Rad Equipment Unit 8

window level

"brightness" midpoint of grayscale

window width

"contrast" ; number of grays ; how long the grayscale is

localizer or scout

2D image used to set up a scan

-1000

CT # for air

1000

CT # for bone

0

CT # for water

acquisition mAs

CT scan pitch uses all of the following technical parameters except

sagital, coronal, transverse

CT sections are available as

DFOV

FOV after scan is done

SFOV

FOV before you capture image

ring

a ______ artifact is caused by detector error

star

a _______ artifact is caused b the presence of metal in the patient

beam hardening

a ________ artifact is caused by attenuation of the beam as it passes through the patient

hounsfield

a series of tissue density values that evovled for CT measurements is called ________ units

gaps

any pitch greater than 1= (overlap/gaps)

overlap

any pitch less than 1 = (overlap/gaps)

low contrast resolution increases

as noise increases in a ct image

detectors

capture x-rays and convert it to binary code; made of sodium iodide crystals

array processor

computer processor that filters back projection

rare earth ceramic scintillators

contemporary CT scanners use solid state detectors. these detectors utilize

hounsfield units

ct #'s calculated by comparing linear attenuation of each pixel to linear attenuation of water

transverse plane and reconstructed in any plane

ct image data is acquired in the

higher

detectors want (higher/lower) capture, absorption, conversion efficiency

fifth generation

electron beam scanners, just used for cardiac imaging

second generation

fan shaped beam (permitting whole body scanning), up to 30 detectors

third generation

fan shaped beam, up to 300 detectors, 360 degree rotation of tube and detectors

head

first generation ct scanners scanned only the

sixth generation

helical/spiral, used slip ring technology, continuous scanning

lower

higher the conversion factors= (higher/lower) patient dose

enter the detector, absorbed by the detector, be converted to light then electrical energy

in order for a CT x-ray photon to be measured, it must

a patient family member should be allowed to attend the patient

in the event a CT patient needs emotional support for a procedure, during the acquisition

fourth generation

like third, but 360 degree rotation of detectors

120 kVp, 1000 mA, 1-5 msec pulses

modern pulsed CT scanners operate at

seventh generation

multidetector CT (MDCT)

pitch

ratio of the distance the table moves during 1 rotation of tube

software program, data acquisition, data display

the CT console provides the radiographer access to

at tube exit, at detector entrance, pre and post patient collimators

the CT radiation beam is collimated

mA

the CT radiographer usually varies the ___ to control the primary beam

conversion efficiency

the __________ is how well the detector converts the absorbed photon info to a digital signal for computer

capture efficiency

the ____________ is how well the detectors receive photons from the patient

contrast resolution

the ability to differentiate between small differences in density within anatomy

attenuation coefficients

the calculation of CT numbers is based upon the calculation of

x ray tube

the gantry of the CT unit contains the

scanogram

the localization image produced by the CT scanner is technically called a

helical

the most recent generation of CT scanners use a _________ motion

fourier

the primary mathematical method used in the creation of computerized medical images is the

convolution

the process of modifying pixel values by a mathematical formula is called

pixel, voxel, matrix size

the resolution of the CT image depends on the

better resolution, faster scan time, less risk of motion

the smaller the scan field size, the

reconfiguration software is implemented

to achieve coronal or sagital sections

first generation

used pencil beam, head only, single detector

topogram, sinogram, scanogram

what are 3 other names of a scout image

P=I/B

what is Pitch formula

axial

what kind of scanning is when the x-ray tube moves around a stationary table

helical/spiral

what type of scanning is used when the x-ray tube and table move together simultaneously

prepatient

which collimator determines slice thickness

postpatient

which collimator produces less scatter which improves image quality