Physics Test 2 part 2

Question 1

What are the 3 steps of xray production?

Answer 1

1.Produce free electrons
2.Accelerate these electrons to a high velocity
3. Suddenly stop these high velocity electrons

Question 2

First xray tube produced?

Answer 2

Crooke’s tube

Question 3

What tube was invented in 1913?

Answer 3

Coolidge tube, still in use today.

Question 4

Tube casing or housing

Answer 4

The metal cover over the outside of the tube, it is usually made of steel with an inner lining of lead
The main purpose is to prevent leakage radiation from exposing the entire examination room and protect the tube from physical damage.

Question 5

Insulating oil

Answer 5

This is placed between the tube housing and the tube itself.
It acts as an electrical insulator as well as helps with heat dissipation.

Question 6

Glass envelope or insert

Answer 6

The outer layer of the tube itself and is made of borosilicate glass (brand name pyrex).

Question 7

Window

Answer 7

The part of the glass envelope where x-rays will pass on the way to the image receptor.

Question 8

Cathode

Answer 8

Negative electrical terminal of the x-ray tube, and made up of two parts: Filament, and focusing cup

Question 9

Filament

Answer 9

functions as the source of electrons and is made up of thoriated tungsten (tungsten with 1 to 2% thorium mixed in) to prolong filament life.

Question 10

Focusing cup or collar

Answer 10

a ring of molybdenum metal that surrounds the filament and functions to focus the cathode stream or projectile electrons into a narrow beam.

Question 11

Thermonic emission

Answer 11

The greater the current, the greater the number of electrons released and therefore, the greater the number of x-rays in the useful beam.
Eventually, electrons are ejected from the filament and situate in a small cloud around the filament called a space charge

Question 12

Anti-cathode or anode

Answer 12

The positive electrical terminal of the x-ray tube that acts as a target for stopping electrons. 2 types: Stationary, and rotating

Question 13

Stationary

Answer 13

consists of a copper rod that has one end cut at an angle and has a small insert of tungsten metal imbedded into it.

Question 14

Why is tungsten used as a target material?

Answer 14

because of its high atomic number (Z = 74) and high melting point (3410 oC).

Question 15

Rotating

Answer 15

invented in 1929 and consists of a molybdenum disk (melting point of 2,620 oC and Z = 42) with a tungsten-rhenium alloy (rhenium has a melting point of 3170 oC and a Z of 45) placed on the focal track.

Question 16

Expose or x-ray

Answer 16

this button applies the potential difference (kVp selected on the control panel) that places the positive charge on the anode.

Question 17

X-ray tube voltage or voltage across the table

Answer 17

This is controlled by the kVp selector on the control console.
Diagnostic x-ray units can range from as low as 25 kVp to as high as 150 kVp.

Question 18

X-ray tube current or current flowing across the tube

Answer 18

This is controlled by the mA selector, can vary from 10 mA to as high as 1500 mA.
This factor controls the amount of filament current, which in turn controls the filament temperature.

Question 19

Exposure time

Answer 19

Measured in seconds (s).
The range available on diagnostic units can vary from as low as 0.001 (1 millisecond) to as long as 10 seconds.

Question 20

Excitation of target atoms

Answer 20

when the electrons from the cathode strike the target atoms, most of their kinetic energy is transferred into the atoms, increasing their kinetic energy.

Question 21

Bremsstrahlung

Answer 21

German word for “braking radiation”.
Also known as brems radiation, general radiation, or white radiation.
This process can be responsible for between 70 and 100% of all x-rays in the useful beam, depending on the kVp selected.

Question 22

Characteristic radiation

Answer 22

can account for up to 30% of all x-rays in the useful beam, depending on the kVp selected.

Question 23

X-ray Emission Spectrum

Answer 23

A graph showing the distribution of x-rays created by bremsstrahlung and characteristic radiation, according to their energy.

Question 24

Tube loading

Answer 24

the amount of energy deposited during an x-ray exposure.

Question 25

Using high kvp and low mas

Answer 25

keeping mAs low will significantly reduce the amount of heat created inside of the x-ray tube.

Question 26

Tube rating

Answer 26

maximum allowable technique during a single exposure.

Question 27

Heat dissipation

Answer 27

after several exposures have been made, you must allow time for the heat dissipation system to remove the heat from previous exposures before new exposures are made.

Question 28

Selecting the proper anode angle for the tube in a particular room

Answer 28

A smaller anode angle has more material and surface area to absorb more of the heat.

Question 29

Using graphite backed anodes

Answer 29

A relatively new innovation, an insert of graphite is bonded to the back of the rotating anode disk.