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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
High-energy X-rays are mainly forward directed, while low-energy X-rays are primarily emitted perpendicular to the incident electron beam. The higher the energy, the more efficient the X-ray production. At low kilovoltage energies (~100 kV), the efficiency of X-ray production is approximately 1% where most of the energy of the electrons (about 99%) is converted into heat. At megavoltage energies (~20 MV), the efficiency of X-ray production is approximately 70%.
Radiotherapy Physics
Published in Debbie Peet, Emma Chung, Practical Medical Physics, 2021
Andrea Wynn-Jones, Caroline Reddy, John Gittins, Philip Baker, Anna Mason, Greg Jolliffe
The use of high linear energy transfer (LET) radiation, such as proton therapy, is also possible. Proton therapy potentially offers some advantages to using high-energy X-rays, relating to the physics of how the radiation dose is distributed in the target, but is not suitable for all patients. NHS proton therapy facilities in the UK are currently limited to a small number of specialist centres.
Proton Therapy Dosimetry
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Michele M. Kim, Eric S. Diffenderfer
Dosimetry for proton therapy makes use of many of the same techniques and equipment that are in widespread use with other modes of external beam radiotherapy. The significant issue to consider when designing a program for proton therapy is that the dosimetric properties of protons depend strongly on the material where the protons deposit dose and the energy of the protons at the point where they deposit dose. This energy and material dependence comes out in the proton stopping powers and is also the primary reason why protons are an attractive alternative to high energy x-ray therapy. Protons stop in tissue and deposit an increased dose at the end of their range. This property can be exploited with the newest scanning and range modulation technologies to precisely sculpt proton dose around a tumor with the goal of sparing healthy tissues. A thorough understanding of the dosimetric properties of protons and the effects of stopping power variation will aid the physicist in choosing appropriate tools and methods to safely and effectively realize the potential of proton therapy.
Pathogenic mechanisms and therapeutic promise of phytochemicals and nanocarriers based drug delivery against radiotherapy-induced neurotoxic manifestations
Published in Drug Delivery, 2022
Ashif Iqubal, Mohammad Kashif Iqubal, Sumit Sharma, Mohd Wasim, Mohamed A. Alfaleh, Shadab Md, Sanjula Baboota, Javed Ali, Syed Ehtaishamul Haque
Another important approach for the treatment of BT is radiotherapy. The radiotherapeutic approach consist of exposure of high-energy X rays and y rays to kill the cancerous cells (Lupattelli et al., 2020). Radiotherapy can either be external or internal (Ho & Stea, 2022). External radiotherapy consists of stereotactic procedure, gamma knife linear accelerator (LINAC) and whole brain radiation (Ho & Stea, 2022). Various clinical studies have shown the benefits of radiotherapy when combined with surgery or chemotherapy, and a significant increase in the survival rate of patients has been reported (Lupattelli et al., 2020). Recent advancements in radiological techniques such as CT scans, MRI, 3 D scans, 3 D-CRT, etc., have tremendously increased the clinical outcomes of radiotherapy (Flores-Castro & Sebastian-Barajas, 2021; Li et al., 2021).
Monte Carlo-based calculation of nano-scale dose enhancement factor and relative biological effectiveness in using different nanoparticles as a radiosensitizer
Published in International Journal of Radiation Biology, 2021
Mostafa Robatjazi, Hamid Reza Baghani, Atefeh Rostami, Ali Pashazadeh
Although employing NPs as a radiosensitizer in high-energy X-ray radiotherapy is a useful approach for more efficient tumor cell killing, NP-assisted low-energy X-ray radiotherapy can result in more remarkable dose enhancement during the treatment. In this way, the results of the MC-based study by Kakade and Sharma (2015) demonstrated that the obtained dose enhancement factor (DEF) at the keV photon energy region is about 188% higher than that attained at MeV one when AuNPs are used during the irradiation. This fact is mainly linked to the large cross-sections of photoelectric interactions at low energy X-ray region, while the Compton scattering is the prevailing interaction at the high energy one. Therefore, the employed NPs during the low energy X-ray radiotherapy can act as promising and reliable radiosensitizers for dose enhancement purposes.
The relative biological effectiveness of high-energy clinical 3 and 6 MV X-rays for micronucleus induction in human lymphocytes
Published in International Journal of Radiation Biology, 2021
G. Tamizh Selvan, Karthik Kanagaraj, Perumal Venkatachalam
The health care benefits derived from utilizing ionizing radiation are increasing day by day in diagnosis and therapy. While diagnostic use predominantly depends upon low energy X-rays, cancer radiation therapy (RT) has been transformed from gamma (γ) sources to high-energy electron linear accelerators (LINACs), owing to the following advantages: LINAC produces a consistent, flexible, and precise radiation beam, which can be turned off when not in use. In addition, delivery of a variety of energies with a single machine is an advantage over radio-isotope-based modalities (Bucci et al. 2005; Connell and Hellman 2009). Even though the probability for health care workers to be exposed to high-energy X-rays is less during their routine work, scenarios such as mishandling and operational human error can result in unintentional exposure to high dose X-rays to technologists as well as the general public. Biodosimetry with a rapid assay is considered as an important tool for medical management when excess-exposure over and above the permissible limits is suspected for health workers or others exposed subjects without having personnel monitoring device (UNSCEAR 2000).