CONTENT PERTAINING TO CT NMTCB
EXAM QUESTIONS AND ANSWERS
100% CORRECT
X-ray Production - ANSWER-produced by accelerating elec trons with a high voltage
and allowing them to collide with the focal spot.
The opening collimates the beam but must first pass through - ANSWER-a layer of
aluminum
Aluminum - ANSWER-Filters out low energy x-rays
Computed Tomography - ANSWER-machine that uses xrays, a powerful form of
electromagnetic energy
combines x radiation and radiation detectors coupled with a computer to create cross
sectional image of any part of the body
Poly-energetic X-ray - ANSWER-produced in a range of keV as the electron beam
sticks and strikes the tungston anode
Increasing the voltage (kVp) to the tube - ANSWER-generates greater energized poly-
energetic x-ray energy
As kVp increases - ANSWER-K and L characteristic x-rays are produced
Brumsstrahlung - ANSWER-occurs at all levels of kVp
Shielding - ANSWER-The lead housing that surrounds the x-ray tubes because xrays
occur in every direction and to absorb secondary xrays
milli-amperes per second (mAs) - ANSWER-the quantity of xrays produced
the greater the current - ANSWER-more xrays produced within a preset kVp
the greater the mAs - ANSWER-the greater the dose to the patient
kVp - ANSWER-applied to increase the xrays penetration
mAs - ANSWER-defines the amount of xrays
Detecting the xrays - ANSWER-Gas Xenon detectors
, Scintallation detectors
Gas Xenon detectors - ANSWER-Xrays are absorbed with chambers, genreating
postive and negative ions, image represents a single row of detectors
Quantum detection efficiency (QDE) is not as efficient as solid state detectors
Scintillation Detection - ANSWER-Similar to a gamma camera, xrays are absorbed by a
NaI crystal, scintillation occurs and a PMT converts the light to an electron event
Issue with scintillation detection - ANSWER-dead time (afterglow)
Solid state detector crystals - ANSWER-either cadium tungstate or ceramic rare earth
oxide
solid state detectors - ANSWER-silicon based semiconductor has greater absorption
based on its density
xrays absorbed causing scintillation where a lens focuses the light
electrons pairs passing from positve to negative side generating a pulse
system contains proportionality
The Transmission Data - ANSWER-as the beam passes through an object it becomes
attenuated by the type of object it encounters
Cone Beam CT - ANSWER-applying a cone beam where the xray tube and the detector
rotate on the same axis
detector area is flat
used in dentistry and interventional radiology
Automatic Exposure Control - ANSWER-method - Automatic Tube Current Modulation
(ATCM)
Image optimization + maintaining image quality
Automatic Tube Current Modulation - ANSWER-regulates optical density by adjusting
mA to the xray tube thus sustaining the same density (area) being scanned.
Angular Modulation - ANSWER-within the scanning field of view, automatic modulation
occurs by mA adjustment in the x-y axis
EXAM QUESTIONS AND ANSWERS
100% CORRECT
X-ray Production - ANSWER-produced by accelerating elec trons with a high voltage
and allowing them to collide with the focal spot.
The opening collimates the beam but must first pass through - ANSWER-a layer of
aluminum
Aluminum - ANSWER-Filters out low energy x-rays
Computed Tomography - ANSWER-machine that uses xrays, a powerful form of
electromagnetic energy
combines x radiation and radiation detectors coupled with a computer to create cross
sectional image of any part of the body
Poly-energetic X-ray - ANSWER-produced in a range of keV as the electron beam
sticks and strikes the tungston anode
Increasing the voltage (kVp) to the tube - ANSWER-generates greater energized poly-
energetic x-ray energy
As kVp increases - ANSWER-K and L characteristic x-rays are produced
Brumsstrahlung - ANSWER-occurs at all levels of kVp
Shielding - ANSWER-The lead housing that surrounds the x-ray tubes because xrays
occur in every direction and to absorb secondary xrays
milli-amperes per second (mAs) - ANSWER-the quantity of xrays produced
the greater the current - ANSWER-more xrays produced within a preset kVp
the greater the mAs - ANSWER-the greater the dose to the patient
kVp - ANSWER-applied to increase the xrays penetration
mAs - ANSWER-defines the amount of xrays
Detecting the xrays - ANSWER-Gas Xenon detectors
, Scintallation detectors
Gas Xenon detectors - ANSWER-Xrays are absorbed with chambers, genreating
postive and negative ions, image represents a single row of detectors
Quantum detection efficiency (QDE) is not as efficient as solid state detectors
Scintillation Detection - ANSWER-Similar to a gamma camera, xrays are absorbed by a
NaI crystal, scintillation occurs and a PMT converts the light to an electron event
Issue with scintillation detection - ANSWER-dead time (afterglow)
Solid state detector crystals - ANSWER-either cadium tungstate or ceramic rare earth
oxide
solid state detectors - ANSWER-silicon based semiconductor has greater absorption
based on its density
xrays absorbed causing scintillation where a lens focuses the light
electrons pairs passing from positve to negative side generating a pulse
system contains proportionality
The Transmission Data - ANSWER-as the beam passes through an object it becomes
attenuated by the type of object it encounters
Cone Beam CT - ANSWER-applying a cone beam where the xray tube and the detector
rotate on the same axis
detector area is flat
used in dentistry and interventional radiology
Automatic Exposure Control - ANSWER-method - Automatic Tube Current Modulation
(ATCM)
Image optimization + maintaining image quality
Automatic Tube Current Modulation - ANSWER-regulates optical density by adjusting
mA to the xray tube thus sustaining the same density (area) being scanned.
Angular Modulation - ANSWER-within the scanning field of view, automatic modulation
occurs by mA adjustment in the x-y axis
