Anode and Energy/Heat

Question 1

What is needed to slow down/stop the electrons that are going at a high rate of speed?

Answer 1

target

Question 2

Focal track

Answer 2

actual area on the target that the incoming electrons hit

Question 3

AFS

Answer 3

actual focal spot

location of photon production

Question 4

EFS

Answer 4

effective focal spot

area on patient the beam is projected onto

Question 5

When the electrons undergo thermionic emission what do they possess and why?

Answer 5

potential energy, since they are at rest

Question 6

When voltage is applied to the anode, what do the electrons possess and why?

Answer 6

kinetic energy, since they are moving

Question 7

What is the term that describes the way the beam travels after being created at the anode?

Answer 7

isotropically

Question 8

What percentage of kinetic energy of electrons is converted to heat?

Answer 8

99.8%

Question 9

What percentage of kinetic energy of electrons is converted to useful x-rays?

Answer 9

less than 1%

Question 10

Radiation

Answer 10

transfer of heat by emission of infrared radiation

Question 11

When is the heat dissipated by the radiation?

Answer 11

during exposure

Question 12

What does the anode emit when it glows red hot?

Answer 12

infrared radiation

Question 13

What is off-focus radiation?

Answer 13

x-rays produced outside of the focal track (electrons bounce off of anode)

Question 14

What does off-focus radiation increase?

Answer 14

patient dose

Question 15

What does off-focus radiation decrease?

Answer 15

spatial resolution and contrast

Question 16

What is leakage radiation?

Answer 16

compromises in the tube housing that allow x-ray photons to exit

Question 17

Conduction

Answer 17

heat is transferred from one area of an object to another

Question 18

What is the path of conduction?

Answer 18

goes from anode, to rotor, to the glass

Question 19

Convection

Answer 19

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

Question 20

What does the heated glass enclosure raise the temperature of?

Answer 20

the oil bath

Question 21

What is the path of convection?

Answer 21

goes from glass to oil bath, oil bath to the tube housing, from tube housing to the room air

Question 22

What does a damaged focal track (target) result in?

Answer 22

an image blur

Question 23

How fast can anodes spin up to in most tubes during exposure?

Answer 23

3400 RPM

Question 24

How fast can anodes spin up to in high capacity tubes?

Answer 24

10,000 RPM

Question 25

What do fast spinning anodes allow for in a tube?

Answer 25

more heat tolerance

Question 26

A pitted anode occurs when…

Answer 26

exposures are made on a non-spinning anode