Radiation Therapy

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• Radiation Therapy
• Nourah Alothman

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Outline

• Accelerators Definition.
• History Of Accelerator .
• Types Of Accelerator.
• Advantages and Disadvantage
• How Does An Accelerator InTherapy Work
• Future of Accelerator .

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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.

• Particle accelerator

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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.".
Lawrences cyclotron

• First Accelerator

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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 .

• Modern Particle Accelerator

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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 paDents 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.

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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 .

• Advantage and Disadvantage for Linear Accelerator

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Linear Accelerator Therapyused 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.

• Linear Accelerator Application

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• Cyclotron

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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.

• Cyclotron

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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.

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Advantages of the cyclotronCyclotrons 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.

• Advantage and Disadvantage of cyclotron

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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.

• Disadvantages of the cyclotron

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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.

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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.

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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)

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Photon Radiation

• The most common form of radiation used in
  practice today is the high-energy 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.

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PHOTON-TISSUE INTERACTIONST

• Three interactions describe photon absorption in
  tissue
• The photoelectric effectIn 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 effectThe 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 620 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.

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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.

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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.

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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
  520 MeV. An electron beam can be used to
  supplement the treatment of areas that have been
  irradiated by X-rays.

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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.

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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.

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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.

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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,

• Advantages and Disadvantage

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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 surgeons
scalpel.CyberKnife consists ofA lightweight
"linear accelerator," which produces high-energy
radiationA robot, which points the linear
accelerator at the correct angleSeveral 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.

• what is the new about accelerator

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• 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.

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• 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.

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