CT P1

Question 1

What is CT

Answer 1

an imaging procedure that uses X-ray equipment and computer processed measurements taken from different angles to produce cross sectional images

Question 2

Name two CT limitations

Answer 2

1: superimposed structures
2: different structures with low contrast

Question 3

what is the function of a CT detector?

Answer 3

conversions of X-ray into electrical signal

Question 4

what are the CT detector characteristics?

Answer 4

1. small in size because better spatial resolution
2. allows many detectors to be connected to form an array
3. high dictation efficiency and high sensitivity to capture a wide dynamic range
4. fast response
5. high stability to function under the high speeds of rotating granty

Question 5

what are the main functions of an Xray tube?

Answer 5

they have longer faster continues exposure times at higher KV and mAS
They have larger and thicker anode to absorb and dissipate large amounts

Question 6

what are the advantages of metal cermaic tubes

Answer 6

1.higher tube loading
2. longer tube life
3.spiral groove bearing uses Liquid Metal alloy as lubricant

Question 7

what does Stratton xray tube do?

Answer 7

allows the entire tube body to rotate rather than just the anode

Question 8

what is a slip ring

Answer 8

a slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure.

Question 9

how many CT scanner generations are there

Answer 9

3

Question 10

what’s the 5th generation

Answer 10

its a developed specifically for cardiac scanning , this is known as electron beam scanners

Question 11

what’s the 6th generation

Answer 11

spiral / he

Question 12

what is the 7th generation?

Answer 12

multi detector array CT

Question 13

what is attenuation?

Answer 13

attenuation is how easily a material can be penetrated by an xray beam.

Question 14

what is attenuation coefficient?

Answer 14

a fraction of a beam of X-rays that absorbed or scattered per unit thickness of the absorber

Question 15

what is the attenuation coeffiecient equation

Answer 15

It= I0e-ux
I0= incident beam
It= transmitted beam
u-attentuation coeffieinct
X= thickness of body part imaged
e= mathematical constant

Question 16

how is an image produced?

Answer 16

CT uses a reconstruction algorithm called black projection

Question 17

what is black projection?

Answer 17

screens are designed to enhance contrast by absorbing ambient light

Question 18

what is filtered back projection

Answer 18

its used to fix the problem caused by black projection: this type of filtration picks up sharp edges within the projection and subtracts out extra smearing caused by black projection

Question 19

what is image filtering?

Answer 19

reduces x-ray intensity, but not the maximum energy of the x-ray beam spectrum.

Question 20

what is iterative reconstruction

Answer 20

Iterative reconstruction refers to an image reconstruction algorithm used in CT that begins with an image assumption, and compares it to real time measured values while making constant adjustments until the two are in agreement

Question 21

what is image matrix

Answer 21

this consist of square Matrix of picture elements which each one represents a voxel of the tissue of the patient

Question 22

What is CT windowing

Answer 22

this is when the CT image grayscale component of an image is manipulated via the CT numbers, this changes the appearance of the picture to highlight the particular structures

Question 23

what is window width (WW)

Answer 23

an images contrast

Question 24

what is WL

Answer 24

the brigthness of an image

Question 25

What is a pitch

Answer 25

speed of the table movement through the gantry defines helical pitch

Question 26

what is interpolation?

Answer 26

an estimate of a value at a certain position using known data from nearby points

Question 27

what are CT detectors and their functions?

Answer 27

1. small in size so its better for spatial resolution
2. allows for multiple detectors too be combined

Question 28

what is the attenuation coefficient?

Answer 28

it describes the fraction of a beam or xray that is absorbed or scattered per unit thickness of the absorber

Question 29

what is image reconstruction?