Two Internal Structures of the X -RayTube

Question 1

electrical device used to generate x-rays

converts electrical energy to x-radiation

Answer 1

X-Ray Tube

Question 2

Most important component of the radiographic system because it is where the x ray is produced

Answer 2

X-Ray Tube

Question 3

Size of X-Ray Tube

Answer 3

30 to 50 cm long; 20 cm in diameter

Question 4

Two Internal Structures of X-ray Tube

Answer 4

Cathode and Anode

Question 5

Two parts of Cathode and their material

Answer 5

o Filament (small coil made up of thoriated tungsten)

o Focusing Cup (made up of NICKEL)

Question 6

Location of the Filament

Answer 6

Inside the focusing cup

Question 7

Filament is controlled by ——, which is ——

Answer 7

• Controlled by mAs
• mAs is directly proportional

Question 8

The area where high-speed electrons are produced

Answer 8

Filament

Question 9

Modern x-ray tubes contain two filaments, what are they?

Answer 9

Small Filament & Large Filament

Question 10

Size of Filament

Answer 10

o Usually about 2 mm in diamter
o 1 cm long: Small Filament
o 2 cm long: Large Filament

Question 11

Once the filament is heated, it will release electrons which produce an ——?

Answer 11

electron cloud or space charged electron

Question 12

repulsion of the space charge or electrostatic repulsion

Answer 12

Space Charge Effect

Question 13

As the space charge becomes more negative by boiling off more electrons, it makes it difficult for the electron to be emitted

Answer 13

Space Charge Effect

Question 14

the outer shell electrons of the filament is “boiled off”

Answer 14

Thermionic Emission

Question 15

3 Characteristics of Tungsten

Answer 15

• makes up the Filament
• Provides higher thermionic emission than other metals (thermal conductivity)
• Has a very HIGH MELTING POINT

Question 16

High Melting Point of Tungsten

Answer 16

3410 C

Question 17

metal cup where the filament is embedded

Answer 17

o Focusing Cup

Question 18

Designed to condensed electron beam to small area on focal track

Answer 18

o Focusing Cup

Question 19

4 FACTORS THAT DETERMINES THE EFFECTIVENESS OF THE CUP

Answer 19

i. Size and Shape
ii. Charge
iii. Filament Size
iv. Position of Filament within the Cup

Question 20

Three Characteristics of Anode

Answer 20

1. Mechanical support for the target
2. Dissipates heat
3. Electrical conductor

Question 21

Two parts of an Anode and their material

Answer 21

• Target (made up from an alloy of TUNGSTEN AND RHENIUM)
• Focal Spot [GRACOMO (Graphite, Copper, Molybdenum)]

Question 22

the area of the anode struck by the projectile electrons

Answer 22

Target

Question 23

actual source of radiation

Answer 23

Focal Spot

Question 24

The Focal Spot is controlled through the ——?

Answer 24

Operating Console

Question 25

The smaller the focal spot, the ——?

Answer 25

the better the resolution of the resultant image (higher spatial resolution and radiographic detail)

Question 26

Sizes of Focal Spot and their measurements

Answer 26

- Small Focal Spot (range of 0.1 mm to 0.5 mm) - Large Focal Spot (0.4 mm to 1.2 mm)

Question 27

For small extremities and is used when better spatial resolution is required

Answer 27

Small Focal Spot

Question 28

Used when technical factors that produce high heat are required (High exposure)

Answer 28

Large Focal Spot

Question 29

Two types of Anode

Answer 29

- Rotating Anode - Stationary Anode

Question 30

- **shaped like a beveled disc** - Used in general purpose x-ray tubes - Provides **greater target area** and **heat dissipation** - Has the ability to attain **greater exposure loads** by providing a **larger area** for the electron beam to interact with the target

Answer 30

Rotating Anode

Question 31

Characteristics of Rotating Anode

Answer 31

- Complex Design; - High Heat Capacity; - Used for High Exposures

Question 32

- Made up of a **tungsten target, embedded with a large copper bar** - Used in other specialized units in which high tube current and power are not required - Used in dental x-rays

Answer 32

Stationary Anode

Question 33

Characteristics of Stationary Anode

Answer 33

- Simple design; - Low Heat Capacity; - Used for Low Exposures

Question 34

Was incorporated into X-ray tube targets to allow a large area for heating while maintaining a small focal spot.

Answer 34

Line Focus Principle

Question 35

The advantage of LFP

Answer 35

provides the detail of small focal spot while allowing the large amount of heat dissipation.

Question 36

It is the electron bombarde by the cathode travelling to the anode.

Answer 36

Incident Electron Beam

Question 37

The size of the incident electron beam is determined by the ———?

Answer 37

width of the filament.

Question 38

Physical area of the anode that when bombarded by the electron beam emits X-ray.

Answer 38

Actual Focal Spot

Question 39

The Actual Focal Spot is determined by ———?

Answer 39

- width of the incident electron beam, - construction of the focusing cup and, - position of the filament in the focusing cup.

Question 40

Area projected onto the patient

Answer 40

Effective Focal Spot

Question 41

Pros of Small Actual Focal Spot

Answer 41

- Thin body parts - Small effective focal spot

Question 42

Con of Small Actual Focal Spot

Answer 42

- Poor heat dissipation

Question 43

Pros of Large Actual Focal Spot

Answer 43

- Good heat dissipation - Thick body parts - Short exposure time

Question 44

Con of Large Actual Focal Spot

Answer 44

- Long effective focal spot

Question 45

Pro of Smaller Anode Angle

Answer 45

Small effective focal spot (INCREASED SPATIAL RESOLUTION)

Question 46

Con of Smaller Anode Angle

Answer 46

- Limits the size of usable field