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The process of creating a cross-sectional tomographic plane of any part of the body:
Computed Tomography
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What measures the radiation exiting the patient and feeds back the primary data to the host computer?
A detector assembly
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In the early 70's, CT scanning was only used clinically for imaging the:
brain
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The first CT scanners were capable of producing only ____ images.
Axial
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The differentiation of densities is referred to as:
contrast resolution
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The improved contrast resolution with CT when compared to conventional is due to a reduction in the amount of:
scattered radiation
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When and by whom was CT first demonstrated?
1970, Godfery Hounsfield
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The early CT scanners were categorized by:
4 generations
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The first generation scanners worked by the process of:
translation/rotation
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First generation scanners produced a ____ beam.
pencil
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First generation scan time was :
3-5 minutes
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The first generation scanner had a linear tube movement known as ____ followed by a rotation of ___.
translation, 1 degree
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Why was early CT limited almost exclusively to neurologic examinations?
Slow scanning and reconstruction time
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Second generation scanners emitted a ____ beam measured by ____ detectors.
fan shaped, 30
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Second generation scanners were _____/______ movement, but the rotation was ____ degrees between each translation.
translation/rotation, 10
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Scan time of second generation scanners was ____ for a single slice.
20 seconds
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Third generation scanners introduced a _____/_____ movement with ____ detectors.
rotate/rotate, 750
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Third generation scanners reduced scan time to ____ per slice.
1-10 seconds
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Fourth generation scanners introduced _____ movement. The tube moves ____ while the detectors are ____.
rotate-only, around the patient, in fixed positions
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In contemporary CT scanners, both ___ and ___ generation designs are incorporated.
3rd and 4th
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A relative comparison of x-ray attenuation of a voxel of tissue to an equal volume of water:
CT Number, or Housefield unit
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Tissues that are denser than water are given ____ CT numbers whereas tissues with less density than water are given ____ CT numbers.
positive, negative
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The scale of CT numbers ranges from _____ for air and _____ for dense bone.
-1000, 14000
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Three main components of the CT scanner:
Computer, Table, and Gantry
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The computer system used in CT has 4 basic functions:
control of data acquisition, image reconstruction, storage of image data, and image display
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CT studies are removed form the limited memory of the host computer and stored independently, a process called:
archiving
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The gantry is a circular device that houses the:
x-ray tube, data acquisition system (DAS), and the detector array
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The gantry can be tilted forward or backward up to ____
30 degrees.
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The opening within the center of the gantry is termed the ____ and measures about ____.
aperture, 28 inches wide
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CT tables are made of ____ or ____ and have weight limits of ____-_____.
low-density carbon composite or wood; 300-600 lbs
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The special device used for head CT examinations is called:
a cradle
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The postprocessing technique which allows image reconstruction in a variety of planes without additional radiation to the patient is:
Multiplanar Reconstruction (MPR)
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Original CT's were used to diagnose:
neurologic disorders
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Most commonly requested CT procedures:
head, chest and abdomen
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Contrast media for CT is of ____ concentration.
low
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Four main factors contributing to image quality:
spatial resolution, contrast resolution, noise and artifacts
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The amount of blurring in an image:
spatial resolution
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The latest technology of detector arrays has ___ rows of elements.
64
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Muli-slice helical CT systems are referred to as ____ CT systems because covering entire body sections is easily accomplished in a single breath-hold.
volume
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The bones of the skull are categorized into ___ facial bones and ____ cranial bones.
14, 8
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The brain is surrounded by three layers of protective membranes called the:
meninges
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From internal to external, the meninges are:
pia matter, arachnoid matter, and dura matter
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The two hemispheres of the brain are connected by the:
corpus callosum
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A unique arterial anastomosis exits in the brain to protect it from sudden loss of blood supply; it is called:
the Circle of Willis
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Venous drainage in the brain is accomplished by two systems:
cerebral veins and dural venous sinuses
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Degree of arc angulation described by the movement of the x-ray tube and cassette during a tomographic motion
exposure angle
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tomographic fulcrum remains at a fixed height
fixed fulcrum
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plane of tissue that is in focus on a tomogram
focal plane
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point of axis of rotation for a tomographic motion
fulcrum
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Basic tomographic movement that occurs when x-ray tube and cassette movement occurs with the longitudinal axis of the tomographic table
linear tomographic motion
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Tomographic principle in which the fulcrum, or axis of rotation, is raised or lowered to alter the level of the focal plane; the tabletop height remains constant.
planigraphic principle
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Storage of CT images on long-term storage device such as cassette tape, magnetic tape, or optical disk.
Archiving
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Same as transverse:
Axial
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Preset amount of contrast injected rapidly per IV administration to visualize high-flow vascular structures
Bolus
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Area of anatomy displayed by the CRT
Field of View
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Determines field of view; also referred to as zoom or focal plane
scan diameter
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Cancer of plasma cells in bone marrow:
Multiple Myeloma
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Acquired language disorder in which there is impairment of any language modality; including producing or comprehending spoken or written language.
Aphasia
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Muscle weakness on one side of the body:
hemiparesis
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Why is a dry head done before administering contrast?
To check for conditions that may be hidden by contras; prior surgeries/calcifications etc.
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Body section radiography:
Tomography
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Basic positions for tomographic examinations:
AP and Lateral
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In tomographic examinations, structures are oriented either:
parallel or perpendicular to the tomographic plane
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