LINAC Flashcards
It is a device that uses high frequency electromagnetic waves to accelerate charged particle such as electrons to high energies through a linear metallic tube
Linear Accelerator
Contains components that distribute and monitor primary electrical power and high voltage pulses to the magnetron or klystron
Modulator Cabinet
Components of Modulator Cabinet
Fan Control, Auxillary Power, Primary Power
Automatically turns the fan off and on as the need arises for cooling the power distribution
The fan control
Contains the emergency off button that shuts off the power to the treatment unit.
Auxillary Power or Distribution System
Primary Power - ___________
Distribution Power
Provides a central location for monitoring and controlling the LINAC.
Take the form of a digital display, push button panel or video display terminal (VDT)
CONTROL CONSOLE
• A stand containing the apparatus that drives the LINAC. Stand is anchored firmly to the floor.
• Open on both sides with swinging doors for easy access to gauges, valves, tanks, and buttons.
GANTRY STAND / DRIVE STAND / SUPPORT
Components of GANTRY STAND / DRIVE STAND / SUPPORT
- Klystron/Magnetron
- Waveguide
- Circulator
- Water Cooling System
Two types of waveguides
RF power transmission waveguide and Accelerating Waveguide
Power source used to generate electromagnetic waves for the accelerator guides
Klystron/Magnetron
Power source used to generate electromagnetic waves for the accelerator guides
Klystron/Magnetron
electron tube that provides microwaves to accelerate electrons and is preferred for lower electron energies (4Mev-6Mev)
Magnetron
Used for high energy LINACS (>6MeV)
Klystron
Hollow tube-like structure that guide the electromagnetic waves from the klystron to the accelerating guide where electrons are accelerated.
Waveguide
Transmits the RF power from power source to the accelerating waveguide
RF power transmission waveguide
Accelerates the electrons in the gantry by means of energy transfer from high power RF fields
Accelerating waveguide
Responsible for directing the photon (x-ray) energy or electron beam to the patient. It rotates 360 degrees around a line/point called the Isocenter.
GANTRY
Components of a gantry
Electron Gun
Accelerator Structure
Treatment Head
Produces electrons and injects them into the accelerator structure
Electron gun
Two types of electron gun:
Diode and Triode.
Two types of electron gun:
Diode and Triode.
Both electron gun types contain a heated filament ______ and perforated _____________; in addition, the triode type also incorporates a _____.
Both electron gun types contain a heated filament CATHODE and perforated GROUNDED ANODE; in addition, the triode type also incorporates a GRID.
A special type of waveguide in which electrons are accelerated.
ACCELERATOR STRUCTURE
After the flowing electrons leave the accelerator structure, they are directed towards the ___________ or __________ located in the treatment head.
After the flowing electrons leave the accelerator structure, they are directed towards the target (for photon production) or scattering foil (for electron production) located in the treatment head.
Designed to shape and monitor the treatment
TREATMENT HEAD
Directs the electrons vertically towards the patient. Bends the pulsed electrons towards the target for x-ray production or the scattering foil for electron treatments. Produces different beam paths for different energies. Needed for energies >6MeV.
BENDING MAGNET
Used for the production of x-ray photons by bombarding the electrons through it. It is located at the focus of Bending Magnet.
X-RAY TARGET
Usually made up of lead, steel, copper etc., Modifies the narrow, non-uniform photon beam at the isocenter into clinically useful beam and scatter into periphery of the beam. It must be carefully positioned in the beam or the beam hitting the patient will be non-uniform, resulting in hot and cold spots.
BEAM FLATTENING FILTER
Are thin metal sheets that lets the electrons to scatter, expanding the useful size of the beam.
Typically consist of dual lead foils to minimize the production of bremsstrahlung x-rays. Narrow beam is usually spread by two scattering foils and converts the pencil beam into usable wide beam.
SCATTERING FOIL
Used for dose monitoring for the safety of the patients. There are two separate ion chambers and they are positioned between the flattening filter or scattering foil and secondary collimators.
ION CHAMBER
Controls the field size by adjusting the upper and lower collimator jaws. Usually, made-up of materials with high atomic (Z) number like Tungsten or Lead. It can define a rectangular shaped beam up to 40cm-by-40cm x-ray beams.
COLLIMATORS
Are heavy metal field-shaping devices with independent moving mechanisms used to create a custom like block to spare normal tissues and direct the radiation dose to the treatment target.
MULTI-LEAF COLLIMATORS (MLCs)
Mounted on a rotational axis around the isocenter.
Moves mechanically in a horizontal and lengthwise direction - must be smooth and accurate allowing for precise and exact positioning of the isocenter during treatment
TREATMENT COUCH (PATIENT SUPPORT ASSEMBLY):
