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RADTHERA > CLINICAL RADIATION GENERATORS > Flashcards

CLINICAL RADIATION GENERATORS Flashcards

1
Q

Adequate dose cannot be delivered to a tumor beyond this depth

A

Orthovoltage
<2 cm

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2
Q

In order for an adequate dose to be delivered to a tumor in DEEP THERAPY;

A

Increase beam filtration or HVL

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3
Q

Disadvantages of Orthovoltage Therapy

A

Increase absorption in bone thus, making it unsuitable for treating tumors behind bone
Increase scattering
Depth dose distribution
Skin dose

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4
Q

In the early days, treatments where given until..

A

skin becomes red or reached its radiation tolerance

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5
Q

Limitation of Low energy beams/machines

A

Decrease depth dose distributions
Do not spare skin and normal tissue

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6
Q

Advantages of Superficial Therapy

A

Limited penetration to underlying tissues
Rapid fall off

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7
Q

KV Therapy Units/Machines

A

Grenz ray therapy
Contact therapy
Superficial therapy
Orthovoltage therapy
Supervoltage therapy

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8
Q

water cooling system is for:

A

heat dissipation

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9
Q

Requirements for Radiation Generators

A

High particle energy for penetration
High particle flux for sufficient dose rate
Energy efficient
Not too expensive
Reliable
Simple to operate
Safe

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10
Q

Megavoltage Units/Machines

A

LINAC
COBALT 60
VAN DE GRAAFF
BETATRON
MICROTRON
CYCLOTRON

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11
Q

electrostatic machine designed to accelerate charged particles

A

Van de graaff

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12
Q

device that produces microwaves

A

Magnetron

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13
Q
  • high power oscillator
  • generate microwave pulses for several microseconds
  • with a repitition rate of several hundred pulses
  • has cylindrical construction: central cathod, outer anode, and resonant cavities
A

Magnetron

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14
Q

operate at 2 MV peak power output to power low energy LINACS (6 MV/less)

A

Magnetron

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15
Q

T/F
electrons emitted from the cathode are accelerated TOWARD the anode by the action of pulsed DC electric field

A

T

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16
Q

not a generator
microwave amplifier

A

klystron

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17
Q

buncher cavity needs to be driven by a low power microwave oscillator

A

Klystron

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18
Q

velocity of electrons is altered by

A

action of electric field known as velocity modulation

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19
Q

series of discs

A

irises

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20
Q

Advantage of Microtron to LINAC

A

simplicity
easy energy selection
small beam energy spread
smaller machine

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21
Q

electrons from the gun

A

velocity of 0.8 c

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22
Q

Used to generate high energy protons and
heavy ions for therapy.
◾Used to accelerate deuterons to produce
neutrons.
◾Used for the production of radionuclide’s . i.e.
for PET

A

Medical application of cyclotron

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23
Q

Low energy photons (4 - 8 MV)

A

external wedges
fixed flattening filter
isocentric mounting
single transmission ionization
symmetric jaws

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24
Q

begin building a LINAC

A

Henry Kaplan & Edward Ginzton 1952

25
Q

Kaplan and Saul Rosenberg

A

begin trials using the LINAC with chemotherapy to treat Hodgkins disease

26
Q

1st use of cyberknife

A

1994

27
Q

High energy

A

Klystron

28
Q

Low energy

A

Magnetron

29
Q

uses changing field in operation

A

LINAC
Betatron
Cyclotron
Microtron

30
Q

uses positive charge

A

Van de graaff
Cyclotron

31
Q

applies thermionic emission

A

LINAC
Microtron
Betatron
Grenz ray
Contact therapy
Superficial therapy
Orthovoltage or deep therapy
Supervoltage therapy

32
Q

Uses filter

A

LINAC
Grenz ray
Contact or Endocavitary therapy
Superficial therapy
Orthovoltage therapy
Supervoltage therapy

33
Q

beam ha a continuous spectrum of:

A

Bremmstrahlung xrays

34
Q

the penetrating power is adjusted through :

A

beam hardening by filtration

35
Q

beam quality depends on

A

accelerating potential and voltage

36
Q

damage DNA directly :

A

electric & proton

37
Q

T/F
oxygen is best radiosensitizer in radthera

A

T

38
Q

Disadvantage of Betatron

A

low dose
limited field size
needs large treatment room due to large size
limited motion

39
Q

allow electrons to travel along the waveguide and focus the beam

A

small holes or irises between copper cells

40
Q

who invented cobalt 60 unit in the 1950s

A

Dr. Harold Johns

41
Q

radioactive cobalt 60 isotope was discovered by?

A

Glenn T. Seaborg

42
Q

cobalt 60 is produced by:

A

irradiating or neutron bombardment of a stable cobalt (59Co) in a nuclear reactor

43
Q

primary treatment for laryngeal cancer

A

cobalt 60

44
Q

components of cobalt60 machine

A

gantry
machine console
patient support
radioactive source
source housing

45
Q

cobalt60 source emits two photons per disintegration with energies of

A

1.33 MeV & 1.17 MeV

46
Q

half life of cobalt60

A

5.26 years

47
Q

uses applicators / cones for field concentration

A

Superficial therapy

48
Q

In supervoltage, the voltage was stepped up in an efficient manner because of:

A

Resonant transformer
- generatws xrays from 300 to 2000 kV

49
Q

Megavoltage Therapy Units

A

Van de graaff
Betatron
Microtron
LINAC
Cyclotron
Cobalt 60

50
Q

machine using isotopes

A

teletherapy
cobalt60
cesium137

51
Q

low energy photons 4-8 MV

A

external wedges
fixed flattening filter
isocentric mounting
single transmission ionization chamber
symmetric jaws

52
Q

medium energy photons 10-15 MV & electrons

A

bent beam
dual transmission ionization chamber
electron cones
flattening filter
movable target

53
Q

high energy photons 18-25 MV & electrons

A

achromatic magnet
automatic wedge selector
dual photon energy
dual scattering foils

54
Q

made to spread the beam to get a uniform electron fluence

A

scattering foil

55
Q

make the beam intensity uniform since LINAC ic strongly forward peaked

A

flattening filter

56
Q

for accelerating guide and RF generator

A

vacuum pumping system

57
Q

used for cooling the accelerating guide, target, RF

A

water cooling system

58
Q

for pneumatic movement of the target and other beam shaping components

A

air pressure system

59
Q

against leakage radiation

A

shielding

RADTHERA (5 decks)

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