X-Ray Machine

Question 1

What are the 3 parts that compose the x-ray machine?

Answer 1

Tubehead
Control Panel
Arm of the machine

Question 2

What are the two types of elecric current

Answer 2

Direct current and alternating current

Question 3

What is direct current?

Answer 3

DC

Current flows in only one direction in an electric circuit

Question 4

What is alternating current?

Answer 4

AC

Current flows in one direction and then flows in the opposite direction in the circuit

Question 5

What is a cycle (in AC)?

Answer 5

refers to the flow of current in one direction, then the reversal, and flowing of the current in the opposite direction

60 cycles/sec

Question 6

What is voltage?

Answer 6

Describes the electric potential or force that drives an electric current through a circuit

Volt= the unit of measurement
kVp= max peak or voltage in AC

Question 7

What is amperage?

Answer 7

amount or quantity

Question 8

What is an ampere?

Answer 8

Measures the amount of current flowing through a circuit

Milliampere (mA)= 1/1000 of an ampere

Question 9

What is a transformer?

Answer 9

Regulates voltage. Can increase or decrease the voltage in an electric current

Question 10

What is a step up transformer

Answer 10

when the transformer increases the voltage (from 110/220 to 65,000-100,000)

Question 11

What is a step down transformer?

Answer 11

When the transformer decreases the voltage (from 110/220 to 3-5v)

Question 12

What does an autotransformer do?

Answer 12

Serves as a voltage compensator that corrects minor fluctuations in the current

Question 13

What is a coolidge tube used for?

Answer 13

Thermionic emission tube invented by Dr. W.D. Coolidge

Question 14

3 Basic elements of an x-ray tube used to produce x-rays

Answer 14

• Source of electrons within the tube
• High voltage potential to accelerate electrons across the tube
• Target to stop the electrons

Question 15

What are the 2 sides of the x-ray tube?

Answer 15

Negative side= cathode
Positive side= anode

Current flows from cathode to anode

Question 16

Devices on control panel for regulating the x-ray beam

Answer 16

On/off switch
Activating button
Regulating devices- kVp regulator, mA regulator, timer

Question 17

What is the main source of electrons in the x-ray tube?

Answer 17

Tungsten filament found at the cathode

Question 18

As the filament becomes hotter, what is happening?

Answer 18

More electrons are being produced at the cathode

Emits electrons at a rate proportional to the temperature of the filament

Question 19

What is Thermionic Emission Effect?

Answer 19

Production, or boiling off, of electrons from the heated tungsten filament

Question 20

How big is the tungsten filament? How is it mounted?

Answer 20

2mm in diameter, 1cm or less in length.

Mounted on 2 stiff wires

Question 21

What does the milliamperage dial do?

Answer 21

Controls the amount of current in the filament circuit and the number of electrons that boil off

Question 22

What is the molybdenum focusing cup?

Answer 22

Negatively charged, concave reflector that surrounds the tungsten filament and directs electrons towards the anode that contains the target

Parabolic shape. Electrostatically focuses the electrons into a narrow beam

Question 23

What is the tungsten target/focal spot?

Answer 23

Small rectangular area on the anode.

Electrons move in this direction and are repelled by the negatively charged cathode and attracted to the positively charged anode

Question 24

Characteristics of tungsten

Answer 24

High atomic number
High melting point
Low vapor pressure

Does not have a high degree of thermal conductivity– embedded in a copper stem to carry the heat generated away to the cooling system

Question 25

What does the on/off switch do?

Answer 25

Completes the filament circuit | Heats tungsten filament

Question 26

What do the milliamperage settings do?

Answer 26

Low voltage current, controls the number of electrons (quantity) Controls temperature of the tungsten coil the higher the mA, the hotter the coil; the greater the # of electrons produced in the cloud to be propelled to the target

Question 27

What does the kVp setting do?

Answer 27

High voltage current, regulates the speed of the electrons (quality) traveling from the tungsten coil to the target The higher the kVp, the faster the electrons will travel

Question 28

What is the exposure time of one impulse?

Answer 28

1/60 of a second

Question 29

What creates the formation of electron cloud at the cathode as filament circuit is activated?

Answer 29

X-ray tube

Question 30

What is the electron cloud?

Answer 30

The electrons that stay at the filament

Question 31

What is the cathode ray?

Answer 31

Stream of electrons crossing the tube from the cathode to the anode

Question 32

What are soft x-rays?

Answer 32

lower energy or less penetrating x-rays Do not penetrate tissue; produce secondary radiation Filtered out before they leave the tube

Question 33

What is used in the tube head for filtration?

Answer 33

An aluminum disc placed below the porte 2.5mm thick

Question 34

What is collimation?

Answer 34

The x-ray beam is limited before it leaves the tube head Diameter of the beam is limited by a lead diaphragm Opening is 2.75" and collimator is placed below the aluminum disk

Question 35

What is the central ray?

Answer 35

x-rays located at the center of the divergent beam

Question 36

What is penumbra?

Answer 36

That part of a shadow of an object which is larger than a point and yet represents a single point on the object Area of partial shadow The unsharpness of the image

Question 37

What is umbra?

Answer 37

Area of total shadow

Question 38

What is the ideal kVp for viewing carious lesions?

Answer 38

65-70 kVp Higher than this results in an image with a broad scale of contrast making viewing caries more difficult

Question 39

What is density?

Answer 39

The degree of blacking on an xray image Controlled by milliamperage and exposure time

Question 40

What is contrast?

Answer 40

The difference in densities between adjacent areas Primary controlling factor for contrast is kVp. High or low contrast images can be produced

Question 41

Properties of a high contrast image

Answer 41

Great deal of black and white with little gray | Produced by low kilovoltage- 45-50kVp range

Question 42

Properties of low contrast image

Answer 42

Also referred to as long scale contrast High kilovoltage range 90-100 kVp Many tones of gray in addition to whites and blacks

Question 43

What is fogging?

Answer 43

Overall grayness on a radiograph resulting from secondary radiation