rad 354 chapt. 28 multi-slice ct in short – ct is a thin band (fan) of radiation directed toward...
TRANSCRIPT
![Page 1: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/1.jpg)
RAD 354 Chapt. 28 Multi-slice CT
• In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt. is measured by a receptor and the response transmitted to a computer for reconstruction of the image(s)
![Page 2: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/2.jpg)
“Slip rings”
![Page 3: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/3.jpg)
Dates/Activities to Remember
• 1970 – Sir Godfrey Hounsfield,Ph.D.., demonstrated the technique of CT scanning – “EMI” head unit
![Page 4: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/4.jpg)
Dates/Activities Con’t.
• 1982 Dr. Hounsfield and Dr. Alan Cormack share the Nobel Peace Prize in physics
• CT Generations and important items:– 1st – translate-rotate; “pencil beam” - one full
rotation for 1 image; head only; 5 min. per image!– 2nd – translate-rotate, but with a “fan” beam;
produced INCREASED INTENSITY at the edge of the beam – “bow-tie” filter used to remedy this; 30 sec. image time
![Page 5: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/5.jpg)
Generations con’t.
– 3rd – used ARRAY of DETECTORS – produced “ring artifacts”
– 4th rotate – stationary, fan beam, detector array; short image time and NO re-con time!
– 5th is NOW here! “Spiral/slip ring” (It is slip ring technology that has enabled this latest generation!)
![Page 6: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/6.jpg)
Major Components of CT
• Gantry – tube-receptor array, collimators (pre-pt. and pre-detector), generator, pt. couch
• Computer – microprocessor – recon time was a BIG issue until recently
• Operating console – usually two monitors – one for RIS/HIS and the second for the imaging portion (often times a “remote” monitor is set up at the radiologist’s desk – can really be a hassle)
![Page 7: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/7.jpg)
Radiation Dose Comparisons
![Page 8: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/8.jpg)
Current – 5th Generation Terms
• Spiral• Helical• 16/32/64 slice• Slip Rings CT
![Page 9: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/9.jpg)
Interpolation/Extrapolation
• Interpolation – information ALONG the axis WITHIN established values
• Extrapolation – information OUTSIDE axis values established, BUT an ESTIMATED value based upon previously measured parameters IF they continue
![Page 10: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/10.jpg)
“Spiral” Terms
• Pitch – relationship between couch movement and x-ray beam collimation (pitch ratio)– Increasing pitch ratio enables much MORE of the pt. to be
imaged in ONE BREATH HOLD! Breath holds = misrepresentation of the images.
• Slip ring technology made “spiral CT” possible• Three slip rings in the gantry (usually)
– One for hi voltage power to the tube and hi voltage generator– Low voltage power to the rotating gantry portion– Transfer of digital data from gantry receptors to the computer
![Page 11: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/11.jpg)
Multi Slice CT
• Multi detector arrays– Two at once with one beam = two slices per 360
degrees– With “spiral” enables two detectors to produce 16
slices• Envision a person on the table/couch in a
screw/nut fashion going through the gantry
![Page 12: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/12.jpg)
Spiral/slip ring
![Page 13: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/13.jpg)
Tube (fan beam)/receptors
![Page 14: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/14.jpg)
Z-axis
![Page 15: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/15.jpg)
Maximum Intensity Projection (MIP)
• Pre selecting pixel levels to be viewed AFTER obtaining a “rubic’s cube of information”– Then only exhibit those at the PRE-DETERMINED
value – like an MRA or CTA
![Page 16: RAD 354 Chapt. 28 Multi-slice CT In short – CT is a thin band (fan) of radiation directed toward the pt. and the remnant radiation emitted from the pt](https://reader035.vdocuments.us/reader035/viewer/2022070413/5697bfa21a28abf838c9627b/html5/thumbnails/16.jpg)
Spiral Advantages of Conventional CT
• Motion blur is reduced – fewer artifacts• Lowered imaging time (fewer breath holds
required = less motion and less mis-representation)
• Larger volumes can be imaged with LESS part overlap artifacts