lecture 2- production of x-rays PART 1

Question 1

control panel options:

Answer 1

time
kVp (voltage using)
mA selectors

then exposure button, indicator light, and audible signal

Question 2

two things inside tube head:

Answer 2

power supply and x-ray tube

Question 3

what filtrates the xray beams

Answer 3

aluminum filter

Question 4

what shapes the final shape of xray

Answer 4

lead collimator

Question 5

cathode has two elements:

Answer 5

filament and focusing cup

Question 6

filament is made of

Answer 6

tungstan

Question 7

focusing cup is made of

Answer 7

molybdenum

Question 8

this is the source of electrons and is heated with LOW voltage and emits electrons at a rate proportional to its temperature:
this action is called:

Answer 8

filament (of cathode)
and action is called thermionic emission

Question 9

what is the charge of the focusing cup of cathode and why

Answer 9

negative because need electrons to move away (toward anode)

Question 10

this focuses the electrons into a narrow beam directed to the focal spot

Answer 10

focusing cup of cathode

Question 11

what are the two elements of the anode

Answer 11

tungsten target and copper stem

Question 12

this transforms the kinetic energy of the colliding electrons into x-ray photons.

Answer 12

tungsten target of the anode

Question 13

what % of the energy from electrons produces x-rays

Answer 13

1%

Question 14

this works as a thermal conductor to remove the heat from the tungsten avoiding target melting

Answer 14

copper stem of anode

Question 15

why is tungsten a good target material?

Answer 15

cheap
high atomic number (effic. production of x-rays)

high melting point (withstand heat)

high thermal conductivity (dissipate heat away)

low vapor pressure
(maintain vaccum)

Question 16

what are the 4 conditions that are necessary for x-ray production

Answer 16

1. separation of electrons
2. production of high-speed electrons
3. concentration of electrons
4. sudden stoppage of electron steam

Question 17

this step is when low voltage filament current heats the tungsten filament to incandescence with result of separation of outer shell electrons from the tungsten atom:

this separation of electrons action is called:

Answer 17

step 1. of the 4 conditions that are necessary for x-ray production: separation of electrons

action: thermionic emission

Question 18

low voltage supply is from the:

Answer 18

step-down transformer
(6-12 volts)

Question 19

this step is where high potential difference is produced between the cathode and anode by applying a high voltage between them.

electrons accelerated to about .5 x speed of light

Answer 19

step 2. of the 4 conditions that are necessary for x-ray production: production of high-speed electrons

Question 20

this step is where the electron beam is focused by the focusing cup (negative charge) and directed towards the focal spot

Answer 20

step 3 of the 4 conditions that are necessary for x-ray production: concentration of electrons

Question 21

this step is where upon striking the focal spot in the anode, the electron stream is stopped abruptly, and kinetic energy of the electron stream undergoes conversion to greater than 99% heat and less than 1% x-radiation

Answer 21

step 4. of the 4 conditions that are necessary for x-ray production: sudden stoppage of electron steam

Question 22

what removes the heat from the tungsten in step

Answer 22

copper stem

Question 23

this is the area on the target to which the focusing cup directs the electrons and from which the x-rays are produced

Answer 23

focal spot

Question 24

what of the focal spot is important for image quality

Answer 24

size

smaller focal spot, higher spatial resolution, more heat accumulates

Question 24

what are 2 ways to overcome the focal spot accumulating more heat:

Answer 24

1. rotating anodes: allows heat at focal spot to spread out over large surface
2. stationary anodes (line-focus principle):
   angling the target to get smaller effective focal spot than the actual focal spot= better quality

Question 25

for line-focus principle, which focal spot size
1. helps with heat
2. helps with image quality

Answer 25

1. heat= actual focal spot size
2. quality= effective focal spot size

Question 26

provides a LOW-voltage current to heat the x-ray tube filament aka:

and generates a HIGH potential difference to accelerate electrons from the cathode to the focal spot on the anode aka:

Answer 26

power supply

1. step-down transformer
2. step-up transformer

Question 27

electromagnetic device that either increases or decreases the voltage in a circuit

Answer 27

transformer part of power supply

Question 28

what are the 3 types of transformer in the x-ray unit

Answer 28

1. step-down transformer (filament transformer)
2. step-up transformer (high voltage)
3. autotransformer

Question 29

the high voltage transformer (step-up) is controlled by

Answer 29

kVp

Question 30

the filament transformer (step-down) is controlled by

Answer 30

mA selector

Question 31

for the power supply, this transformer is used to convert 110 or 220 volts to 3-5 volts to heat the filament:

this is also regulated by the:

Answer 31

step-down transformer

regulated by mA switch

Question 32

increasing mA setting will increase the number of what

Answer 32

number of electrons emitted

Question 33

for the power supply, this transformer is used to convert 110 or 220 volts to 60,000 - 100,000 to move electrons across the tube:

this is regulated by:

Answer 33

step-up transformer
regulated by kVp setting

Question 34

increasing the kVp will increase the

Answer 34

energy of the electrons traveling from the cathode to anode

Question 35

this determines amount of time the high voltage circuit is applied across the x-ray tube (amount of time x-rays are produced)

Answer 35

exposure time

Question 36

time delay circuit:

Answer 36

1/3 second to heat filament

Question 37

timing circuit:

Answer 37

actual time of exposure

Question 38

on the control panel, this controls the acceleration of electrons from cathode to anode

Answer 38

kV

Question 39

on the control panel, this controls heating of the filament

Answer 39

mA