5. The x-ray tube (P1)

Question 1

What movement does a floor mounted support system do?

Answer 1

Limited:
-Vertical
-Transverse
-Longitudinal

Question 2

What is a C/U arm system used for?

Answer 2

IV radiography suites

Question 3

What 4 types of protection does the protective housing provide?

Answer 3

1. Radiation protection
2. Electrical protection
3. Thermal protection
4. Physical protection

Question 4

What type of physical protection is in the x ray tube

Answer 4

Lead lined except for window

Question 5

What type of electrical protection is used in the x-ray tube?

Answer 5

-High V receptacles
-Tube made of glass
-Oil

Question 6

Why is it beneficial to have the tube made of glass and filled with oil?

Answer 6

It doesn’t transmit current and oil moves heat away

Question 7

What thermal protection is used in the tube?

Answer 7

Oil-moves the heat away by absorbing it
Cooling fan

Question 8

What type of glass is the tube made of and why is it beneficial?

Answer 8

Pyrex:
-It has a VERY high heat capacity
-Is an insulator

Question 9

When would you use a metal tube?

Answer 9

When you use high techniques like CT

Question 10

What are the benefits to a metal tube?

Answer 10

-Tungsten does not build up
-You can control the potential
-Less tube wear, higher lifespan

Question 11

What are the two filaments used for?

Answer 11

-Small focal spot size
-Large focal spot size

Question 12

What is the benefits of a tungsten coil around the filaments?

Answer 12

-Has a high melting point (prevents wire from melting)
-Has a low vapour pressure

Question 13

What is the filament?

Answer 13

The source of electrons

Question 14

Explain thermionic emission in an x ray tube:

Answer 14

1. Current makes heat (2200 C) in the tungsten wire
2. Heat gives more energy to e-
3. Electrons escape conduction band forces (essentially burned off wire and travel)

Question 14

What is space charge?

Answer 14

It is when e- form a cloud around the filament (+) when you have your finger halfway down on the exposure button

Question 15

When you select a high kVp, what happens to the filament heating current and the space charge size? What would happen with low kVp?

Answer 15

High kVp:
It decreases as its easier to pull mA across tube

Low kVp:
It increases

Question 16

What are compensation circuits?

Answer 16

IT is a space charge compensating circuit that ensures mA is what we choose

Question 17

What is the difference between filament current and tube current?

Answer 17

Filament current: Creates a space charge/during prep button, measured in A

Tube current: Allows the mA to flow across the tube/during exposure button, measured in mA