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Carlton Adler Ch44
| Question | Answer |
|---|---|
| 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
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