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External Beam Therapy Equipment
Published in Kwan Hoong Ng, Ngie Min Ung, Robin Hill, Problems and Solutions in Medical Physics, 2023
Kwan Hoong Ng, Ngie Min Ung, Robin Hill
Solution:Advantages: Linear accelerator can provide either megavoltage electron or X-ray therapy with a wide range of energies, allowing radiation oncologists to tailor treatment to the required depth.Most modern linear accelerator features such as high dose rate modes, MLC, electron arcs therapy, dynamic wedges and dynamic MLC operation during treatment.No radioactive source contamination.Higher dose rate (1–10 Gy min−1) allowing shorter treatment time.Have a sharp dose fall-off at the beam edge than Co-60 beam.The trimmer consists of heavy metal bars used to attenuate the beam in the penumbra region, thus ‘sharpening’ the field edges.
Introduction and History
Published in Volker Ziemann, ®, 2019
As we saw in the previous paragraphs, electron accelerators were developed in parallel to the high-energy proton machines. But the small mass of the electrons makes reaching high energies more difficult compared to protons. Moreover, it was already known in the late 1940s that forcing electrons on a circular orbit causes them to emit synchrotron radiation. The emitted energy is inversely proportional to the bending radius ρ and to the fourth power of the mass of the radiating particle. Electrons therefore require either large rings or linear accelerators. But in linear accelerators, the acceleration structures can only be used once and many of them are required in order to reach high energies. To power the structures, efficient sources of radio-frequency power are needed. This technology became available after the Second World War through developments during the war, both in vacuum and in radio-frequency technology for radar. In particular, power-amplifiers for RF signals, called klystrons, became available to generate radio-frequencies in the multi-MHz and even GHz rage at MW power levels. This development triggered the construction of the 3 km linear accelerator at the Stanford Linear Accelerator Center (SLAC) from 1962 onwards. In the SLAC linac, 240 klystrons were used to accelerate electrons to a maximum energy of 20 GeV.
Proven Technology Drives Down Medical Waste Treatment Costs
Published in Gregory D. Boardman, Hazardous and Industrial Wastes, 2022
Gary F. Bowser, Martha R. Black
When the voltage, currents, and energy deposited are low, the tube used to accelerate the electrons can be an evacuated glass tube—a cathode ray tube. When the voltages, currents, and energy to be deposited are high, a linear accelerator is often used to accelerate the electrons in a straight line by means of electric fields developed across a series of accelerating gaps. A linear accelerator consists of a cathode as a source of electrons and a tube made of a very good electrical insulator to sustain a very high voltage along its walls. It also has sophisticated power supplies, vacuum pumping and cooling systems, pulse and radio frequency supply assemblies, and radiation shielding.
Spectroscopy of High-Intensity Bremsstrahlung Using Compton Recoiled Electrons
Published in Nuclear Science and Engineering, 2020
C. V. Midhun, M. M. Musthafa, Shaima Akbar, Swapna Lilly Cyriac, S. Sajeev, Antony Joseph, K. C. Jagadeesan, S. V. Suryanarayana, S. Ganesan
For use in radiation therapy, medical linear accelerators typically accelerate electrons to medium energies, up to 20 MeV. Interestingly, such medical accelerators can also be utilized for small-scale research using photon- and neutron-induced reactions in nuclear and radiation physics subjects. In medical accelerators, the photon beams are produced in thick target bremsstrahlung mode by the accelerated electron beam falling on a built-in high-atomic-numbered target. The availability of this feature is limited to a few of the preconfigured photon energies. Further, other bremsstrahlung energies can be generated with available electron energies by introducing an external target at the end of an electron applicator.aAn electron applicator is a device used to guide the electron beam into the required field size and is used in medical accelerators.
Study of dielectric properties of electron beam irradiated luffa fiber/PLA composites
Published in Radiation Effects and Defects in Solids, 2022
Sonismita Dalai, Subhashree Patra, Chhatrapati Parida
Electrons are accelerated to high energy of 6 MeV while exiting from the linear accelerators. These electron beams are directed to a target having high Z to generate X-rays/gamma rays by bremsstrahlung interactions using microwave technology. Varian and Elekta instruments are two major players in designing medical linear accelerators which are used for cancer radiation therapy. These accelerators employ intensity modulated radiotherapy (IMRT) where the radiation dose is delivered only to the target with minimum exposure to the surrounding.