Mosby's Exam Review Image Production
UPDATED ACTUAL Exam Questions and
CORRECT Answers
Which of the following reduces the scatter radiation reaching the detectors? - CORRECT
ANSWER - both a and c
(Pre-detector collimation and post-patient collimation are synonymous. Both terms describe a
device designed to remove scatter radiation before it reaches the detector.)
Which of the following is the primary interaction between x-ray photons and tissue during
computed tomography? - CORRECT ANSWER - Compton effect
(Owing to the high-energy beam used in CT, the Compton effect is the predominant interaction
between x-ray and matter. CT scanners use between 120 and 140 kVp, yielding x-ray energies
with averages between 70 and 80 keV.)
The process by which electrons are produced at the cathode of a CT x-ray tube is known as: -
CORRECT ANSWER - thermionic emission
(When the cathode of an x-ray tube is heated, electrons are released through the process of
thermionic emission. It is these electrons that are then accelerated toward the anode for x-ray
production.)
The assignment of different generations to CT scanners is based on the configuration of the: -
CORRECT ANSWER - tube and detectors
(CT scanners are often placed into one of several different "generations." The differences in
generations are based on the relationship of the tube and detectors and the position of each
during data acquisition.)
When one is using a third-generation CT scanner, it is important that reference detectors
positioned at the peripheral portions of the detector array be exposed to: - CORRECT
ANSWER - unattenuated radiation
(Reference detectors are used to measure incident radiation intensity. This information is used by
the computer during the calculation of the linear attenuation coefficient. If the patient is placed
,incorrectly within the gantry, the reference detectors may be partially blocked, causing an out-of-
field artifact.)
In 1979, the scientists __________ and __________ shared the Nobel Prize for their research in
computed tomography. - CORRECT ANSWER - Hounsfield and Cormack
(Dr. Godfrey Hounsfield and Dr. Allan Cormack shared the Nobel Prize for their work on the
development of computed tomography in 1979.)
The type of compensating filter used at the x-ray tube of a CT scanner is called a: - CORRECT
ANSWER - bow-tie filter
(The bow-tie filter used at the x-ray tube of a CT scanner absorbs a larger amount of radiation at
the periphery of the patient, where the part thickness is reduced. The center of the patient is
placed at the center of the filter, where the largest amount of radiation is allowed to pass through.
The use of this type of filter attempts to compensate for the differences in thickness of the often
oval-shaped patient.)
The interaction between x-ray and matter that is responsible for the production of the scatter
radiation absorbed by the patient and detectors is: - CORRECT ANSWER - Compton
effect
(In the Compton interaction, an x-ray photon ejects an outer-shell electron of an atom. The
photon loses some of its energy in the collision and then continues on in a different, scattered
direction. This interaction is the major source of the scatter radiation involved in the formation of
the CT image.)
The types of detectors used in computed tomography are:
1. Gas ionization
2. Stimulable phosphor
3. Scintillation - CORRECT ANSWER - 1 and 3 only
(The types of detectors used in computed tomography are scintillation and gas ionization
detectors. Both operate by measuring the amount of transmitted radiation passed through the
patient and transmitting this information to the computer for image reconstruction. Newer
MDCT systems utilize solid-state scintillation detectors exclusively.)
, Which of the following is used in gas ionization CT detectors? - CORRECT ANSWER -
xenon
(Gases with high atomic numbers, such as xenon, are used in ionization-type CT detector
systems. The high atomic number of the xenon gas (Z = 54) increases the incidence of
interaction with x-ray photons, thus improving the efficiency of the detector.)
Which of the following statements concerning the translate-rotate mode of CT data acquisition
is/are correct?1. 360-degree circular detector arrays are used.2. Data are collected only during
translation.3. Was used in first- and second-generation CT scanners. - CORRECT
ANSWER - 2 and 3 only
(The first- and second-generation CT scanners used a translate-rotate method of data acquisition.
The x-ray tube and detector(s) translated across the patient's head, recording transmission
measurements. The entire system then rotated 1 degree. This process of translation-rotation then
repeated itself for a total of 180 degrees. First- and second-generation CT scanners used
anywhere from 2 to 30 detectors.)
Which of the following terms accurately describes the type of x-ray beam used in a third-
generation CT scanner? - CORRECT ANSWER - Fan beam
(The third-generation CT scanner uses a fan beam projected onto a wide detector array. The
third-generation CT x-ray beam is commonly mistaken for the "pencil beam" used with only two
detectors in the first-generation CT scanner.)
Which of the following technologic advances has led to the development of spiral/helical CT
scanning?
1. Slip-ring technology
2. Electron beam technology
3. High-efficiency x-ray tubes - CORRECT ANSWER - 1 and 3 only
(Spiral/helical CT scanners are a recent development in computed tomography technology. The
advents of slip-ring technology and improvements in x-ray tube design have made this
innovation possible. Slip-rings have taken the place of the cumbersome cables previously used to
transmit the CT signal and supply power to the tube and detectors. This development enables the
tube and detectors to rotate continuously around the patient, acquiring data in the form of a helix.
The longer exposure times of up to 60 seconds require extremely efficient x-ray tubes with
enormous heat capacities.)
UPDATED ACTUAL Exam Questions and
CORRECT Answers
Which of the following reduces the scatter radiation reaching the detectors? - CORRECT
ANSWER - both a and c
(Pre-detector collimation and post-patient collimation are synonymous. Both terms describe a
device designed to remove scatter radiation before it reaches the detector.)
Which of the following is the primary interaction between x-ray photons and tissue during
computed tomography? - CORRECT ANSWER - Compton effect
(Owing to the high-energy beam used in CT, the Compton effect is the predominant interaction
between x-ray and matter. CT scanners use between 120 and 140 kVp, yielding x-ray energies
with averages between 70 and 80 keV.)
The process by which electrons are produced at the cathode of a CT x-ray tube is known as: -
CORRECT ANSWER - thermionic emission
(When the cathode of an x-ray tube is heated, electrons are released through the process of
thermionic emission. It is these electrons that are then accelerated toward the anode for x-ray
production.)
The assignment of different generations to CT scanners is based on the configuration of the: -
CORRECT ANSWER - tube and detectors
(CT scanners are often placed into one of several different "generations." The differences in
generations are based on the relationship of the tube and detectors and the position of each
during data acquisition.)
When one is using a third-generation CT scanner, it is important that reference detectors
positioned at the peripheral portions of the detector array be exposed to: - CORRECT
ANSWER - unattenuated radiation
(Reference detectors are used to measure incident radiation intensity. This information is used by
the computer during the calculation of the linear attenuation coefficient. If the patient is placed
,incorrectly within the gantry, the reference detectors may be partially blocked, causing an out-of-
field artifact.)
In 1979, the scientists __________ and __________ shared the Nobel Prize for their research in
computed tomography. - CORRECT ANSWER - Hounsfield and Cormack
(Dr. Godfrey Hounsfield and Dr. Allan Cormack shared the Nobel Prize for their work on the
development of computed tomography in 1979.)
The type of compensating filter used at the x-ray tube of a CT scanner is called a: - CORRECT
ANSWER - bow-tie filter
(The bow-tie filter used at the x-ray tube of a CT scanner absorbs a larger amount of radiation at
the periphery of the patient, where the part thickness is reduced. The center of the patient is
placed at the center of the filter, where the largest amount of radiation is allowed to pass through.
The use of this type of filter attempts to compensate for the differences in thickness of the often
oval-shaped patient.)
The interaction between x-ray and matter that is responsible for the production of the scatter
radiation absorbed by the patient and detectors is: - CORRECT ANSWER - Compton
effect
(In the Compton interaction, an x-ray photon ejects an outer-shell electron of an atom. The
photon loses some of its energy in the collision and then continues on in a different, scattered
direction. This interaction is the major source of the scatter radiation involved in the formation of
the CT image.)
The types of detectors used in computed tomography are:
1. Gas ionization
2. Stimulable phosphor
3. Scintillation - CORRECT ANSWER - 1 and 3 only
(The types of detectors used in computed tomography are scintillation and gas ionization
detectors. Both operate by measuring the amount of transmitted radiation passed through the
patient and transmitting this information to the computer for image reconstruction. Newer
MDCT systems utilize solid-state scintillation detectors exclusively.)
, Which of the following is used in gas ionization CT detectors? - CORRECT ANSWER -
xenon
(Gases with high atomic numbers, such as xenon, are used in ionization-type CT detector
systems. The high atomic number of the xenon gas (Z = 54) increases the incidence of
interaction with x-ray photons, thus improving the efficiency of the detector.)
Which of the following statements concerning the translate-rotate mode of CT data acquisition
is/are correct?1. 360-degree circular detector arrays are used.2. Data are collected only during
translation.3. Was used in first- and second-generation CT scanners. - CORRECT
ANSWER - 2 and 3 only
(The first- and second-generation CT scanners used a translate-rotate method of data acquisition.
The x-ray tube and detector(s) translated across the patient's head, recording transmission
measurements. The entire system then rotated 1 degree. This process of translation-rotation then
repeated itself for a total of 180 degrees. First- and second-generation CT scanners used
anywhere from 2 to 30 detectors.)
Which of the following terms accurately describes the type of x-ray beam used in a third-
generation CT scanner? - CORRECT ANSWER - Fan beam
(The third-generation CT scanner uses a fan beam projected onto a wide detector array. The
third-generation CT x-ray beam is commonly mistaken for the "pencil beam" used with only two
detectors in the first-generation CT scanner.)
Which of the following technologic advances has led to the development of spiral/helical CT
scanning?
1. Slip-ring technology
2. Electron beam technology
3. High-efficiency x-ray tubes - CORRECT ANSWER - 1 and 3 only
(Spiral/helical CT scanners are a recent development in computed tomography technology. The
advents of slip-ring technology and improvements in x-ray tube design have made this
innovation possible. Slip-rings have taken the place of the cumbersome cables previously used to
transmit the CT signal and supply power to the tube and detectors. This development enables the
tube and detectors to rotate continuously around the patient, acquiring data in the form of a helix.
The longer exposure times of up to 60 seconds require extremely efficient x-ray tubes with
enormous heat capacities.)
