X-Ray Units

Question 1

What is the purpose of the lead shield in X-ray units?

Answer 1

To prevent electrons from traveling outside of it

Question 2

What is the purpose of the oil bath?

Answer 2

To absorb heat

Question 3

What is the purpose of copper?

Answer 3

To absorb heat

Question 4

What are the two components of the cathode?

Answer 4

filament

focusing cup

Question 5

What are the two desired properties of the cathode?

Answer 5

electrical conductivity

high vapor pressure

Question 6

How are electrons produced in the cathode?

Answer 6

By thermionic emission

Question 7

The process by which the cathode filament is heated, the electrons are boiled off and the electrons are then accelerated toward a tungsten target is called ______.

Answer 7

thermionic emission

Question 8

What is the sequence of thermionic emission and at what point are X-rays generated?

Answer 8

1. Cathode
2. Electrons
3. Anode (X-rays generated here)
4. X-rays

Question 9

What are the three desired properties of the anode?

Answer 9

electrical conductivity
high melting point
high atomic number; i.e., Tungsten

Question 10

To take advantage of a small focal spot while distributing the electrons over a larger area of the target, the target is placed at an angle to the electron beam. This is called ________.

Answer 10

line focus principle

Question 11

True or False? The angle of the target to the central ray of the x-ray beam has a strong influence on the apparent size of the focal spot.

Answer 11

True

Question 12

When are rotating anode tubes used?

Answer 12

When heavy use is demanded such as in hospitals

Question 13

How are current and voltage related?

Answer 13

They are inversely related

Question 14

The movement of electrons is known as _____.

Answer 14

electrical current

Question 15

The rate of current is the number of electrons moving past a point in a second and is measured in ______.

Answer 15

amperes

Question 16

The flow of electrons through the x-ray tube is referred to as _________.

Answer 16

tube current

Question 17

Tube current is measured in _____.

Answer 17

milliamperes mA

Question 18

The energy of the electrons is the _____.

Answer 18

voltage

Question 19

Voltage is measured in ______ and in dental radiography in _______.

Answer 19

volts, kilovolts kV

Question 20

______ translates to maximum energy of x-ray photons in a beam.

Answer 20

Peak kV or kVp

Question 21

What is the potential difference between the anode and the cathode?

Answer 21

tube voltage

Question 22

Tube voltage is measured in _____.

Answer 22

kVp or peak kilovoltage

Question 23

What is the normal voltage for dental radiography?

Answer 23

60-70kV

Question 24

What are the two primary functions of the power supply of an x-ray machine?

Answer 24

• provide a low voltage current to heat the x-ray tube filament by use of a step-down transformer
• generate a high potential difference between the anode and cathode by use of a high-voltage step up transformer

Question 25

What reduces the voltage at the cathode from 110 to 10 volts which in turn requires an increase in the amperage of the filament circuit by a factor of ten from about 500mA to 5000 mA or 5 Amps?

Answer 25

step-down transformer

Question 26

What transforms the 110 volts from the wall outlet to 65,000 to 70,000 volts which in turn requires a reduction in the amperage from 500mA to 5 to 7 Amps due to increased voltage?

Answer 26

Step-up transformer

Question 27

What are the three purpose of recitification?

Answer 27

• increased efficiency
• shortened exposure time
• more reliable radiation output

Question 28

What are the four purposes of X-ray generation?

Answer 28

• increased efficiency
• increased mean of energy of beam
• shortened exposure times
• more reliable radiation output

Question 29

_____ relates to the frequency with which successive exposures can be made.

Answer 29

Duty cycle

Question 30

What are the desired characteristics of x-ray tube housing?

Answer 30

• x-ray absorptive

- heat conductive