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Radiation Therapy
Nourah Alothman
Outline
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Accelerator’s Definition.
•
History Of Accelerator .
•
Types Of Accelerator.
•
Advantages and Disadvantage
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How Does An Accelerator InTherapy Work
•
Future of Accelerator .
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields
to propel charged particles to high speeds and to contain them
in well-defined beams.
First Accelerator
Lawrence’s cyclotron
The difficulties of maintaining high
voltages led several physicists to propose
accelerating particles by using a lower
voltage more than once. Lawrence learned
of one such scheme in the spring of 1929,
while browsing through an issue of Archiv
für Elektrotechnik, a German journal for
electrical engineers. Lawrence read
German only with great difficulty, but he
was rewarded for his diligence: he found
an article by a Norwegian engineer, Rolf
Wideröe, the title of which he could
translate as "On a new principle for the
production of higher voltages.".
Modern Particle Accelerator
Linear particle accelerator : is a type of
particle accelerator that greatly increases
the kinetic energy of charged subatomic
particles or ions by subjecting the
charged particles to a series of oscillating
electric potentials along a linear beamline
.
How does liner accelerator work
•
The linear accelerator (Linac), uses microwave technology to accelerate electrons in
a part of the linac called waveguide, then allows these electrons to collide with a
heavy metal target. As a result of these collisions, high energy X-Rays (Photons) are
produced from the target.
• These high energy photons will be directed to the paDent’s tumor and shaped as they
exit the linac to conform to the shape of the tumor.
• Radiation can be delivered to the tumor from any angle by the gantry and moving the
treatment couch.
Advantage and Disadvantage for Linear Accelerator
The main advantage of linear accelerators
is that the particles are able to reach very
high energies without the need for
extremely high voltages.
The main disadvantage is that, because the
particles travel in a straight line, each
accelerating segment is used only once.
This means that the only way of achieving
particle beams with even higher energy is to
undertake the expense of adding segments
to the length of the linac .Also, the cost for
liner accelerator is between 20 millions and
50 millions .
Linear Accelerator Application
Linear Accelerator Therapy:
used for external beam radiation
treatments for patients with cancer. The
linear accelerator is used to treat all
parts/organs of the body. It delivers
high-energy x-rays to the region of the
patient's tumor. These x-ray treatments
can be designed in such a way that they
destroy the cancer cells while sparing
the surrounding normal tissue. The
LINAC is used to treat all body sites,
using conventional techniques.
Cyclotron
Cyclotron
The Cyclotron uses a magnetic field to bend charged particles into a circular path so that they can be
repeatedly accelerated by the same electric field.
How does Cyclotron accelerator work in therapy
A cyclic high frequency accelerator, which accelerates protons up to an extremely high
speed - thereby producing a beam of high energy (E = 230 MeV). A proton beam of a
particular energy and intensity is then safely transported to the body of the patient through a
'Beam Transport System', and this beam is modulated (by an 'Energy Selection System')
via individual nozzles within the treatment room before being directed at the target tumor.
Advantage and Disadvantage of cyclotron
Advantages of the cyclotron:
Cyclotrons have a single electrical driver, which saves both money and power, allowing more
funds to be allocated to increasing efficiency.
Cyclotrons produce a continuous stream of particles at the target, so the average power is
relatively high.
The compactness of the device reduces other costs, such as its foundations, radiation shielding,
and the enclosing building.
Disadvantages of the cyclotron:
The use of magnets has cost implications.
If two particles of the same mass are accelerated in opposite directions to the same speed, the total momentum
before the collision will equal zero, and since Ek = p2/2m, there will be no energy left over for the creation of new
particles.
The energy was limited by the size of the machine and the magnetic field.
Cyclotron Accelerators Applications
•
•
Cyclotrons can be used in particle therapy to treat cancer.
Ion beams from cyclotrons can be used, as in proton therapy, to penetrate the body and kill tumors by radiation
damage, while minimizing damage to healthy tissue along their path.
•
Cyclotron beams can be used to bombard other atoms to produce short-lived positron-emitting isotopes suitable
for PET imaging.
•
cyclotrons currently installed at hospitals for particle therapy have been retrofitted to enable them to produce
technetium-99m.
Radiation Therapy
Radiation used for cancer treatment is called ionizing radiation
because it forms ions (electrically charged particles) in the cells of the
tissues it passes through. It creates ions by removing electrons from
atoms and molecules. This can kill cells or change genes so the cells
stop growing.
Types of Radiation Therapy
Ionizing radiation:
Ionizing radiation can be sorted into 2 major types:
• Photon radiation (x-rays and gamma rays)
• Particle radiation (such as electrons, protons, neutrons, carbon ions, alpha particles, and beta
particles)
Photon Radiation
The most common form of radiation used in practice today is the highenergy photon. Photons that are released from the nucleus of a
radioactive atom are known as gamma rays. When photons are created
electronically, such as in a clinical linear accelerator, they are known
as x-rays. Thus, the only difference between the two terms is the origin
of the photon.
PHOTON-TISSUE INTERACTIONS
T
Three interactions describe photon absorption in tissue:
•The photoelectric effect:In this process, an incoming photon undergoes a collision with a tightly bound
electron. The photon transfers practically all of its energy to the electron and ceases to exist. The electron
departs with most of the energy from the photon and begins to ionize surrounding molecules. This
interaction depends on the energy of the incoming photon, as well as the atomic number of the tissue; the
lower the energy and the higher the atomic number, the more likely that a photoelectric effect will take place.
•. Compton effect:The Compton effect is the most important photon-tissue interaction for the treatment of
cancer. In this case, a photon collides with a “free electron,” ie, one that is not tightly bound to the atom.
Unlike the photoelectric effect, in the Compton interaction both the photon and electron are scattered. The
photon can then continue to undergo additional interactions, albeit with a lower energy. The electron begins
to ionize with the energy given to it by the photon.The Compton effect is the most common interaction
occurring clinically, as most radiation treatments are performed at energy levels of about 6–20 MeV .
•Pair production.
•In this process, a photon interacts with the nucleus of an atom, not an orbital electron. The photon gives up
its energy to the nucleus and, in the process, creates a pair of positively and negatively charged electrons.
The positive electron (positron) ionizes until it combines with a free electron. This generates two photons
that scatter in opposite directions.
ELECTRON BEAMS
With the advent of high-energy linear accelerators, electrons have become a
viable option in treating superficial tumors up to a depth of about 5 cm.
Electron depth dose characteristics are unique in that they produce a high
skin dose but exhibit a falloff after only a few centimeters.
Electron absorption in human tissue is greatly influenced by the presence of
air cavities and bone. The dose is increased when the electron beam passes
through an air space and is reduced when the beam passes through bone.
Electron Properties
Electron beams have a finite range, after which
dose falls off rapidly. Therefore they spare
deeper healthy tissue. The depth of the
treatment is selected by the appropriate energy.
Electron Radiation Treatment
Linear particle accelerators generate electron beams for treatment of superficial
tumors in radiation therapy. Electron therapy can treat such skin lesions as
basal-cell carcinomas because an electron beam only penetrates to a limited
depth before being absorbed, typically up to 5 cm for electron energies in the
range 5–20 MeV. An electron beam can be used to supplement the treatment of
areas that have been irradiated by X-rays.
Protone Radiation
Proton therapy is an advanced type of radiation treatment that uses a
beam of protons to deliver radiation directly to the tumor, destroying cancer
cells while sparing healthy tissues. Protons enter the body with a low
radiation dose, stop at the tumor, match its shape and volume or depth,
and deposit the bulk of their cancer-fighting energy right at the tumor.
Who does the Proton Radiation Work
A machine called a synchrotron or cyclotron accelerates (speeds up) the
protons. The speed of the protons is a sign of their high energy. The
protons travel to a specific depth in the body based on their energy. After
the protons reach the desired distance, they deposit the specified radiation
dose around the tumor, leaving minimal radiation doses behind.
The difference between proton and other traditions
Proton beams differ from photon beams mainly in the way they deposit
energy in living tissue. Whereas photons deposit energy in small packets all
along their path through tissue, protons deposit much of their energy at the
end of their path (called the Bragg peak) and deposit less energy along the
way.
Advantages and Disadvantage
Compared with standard radiation treatment, proton therapy has several benefits. It
reduces the risk of radiation damage to healthy tissues; may allow a higher radiation
dose to be directed at some types of tumors, which may keep the tumor from growing or
spreading; and may result in fewer and less severe side effects (such as low blood
counts, fatigue, and nausea) during and after treatment.
Treating brain tumors with protons, doctors can spare the nerve going to the eye or the
cochlea to preserve vision and hearing. Data also show that children with brain tumors
treated with protons have better scores on math and spelling tests than children treated
with x-rays,
what is the new about accelerator
The accelerators are used in Saudi Arabia
The CyberKnife is used in a type of radiation therapy called stereotactic radiosurgery (also known as stereotactic
radiotherapy). This treatment destroys tumors with extremely precise, very intense doses of radiation while
minimizing damage to healthy tissue, offering accuracy akin to the sharpness of a surgeon’s scalpel.
CyberKnife consists of:
A lightweight "linear accelerator," which produces high-energy radiation
A robot, which points the linear accelerator at the correct angle
Several x-ray cameras, which, along with computer software, track the position of the patient and tumor.
advantages :
Lung cancer can be especially hard to treat, as the tumors move with each breath. CyberKnife, however, allows for
precise treatment as you breathe.
TomoTherapy is a treatment system that is one of the most advanced
and versatile radiation therapy systems available for the treatment of a
wide variety of cancers. The approach is for
the beam to reach the tumor as planned and not harm healthy tissue
around the tumor.
TomoTherapy is a treatment system that uses its unique CT scanner
design to deliver radiation continuously from all angles around the
patient. More angles and more precise modulation result in dose
distributions that conform to tumors like never before. This, in turn,
minimizes damage to surrounding healthy tissue. High energy x-rays
are produced and used inside the TomoTherapy unit.
advantage of TomoTherapy TomoTherapy's helical delivery reduces
chances of skin irritation and hair loss, since there is no one specific
dose entry or exit spot. With TomoTherapy, it is entirely possible that
many brain tumor patients will have no hair loss, and spine tumor
patients will have complete relief of pain with no side effects. Prostate
cancer patients may have noticeably fewer bladder and rectal side
effects.
Rapid Arc :
RapidArc is a radiotherapy technology that is among the most advanced forms of intensity modulated radiation
therapy (IMRT). IMRT is a computer-based form of radiotherapy that allows radiation oncologists to send
external beams in the 3-D shape of tumors in small multiple doses with precision.
How does RapidArc work?
First, it uses computed tomography (CT) or other imaging technology to pinpoint a tumor. Then, the
technology system uses this image to guide the radiation beam to the tumor in one or two rotations of the
machine around the patient. During treatment, the radiation beam is shaped and reshaped as it continuously
delivers beams at virtually every angle in a 360-degree revolution. In short, it allows us to deliver a high dose
of radiation to kill or sterilize cancer cells in an extremely precise, targeted manner, which spares healthy
tissues from damage, and it is used for brain, head and neck, lung, prostate, and spine cancers.
resources
http://en.wikipedia.org/wiki/Particle_accelerator
http://www.health-quest.org/body_vb.cfm?id=711
http://en.wikipedia.org/wiki/Tomotherapy
http://www.bmc.org/thoraciconcology/treatments/cyberknife.htm
http://www.cancer.org/treatment/treatmentsandsideeffects/treatmenttypes/radiation/radiationtherapy
principles/radiation-therapy-principles-types-of-radiation
http://www.cancer.gov/cancertopics/factsheet/Therapy/radiation
https://www.fnal.gov/pub/science/inquiring/timeline/34.html
http://www.cancer.net/navigating-cancer-care/how-cancer-treated/radiation-therapy/proton-therapy
http://en.wikipedia.org/wiki/Electron#Particle_beams
http://www.sibley.org/radonc/about_tomotherapy.aspx