Clinical Radiation Generators Flashcards
used to describe treatment with beams of very soft (low-energy) x-rays produced at potentials below 20 kV.
grenz-ray therapy
A ______ or _____ operates at potentials of 40 to 50 kV and facilitates irradiation of accessible lesions at very short source (focal spot) to surface distances (SSD).
contact therapy, endocavitary machine
have been used in the treatment of superficial rectal cancers.
Endocavitary x-ray machines
The term _____ applies to treatment with x-rays produced at potentials ranging from
50 to 150 kV.
superficial therapy
This machine operates typically at a tube current of 2 mA.
Contact therapy
A filter of 0.5- to 1.0-mm-thick aluminum is usually interposed in the beam to absorb the very soft component of the energy spectrum. What type of machine is this?
Contact therapy
This machine is usually operated at a tube current of 5 to 8 mA.
Superficial therapy
The term _____, or deep therapy, is used to describe treatment with x-rays produced at potentials ranging from 150 to 500 kV.
orthovoltage therapy
Most orthovoltage equipment is operated at ____ kV and ___ mA.
200 to 300, 10 to 20
X-ray therapy in the range of 500 to 1,000 kV has been designated as ____.
high-voltage therapy or supervoltage therapy
_____ units have been used to generate x-rays from 300 to 2,000 kV.
Resonant transformer
X-ray beams of energy 1 MV or greater can be classified as ____
megavoltage beams
The ______ machine is an electrostatic accelerator designed to accelerate charged particles.
Van de Graaff
Van de Graaff machines are capable of reaching energies up to ____
10 MV
This generator is enclosed in a steel tank
and is filled with the gas mixture at a
pressure of about 20 atm.
Van de graff
_____are used for generating high-energy x-ray beams, mostly in the range of 4 to 25 MV, and electron beams in the range of 4 to 25 MeV.
Medical linear accelerators (LINAC)
Medical linear accelerators (LINAC) are
used for generating high-energy x-ray
beams, mostly in the range of _____,
and electron beams in the range of ____
4 to 25 MV, 4 to 25 MeV
‒The _____ in which the electrons are accelerated by microwaves, consists of a highly evacuated vacuum tube with its
interior divided by copper discs or diaphragms of varying aperture
and spacing.
ACCELERATOR STRUCTURE
‒ A section of electronics where direct current (DC) voltage is converted
into high-voltage flat-topped DC pulses of a microseconds in duration.
MODULATOR
This prevents the microwave reflections from returning to the microwave power source (magnetron/ klystron).
Circulator
‒A rectangular copper tube to provide a path for microwaves to travel from the source (magnetron or klystron) to the accelerator structure.
WAVE GUIDE
‒ A device that produces microwaves.
MAGNETRON
It functions as a high-power oscillator,
generating microwave pulses of several microseconds duration and with a
repetition rate of several hundred pulses per second.
Magnetron
is a microwave amplifier
Klystron
Treatment head consists of a well-shielded shell of ____ alloy.
lead-tungsten
In LINAC, the focal spot is approximately ____ in diameter.
2 to 3 mm
The ____ is usually made of thick piece of lead and has a conical shape-thick in the middle and thin around the periphery to provide differential attenuation.
flattening filter
The point of intersection of the collimator axis and the axis of rotation of the gantry is known as the ______.
isocenter
____ is an electron accelerator that combines the principle of both linear accelerator and cyclotron.
Microtron
uses a standing wave linac structure (instead of single cavity as in a circular microtron) to accelerate electrons. Such an accelerator is suited for higher energy beams (e., 50 MV).
racetrack microtron
Betatron is developed by _____ in ___
Donald William Kerst, 1941
Can provide x-ray and electron therapy
beams over a wide range of energies,
from less than 6 to more than 40 MeV,
they are inherently low-electron-beam
current devices.
Betatron
A charged particle accelerator, mainly
used for nuclear physics research.
Cyclotron
In radiation therapy, these machines have
been used as a source of high-energy
protons for proton beam therapy.
Cyclotron
Half life of C-60
5.26 years
Y ray energy of C-60
1.17, 1.33 MeV
Of all the radionuclides, it has proved to be the most suitable for external beam radiotherapy.
60Co
usually in the form of
solid cylinder, discs, or pellets, is
contained inside a standard stainless-steel
capsule and sealed by welding.
60Cobalt source
The term ___ means the region, at the edge of a radiation beam, over which the dose rate changes rapidly as a function of
lateral distance.
penumbra
§ It is the transmission through the edge of the collimator block.
§ The region irradiated by photons which are transmitted through the edge of the collimator block.
§ The inner surface of the blocks is made parallel to the central axis of the beam.
§ The extent of this penumbra will be more
pronounced for larger collimator opening.
Transmission Penumbra
Caused by the source (or focal spot) having finite size
Geometric penumbra
Is dose gradation zone caused by the combined effect of transmission penumbra, and lateral scatter of radiation (photon and
electrons) within the patient.
Physical Penumbra
