System Operation And Components.

Question 1

Console:

Answer 1

Where instructional commands are entered by the CT tech and images are viewed.

Question 2

Host computer:

Answer 2

Each command is shuttled through the host computer, translated into the system machine’s language, and passed on to the scan controller. Final images are also transferred to the host computer so it can be stored in PACS or displayed on the console.

Question 3

Scan controller:

Answer 3

Is responsible for the timing and operation of the pt table, gantry & high-voltage generator.

Question 4

DAC:

Answer 4

Digital Analog Converter: receives electronic signals from the scan controller and converts these digital signals to analog.

Question 5

High voltage generator:

Answer 5

Produces high voltage potential that exists between the cathode and anode.

Question 6

Amplifier:

Answer 6

Amplifies electrical signals from the detectors.

Question 7

S/H component:

Answer 7

Where amplified signals are sampled and then sent to the ADC.

Question 8

ADC:

Answer 8

Analog to Digital Converter. Electrical signals are received from the S/H component and digitized here, then sent to the array processor.

Question 9

Array processor:

Answer 9

Where the raw digitized information is calculated into an image.

Question 10

When was the first CT system introduced for clinical use?

Answer 10

1973

Question 11

What kind of beam & detectors did first generation scanners use?

Answer 11

Pencil beam & single detector.

Question 12

What was the shortest scan time for a first generation scanner?

Answer 12

5 minutes.

Question 13

What part of the body was first generation scanners used for and why?

Answer 13

Head, patient motion was more easily controlled for head images.

Question 14

What kind of beam and detector does second generation scanners use?

Answer 14

Fan beam and a detector array (a group of detectors.).

Question 15

How fast can a second generation scanner scan?

Answer 15

As little as 20 seconds vs a first generation scanning 5 minutes.

Question 16

What are the two most important features of second generation scanners?

Answer 16

Fan beam geometry and the introduction of the detector array.

Question 17

When were third generation scanners introduced?

Answer 17

1975

Question 18

What improvements do third generation scanners have?

Answer 18

Curved detector array (improves reproducibility and minimizes artifacts), Tube & detector rotate around pt, detectors range from several hundred to several thousand, & scan times can be less than 1 second per image.

Question 19

Fourth generation scanner improvements:

Answer 19

4th generation scanners did not end up with more advancements, rather different approaches to achieve similar results (stationary detector ring that angles during the scanning process.).

Question 20

What was the major improvement introduced with continuous rotation scanners?

Answer 20

The slip ring, solving the problem of needing to “unwind” the cables after each scan. This led to the development of helical scanning.

Question 21

All major manufacturers offered MDCT by what year?

Answer 21

1998

Question 22

Improvements seen with MDCT:

Answer 22

*Faster scans
*Increased anatomical coverage
*Scanning with thinner slices to improve resolution along slice direction.

Question 23

EBCT: what does it stand for & when was it made available?

Answer 23

Electron beam CT & 1980’s

Question 24

What was EBCT used for until MDCT scanners were introduced?

Answer 24

Cardiac images

Question 25

EBCT does not use an xray tube. What does it use?

Answer 25

An electron beam is streamed from an electron gun that is electromagnetically directed toward an array of tungsten anodes.

Question 26

How fast does EBCT complete a rotation?

Answer 26

50-100 milliseconds, making it useful for cardiac imaging.

Question 27

PET/CT benefits

Answer 27

Because PET scans are low resolution, overlaying a high-res CT image helps ID a metabolic change in a specific structure.

Question 28

What is cone beam CT used for?

Answer 28

Oncology. Helps to verify patient positioning prior to receiving radiation.

Question 29

Gantry:

Answer 29

Contains xray tube & detectors, pt table is fed through the aperture, & slip ring & high voltage generator are in the gantry.

Question 30

Z-axis:

Answer 30

Long axis of body. Head to feet.

Question 31

X-axis:

Answer 31

Pt’s left to right.

Question 32

Y-axis:

Answer 32

Pt’s anterior to posterior.

Question 33

Bremsstrahlung:

Answer 33

When a fast moving electron directly collides with the nucleus (highly unlikely) or enters the vicinity of the nucleus, and causes the electron the slow down, losing energy and in result, causing an xray photon.

Question 34

Characteristic radiation:

Answer 34

When a fast moving electron collides within the inner ring of a target atom, ejecting an inner shell electron which is replaced with an outer shell electron, forming an xray photon.

Question 35

What percentage of an xray beam is usually characteristic radiation?

Answer 35

10-12%