Exam (elaborations)
CT Chapters 1,2, & 3 Questions and Answers 2024
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CT Chapters 1,2, & 3
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CT Chapters 1,2, & 3Names for preliminary images - answer Topogr am, scout and scanogram
Spiral or helical scanning - answer Isotropic, continuous acquisition scanning
Spatial resolution - answerThe ability of a system to differ small objects distinctly
Low contrast resolution - answerThe ability of a system to differentiate, on the image,
objects with similar densities
Temporal resolution - answerThe speed that the data can be acquired; this speed is
important to reduce or eliminate artifacts that result from object motion, such as
commonly seen when imaging the heart
X Axis - answerWidth, left to right
Y axis - answerHeight, anterior to posterior
Z axis - answerThickness of the plane, top to bottom
Pixel - answerTwo dimensional square, picture element
Voxel - answerVolume element, 3 dimension, cube, takes x, y, and z axis into accoung
Matrix - answerThe grid formed from rows and columns of pixels
Attenuation - answerDegree to which an X-ray beam is reduced by an object
Hounsfield units - answerQuantify the degree that a structure attenuates an X-ray beam
Hounsfield units also called - answerCT numbers or density values
Hounsfield Unit for water - answer0
Hounsfield Unit for bone - answer+150 to + 1000
Hounsfield Unit for air - answer-1000
Hounsfield Unit for blood- fluid - answer+20 to +50
Hounsfield Unit for blood-clotted - answer+50 to +75
, Hounsfield Unit for blood-old - answer+10 to +15
Hounsfield Unit for cyst - answer-5 to +10
Inaccurate Hounsfield Unit are called - answerArtifacts
Types of artifacts - answerBeam hardening artifacts
Polychromatic x-ray beam - answerVarying energies
How to fix beam hardening artifacts - answerFiltering
Volume averaging - answerProcess in CT by which different tissues attenuation values
are averaged to produce one less accurate pixel reading
How to fix volume averaging - answerThinner slices
Axial imaging plane - answerSuperior/inferior
Coronal imaging planes - answerAnterior/ posterior
Sagittal imaging planes - answerRight/left
Oblique imaging planes - answerAngle to a standard plane
Why are different imaging planes used? - answerAnatomy lies vertically rather than
horizontal or a different plan reduces artifacts created by surrounding structures
Gantry aperture size - answer70-90 cm
Components located within gantry - answerX-ray tube, high voltage generator, detector
array, and cooling system
Tilt range of gantry - answer15-30
Slip rings - answerPermit the gantry Frame to rotate continuously making helical scan
possible
Type of generator - answerHigh frequency
Purpose of the generator - answerConverts low voltage AC current to high voltage DC
Typical output for generator - answer60-100 kW
X-ray tube target material - answerTungsten
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