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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.
Non-FDG radionuclide imaging and targeted therapies
Published in Anju Sahdev, Sarah J. Vinnicombe, Husband & Reznek's Imaging in Oncology, 2020
Luigi Aloj, Ferdia A Gallagher
Recently, alpha emitters have been introduced in clinical practice, although applications are currently limited. These so-called high linear energy transfer (LET) emitters have the advantage of releasing a high-mass particle (a helium nucleus) which produces multiple ionizations in tissue with a short particle range (10–500 μm), resulting in significant radiation damage within the distance of a few cells from the site of decay, which can minimize normal tissue damage.
Physics of Radiation Biology
Published in Kedar N. Prasad, Handbook of RADIOBIOLOGY, 2020
The specific ionization (SI) is the number of primary and secondary ion pairs produced per unit length of path of the incident radiation. The specific ionization of α particles in air varies from about 30,000 to 70,000 ion pairs per centimeter. The specific ionization of protons and deuterons is slightly less than that for α particles. The linear energy transfer (LET) is the average loss in energy per unit length of path of the incident radiation and is expressed as keV/μm or erg/μm. LET depends upon the mass, charge, and velocity of the particles. A particle with greater mass and charge, but with lower velocity, will have the higher LET.
The enduring legacy of Marie Curie: impacts of radium in 21st century radiological and medical sciences
Published in International Journal of Radiation Biology, 2022
Rebecca Abergel, John Aris, Wesley E. Bolch, Shaheen A. Dewji, Ashley Golden, David A. Hooper, Dmitri Margot, Carly G. Menker, Tatjana Paunesku, Dörthe Schaue, Gayle E. Woloschak
The clinical experience with radon therapy, including in more recent prospective, randomized, double-blind and placebo-controlled settings has been one of fairly consistent anti-inflammatory and prolonged analgesic effects (Franke et al. 2000; Deetjen et al. 2005; Rühle et al. 2017). Compared to other treatments, these benefits are slow to develop and tend not to reach a level of significance until months later but can be long-lasting (Falkenbach et al. 2005; Rühle et al. 2019). Even though the reports of reduction in painkiller usage by many radon-treated patients appear at first sight to be fairly trivial, they should not be dismissed too easily as side effects of prolonged drug treatment and can be especially severe in the elderly. The fact that treatment-induced pain reduction can coincide with a rise in circulating TGF-β and/or a fall in TNF-β adds some weight to the general concept as does the drop in activation markers on lymphocytes and reduced reactive oxygen species (ROS) output by phagocytes (Reinisch 1999; Shehata et al. 2004; Rühle et al. 2017; Kullmann et al. 2019). Those familiar with the topic will recognize parallels to the use of low-dose radiotherapy for the treatment of chronic benign conditions of different disease etiology, using low linear energy transfer (LET) and slightly higher radiation dose levels than radon therapy.
FLASH ultra-high dose rates in radiotherapy: preclinical and radiobiological evidence
Published in International Journal of Radiation Biology, 2022
Andrea Borghini, Cecilia Vecoli, Luca Labate, Daniele Panetta, Maria Grazia Andreassi, Leonida A. Gizzi
The linear energy transfer (LET) for a particular radiation influences its effectiveness in evoking a biological response (i.e. relative biological effectiveness, RBE). DNA represents the most critical target for radiation-induced lethal damage, but other cellular sites such as membranes and organelles may be crucial (Hall and Giaccia 2012). Low LET radiation (X-rays, gamma rays and beta particles) induces lower concentrations of ionization events and deposits a relatively small amount of energy in a highly dispersed manner (Hall and Giaccia 2012; Phillips and Griffin 1999). Hadrons (protons, alpha rays, and other heavier ions) have an increased ionization density and deposit more energy on the biological target, inducing more effects than the low LET radiations (Figure 1). Radiation-induced ionizations may operate directly on the DNA molecule or indirectly on water, causing the production of reactive species, including the aqueous electron (e−aq), the highly reactive hydroxyl radical (OH•) and the radical H• (Ward 1988).
Does the combination of hyperthermia with low LET (linear energy transfer) radiation induce anti-tumor effects equivalent to those seen with high LET radiation alone?
Published in International Journal of Hyperthermia, 2021
Pernille B. Elming, Brita S. Sørensen, Harald Spejlborg, Jens Overgaard, Michael R. Horsman
Radiation at low LET (linear energy transfer) is an effective cancer therapy whether applied in a conventional fractionated schedule or hypofractionated [1,2]. However, its success is limited by the presence of regions of low oxygenation (hypoxia) within tumors [3,4]. The growth and development of tumors require they have an adequate supply of oxygen and nutrients [5,6]. This originally comes from the vascular supply of the host tissue in which the tumor arises. However, due to the rapid growth of the tumor mass the tumor outgrows this supply and must then form its own vascular supply. It has been proposed that there are three patterns of tumor derived blood vessels [7]. These are vascular mimicry in which tumor cells organize themselves in three-dimensional channel-like structures [8]; mosaic vessels whereby both endothelial cells and tumor cells form the luminal surface [9]; and the more typical endothelial-dependent vessels [10]. Regardless of the vascular pattern, the system that develops is primitive and chaotic, and is unable to meet the oxygen demands of the growing tumor mass [5,6] thus hypoxia develops. This is a universal finding, making hypoxia a characteristic feature of virtually all animal [11] and human [5] solid tumors. Although hypoxia has a negative impact on low LET radiation, it is much less of a problem with high LET radiation [12,13]. Unfortunately, there are currently only 13 facilities world-wide capable of treating cancer patients with high LET and almost 70% of these are located in Asia [14].