Basic Principals Of CT Flashcards by Devon Pardue

Q

What is a CAT scan

A

Computed axial tomography

Axial is with an angle

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Q

Who developed CT

A

Sir Godfrey Hounsfield

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Q

When was the clinical CT scan

A

1971

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Q

How does CT work

A

X tray tube revolves around the patient

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Q

What are the advantages of CT over xray

A

3 dimensional
greater sensitivity to tissue type

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Q

Define a 1st generation CT

A

Slow
Minutes per slice
Stop & Go

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Q

Define a 2nd generation CT

A

Faster
20 second slices

Scan - translate

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Q

Define a 3rd generation CT scan

A

Fan beam
Detectors rotate with tube
0.5 seconds slice

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Q

Define a 4th generation CT

A

Stationary ring detectors

Fasterer

Complete in seconds

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Q

Define a 5th generation CT scan

A

Uses electron beam rather than x rays (EBCT)

Used for cardiac imaging only

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Q

What is a spiral CT

A

Patient moves continuously
Scan is continuous

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Q

What is the slice thickness on a Multi scanner

A

5mm to 0.5mm

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Q

What are the parts of the CT machine

A

Gantry
Table
Aperature ( bore)

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Q

What does an analog to digital converter (ADC)

A

Coverts xray photons into digital code

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Q

Photons are

A

Analog

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Q

Code is numbers

A

Digital

Q

What do the beam collimators do?

A

Control the thickness of the beam
Near xray tube

Q

What do the detector collimators do?

A

Near the detectors,
Controls slice thickness

Q

What do power injectors do

A

Deliver contrast
Saline flush

Q

What is CT fluoro

A

Continuous scan of same
Spot

Biopsies

Q

What is a virtual CT

A

CT scans reconstructed into 3-D images

Q

What are voxels

A

A 3 dimensional volume of tissue/pt/ stuff

Q

What are the units for voxels

A

Hounsfield units (HU)

Q

How are voxels produced

A

By assigned grayness based on HU’s

Q

What do thin slices give you

A

More info
More dose

Q

How many Hounsfield units are a bone

A

+1000

Q

How many hounsfield units is water

A

0

Q

How many hounsfield units are air

A

-1000

Q

What does CT linearity describe

A

The amount in which the CT # for the material is precisely proportional to the density

Q

What does the window level control

A

Image brightness

Q

What is window width

A

Number of grays

Q

What will your image look like if there’s metal

A

Starburst affect

Q

What is one post processing techniques

A

Multiplanar reconstruction (MPR)