Advanced Image Flashcards
what is derived from the greek word “tomes” meaning section
tomography
ct provides views from _ planes
coronal
axial
sagittal
these cuts or slices are often only _ thick
mm
there are _ generations of CT machines
4
first generation systems had only _ detector and only rotated _ degrees
one
180
second generation improved the _ of detector and used a _ shaped beam
# fan
third and fourth generation systems used _ detectors, (_) and _ degree
many
900-4800 (detectors)
360
early CT systems were limited to
rotating in one direction only
what were added to allow the tube to continuously rotate while the patient moved through the gantry
slip rings
this describes “_” and increases the _ while decreasing _
volume scanning
data produced
scan time
multi slice scanners were introduced in
1998
multi slice CT produce _
4 image slices simultaneously
for multi slice scanners currently as many as _ slices may be produced from a _ x-ray tube rotation
64
single
advantages of multi-slice scanners
shorter acquition time
decreased volume of contrast media
improved spatial resolution
improved image quality as well as thinner slices
disadvantages of multi-slice scanners
increased cost (30-50%)
there are three basic parts of the CT scanner
gantry
computer
operator console
similar to a basic x-ray tube modified to rotate in 360 degrees and withstand higher heat loading
x-ray tube
solid state detector composed of photodiodes with crystal scintillation materials
detector array
set of 2 collimators one pre-patient and one post-patient
collimator assembly
the collimator assembly do what to the beam
shape and limit the size and direction of the beam
the gantry has three components
x-ray tube
detector array
collimator assembly
the CT requires _ types of sophisticated software
2
the 2 types of software is
one for the operating system
one for the applications
the operating system is a
window base program controls the hardware
application software manages
the image processing, reconstruction and post-processing operation
the operating console includes a
keyboard, mouse, and monitors
this allows the tech to _ and _
control the system
set the parameters of the exam
this is termed the _ and includes
protocol
kV, mA, FOV, pitch, slice # and thickness image reconstruction and display
a computer is often set with more than one _ these are _ and allow the tech and radiologist to view the CT images
workstation
linked
(networking and archiving)
these station may be located on _ or be
site
remote areas w/electronic transmission of data
the display matrix is a digital image composed of pixels in two dimensions to represent a three dimensional piece of tissue
volume element
three dimensional volumes of tissue are called
volume elements or voxels
what is selected by the tech
the depth of the voxel
each voxel in a slice is assigned a _ by the computer that is _ to the degree of x-ray attenuation of that area
number value
proportional
once the degree of attenuation is set the image is displayed on the scree as a _ with each voxel being presented as a pixel on the screen
two dimensional picture
the computer uses a _ to determine the degree of x-ray attenuation for each voxel
linear coefficient
this value is then converted into a numeric scale called
CT #’s
shades of gray are assigned to each CT # with the base value being
0
water is set as the
base value
window width and window level refers to the
grayscale and brightness of the display
a wide window width indicates a
long scale of gray(contrast)
is determined by the tissue density most common to an area w/in that anatomic structure
window level
the tube/detector array and the pt. are in _ during the scan. The amount of anatomy scanned is determined by _
continuous motion
pitch
Pitch is
couch movement (mm/sec)/rotation of the tube collimation
undesirable density on the image
artifact
computed tomography
CT
value set for each pixel in the image relative to water
CT #
houses the tube, detectors and collimators
gantry
numerical expression of the radiation intensity through matter
linear attenuation coefficient
total # of pixels in the image (rows and columns)
matrix
MPR is
multi-planar reconstruction
refers to the parameters of the exam
protocol
one section of the object being scanned
slice
device that allows the continuous rotation of the tube during the scan
slip rings
CT data taken while the pt. moves uninterrupted through the gantry
volume scanning
three dimensional piece of tissue
voxel
computer that serves as the digital post processing station and or image viewing area
workstation
