ARRT CT: Physics and Instrumentation || QUESTIONS WITH ACTUAL ANSWERS!!
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Course
ARRT CT
Institution
ARRT CT
The general process of CT imaging may be divided into what 4 steps? correct answers 1) data acquisition
2) data reconstruction
3) multidimensional image display
4) image archival and communication
The measurement of the attenuation that occurs along each path through the patient from x-ray tu...
ARRT CT: Physics and Instrumentation || QUESTIONS
WITH ACTUAL ANSWERS!!
The general process of CT imaging may be divided into what 4 steps? correct answers 1) data
acquisition
2) data reconstruction
3) multidimensional image display
4) image archival and communication
The measurement of the attenuation that occurs along each path through the patient from x-
ray tube to detector correct answers Data acquisition
The computerized processing of the transmission measurements into the CT image correct
answers Data reconstruction
Display of the reconstructed gray-scale image in two-dimensional (2D) and/or three-
dimensional (3D) format; an attenuation that occurred across the scanned volume of tissue
correct answers Multidimensional image display
What display as well as storage, both short-term and long-term (archival), of images on
computer workstations? correct answers Image archival and communication
What is the most basic scan mode utilized by a CT system? correct answers Scout image
acquisition
The angle of the tube and detectors in relationship to the patient position during scout
acquisition correct answers Azimuth
What is used as a localizer for the prescription of the subsequent cross-sectional CT
acquisition? correct answers Scout image
What consisted of the complete revolution of the x-ray tube around the patient, acquiring a
single data set at a precise anatomic location? To acquire the next CT image, the table would
translate (index) a predetermined amount to the next anatomic position and the system would
again rotate around the patient correct answers Conventional axial or step-and-shoot CT
scanning
The CT system is generally composed of what 3 things? correct answers 1) computer and
display system
2) patient bed
3) gantry components
What houses the majority of the mechanical components of CT system operation, including
the generator, x-ray tube, assorted collimators, the data acquisition system (DAS), slip-rings,
and the detectors? correct answers CT gantry
The x-ray and detector components of a CT system were originally limited by what? correct
answers Hard-wired cables
, What eliminates the need for cables by utilizing a system of contact brushes that supply
electricity to power the system and enable the passage of transmission data to the computer
system? correct answers Slip-ring technology
What are the 4 technical elements of helical CT acquisition? correct answers 1) continuous
rotation of the gantry components (slip-ring technology)
2) a powerful x-ray tube capable of long exposure output
3) continuous movement of the patient bed
4) specialized mathematical reconstruction techniques
Dual filaments allow for a choice of two focal spot sizes ranging from what to what in
diameter? correct answers 0.5 to 1.2 mm in diameter
What focal spot improves the geometric efficiency of the x-ray beam, leading to greater
spatial resolution? correct answers Smaller focal spots
What involves the electromagnetic steering of the electron beam emitted from the cathode?
correct answers Flying focal spot technology
The long acquisition times and relatively high exposure rates of helical single-slice CT
(SSCT) and MSCT require an x-ray tube with what? correct answers With very high heat
storage capacity
The x-ray tube must be very efficient at dissipating the tremendous heat generated during a
CT exam. What are several methods that's utilized to improve heat capacity? correct answers
1) oil- and air-cooling
2) increased anode diameter
3) conduction by tube rotation
What are the 3 characteristics that enables the modern CT x-ray tube to achieve the
performance demanded by state-of-the-art MSCT? correct answers 1) high heat rating - must
have the ability to absorb tremendous heat, while dissipating it quickly
2) small size, lightweight - must be capable of rotating within the CT gantry at a high rate of
speed
3) stable and long-lasting - must be capable of withstanding huge centrifugal forces with an
extended useful life
Quantity of x-radiation correct answers Photon influence
Rate at which the photon fluence passes through a unit area over time is termed what? correct
answers Photon flux
How does mAs relate to patient radiation dose and image noise? correct answers - directly
proportional to patient radiation dose
- inversely proportional to image noise
What is the main controlling factor of effective mAs? correct answers Table speed
What determines the speed at which the patient translates through the gantry for each tube
revolution? correct answers Pitch
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