RTE1000 Final Exam Review UPDATED
Questions and CORRECT Answers
How is the primary beam attenuated? - CORRECT ANSWER - When the primary beam
passes through a patient, the individual x-ray photons interact with the various materials that
make up the human body. Depending on the characteristics of these materials, the quantities of
the photons are lessened by differing degrees as they pass through matter; The degree to which
the x-rays are attenuated depends on patient thickness and tissue characteristics, such as cell
composition, relative atomic number, and tissue density. In addition, pathologic conditions can
change the way in which the radiation is attenuated.
Describe mAs & its effect on exposure - CORRECT ANSWER - (mAs) is the parameter
that controls the amount of x-radiation produced by the x-ray tube; it is the product of
milliamperage (mA) multiplied by seconds. It directly controls the quantity of x-ray photons
produced. mA is a measure of the electrical current passing through the x-ray tube. Time (in
seconds) is a measure of the duration of the exposure
Describe kV & its effect on exposure - CORRECT ANSWER - (kVp) is a measure of the
electrical pressure (potential difference) forcing the current through the tube. It controls the
penetrating ability of the beam and primarily affects the quality but also the quantity of the x-ray
photons produced.
Describe SID & its effect on exposure - CORRECT ANSWER - (SID) is the distance
between the point of x-ray emission in the x-ray tube (the focal spot) and the IR. It affects the
relative intensity of the radiation that reaches the IR and affects the beam geometry.
What is the purpose of filtration? - CORRECT ANSWER - remove very-low-energy
nondiagnostic x-ray photons in the primary beam to decrease patient exposure. As more material
is placed in the path of the beam, the resultant intensity decreases
How does collimation affect scatter & IR exposure? - CORRECT ANSWER - By
restricting the primary beam and decreasing scatter, we are, in effect, subtracting photons from
the remnant beam; A decrease in scatter causes a decrease in IR exposure (signal value).
,What is the main purpose of a grid? - CORRECT ANSWER - A grid is a device that is
designed to remove as many scattered photons exiting the patient as possible before they reach
the IR
What are grids designed to "trap"? - CORRECT ANSWER - scatter radiation that exits the
patient
How does changing kV affect contrast? - CORRECT ANSWER - As long as the kVp is
adequate to penetrate the part being examined, low kVp will produce high subject contrast
because most of the low-energy photons are absorbed by thicker parts while more penetrate the
thin part. However, when the kVp is too low, most of the photons do not reach the image
receptor because they are absorbed in the patient. With high kVp, subject contrast is decreased
because both thick and thin body parts are penetrated
Define the terms short & long-scale contrast - CORRECT ANSWER - high contrast, short-
scale contrast, and narrow window width: Displayed digital images with relatively few gray
tones
low contrast, long-scale contrast, and wide window width: Images with greater numbers of gray
tones
What is the purpose of contrast media? - CORRECT ANSWER - Contrast media are
substances that attenuate the beam to a different degree than the surrounding tissue; Because the
contrast medium introduces an additional subject density to the body, technical factors,
particularly kVp, must be adjusted for adequate penetration.
What does an exposure index (EI) number represent? - CORRECT ANSWER - Exposure
indicator is a numeric representation of the quantity of exposure received by a digital IR. The
total exposure received by the image receptor is not a measure of the dose to the patient, but
rather indicates how much radiation was absorbed by the IR, which gives only an idea of what
the patient received
, Define size & shape distortion - CORRECT ANSWER - Distortion is the
misrepresentation of the true size or shape of an object. Magnification is the only possible size
distortion in radiography
How do changes in SID affect magnification (size distortion)? - CORRECT ANSWER - If
the SID decreases, magnification of the image increases. Magnification decreases as SID
increases
If the object is then moved farther from the receptor, magnification increases. Magnification
decreases as OID decreases
In terms of spatial resolution and magnification, the best image is produced with a small OID
and a large SID
How does beam angulation affect shape distortion? - CORRECT ANSWER - A sphere
that is imaged by a straight perpendicular beam is represented as a circular image. An image of
the same sphere, when imaged by an angled beam, appears as an oval. Objects may appear as
elongated or foreshortened.
How does focal spot size affect detail? - CORRECT ANSWER - In general, the small
focal spot is used when fine detail is required, as in the radiography of small bones. The large
focal spot is used for most general radiographic examinations.
What unit is used to measure the energy of an x-ray beam? - CORRECT ANSWER -
coulombs per kilogram (C/kg) (*coulomb is a quantity of electric charge)
SI Units:
Exposure (X) Coulombs per kilogram (C/kg)
Air Kerma Gray (Gy)
Absorbed Dose (D) (Efd) Gray (Gy)
Effective Dose (EfD) Sievert (Sv)
Dose Equivalent (EqD) Sievert (Sv)
Questions and CORRECT Answers
How is the primary beam attenuated? - CORRECT ANSWER - When the primary beam
passes through a patient, the individual x-ray photons interact with the various materials that
make up the human body. Depending on the characteristics of these materials, the quantities of
the photons are lessened by differing degrees as they pass through matter; The degree to which
the x-rays are attenuated depends on patient thickness and tissue characteristics, such as cell
composition, relative atomic number, and tissue density. In addition, pathologic conditions can
change the way in which the radiation is attenuated.
Describe mAs & its effect on exposure - CORRECT ANSWER - (mAs) is the parameter
that controls the amount of x-radiation produced by the x-ray tube; it is the product of
milliamperage (mA) multiplied by seconds. It directly controls the quantity of x-ray photons
produced. mA is a measure of the electrical current passing through the x-ray tube. Time (in
seconds) is a measure of the duration of the exposure
Describe kV & its effect on exposure - CORRECT ANSWER - (kVp) is a measure of the
electrical pressure (potential difference) forcing the current through the tube. It controls the
penetrating ability of the beam and primarily affects the quality but also the quantity of the x-ray
photons produced.
Describe SID & its effect on exposure - CORRECT ANSWER - (SID) is the distance
between the point of x-ray emission in the x-ray tube (the focal spot) and the IR. It affects the
relative intensity of the radiation that reaches the IR and affects the beam geometry.
What is the purpose of filtration? - CORRECT ANSWER - remove very-low-energy
nondiagnostic x-ray photons in the primary beam to decrease patient exposure. As more material
is placed in the path of the beam, the resultant intensity decreases
How does collimation affect scatter & IR exposure? - CORRECT ANSWER - By
restricting the primary beam and decreasing scatter, we are, in effect, subtracting photons from
the remnant beam; A decrease in scatter causes a decrease in IR exposure (signal value).
,What is the main purpose of a grid? - CORRECT ANSWER - A grid is a device that is
designed to remove as many scattered photons exiting the patient as possible before they reach
the IR
What are grids designed to "trap"? - CORRECT ANSWER - scatter radiation that exits the
patient
How does changing kV affect contrast? - CORRECT ANSWER - As long as the kVp is
adequate to penetrate the part being examined, low kVp will produce high subject contrast
because most of the low-energy photons are absorbed by thicker parts while more penetrate the
thin part. However, when the kVp is too low, most of the photons do not reach the image
receptor because they are absorbed in the patient. With high kVp, subject contrast is decreased
because both thick and thin body parts are penetrated
Define the terms short & long-scale contrast - CORRECT ANSWER - high contrast, short-
scale contrast, and narrow window width: Displayed digital images with relatively few gray
tones
low contrast, long-scale contrast, and wide window width: Images with greater numbers of gray
tones
What is the purpose of contrast media? - CORRECT ANSWER - Contrast media are
substances that attenuate the beam to a different degree than the surrounding tissue; Because the
contrast medium introduces an additional subject density to the body, technical factors,
particularly kVp, must be adjusted for adequate penetration.
What does an exposure index (EI) number represent? - CORRECT ANSWER - Exposure
indicator is a numeric representation of the quantity of exposure received by a digital IR. The
total exposure received by the image receptor is not a measure of the dose to the patient, but
rather indicates how much radiation was absorbed by the IR, which gives only an idea of what
the patient received
, Define size & shape distortion - CORRECT ANSWER - Distortion is the
misrepresentation of the true size or shape of an object. Magnification is the only possible size
distortion in radiography
How do changes in SID affect magnification (size distortion)? - CORRECT ANSWER - If
the SID decreases, magnification of the image increases. Magnification decreases as SID
increases
If the object is then moved farther from the receptor, magnification increases. Magnification
decreases as OID decreases
In terms of spatial resolution and magnification, the best image is produced with a small OID
and a large SID
How does beam angulation affect shape distortion? - CORRECT ANSWER - A sphere
that is imaged by a straight perpendicular beam is represented as a circular image. An image of
the same sphere, when imaged by an angled beam, appears as an oval. Objects may appear as
elongated or foreshortened.
How does focal spot size affect detail? - CORRECT ANSWER - In general, the small
focal spot is used when fine detail is required, as in the radiography of small bones. The large
focal spot is used for most general radiographic examinations.
What unit is used to measure the energy of an x-ray beam? - CORRECT ANSWER -
coulombs per kilogram (C/kg) (*coulomb is a quantity of electric charge)
SI Units:
Exposure (X) Coulombs per kilogram (C/kg)
Air Kerma Gray (Gy)
Absorbed Dose (D) (Efd) Gray (Gy)
Effective Dose (EfD) Sievert (Sv)
Dose Equivalent (EqD) Sievert (Sv)
