CT Chapter Flashcards
What is CT
The process of creating a cross-sectional tomographic plane of any part of the body
What is exit radiation measured by
Detector assembly
how does CT have less scatter
Fan beam uses filters to shape beam and reduce scatter
Who is credited with the invention of Ct
Godfrey hounsfield and Allen cormack
Most scanners are what generation
3rd generation
EBCT
Election beam computed tomography
Ebct gives increased
temporal resolution
EBCT is usually used for
Cardiac scans
6th generation CT scanner
Dual - source CT scanner
Raw dat
Measured X-ray transmission values
Volume element
Voxel
Field of view
Determines amount of data displayed on monitor
Numbers are called CT numbers or
Hounsfield units
Hounsfield units air and gas
- 1000
Water has a hounsfield unit of
Zero
DAS
Data acquisition system
Devices within the gantry
X-ray tube, das, and detect array
Gantry can be titled up to
30 degrees
Opening of the gantry
Aperture
Table is made of
Low density carbon fiber composite
Movement of the tube is called
Indexing
Narrow window =I
Fewer shades of gray 08 high contrast
Wide window =
More shades of gray , longer scale contrast
Window level
Sets the mid point of gray levels
MPR
Multiplanar reconstruction
Multiplanar reconstruction
Ability to reconstruct axial images into coronal, Sagittal or oblique body planes without additional radiation to patient
Exam of choice for head trauma
Ct
Spatial resolution
Ability to see small structures that are near similar small structures
Contrast resolution
Ability to differentiate between small density differences
Streaking artifact is also called
Beam hardening artifact
Isotropic viewing
Viewing in all directions
VCT
Volume Ct
Smaller the beam pitch
Better the spatial resolution
Isocenter
The point in space where radiation beams interact when gantry is rotated
Dose reporting must be part of
The permanent record for each exam
Most common reporting method
Dose-length product
Dose times length of exam
Units used for DLP
MGy/cm
Thinner the slice
The higher the dose
what award was given to Hounsfield and Cormack and in what year
Nobel prize in 1979
which generation CT machine is the tube very close to the patient, increasing the patient dose
4th
6th generation computer has
two sets of detectors
6th generation CT machine has increases
temporal resolution
which generation uses an electron beam
5th generation
what is the abbreviation for electron beam CT
EBCT
which generation is dual source
6th
resolution of something moving
temporal resolution
which generation scanners are classified at high speed CT scanners
5th generation
what beam type does a 5th generation have
fan beam
what does dual energy source mean and what is the abbreviation
it has two x-ray beams, DSCT
voxel volume
the product of the pixel area and slice thickness
what determines the amount of data displayed on the monitor
field of view
CT numbers are also called
Hounsfield units
DAS
detector array system
slip ring technology
low voltage electrical contacts within the gantry are designed to allow continuous rotation of an x-ray tube without the use of cables connecting internal and external components
another work for voxel
volume unit
gantry can be tilted how many degrees
30
opening in the center of the gantry is called
apature
CT table is made of
carbon fiber
window width determines the number of
gray levels to be displayed in the image
narrow window width results in
fewer shades of grey, so higher contrast
window level determines the
midpoint of the range of grey levels to be displayed on the monitor
what should the window level be set to
The CT number of the tissue of interest
what should the window width be set with
a range of values that would optimize the contrast between the tissues in the image
would a high-resolution CT scan protocol use thin-slice or thick-thickness protocols
higher resolution used thinner slice
thinner slices increase/decrease pt dose
increase pt dose because of the increase in mAs
Multiplanar reconstruction (MPR)
sectional image can be generated in any desired plane by selecting a particular plane of data
Helical CT, single slice Helical CT
slip ring technology allows 360 degree continuous rotation of tube and detector, reduces scan times to sub-second per slice
what does VCT stand for
volume CT
VCT
multislice scanners with 64 detector rows or more, must be a cone configuation
CTA
computed tomography angiography
What is CTA
an application of spiral CT that uses three dimensional imaging techniques
Advantages to CTA over conventional angiography
images can be reconstructed without additional radiation exposure, overlying structures can be eliminated, does not require arterial puncture
