X-Ray Tube Test

Question 1

Cathode Assembly

Answer 1

Negative side of X-Ray tube

Question 2

Filament

Answer 2

Small, thin coil of thoriated tungsten wire.

Tungsten used due to high melting point and difficulty vaporizing

Question 3

Dual-Focus Arrangement

Answer 3

Most X-Ray tubes have dual filaments

Question 4

One reason to hold in rotor?

Answer 4

Quick exposure for pediatric patients

Question 5

Focusing Cup

Answer 5

Negatively charged, shallow depression in cathode assembly designed to house filament

Question 6

Space Charge Effect

Answer 6

Phenomenon as more and more electrons build up in area of filament, negative charges begin to oppose emission of additional electrons

Question 7

Filament saturation current

Answer 7

Achieved when no further thermionic electrons are driven towards anode

Question 8

Grid Based Tubes

Answer 8

Make it possible to regulate, pulse and synchronize x-ray production precisely

Question 9

Anode Assembly

Answer 9

Positive side of tube. Serves as primary thermal conductor

Question 10

Stationary anode X-ray tube

Answer 10

Limited to low power functions such as dental units

Question 11

Why is it important to warm up anode?

Answer 11

To bring anode from room temp to near range of operation

Question 12

Target area

Answer 12

Area on anode where electron stream hits. Also called, target, focus, focal point, focal spot and focal track

Question 13

Actual Focal Spot

Answer 13

Physical area of focal track that is impacted

Question 14

Effective focal spot

Answer 14

Area of focal spot that is projected out of tube toward object being radiographed

Question 15

Line focus principle

Answer 15

Angling of anode results in effective focal spot being smaller than actual focal spot

Question 16

Most common radiography target angle?

Answer 16

12 degrees

Question 17

Anode heel effect

Answer 17

Problem caused by use of like focus principle. Radiation intensity is greater on cathode side.
Anode is at head of x-ray table

Question 18

Stator

Answer 18

Electromagnets. Only part of cathode and anode assembly located outside vacuum of envelope

Question 19

Rotor

Answer 19

Hollow copper cylinder or cuff attached to anode disk by molybdenum shaft

Question 20

Where is cathode and anode assembly located?

Answer 20

All located in glass or metal envelope called tube. Stator not located in these structures

Question 21

Vacuum

Answer 21

Primary function is to maintain vacuum between cathode and anode

Question 22

Protective housing

Answer 22

X-ray photons a good emitted isotropically (in all directions) tube housing is designed to absorb them

Question 23

Leakage radiation

Answer 23

Any photons escaping from housing except through window. Must not exceed 100 mR/hr at 1 meter

Question 24

Off focus, or extra focal radiation

Answer 24

Photons not produced at focal spot

Question 25

X-ray production

Answer 25

Only possible under certain conditions including:
Source of electrons
Appropriate target material
High voltage
A vacuum

Question 26

Rating charts

Answer 26

3 rating charts designed to help radiographers avoid thermal damage to x-ray tube

Question 27

Extending tube life

Answer 27

Warming up anode
Not holding rotor switch unnecessarily
Using lower MA stations when possible
Using lower rotor speeds
Not making repeated exposures near tube limit
Not rotating tube housing rapidly
Not using tube when loud rotor bearings can be heard