Radiation Therapy Nourah Alothman

Outline Accelerator’s Definition. History Of Accelerator . Types Of Accelerator. Advantages and Disadvantage 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.

Lawrence’s cyclotron First Accelerator 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 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.

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/radiationtherapyprinciples/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