Chapter 5

Question 1

What is general tube construction?

Answer 1

• lead lining
• oil bath
• cooling fans
• electrical insulation
• large cables
• absorbs stray photons

Question 2

Why would a tube housing get hot?

Answer 2

With continuous use

Question 3

X-ray tubes act as a what?

Answer 3

As an electronic vacuum

Question 4

What does an x-ray tube consist of?

Answer 4

• anode
• cathode
• induction motor
• encased in a glass or metal enclosure

Question 5

What is a glass envelope made up of?

Answer 5

Generally made of borosilicate glass because its heat resistant

Question 6

What is a metal envelope made up of?

Answer 6

Strong metal like copper or steel, it provides constant electrical potential

Question 7

What is the positive side of an x-ray tube?

Answer 7

Anode

Question 8

Anodes provide a _____ for electrons to produce x-rays.

Answer 8

A target

Question 9

An anode serves as?…

Answer 9

An electrical and thermal conductor

Question 10

What are 2 types of anode?

Answer 10

• stationary anode
• rotating anode

Question 11

Stationary anode is made up of?

Answer 11

It’s a tungsten button embedded in a copper rod

Question 12

What is the advantage and disadvantage of a stationary anode?

Answer 12

Advantage:
Disadvantage: rapidly building heat can damage the tube which limits use

Question 13

Rotating anode is made up of?

Answer 13

Rotating tungsten-coated molybdenum disc mounted on a copper shaft with a molybdenum core

Question 14

What is the advantage and disadvantage of a rotating anode?

Answer 14

Advantage: spreads heat produced during x-ray production over a larger surface area
Disadvantage:

Question 15

Copper is used a part of ?…

Answer 15

Is part of the shaft because it has excellent thermal and electrical conductive properties

Question 16

Molybdenum is part of?…

Answer 16

Is used as a disc base & core because it has a low thermal conductivity and it is a light but strong alloy

Question 17

Tungsten is used for?

Answer 17

It’s used because it has a very high melting point and a high atomic # (74), improving the efficiency of x-ray production

Question 18

What is rhenium used for?…

Answer 18

It can be added to the tungsten to increase thermal capacity and tensil strength

Question 19

What does an induction motor consist of and do?

Answer 19

Consist of : stator and rotor
It allows the rotation of the anode in a vacuum without engineering a motor into the vacuum

Question 20

What is a stator?

Answer 20

Is made up of electromagnet arranged in pairs around the rotor

Question 21

What is the rotor?

Answer 21

an iron core surrounded by coils.

Question 22

What is the line focus principle?

Answer 22

A large actual focal spot size can be maintained and a small effective focal spot size can be created

Question 23

Target face less than 45 degrees is ?…

Answer 23

An effective focal spot will be smaller than the actual

Question 24

Target angles 7 to 18 degrees are?…

Answer 24

Are for a general purpose tube (12 degrees is the most common)

Question 25

The smaller the effective focal spot, the?…

Answer 25

The sharper the image will be

Question 26

What is the anode heel affect?

Answer 26

Decreases the intensity of the x-ray beam to be less because it is absorbed in the target heel

Question 27

What does a cathode do?

Answer 27

It provides the source of the electrons needed for x-ray production

Question 28

Where is the cathode located?

Answer 28

It’s the negative end of the tube

Question 29

What is the dual focus tubes?

Answer 29

General purpose tubes with two filaments

Question 30

What is a focusing cup made up of?

Answer 30

Nickel and surrounding the filaments back and sides

Question 31

What shortens an x-rays tube life?

Answer 31

- frequent high or maximum exposure factors - low but longer exposure factors - overloading the Filament

Question 32

what are the 3 processes of heat transfer?

Answer 32

- Conduction of heat by tolerant materials - Radiation of heat energy from anode to oil bath - Convection of heat into the room by cooling fans

Question 33

Heat units are a measure of what?

Answer 33

a measure of the amount of heat stored in a particular device

Question 34

how to calculate heat units?

Answer 34

kVp * mA * s * c If there are multiple exposures, the formula is multiplied by the # of exposures

Question 35

how do you extend x-ray tube life?

Answer 35

- warm up machine - do not prep the rotor exclusively - do not routinely use extremes of exposure factors