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Carlton Adler Ch44

movable frame of the CT unit. maintains alignment of tube & detectors, contains equipment necessary to perform the scanning gantry
size of aperture of the gantry 50-85 cm
only capable of scanning the head first generation CT
eliminated air spaces in first generation CT? water bag
how long did the first generation CT take to scan? 4.5-5 min
first CT to use a fan shaped beam? second generation
# of detectors did the second generation CT use? 30
drawback of the second generation CT scanner? increased amount of scatter present in images
benefit of second generation CT? time greatly reduced
CT scanner that used a wider fan beam array and 250-750 detectors? third generation CT
first CT to use 360 degree rotation? third generation
major drawback of the third generation CT? run artifact due to single detector failure
major advantage of third generation CT? time greatly reduced, and allowed for dynamic imaging
CT that used single fan shaped beam with 600-2000 stationary detectors 360 degrees around the gantry fourth generation
advantage of the fourth generation CT 2-10 second scans, greater dynamic imaging, ring artifact eliminated
first CT to use bounce concept fifth generation
consisted of electron beam scanners, stationary tube, annular targets, used for cardiac imaging fifth generation CT
first utilized computer to control movement of table, continuous scanning throughout exam sixth generation helical/spiral CT
advantaged of sixth generation CT scan time improvements, lower dose of contrast media needed, patient continually moved through bore, motion artifact reduced
CT that used slip ring technology sixth generation
relationship between patient couch and x-ray beam width pitch
formula for pitch P=I/B
optimal pitch value 1.0 or less
pitch values of less than 1 mean? overlapping data
pitch values of more than 1 mean? missed data
cut scanning time in half by using dual beam from double focus x-ray tube/ dual detector system double helix CT
disadvantages of sixth generation CT full 360 degree data not acquired for each section, section reconstructed to represent appx acquisition of planar data
most appropriate term to describe multi detector CT multisection computed tomography (MSCT)
major advantage of seventh generation MSCT unit narrower section thickness possible, all detectors exposed at once- shorten exam time, greater flexibility in reconstruction
most visible part of CT unit gantry
5 components of the gantry tube, detector array, couch, high voltage generator, mechanical support system
table composition material & why carbon graphite fiber, decrease beam attenuation
how much heat load does the CT anode need to be able to withstand? at least several million heat units (MHU)
what helps reduce heat load in the CT scanner small focal spot size & pulsed scanner
modern pulsed scanner tube operates at___ 120 kVp, 1-5 sec pulses, and up to 1000 mA
continuous x-ray beam operates at ___ 400 mA & 120 kVp
expected tube life of CT tube less than 1 year
group of detectors and interspace material used to separate them, the image receptor in computed tomography detector array
SID in CT 44"
2 ways to collimate in MSCT pre-pt. collimation & post pt. collimation.
sum of the capture efficiency, absorption efficiency, and conversion efficiency detector dose efficiency
how well the detector receives the photon from the patient capture efficiency
how well the detector converts incoming x-ray photons absorption efficiency
how well the detector converts absorbed photon information to a digital image for the computer conversion efficiency
3 types of detectors scintillation, xenon gas, solid state
major disadvantage of scintillation-PM detectors size & interspace material. afterglow.
type of detector used in all helical and MSCT scanners solid state detectors
localization image similar to scout in traditional radiography sinogram or scanogram
primary mathematical method used in the creation of computerized medical images Fournier Transformation
process of modifying pixel values by a mathematical formula convolution (sometimes called a mask)
process of returning pixel values to their original level by a reverse process deconvolution
average dose a patient would receive during an exam, includes numerous individual scans. actual tissue dose, not just ESE. multiple scan average dose (MSAD)
Created by: jen.studer