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MI 132 > mi 132 unit 3 > Flashcards

mi 132 unit 3 Flashcards

1
Q

what are the 4 conditions needed for xray production?

A

source, acceleration, deceleration and focusing

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2
Q

what type of efficiency is creating xrays?

A

non-efficient

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3
Q

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

A

heat and photons. 99% heat and 1% photon

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4
Q

what are the three main xray components

A

cathode, anode and rotor (all in envelope)

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5
Q

what is crooks tube?

A

1st tube used when xrays were discovered

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6
Q

what is the coolidge tube

A

second tube used that had enough power to create thermionic emission

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7
Q

what does the cathode do?

A

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

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8
Q

where is the filament ?

A

it sits in the focusing cup

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9
Q

what is the focusing cup ?

A

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

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10
Q

what is the focusing cup made up of?

A

its made of nickel and surrounds the filaments

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11
Q

what is electrostatic repulsion ?

A

in the anode and cathode, it repels electrons away

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12
Q

what is the space charge effect?

A

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

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13
Q

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

A

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

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14
Q

what is tungsten

A

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

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15
Q

when would you use different size filaments ?

A

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

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16
Q

what is the anode disk and stem made from?

A

tungsten (#74), molybdenum, rhenium and thorium

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17
Q

what is the purpose of the anode ?

A

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

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18
Q

where does deceleration occur?

A

in the anode

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19
Q

what is the stationary anode made up of

A

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

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20
Q

rotating anode

A

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

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21
Q

purpose of molybdenum

A

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

22
Q

purpose of rhenium

A

its added to tungsten because it allows for greater elasticity

23
Q

set up of the anode

A

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

24
Q

anode heel effect

A

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

25
Q

what does thorium do

A

extends tube life

26
Q

effective focal spot

A

origin of electrons before turning into xray photons

27
Q

focal spot

A

physical area that is impacted or hit

28
Q

line focus principle

A

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

29
Q

what is a good angle for focal spot size

A

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

30
Q

why should the cathode be bigger

A

cathode has higher electron density that can penetrate through thickness

31
Q

what is the induction motor?

A

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

32
Q

stator

A

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

33
Q

rotor

A

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

34
Q

ball bearings

A

little balls that reduce friction and help with rotation

35
Q

what is the induction motor speed

A

3400 rpm

36
Q

purpose of the envelope

A

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)

37
Q

main components of xray housing

A

-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)

38
Q

what is leakage radiation

A

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

39
Q

what is anode also made out of

A

lithium

40
Q

what does the 1st part of the anode do?

A

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

41
Q

what type of transformer occur in the anode ?

A

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

42
Q

why do we need potential difference?

A

we need an acceleration of electrons

43
Q

what are tube rating charts ?

A

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

44
Q

what is the cooling chart?

A

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

45
Q

what are the heat units and the phases ?

A

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

46
Q

three stage process of heat transfer

A

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

47
Q

what factors damage the xray tube?

A

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

48
Q

what can we do to extend xray tube life?

A

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

49
Q

line focus principle

A

small effective focal spot size and large actual focal spot size

50
Q

what does the anode heel effect result in

A

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

MI 132 (2 decks)

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