Part V [Clinical Radiation Generators] Flashcards
[1952, persons] begin building a medical linear accelerator
1952
Henry Kaplan and Edward Ginzton
[year] first medical linac
1956
[year, persons] begin trials using the linac with chemotherapy to treat Hodgkin’s disease
1942
Kaplan and Saul Rosenberg
[ linac generation] isocentric and could rotate 360 degrees around the gantry axis
1962-1982, increased accuracy and precision of dose delivery
Second Generation
Low Energy Photons
S.F.E.S.S.I
4-8MV
Straight through beam
Fixed flattening filter
External wedges
Symmetric jaws
Single transmission ionization chamber
Isocentric mounting
Medium Energy Photons and Electrons
B.F.D.E
10-15MV
Bent beam, movable target
Flattening Filter
Dual transmission ionization chamber
Electron cones
High Energy Photons and Electrons [1]
D.A.D.A.I
18-25MV
Dual photon energy and multiple electron energies
Achromatic bending magnet
Dual scattering foils or scanned electron beam
Automatic wedge selector
Independent collimator jaws
High Energy Photons and Electrons [2]
C.D.I.M
Computer controlled operation
Dynamic wedge
Electronic portal imaging device
Multi leaf collimator
High Energy Photons and Electrons [3]
P,MLC.F, I.
Photon beam intensity with MLC
Ull dynamic conformal dose delivery with Intensity modulated beams
A type that greatly increases the velocity of charged subatomic particles are ions play subjecting the charge particles do I series oscillating electrical potential’s
Linac
A part of the accelerator that uses microwave technology and accelerate electrons 
Waveguide
MAIN OPERATING COMPONENTS OF A MEDICAL LINAC
- Injection system
- RF Generating power
- Accelerating waveguide
- Auxiliary system
- Beam transport system
- Beam collimation and
beam monitoring system
three major components modulator cabinet 
- Fan control (cooling the power-distribution system).
- Auxiliary power distribution system
(contains the emergency off button that shuts off the power to the treatment unit ). - Primary power- distribution system
A power supply provides [..] power to the modulator, which includes the pulse-forming network and a switch tube known as [..].
● High voltage pulses from the modulator section are flat-topped DC pulses of a few microseconds in duration.
● These pulses are delivered to the magnetron or klystron and simultaneously to the electron gun
DC
hydrogen thyratron
This is. where electrons are produced by thermionic emission
Electron gun
Two types of electron gun
Diode type
Triode type
In the [..] the voltage applied to the cathode is pulsed so producing bunches of electrons rather than a continuous stream
Diode type
Produces discrete bunches of electrons by introducing a grid between cathode and anode
Triode type
It produces microwave required for electron acceleration
Function as a high frequency oscillator
Magnetron
Peak power of magnetron
5MV
Acts as a RF power amplifier
mainly in high energy LINACS
Klystron
Peak power of Klystron
7 MW
Velocity of the electron is altered by the action of electric field in the Buncher cavity produced by [..]
Electrons arrive catcher cavity [..] due to [..] thus [..] of electrons is converted into high power microwaves
Low power microwave
Suffer deceleration
Retarding electric field
Kinetic energy
Two types of accelerating wave guides
Standing or a station are you wave accelerator Traveling wave accelerator
Uses electromagnetic RF Wave to accelerate electrons to very high velocity is onto target or electron window
Accelerating Waveguide
Require a terminating or dummy, load to absorb the residual power at the end of the structure, thus preventing backward reflected wave
Traveling waveguide
Provide maximum reflection off the waves at both ends of the structure so that the combination of forward and reverse traveling waves will give rise to stationary waves
Standing waveguide
In this microwaves absorbed at the end of the wave guide or exit the wave guide to be absorbed in a resistive load are fed back to the input and off the wave guide
Traveling wave guide
Microwaves are affected from the distal surface to produce a standing wave
each end of the wave guide terminate with a conducting disk to reflect the microwave power
Standing waveguide
Consist of Evacuated drift tubes and bending magnets which are used in transporting the electron beams from the accelerating wave guide to the x-ray target or to the exit window for electron beam therapy
Electron beam transport
Changes that direction off the electron beam downwards towards the patient
Needed for energy is greater than 6 MeV
Bending magnet
Three systems for electric been bending
90° bending
270° bending
112.5° bending
Three types of target
Thin, intermediate and thick
Efficiency for photon production in target is [..] to the atomic number of the target material
proportional
It defines the largest available circular field size end is essentially conical opening projecting into a tungsten shielding block
Primary collimator
One end of the conical opening of the collimator projecting onto[..] and the other to the[…]
edges of the target
flattening filter
Make the beam intensity across the field uniform since photon dose is strongly forwardly peaked
Flattening filer
Filter is usually made up of [..]
Lead
(Tungsten, uranium, steel, al or combi)
Made spread the beam to get a uniform electron fluence across the treatment field
Scattering foil
 components of a scattering foil
thin high-Z metallic foil (e.g., lead, tantalum).
Usual type of chambers
Transmission type
Ei flat parallel plate Or cylindrical thimble chamber
Consist of four blocks two forming the upper end to forming the lower jaws
Provide rectangular or square field at the linac isocenter
Secondary collimator
Component of secondary collimator
Lead or tungsten
Functions of auxiliary system
Vacuum pumping system for accelerating guide
Water cooling system for cooling the accelerating guide
Air pressure system
Shielding against leakage radiation
We are patiently still to receive 30 Dacian treatment made with carbon fiber top
Treatment couch
