China
Africa
Explore chapters and articles related to this topic
Electron Beam Physics
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:Bremsstrahlung contamination is produced in the head of the accelerator through interaction with materials acting as ‘targets’ such as the waveguide window, scattering foils, ionisation chamber, and collimators, present in the path of the electron beam. Using low Z materials in the scattering foils can reduce this unwanted contamination. Bremsstrahlung is also generated in the air between the accelerator window and the patient, and in the irradiated medium.Bremsstrahlung contamination is featured as ‘a tail’ extending beyond the range of the most energetic electron on an electron depth dose curve (Figure 3.3). Factors affecting the fraction of bremsstrahlung radiation generated are (i) electron energy – fraction of bremsstrahlung radiation generated increases with increasing electron energy; (ii) materials of collimation system – rate of bremsstrahlung production is proportional to the atomic number of the collimation system; and (iii) thickness of the scattering foils – fraction of bremsstrahlung radiation generated increases with increasing thickness of scattering foils.
Projection Radiography and Computed Tomography
Published in Bethe A. Scalettar, James R. Abney, Cyan Cowap, Introductory Biomedical Imaging, 2022
Bethe A. Scalettar, James R. Abney, Cyan Cowap
When electrons collide with the anode, they lose energy and generate bremsstrahlung and characteristic X-rays (Fig. 11.11). Bremsstrahlung (braking) radiation is generated when electrons interact electrically with nuclei and their paths are altered, leading to deceleration. Importantly, a decelerating charge produces radiation. Thus, a sufficiently energetic deflected electron emits X-ray radiation and undergoes an equivalent loss of kinetic energy, which is the origin of the name “braking” radiation. The bremsstrahlung energy spectrum, like loss of kinetic energy, is continuous but is bounded above by the maximum possible kinetic energy of the electron. This is the energy imparted to the electron by the maximum voltage applied between the cathode and anode, which is known as the peak kilovoltage (kVp) (Fig. 11.11).
Generation of Bremsstrahlung Radiation from Different Low- to High-Z Targets for Medical Applications: A Simulation Approach
Published in Pandit B. Vidyasagar, Sagar S. Jagtap, Omprakash Yemul, Radiation in Medicine and Biology, 2017
Bhushankumar Jagnnath Patil, Vasant Nagesh Bhoraskar, Sanjay Daga Dhole
One of the major applications of the bremsstrahlung radiation is for radiotherapy. Photon beams with energies higher than 10 MeV are preferred when doses need to be delivered to greater depths (e.g., for the treatment of prostate cancer) and to enhance the skin sparing. The requirement for the production of clinical photon beam using high-energy electron is that the photon beam should have a spatially uniform fluence and well collimated in a reference plane that is perpendicular to the beam axis. Generally, this plane is defined at a depth of 10 cm in a water phantom. The surface of water phantom is 100 cm away from the photon source, i.e., the surface–source distance (SSD) is 100 cm. When the required condition is met, the radiation beam will produce a uniform dose distribution across the reference plane.
Recent research and development programs for infrastructures maintenance, renovation and management in Japan
Published in Structure and Infrastructure Engineering, 2020
Yozo Fujino, Dionysius M. Siringoringo
The system is a portable X-band linac-based X-ray that consists of three units: X-ray head, magnetron and power unit (Figure 12). In this system, the electrons are accelerated to 950 keV and then injected into Tungsten target, which generates bremsstrahlung X-rays. The maximum energy of the bremsstrahlung X-rays is 950 keV. The generated X-rays are collimated by a Tungsten collimator to the shape of a cone with an opening angle of 17 degrees. On the opposite side of the X-ray source, behind the object, a flat panel detector (FPD) is placed to obtain the transmitted X-rays through the object (Figure 12(b)). The FPD is an XRD1622 from Perkin Elmer Corporation. It has a sensitive area of about 400 × 400 mm2. The sensitivity range of the X-ray energy is from 20 keV to 15 MeV. A scintillator is used in the FPD and the size of a pixel of the FPD was 200 × 200 μm2. Inside the FPD, there is a copper filter in front of the detector pixels. This filter is used to cut the lower energy noise X-rays, which resulted from the Compton scattering by the concrete structure. In Japan the use of X-ray source for energy <4 MeV is allowed as long as its application is limited to bridge inspection.
Validation and Verification of the Evaluated Electron Data Library in FRENSIE
Published in Nuclear Science and Engineering, 2019
Luke J. Kersting, Douglass Henderson, Alex Robinson, Eli Moll
In a bremsstrahlung interaction, an electron interacts with the Coulomb field of the nucleus, which causes the electron to decelerate and a photon to be emitted. The EEDL provided DCSs for the energy of the emitted photon as well as an integrated cross section. The angular deflection of the incident electron is considered to be negligible, and the direction of the electron remains unchanged.5 Since there is no coupled electron-photon transport, the bremsstrahlung photon is assumed to be locally absorbed. The outgoing energy of the electron can be calculated by subtracting the energy of the generated photon
MLEM Neutron Spectra Unfolding in a Radiotherapy Bunker Using Bonner Sphere Spectrometer
Published in Nuclear Science and Engineering, 2023
S. Oliver, S. Morató, B. Juste, R. Miró, G. Verdú, N. Tejedor, J. Pérez-Calatayud
A medical linear accelerator (LinAc) is a device for external beam radiation treatments for patients with cancer, being one of the most widely used in radiation therapy departments. LinAcs can operate with different energy beams depending on the planned treatment. Commonly, the device generates a monoenergetic electron beam producing high-energy X-rays by bremsstrahlung when electrons hit the heavy target material. The generated electrons and photons can be absorbed and interact with the high-atomic-number material constituting the accelerator head. If these photons have energies above 8 MeV, neutron emission is possible because of photonuclear reactions.1,2