Physics - Chapter 7

Question 1

What are the essential components or the xray tube?

Answer 1

Support system
Protective housing
Glass or metal enclosure

Question 2

Protects patient and MRTs from unnecessary radiation exposure and protects from electric shock

Answer 2

Protective housing

Question 3

T/F
Leakage radiation is less than 1 mGya/s at 1 meter

Answer 3

True

Question 4

What is the window called where X-rays are emitted?

Answer 4

Useful beam

Question 5

What are X-rays called that escape through the protective housing?

Answer 5

Leakage radiation

Question 6

What is the xray tube contained in?

Answer 6

A vacuum

Question 7

What is the purpose of the xray vacuum?

Answer 7

-Efficient xray production
-Extends tube life
-Less heat produced

Question 8

What is the length and diameter of an xray vacuum?

Answer 8

Length = 30-50cm
Diameter = 20cm

Question 9

Negative side of the xray tube

Answer 9

Cathode

Question 10

What are the 2 primary components of the cathode?

Answer 10

-filament
-focusing cup

Question 11

What is the size of the filament?

Answer 11

Length = 1-2cm
Diameter = 2mm

Question 12

Emits electrons when heated

Answer 12

Filament

Question 13

Outer shell electrons are boiled off the filament and and ejected

Answer 13

Thermionic emission

Question 14

What are filaments usually made from?

Answer 14

Thoriated tungsten

Question 15

T/F
The boiling point of tungsten is 3410 degrees Celsius and it does not vaporize easily

Answer 15

True

Question 16

What charge does the focusing cup have?

Answer 16

Negative

Question 17

What is it called when an xray tube has two focusing cups side by side?

Answer 17

Small and large focal spot

Question 18

What is the purpose of the focusing cup?

Answer 18

Negatively charged cup confines electrons to a small area of the anode

Question 19

Electron cloud formed around the filament

Answer 19

Space charge

Question 20

What defines the focal spot size?

Answer 20

The size of the filament

Question 21

What is the size of a small filament?

Answer 21

0.1-1cm

Question 22

What is the size of a large filament?

Answer 22

0.3-2cm

Question 23

Positive side of the xray tube

Answer 23

Anode

Question 24

What are the two types of anodes?

Answer 24

Stationary and rotating

Question 25

What are the functions of the anode?

Answer 25

Conducts electricity Radiates heat and X-rays from the target

Question 26

How much of the kinetic energy is transferred to thermal energy when the electrons strike the target

Answer 26

99%

Question 27

What are the most common anode materials?

Answer 27

Copper, molybdenum, graphite

Question 28

Area of the anode struck by the electrons

Answer 28

Target

Question 29

What is the target made of?

Answer 29

Tungsten

Question 30

What is the atomic number of tungsten?

Answer 30

74

Question 31

Thin shaft between the anode and rotor, usually made of molybdenum

Answer 31

Anode stem

Question 32

What is used to turn the anode?

Answer 32

Induction motor

Question 33

The part outside the glass or metal enclosure, consists of a series of electromagnets equally spaced around the neck of the tube

Answer 33

Stator

Question 34

Inside the glass or metal enclosure, a shaft made of bars of copper and soft iron fabricated into one mass

Answer 34

Rotor

Question 35

Spot of interaction between electrons and anode to produce xray photons

Answer 35

Focal spot

Question 36

When the target angle is smaller, the effective focal spot is…

Answer 36

Smaller

Question 37

What is the angle of the target in diagnostic xray tubes?

Answer 37

5-20 degrees

Question 38

T/F Effective focal spot increases with with increasing angle

Answer 38

True

Question 39

The xray beam has a higher intensity on the cathode side than the anode side, what is this called?

Answer 39

Anode heel effect

Question 40

What can the intensity vary up to with the anode heel effect?

Answer 40

45%