mi 132 unit 3

Question 1

what are the 4 conditions needed for xray production?

Answer 1

source, acceleration, deceleration and focusing

Question 2

what type of efficiency is creating xrays?

Answer 2

non-efficient

Question 3

what are the two things produced from xray and what is their percentage

Answer 3

heat and photons. 99% heat and 1% photon

Question 4

what are the three main xray components

Answer 4

cathode, anode and rotor (all in envelope)

Question 5

what is crooks tube?

Answer 5

1st tube used when xrays were discovered

Question 6

what is the coolidge tube

Answer 6

second tube used that had enough power to create thermionic emission

Question 7

what does the cathode do?

Answer 7

it produces a thermionic cloud where high voltage is and streams focus
-its the negative side of the tube
-it focuses electrons to the anode

Question 8

where is the filament ?

Answer 8

it sits in the focusing cup

Question 9

what is the focusing cup ?

Answer 9

it narrows the electron stream to the target
-it is connected to the secondary circuit

Question 10

what is the focusing cup made up of?

Answer 10

its made of nickel and surrounds the filaments

Question 11

what is electrostatic repulsion ?

Answer 11

in the anode and cathode, it repels electrons away

Question 12

what is the space charge effect?

Answer 12

it is a cloud that builds up to a point where it cant hold anymore electrons

Question 13

what is the filament and what is it made up of ?

Answer 13

it creates electron clouds and it is made up of Tungsten and thorium

Question 14

what is tungsten

Answer 14

material in the anode that had a high melting point
-does not vaporize easily

Question 15

when would you use different size filaments ?

Answer 15

small filament is for smaller body parts
large filament is for larger body parts

Question 16

what is the anode disk and stem made from?

Answer 16

tungsten (#74), molybdenum, rhenium and thorium

Question 17

what is the purpose of the anode ?

Answer 17

it is the positive side of the tube that acts as a target or source for xray photons
-it takes heat and energy and puts it back into the xray circuit
-electrical and thermal conduction occurs here
-dissipates heat during xray production

Question 18

where does deceleration occur?

Answer 18

in the anode

Question 19

what is the stationary anode made up of

Answer 19

it is made of tungsten and copper (They do not move)

Question 20

rotating anode

Answer 20

have a large target area and use in most tubes today
-anout 5-13 cm in diameter

Question 21

purpose of molybdenum

Answer 21

It can double the heat producing activities with a high melting point

Question 22

purpose of rhenium

Answer 22

its added to tungsten because it allows for greater elasticity

Question 23

set up of the anode

Answer 23

made of molybdenum, coated with tungsten, mounted on copper with rhenium cord

Question 24

anode heel effect

Answer 24

-has greater intensity on the cathode side
-impacted by: decreased angle, lower SID and increased field size (they all increase the anode heel effect)

Question 25

what does thorium do

Answer 25

extends tube life

Question 26

effective focal spot

Answer 26

origin of electrons before turning into xray photons

Question 27

focal spot

Answer 27

physical area that is impacted or hit

Question 28

line focus principle

Answer 28

goal is to have LARGER focal spot size with SMALL effective focal spot size -smaller the angle, the better -we want a larger focal spot because we want to spread heat out -smaller focal spot is sharper or produces better quality image

Question 29

what is a good angle for focal spot size

Answer 29

angle between 7-18 degrees, 12 is the most common (smaller tube angle creates greater anode heel effect)

Question 30

why should the cathode be bigger

Answer 30

cathode has higher electron density that can penetrate through thickness

Question 31

what is the induction motor?

Answer 31

last part inside the actual xray tube -where mutual induction is -where electricity of coil to the secondary coil touches

Question 32

stator

Answer 32

stationary part on the outside -rotor is on the outside of the envelope -pairs of electromagnets will create electromagnet energy -SUPPLIED WITH ALTERNATING CURRENT

Question 33

rotor

Answer 33

iron core, surrounded by copper shaft -will spin and align itself for mutual induction

Question 34

ball bearings

Answer 34

little balls that reduce friction and help with rotation

Question 35

what is the induction motor speed

Answer 35

3400 rpm

Question 36

purpose of the envelope

Answer 36

provide a vacuum -focus electrons -provide thermionic emission -create xrays -we prefer metal ones -has window, which is the exit point for xrays to leave (5 cm)

Question 37

main components of xray housing

Answer 37

-lead/ steal housing (absorbs leakage) -insulating oil (diametric oil that doesn't boil) -cooling fan ( draws heat away from tube) -large electric cords (power tube)

Question 38

what is leakage radiation

Answer 38

photons that escape from the housing (except for the window or rotator) -NO GREATER THAN 1 MGRY A HOUR AT A DISTANCE OF 1 METER

Question 39

what is anode also made out of

Answer 39

lithium

Question 40

what does the 1st part of the anode do?

Answer 40

heats up and creates speed -has the induction motor -filament is energized here -thermionic cloud builds here -we need speed for exposure to happen

Question 41

what type of transformer occur in the anode ?

Answer 41

auto transformer goes to step up transformer so that potential difference can happen

Question 42

why do we need potential difference?

Answer 42

we need an acceleration of electrons

Question 43

what are tube rating charts ?

Answer 43

they tell the technologist what techniques to use and which ones are unsafe

Question 44

what is the cooling chart?

Answer 44

it tells how long it will take the tube to cool down and how long it will take for housing to cool down

Question 45

what are the heat units and the phases ?

Answer 45

-three phase, 6 pulse = 1.35 -three phase 12 pulse = 1.41 -high frequency = 1.45 single phase = 1

Question 46

three stage process of heat transfer

Answer 46

-convection= movement of heat from one place to another -conduction -radiation -oil baths are the most common

Question 47

what factors damage the xray tube?

Answer 47

-thermal problems -rotating tube housing too quickly -slow leak -arching -anode cracking/ pitting -rough handling

Question 48

what can we do to extend xray tube life?

Answer 48

-follow warm up guidelines -pressing switch in motion -slower mA stations

Question 49

line focus principle

Answer 49

small effective focal spot size and large actual focal spot size

Question 50

what does the anode heel effect result in

Answer 50

less exposure on the anode side because the heel is on the path of the beam