Clinical Radiation Generators Flashcards
Machines that can generate x-rays at voltages up to 300 kVp.
Kilovoltage Therapy Units
Used up to about 1950 and succeeded by Megavoltage units specifically the Cobalt 60 unit
Kilovoltage Therapy Units
Useful in the treatment of skin cancer extending no more than about 1 cm below the surface
Kilovoltage Therapy Units
Types of Kilovoltage Theray Units
Grenz Ray
Contact Therapy
Superficial Therapy
Deep Therapy Unit
A german word means “border”
Grenz
CHARACTERISTICS
• Very soft x-rays
• Operates at a potential below 20 kV
• Results to very low depth penetration
Grenz Rays
CLINICAL APPLICATION:
• Dermatological use (penetrating nickel sensitive patient: supress allergic contact dermatitis)
Grenz Rays
Its the names was delivered by the way the treatment unit actually came in contact with the patient
Contact therapy
Contact therapy’s potential
40 to 50 kV
Contact therapy’s tube current
2 mA
Contact therapy’s SSD
2.0 cm or less
Used to absorb the very soft component of the energy spectrum
A filter of 0.5 to 1.00 mm think Al
Useful for tumors not deeper than 1.2 mm.
Used to treat superficial skin lesions
Contact therapy
2 major types of Radiation Generators
- Kilovoltage Therapy Units
2. Megavoltage Therapy Units
Superficial therapy’s tube current
5 - 8 mA
Superficial therapy’s SSD
15 - 20 cm
Varying thickness (1-6 mm Al) of filtration is used
Superficial therapy
Useul for tumors confined to about 5mm depth
Superficial therapy
Deep therapy unit also called…
Orthovoltage
Deep therapy unit’s potential
150 - 500 kV
Deep therapy unit’s tube current
10-20 mA
Deep therapy unit’s SSD
50 cm
Useful for tumors within 2cm depth
Deep therapy unit
Some disadvantages of kV units
Large skin dose
Poor depth dose distriction
Increased absorbed dose in bone
Increased scattering
Radiotherapy equipments that deliver beams with high dose rate in the “multimillion volt” (1 MV or higher) range.
Megavolage therapy units (high-energy theraphy units)
Telecurie Beam Units use _, _, _ as radioactive sources
Radium 226
Cobalt 60
Cesium 137
__ rays are emitted from these sources as they undergo radioactive disintegration
Gamma
Placed in contact with patient’s skin for treatment of underlying skin lesions. This was the birth of “brachytherapy”
Radium pack
Replaced radium as the active source in telecurie therapy units with the rapid growth of nuclear reactor technology
Cobalt 60
Advantages of Cobalt 60
Higher specific activity
Greater radiation output per curie
Higher average photob energy
Has a relatively long half-lifeb(30 years) which promised to be a desirable source for telecurie therapy
Cesium 137
Cesium 137 disadvantage
Linited specific activity limits its application to head and neck
Primarily used in hed and neck therapy
Cesium 137
Megavoltage X-ray Generators
Van de Graaf
Betatron
Linear Accelerator
Microtron
Heavy-Charged Particle Accelerator
Cyclotron
Synchrocyclotron
Neutron Beam Generator
It is an electrostatic accelerator designes to accelerated electorns to produce high energy x-rays, typically at MV, but can generated beam with energy as high as 10 MV.
Van de Graaf Generator
Its uses can be found in sterikizing foods and process materials, accelerating protons for nuclear physics experiments, drving x-ray tubes etc
Van den Graaf Generator
A machine capable of accelerating electrons to 2.3 MeV
Betatron
Can probide x-ray and electron therapy beams from less than 6 yo more than 40 MeV
Betatron
A device which used high frequency electromagnetic waves to accelerate charged particles
Linear Accelerator (LINAC)
Can be used to treat superficial tumors or it can be made to strike a target to produce x-rays to treat deep seated tumors
Linear Accelerator (LINAC)
The first linear accelerator was installed in ___
Hammersmith Hospital in London
Had an 8 MeV x-ray beam and limited gantry rotation
LINAC (in Hammersmith Hospital)
An electron accelerator which combines the principles of both the linear accelerator and the cyclotron
Microtron
Cape of producing both x-rays and electron beams
Microtron
Superficial therapy’s potential
50 to 150 kV
Source of high energy proton for proton beam therapy
Cyclotron
Other uses of cyclotron:
- Generation of neutron beam
- Production of a certain radionuclide
Used to generate higher energy charged particles such as Deuterons, Protons, Alpha Particle
Synchrocyclotron
Designed to accelerate electrons and protons by means of radiofrequency-modulated magnetic fueld to compensate for the relativistic increase in particle mass
Neutron beam generator
2 kinds of neutron beam generator
Electron synchrotron
Proton synchrotron
Electron energies of 10 to 100 MeV results to energy in Giga or billion of electron volts
Electron synchrotron
The largest proton synchrotron in Fermi National Accelerator Laboratory can generated as 400 GeV energy
Proton synchrotron
The world’s largest and most powerful particle accelerator.
Large Hadron Collider at CERN
It consists of a 27-kilometer ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way
LHC
