Clinical Radiation Generators Flashcards
Two Major types of radiation generators
Kilovoltage Theraphy Units
Megavoltage Theraphy Units
machines that can generate xray voltages up to 300kVp
Kilovoltage Theraphy Units
Used up to about 1950
Kilovoltage Theraphy Units
Kilovoltage Theraphy Units is useful in the treatment of skin cancer extending no more than
1 cm below the surface
types of Kilovoltage Theraphy Units
Grenz Ray
Contact Therapy
Superficial Therapy
Deep Therapy Unit
German word which means border
Grenz
Characteristic of Grenz Ray
very soft xrays
operates below 20kV
very low depth penetration
Clinical Application of Grenz Ray
Dermatological use
derived by the way the treatment unit actually came in contact with the patient
Contact Therapy
Characteristic of contact therapy
potential
40-50kV
Characteristic of contact therapy
tube current
2mA
Characteristic of contact therapy
SSD
2cm or less
Characteristic of contact therapy
filter
0.5 to 1mm thick aluminum
Clinical application of contact therapy
tumors not deeper than 1mm
primarily used to treat superficial skin lesions
Characteristic of Superficial therapy
potential
50-150kV
Characteristic of Superficial therapy
tube current
5-8 mA
Characteristic of Superficial therapy
SSD
15 to 20 cm
Characteristic of Superficial therapy
filtration
1-6mm aluminum
Clinical Application of Superficial therapy
5mm depth
also called Orthovoltage
Deep Therapy Units
Characteristic of Deep Therapy Units
potential
150-500 kV
Characteristic of Deep Therapy Units
tube current
10-20 mA
Characteristic of Deep Therapy Units
SSD
50cm
Clinical Application of Deep Therapy Units
tumors within 2cm depth
Disadvantages of kV units
large skin dose
poor depth dose distribution
increased absorbed dose in bone
increased scattering
radiotherapy equipments that deliver beams with high dose rate in the multimillion volt range
Megavoltage Therapy Units
Telecurie therapy units use
Radium 226
Cobalt 60
Cesium 137
are emitted from these sources as they undergo radioactive disintegration
Gamma (y) rays
placed in contact with patient’s skin for treatment of underlying skin lesions
brachytherapy
larger amount of radium placed at some distance from the skin with subsequent improvement in depth dose
teletherapy
replace radium as the active source in telecurie units
Cobalt 60
advantages of cobalt 60
higher specific activity
greater radiation output per curie
higher average photon energy
relatively long half-life which promised to a desirable source
cesium 137
disadvantages of cesium 137
limited specific activity limits its application to head and neck
Clinical Application of cesium 137
Used in head and neck
electrostatic accelerator designed to acceleate electrons to produce high energy xrays typically at 2MV, but can generate beam energy of 10MV
Van de Graaf Generator
Machine capable of accelerating electrons to 2.3 MeV
Betatron
Operates on the principle that an electron on a changing magnetic field experiences acceleration in a circular orbit
Betatron
Can provide xray and electron therapy beams from less than 6 to more than 40 MeV
Betatron
uses high frequency electromagnetic waves to accelerate charged particles such as electrons to high energies through linear tube
Linear Accelerator
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
first linear accelerator was installed in
Hammersmith Hospital in London, had an 8 MeV xray beam and limited gantry rotation
An electron accelerator which combines the principles of both the linear accelerator and the cyclotron
Microtron
Capable of producing both x-rays and electron beams
Microtron
Source of high energy proton for proton beam therapy
Cyclotron
Other uses of Cyclotron
generation of neutron beam
production of certain radionuclide
cyclotron consists of short metallic cylinders divided into 2 sections
Dees (Ds)
Used to generate higher energy charged particles such as deuterons, protons and alpha particles
Synchocyclotron
Deuterons
200 MeV
Protons
680 MeV
Alpha particle
400 MeV
Machines designed to accelerate electrons and protons by means of radiofrequency-modulated magnetic field to compensate for the relativistic increase in particle mass
Neutron Beam Generator
Electron energies of 10 to 100 MeV results to energy in Giga or billion of electron volts
Electron synchrotron
Largest proton synchotron in Fermi Nat. Accelerator Lab can generate as much as
400 GeV energy