NMTCB-CT Review Exam Questions with
Complete Solutions 2023-2024
Where are x-rays made? - 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-following the ionization of an atom that
leaves an inner shell, outer shell electrons drop down to refill the inner shell. As these
electrons drop down, they lose energy, which is released as x-rays.
What does pre-collimation do? - Answer-(used before x-rays enter the patient) defines
the beam shape and width (which is usually fan or cone shaped) and protects the
patient from excess radiation
What does post-collimation do? - Answer-(used to reduce scatter after leaving the
patient) is used before the radiation strikes the detectors
What are advantages of thinner collimation? - Answer-A: less volume averaging
B: increased spatial resolution
C: decreased spatial resolution
D: fewer artifacts
E: all of the above
F: a,b,d **
True or false: in 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 happens when pitch is decreased? - Answer---the number of views per linear
scan distance increases,
, --spatial resolution is increased
--noise decreases
--exposure is also increased
In diagnostic CT, when might a change in pitch be useful? - Answer-when there is a
need for faster imaging time (during trauma, inability of the patient to
comply/cooperate/tolerate scanning, CTA)
What is the kilovolt potential (kvP)? - 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
-- reduces beam hardening artifacts
--increases radiation exposure to patient
What happens when mA's are increased? - Answer---noise decreases
-- resolution increases
--patient dose increases
hounsfield units - Answer-pixel values assigned to a CT image, computed by calculating
the difference between the linear attenuation coefficients of tissue, and water
How often should tube warn up QC be done? - Answer-A: daily **
B: weekly
C: quarterly
D: yearly
E: before every scan
What is the purpose of the daily tube warm up? - Answer-to prevent damage to the
anode as energy is created
How often should the cylindrical water phantom QC be performed? - Answer-daily (or
before use)
What is the purpose of the water phantom in QC? - Answer-to test CT number values,
noise levels, and resolution
What is the HU for air? - Answer-A: -100
B: 0
C: -1000 **
D: none of the above
Attenuation - Answer-the reduction of the number of X-ray
Complete Solutions 2023-2024
Where are x-rays made? - 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-following the ionization of an atom that
leaves an inner shell, outer shell electrons drop down to refill the inner shell. As these
electrons drop down, they lose energy, which is released as x-rays.
What does pre-collimation do? - Answer-(used before x-rays enter the patient) defines
the beam shape and width (which is usually fan or cone shaped) and protects the
patient from excess radiation
What does post-collimation do? - Answer-(used to reduce scatter after leaving the
patient) is used before the radiation strikes the detectors
What are advantages of thinner collimation? - Answer-A: less volume averaging
B: increased spatial resolution
C: decreased spatial resolution
D: fewer artifacts
E: all of the above
F: a,b,d **
True or false: in 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 happens when pitch is decreased? - Answer---the number of views per linear
scan distance increases,
, --spatial resolution is increased
--noise decreases
--exposure is also increased
In diagnostic CT, when might a change in pitch be useful? - Answer-when there is a
need for faster imaging time (during trauma, inability of the patient to
comply/cooperate/tolerate scanning, CTA)
What is the kilovolt potential (kvP)? - 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
-- reduces beam hardening artifacts
--increases radiation exposure to patient
What happens when mA's are increased? - Answer---noise decreases
-- resolution increases
--patient dose increases
hounsfield units - Answer-pixel values assigned to a CT image, computed by calculating
the difference between the linear attenuation coefficients of tissue, and water
How often should tube warn up QC be done? - Answer-A: daily **
B: weekly
C: quarterly
D: yearly
E: before every scan
What is the purpose of the daily tube warm up? - Answer-to prevent damage to the
anode as energy is created
How often should the cylindrical water phantom QC be performed? - Answer-daily (or
before use)
What is the purpose of the water phantom in QC? - Answer-to test CT number values,
noise levels, and resolution
What is the HU for air? - Answer-A: -100
B: 0
C: -1000 **
D: none of the above
Attenuation - Answer-the reduction of the number of X-ray
