System Components & Operations

Question 1

What are the components of the ‘Rotating Frame Assembly’?

Answer 1

1. Xray Tube
2. Collimator Assembly
3. Detector Array
4. Data Acquisition System (DAS)
5. High Voltage Generator
6. Various other electrical components

Question 2

Rotation speed of the rotating frame assembly?

Answer 2

80 - 200 RPM (Rotations Per Minute)

Question 3

Purpose of the slip ring?

Answer 3

Transmits electrical power and data to components thru tiny electrical brushes

Question 4

How is an xray produced?

Answer 4

When a High Voltage (tube voltage, kV) is applied to the Cathode and Anode at a specific tube current (mA), an electron beam flows from the cathode and collides with the target material on the anode.

Question 5

Expels electrons from the circuit and focuses them in an electron beam

Answer 5

Cathode

Question 6

Shapes the electron beam width and length

Answer 6

Focusing Cup

Question 7

The process by which voltage and current are applied to the cathode which results electrons being emitted.

Answer 7

Thermionic Emission

Question 8

What determines the xray tube current?

Answer 8

mAs (milliampere per second)

Question 9

What is responsible for increasing the energy of the electron beam?

Answer 9

kVp (tube voltage)

Question 10

Range of kVp typically found on a CT scanner

Answer 10

80-140 kVp

Question 11

Theory that states that when kVp increases by 15%, then mAs will indirectly double.

Answer 11

15% rule

Question 12

What is applied to the tube filament in order to limit the amount of electrons produced when the kVp increases?

Answer 12

Space Charge Compensator

Question 13

Target that can withstand high amounts of heat made of Tungsten-Rhenium

Answer 13

Anode

Question 14

Minimum amount of time that must pass between the end of one scan and the beginning of another.

Answer 14

Interscan Delay

Question 15

How can one minimize Tube Arcing?

Answer 15

Run Tube Warmup when system has not been in use for some time.

Question 16

Two types of radiation caused by producing X-rays

Answer 16

1. Bremstrahlung radiation

2. Characteristic radiation

Question 17

Known as “braking radiation” and makes up of 90% of X-ray beam

Answer 17

Bremstrahlung radiation

Question 18

What is Tungsten’s K-Shell energy level?

Answer 18

69.5 keV

Question 19

Percent of Characteristic radiation produced in an X-ray?

Answer 19

10%-12%

Question 20

Helps to reduce the amount of low energy photons exposed to the patient.

Answer 20

Filters

Question 21

Helps to reduce scatter radiation of low energy photons.

Answer 21

Collimation

Question 22

What type of scanner does pre-patient collimation determine the slice thickness?

Answer 22

Single Slice Scanner

Question 23

What type of scanner determines the slice thickness by reconstruction?

Answer 23

Multi-Slice Scanner

Question 24

Restricts unwanted low energy x-rays from entering the detector after interacting with the patient.

Answer 24

Post-Patient Collimation

Question 25

What factors affect the efficiency and quality of a CT Scanner?

Answer 25

1. Capture Efficiency
2. Absorption Efficiency
3. Stability
4. Response Time
5. Dynamic Range
6. Reproducibility

Question 26

2 Types of detectors

Answer 26

Xenon Gas and Solid-State

Question 27

Device that converts light into usable electrical impulses

Answer 27

Photodiode