What affects the quantity of x-rays that completely penetrates the patient? - Answer
The x-rays are impeded, or attenuated by any molecular substance in their path. This
includes various tissues of the body, the amount, or thickness of each tissue.
As the path that the x-ray must travel increase...
CT registry exam Questions Solved 100%
Correct Answers
What affects the quantity of x-rays that completely penetrates the patient? - Answer
The x-rays are impeded, or attenuated by any molecular substance in their path. This
includes various tissues of the body, the amount, or thickness of each tissue.
As the path that the x-ray must travel increases, what happens to the photon? - Answer
The x-ray photons become more attenuated. This results in fewer photons that will
completely penetrate the body.
Where is the high voltage generator mounted in a system with a low voltage slip ring? -
Answer next to the CT x-ray tube on the rotating ring assembly in the gantry. It rotates
along with the tube assembly.
The tube rotates and emits x-rays while the detectors measure attenuated photons
from various projections around the patient.
How is CT projection data collected? - Answer By passing x-rays through the patient at
many different angles.
The data from the resulting set of projections is reconstructed where - Answer In the
array processor to generate a final image.
Short scan times minimize what? - Answer The chance that motion artifacts will be
introduced into the image.
What is a component located in the gantry of a modern CT system? - Answer The x-ray
tube, the detectors (solid state or xenon), and the collimators (pre-patient and post-
patient).
,Where is the array processor located? - Answer Near the host computer and away from
the gantry and patient table area.
The array processor is the site where what occurs? - Answer Reconstruction of the CT
raw data into image data.
Why are X-rays used in CT? - Answer They penetrate the body according to specific
attenuation characteristics of each tissue.
X-rays are produced whenever fast-moving electrons collide with any form of matter
because: - Answer The electron loses kinetic energy which is converted into the
emissions of an x-ray photon.
Bremsstrahlung radiation inclues which type of electron activity? - Answer 1) the
electron collides with the nucleus of the target atom
2) the electron is slowed down as it passes the nucleus of the target atom due to the
interaction with the positive charge of that nucleus.
Bremsstrahlung radiations occurs when an incoming electron loses some of its kinetic
energy which is converted into the emission of an x-ray photon under which 2
conditions? - Answer 1) the electron collides with the nucleus of the target atom
2) the electron is slowed down as it passes the nucleus of the target atom due to the
interaction with the positive charge of that nucleus.
Why is tungsten used as the target material on the tube's anode: - Answer It has a high
atomic weight and a high melting point.
,What is the main reason that the majority of x-rays used in CT are derived from general
radiation and not from characteristic radiation? - Answer Many more x-rays are
produced from general radiation than those from characteristic radiation.
The enormous heat that builds up in the CT tube is caused by? - Answer The collision of
the electron beam with the tungsten target on the tube anode.
The number of electrons that flow from the cathode to the anode in the tube is
controlled by? - Answer The mA
What does the continuous slip ring do? - Answer Eliminates the problem of the high
voltage cable winding up since communication with the rotating gantry ring occurs
through the slip ring, rather than a cable.
It makes it unnecessary to stop the gantry after each scan in order to reverse the
direction of the gantry rotation.
Improves patient throughput.
Increases patient comfort.
Makes possible the ability to scan multiple slices with a single breath-hold.
Especially useful for volume, or helical imaging.
What is part of the CT tube? - Answer The filament, which is located on the tube's
cathode, and tungsten target, which is located on the tube's rotating anode, for the
electrical circuit to which the high voltage, generated by the high voltage generator, is
applied.
What are relatively insensitive to scatter? - Answer Xenon detectors
Which system component converts the projection attenuation data into the proper
digital form for the array processor? - Answer Analog-to-digital converter
, X-ray photons are produced by: - Answer whenever a fast-moving proton collides with
matter. This is constituted by an electron colliding with an atomic nucleus or colliding
with an electron and ejecting it. Even a fast-moving electron passing close to an atomic
nucleus will generate x-ray photons.
What do solid state detectors generate? - Answer A flash of light which is converted to
an electrical signal by means of a photodiode.
Solid state detectors are well suited for which generation of scanners? - Answer Fourth-
generation systems because they are sensitive to x-rays entering at a wide range of
incident angles.
They can be used in 3rd generation scanners.
Can Xenon detectors be used in fourth-generation scanners? - Answer No
What does mAs determine? - Answer The quantity of x-ray photons
What will increase the likelihood that a given x-ray will penetrate a material? - Answer
Increased kV
What physically blocks x-rays? - Answer Collimation
What is scatter radiation caused by? - Answer Deflections from the original trajectory of
an x-ray photon through the patient.
What is the difference between second and fourth-generation CT scanners? - Answer
Both designs incorporate fan beam geometry
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