens as the kVp is increased? - ANSWER --the penetration energy of the x-rays
is increased
--noise is decreased
Where are x-rays created? - ANSWER in the electron shell structure of an atom
What is Bremsstrahlung radiation? - ANSWER energetic electrons pass very near the
nucleus of an atom. The strong forces of th positive charged atom causes the negatively
charged electron to decelerate; the path of the electron is changed, and some of the
kinetic energy of the electron is lost, and converted into x-rays
what is characteristic x-ray radiation? - ANSWER produced following the ionization of an
atom that leaves an inner shell, outer shell electrons fall down to re-fill the inner shell. In
falling down, the electrons lose energy that is released as x-rays.
What does pre-collimation do? - ANSWER ELO (used before x-rays enter the patient)
defines the shape and width of the beam-usually fan or cone shaped-and protects the
patient from excess radiation
What does post-collimation do? - ANSWER ELO (used to reduce scatter after leaving the
patient) is used prior to the radiation striking the detectors
What are advantages of thinner collimation? - ANSWER A: less volume averaging
B: increased spatial resolution
A: decreased slice collimation
B: increased matrix
C: decreased spatial resolution
D: less artifacts
E: all the above
F: a,b,d **
, True or False: True or False: During CT, the gantry rotates continuously in one direction
on a slip ring system - ANSWER true
What is a scout imaged used for? - ANSWER Positioning /localization
Pitch - ANSWER the ratio of patient's movements through the gantry during one 360
degree beam rotation relative to the beam collimation (in single slice CT)
The table distance traveled in 1 gantry rotation of 360o divided by the total thickness of
all acquired slices—in multi detector CT
How is pitch calculated? - ANSWER pitch = table movement per rotation (mm)/ (number
of slices)(slices width in mm)
What happen if the pitch is decreased? - ANSWER --the number of views per linear scan
distance increases,
--spatial resolution is increased
--noise decreases
--exposure is also increased
Diagnostic CT-Change in pitch may be useful when: -ANSWER when there is need for
faster imaging time (during trauma, inability of the patient to comply/cooperate/tolerate
scanning, CTA)
What does the kilovolt potential (kvP) determine? -ANSWER determines the kinetic
energy given to the emitted electrons produced from the potential difference between
the cathode and the anode-- designates the maximum x-ray energy
What happens as the kVp is increased? - ANSWER --the penetration energy of the x-rays
is increased
--noise is decreased
