Introduction To CT

Question 1

What does the x-ray tube in CT do?

Answer 1

It spins around to produce cross sectional images through anatomy (it produces slices of the patient’s body)

Question 2

What part of CT is this?

Answer 2

CT x-ray tube

Question 3

What does CT stand for?

Answer 3

Computed Tomography

Question 4

What are the advantages of CT?
(6)

Answer 4

The images are acquired in slices

We can see soft tissue

Blood vessels can be visualised

Large areas can be imaged in a short space of time

Functional information

It can indicate what type of lesions someone has by how the lesion interacts with the contrast

Question 5

How was CT founded?

Answer 5

Godfrey Hounsfield discovered that if an x-ray beam was passed through an object from all directions and measurements were made, information about the internal structure of the body could be obtained

Question 6

Label the CT scanning room:

Answer 6

Question 7

What is the gantry?

Answer 7

Where the x-ray tube is

Question 8

What is the injector pump?

Answer 8

It’s what we connect the patient to when injecting the contrast into them

Question 9

What is found inside the gantry?
(2)

Answer 9

X-ray tube

Detectors

Question 10

What part of the CT scanning room is this?

Answer 10

The gantry

Question 11

Label the operator console in CT:

Answer 11

Question 12

What are the principles of CT scanning?
(4)

Answer 12

The CT scanner is an x-ray tube with a collimation device

The tube emits a very narrow, flat fan beam

The beam is aligned to an array of detectors in the form of an arc

Each detector is equidistant (on a curve) to the focal spot

Question 13

What happens to the patient during CT scanning?
(3)

Answer 13

The patient continually rotates around while the patient moves through the gantry

The x-ray beam is attenuated (absorbed) by the patient on the way to the detector (depending on their tissue, which affects how much is attenuated)

The detector will measure the amount of attenuation

Question 14

Label the CT scanner:

Answer 14

Question 15

Label the patient in the CT scanner:

Answer 15

Question 16

The denser the tissue, the … attenuation will occur

Answer 16

More

Question 17

In CT, do bones or fat attenuate more x-rays?

Answer 17

Bones

Question 18

How do the detectors work?
(3)

Answer 18

The array of detectors divide the body into linear strips

Each detector measures the attenuation that has occurred within its own strip

This information is then digitised and fed into a computer

Question 19

How is a computer used in CT?
(3)

Answer 19

The computer assigns a numerical value to the data from each detector

This value is based upon the amount of attenuation that has taken place.

This is how the image starts being produced

Question 20

What has to be done to obtain enough data to reconstruct an image?

Answer 20

Throughout the examinations, many exposures are undertaken as the patient passes through the gantry

Question 21

Where is the data needed to reconstruct an image stored?
(2)

Answer 21

In a matrix or
Data set

Question 22

What is a pixel?

Answer 22

A single square within the matrix

Question 23

What does each pixel correspond to?

Answer 23

The volume of tissue

Question 24

What is the volume of tissue known as?

Answer 24

A voxel

Question 25

What are hounsfield units?

Answer 25

The numerical value that each pixel is assigned based on the average attenuation value of the whole voxel