Tube rating charts

Question 1

Name the external components of an x-ray tube

Answer 1

1. Ceiling Support system
2. Floor to ceiling support system
3. C-arm support system
4. Protective housing
5. Glass/metal enclosure

Question 2

Which x-ray unit is most common

Answer 2

The ceiling support system

Question 3

Leakage radiation must be no more than ____>

Answer 3

1 mGy/hr @ 1 meter from the source

Question 4

What is the purpose of protective housing

Answer 4

guards against excessive radiation exposure & electric shock

Question 5

What is the tube ( anode & cathode) enclosed by?

Answer 5

Glass vacuum

Question 6

What surrounds the glass vacuum x-ray tube

Answer 6

metal housing

Question 7

What happens when the area inside the glass tube housing is not a vacuum?

Answer 7

the electrons collide with other atoms when traveling from the cathode to the anode and thus, creates less x-rays or lower energy xrays, AND decreases the efficiency of the tube.

Question 8

What are the internal components of the x-ray tube

Answer 8

Cathode and Anode

Question 9

Where does thermionic emission take place

Answer 9

in the cathode side of the tube

Question 10

What does the cathode consists of

Answer 10

• negative side of tube*
  Contains:
  -Filaments
  -Focusing cup

Question 11

What is the positive side of the x-ray tube

Answer 11

anode

Question 12

What are the 2 types of anodes

Answer 12

1. Rotating
   (used in x-ray)
   2.Stationary
   (used in dental)

Question 13

Why are rotating anodes used in general x-ray

Answer 13

because they can produce high intensity x-ray beam in a short amount of time

Question 14

What is the anode made of

Answer 14

1. Tungsten
2. Molybdenum
3. Rhodium

Question 15

Why is tungsten used in the anode

Answer 15

1. High atomic #
2. Thermal conductivity
3. High melting point

Question 16

What is the element for:

1. Tungsten
2. Molybdenum
3. Rhodium

Answer 16

1. W
2. Mo
3. Rh

Question 17

Fixed electromagnets of the tube are called

Answer 17

Stators

Question 18

What is the purpose induction motor of anode

Answer 18

It is an electric motor where magnetic field is supplied to fixed electromagnets called stators to rotate the rotor of the anode

Question 19

Electric motor where magnetic field is supplied to fixed electromagnets called stators to rotate the rotor of the anode

Answer 19

Induction motor of anode

Question 20

What is the line focus principal

Answer 20

A designed added to x-ray tube targets that allow for larger heating areas while a small focal spot is maintained

Question 21

How is focal spot size controlled

Answer 21

Controlled by angle of the target

Question 22

Effective focal spot size is _____ than the actual spot size

Answer 22

less than the actual spot size

Question 23

The larger the target angle the ____ focal spot size

Answer 23

larger

Question 24

How does a change in focal spot affect the anode

Answer 24

the tube changes the location of the anode

small= towards center of anode

Large= edge of anode

Question 25

What is an undesirable result of line focus principal

Answer 25

unequal radiation intensity across the anode & the cathode

Question 26

Intensity is greater on the ___ side, as a result of electrons hitting the target at different depths

Answer 26

Cathode

Question 27

The ___________ the anode angle, the larger the heel effect

Answer 27

smaller

Question 28

What are some of the things we use to reduce the anode heel-effect

Answer 28

Filters

Question 29

What are 3 ways that heat is dissipated from the x-ray tube

Answer 29

1. Radiation 2. Conduction 3. Convection

Question 30

The transfer of heat by the emission of infrared radiation is _____

Answer 30

Radiation

Question 31

The transfer of energy from one area of an object to another is _____

Answer 31

Conduction

Question 32

The transfer of heat by a movement of a heated substance from one place to another

Answer 32

Convection

Question 33

Excessive heat results in ____

Answer 33

reduced x-ray tube life

Question 34

What do we do as technologists to prolong tube life?

Answer 34

Tube warm up

Question 35

Name factors that prolong tube life

Answer 35

1. Tube warm up 2. Low techniques 3. Faster IR's/screens

Question 36

Maximum radiographic techniques should never be applied to a cold anode. Why?

Answer 36

anode pitting occurs = this means that the tungsten removed during pitting get deposited in the glass envelope of tube housing which causes tube arching

Question 37

What are the 3 types of tube failure

Answer 37

1. excessive heat during single exposure 2. maintaining anode at elevated temperatures 3. Filament

Question 38

What does excessive heat during exposure cause?

Answer 38

causes anode to crack which is then unstable during rotation

Question 39

Name the 3 types of rating charts

Answer 39

1. Radiographic` tube rating charts 2. Anode cooling chart 3. Housing cooling chart

Question 40

Which rating chart is most important and why

Answer 40

Radiographic rating chart because it details which techniques are safe to use and which are not for tube operation

Question 41

Phase refers to what type of generator the tube is powered by…. What are some types of generators?

Answer 41

``` single phase three phase high frequency half wave full wave ```

Question 42

Large effective focal spot has which anode angle?

Answer 42

Large

Question 43

How is thermal energy in x-ray applications measured in

Answer 43

Heat Units (HU) or Joules (J)

Question 44

The capacity of the anode and the housing to store heat is measured in ___?

Answer 44

HU | Heat units

Question 45

1 heat unit is equal to ___ kVp ___mA ___ s

Answer 45

1 kVp 1 mA 1 s

Question 46

How would you find a HU for single phase

Answer 46

kVp x mA x time

Question 47

How would you find HU for High frequency circuit

Answer 47

kVp x mA x time x 1.4

Question 48

The ____ will overheat long before the tube housing will

Answer 48

anode

Question 49

Why does the anode overheat before the tube housing?

Answer 49

1. the anode is being directly bombarded with electrons, where the tube housing is indirectly bombarded AND 2. the anode is made of tungsten where the tube housing is made of an insulator material)