Basic Principals Of CT Flashcards
What is a CAT scan
Computed axial tomography
Axial is with an angle
Who developed CT
Sir Godfrey Hounsfield
When was the clinical CT scan
1971
How does CT work
X tray tube revolves around the patient
What are the advantages of CT over xray
- 3 dimensional
- greater sensitivity to tissue type
Define a 1st generation CT
Slow
Minutes per slice
Stop & Go
Define a 2nd generation CT
Faster
20 second slices
Scan - translate
Define a 3rd generation CT scan
Fan beam
Detectors rotate with tube
0.5 seconds slice
Define a 4th generation CT
Stationary ring detectors
Fasterer
Complete in seconds
Define a 5th generation CT scan
Uses electron beam rather than x rays (EBCT)
Used for cardiac imaging only
What is a spiral CT
Patient moves continuously
Scan is continuous
What is the slice thickness on a Multi scanner
5mm to 0.5mm
What are the parts of the CT machine
Gantry
Table
Aperature ( bore)
What does an analog to digital converter (ADC)
Coverts xray photons into digital code
Photons are
Analog
Code is numbers
Digital
What do the beam collimators do?
Control the thickness of the beam
Near xray tube
What do the detector collimators do?
Near the detectors,
Controls slice thickness
What do power injectors do
Deliver contrast
Saline flush
What is CT fluoro
Continuous scan of same
Spot
Biopsies
What is a virtual CT
CT scans reconstructed into 3-D images
What are voxels
A 3 dimensional volume of tissue/pt/ stuff
What are the units for voxels
Hounsfield units (HU)
How are voxels produced
By assigned grayness based on HU’s
