Computed Tomography- Lecture One

Question 1

What is the most significant development in radiology in the past 40 years?

Answer 1

Computed Tomography

Question 2

Do MRI and Ultrasound use x-ray to produce image?

Answer 2

No

Question 3

How does the x-ray tube move for computed tomography?

Answer 3

It spins around the patient

Question 4

When does tomography trace back to?

Answer 4

1920’s

Question 5

How does tomography “cut” the body?

Answer 5

For a specific layer or section of the body

Question 6

What is axial tomography?

Answer 6

The images parallel to the long axis of the body

Question 7

What is a transverse image or one perpendicular to the long axis of the body?

Answer 7

The x-ray tube moves across the image

Question 8

How is conventional tomography and computed tomography different?

Answer 8

Conventional uses axial tomography (parallel to the long axis of the body)
Computed uses transverse image
(One perpendicular to the axis of the body)

Question 9

Who laid down the roots of tomography in terms of mathematics? And when?

Answer 9

Radon; 1917

Question 10

What did Godrey Hounsfield conclude from his investigational work with pattern recognition and reconstruction techniques by using computers? And when?

Answer 10

He found that when an x-ray beam passed through a body from all directions and measurements were made of all of these transmissions, information about the internal structures of the body can be obtained
1967

Question 11

When was CT developed by Godrey Hounsfield?

Answer 11

1969

Question 12

What was the EMI scanner used for?

Answer 12

To CT brains only

Question 13

Who did Hounsfield share the Nobel Prize in Medicine and Physiology with?

Answer 13

Alan Cormack of Tufts University.

Question 14

How did Cormack contribute to win the Nobel Prize?

Answer 14

He worked out the mathematical solutions to problems in CT

Question 15

How many major design advancements has CT been through since 1970?

Answer 15

Five

Question 16

What did each major design advancement improve?

Answer 16

Scan time and resolution or image quality

Question 17

Scan times have been reduced from _____ to ______

Answer 17

5 minutes to 50 ms

Question 18

What did the first scanner use?

Answer 18

a very tightly collimated pencil beam

Question 19

How many degrees did the 1st generation CT scanner rotate?

Answer 19

180 degrees

Question 20

How many degrees would the 1st generation CT scanner rotation per image?

Answer 20

1 degree

Question 21

How long would it take for one image from the 1st generation CT scanner to process?

Answer 21

5 minutes

Question 22

How many detectors did the 1st generation CT scanner have?

Answer 22

1 detector

Question 23

How many degrees would the 2nd generation CT scanner rotate?

Answer 23

180 degrees

Question 24

Why was there more scatter radiation from the 2nd generation CT scanner?

Answer 24

It used fan beam collimation

Question 25

How many detectors did the 2nd generation CT scanner have?

Answer 25

5 to 30 detectors

Question 26

How many degrees would the 2nd generation CT scanner rotate per image?

Answer 26

10 degrees per translation & 18 per scan

Question 27

Which had a faster scan time the 1st or 2nd generation CT scanner?

Answer 27

2nd

Question 28

How much would the 3rd generation CT scanner rotate?

Answer 28

360 degrees

Question 29

What kind of beam was used in the 3rd generation CT scanner?

Answer 29

A fan shaped beam of 30-60 degrees for full coverage

Question 30

How did the 3rd generation CT scanner have constant Source to detector distance?

Answer 30

Due to curvilinear detector array

Question 31

What happens if one detector fails in a 3rd generation CT scanner?

Answer 31

A ring appears

Question 32

Will a radiologist read a scan if there is a ring artifact?

Answer 32

NO

Question 33

What is the scan time for the 3rd generation CT scanner?

Answer 33

1 sec

Question 34

What does the 3rd generation have compared to the 1st and 2nd?

Answer 34

Superior reconstruction and resolution

Question 35

Why didn't the 4ht generation Ct scanners last long?

Answer 35

-Cost of the detectors -Too much scatter given off

Question 36

How many detectors are used in the 4th generation CT scanner?

Answer 36

As many as 8000 detectors

Question 37

What is the scan time for the 4th generation CT scanner?

Answer 37

1 sec

Question 38

What was eliminated from the 4th generation compared to previous scanner and how?

Answer 38

The ring artifact because it uses auto-detector calibration

Question 39

What kind of beam does the 4th generation CT scanner use?

Answer 39

Fan beam; high radiation dose compared to earlier scanners

Question 40

How does the 4th generation take an image?

Answer 40

The tube rotates around the stationary ring of detectors

Question 41

What was the 5the generation specifically used for?

Answer 41

Cardiac

Question 42

What does the 5th generation allow?

Answer 42

For continuous rotation of the tube for spiral CT

Question 43

What did the Heartscan by Imatron use?

Answer 43

An electron beam instead of x-ray tube and 50ms scan times

Question 44

What does spiral CT allow for?

Answer 44

Continuous or even overlapping data acquisition

Question 45

What would happen as the tube spins in the 5th generation?

Answer 45

the table would move

Question 46

Spiral Ct was made possible by what?

Answer 46

Slipring technology

Question 47

How did the slipring change CT?

Answer 47

It allowed the tube to continuously rotate 360 degrees versus previously without it, it needed to stop after each rotation with conventional CT

Question 48

How many detectors are used in Spiral CT?

Answer 48

As many as 14,600, each 1.25mm wide

Question 49

What does the large amount of detectors in Spiral CT allow?

Answer 49

Allows multiple slices to be made with one scan and move tissue volume to be imaged

Question 50

What are benefits of Spiral CT?

Answer 50

-Less motion artifacts -Improve lesion detection because the reconstructed image can be at arbitrary intervals -Reduced partial volume because of overlapping reconstruction intervals -Reduced scan time -Advances in computer processing allows for multi-planar reconstruction and even 3D reconstruction

Question 51

What are basic CT scanner components?

Answer 51

-Gantry includes the pedestal or table, tube, collimators, detectors, and high voltage generator -Mechanical supports -Operators Console -Computers

Question 52

How many steps does the formation of CT images by a CT scanner involve and what are they?

Answer 52

3 steps 1- Date Acquisition 2- Image reconstruction 3- Image Display

Question 53

What is Data acquisition?

Answer 53

Refers to the collection of x-ray transmission measurements from the patients

Question 54

What are components of data acquisition?

Answer 54

-Generator, Gantry, and patient table

Question 55

What are power ratings for the high-frequency generator?

Answer 55

Typically from 30 to 60 kilowatts