Particle therapy is an external radiotherapy form using energetic proton beams, neutrons, or positive ions for cancer treatment. The most common type of particle therapy in 2012 is proton therapy. Although photons, used in X-ray or gamma-ray therapy, may also be considered particles, photon therapy is not considered here. In addition, electron therapy is generally incorporated into its own category. Therefore, particle therapy is sometimes referred to, more precisely, as hadron therapy (ie therapy with particles made of quarks).
Neutron-capture therapy may be considered a type of particle therapy, but it is not discussed here, because the damage that occurs to the tumor is largely derived from the energetic ions produced by secondary nuclear reactions after neutrons in external beams are absorbed into boron-10. (or sometimes some other nuclides), and not primarily due to the neutron itself. Therefore it is a kind of secondary particle therapy.
Muon Therapy, a type of rare particle therapy not included in the above category, has sometimes been tried.
Video Particle therapy
Metode
Particle therapy works by targeting energetic ionizing particles on target tumors. These particles damage the DNA of tissue cells, eventually causing their death. Due to its reduced ability to repair damaged DNA, cancer cells are particularly susceptible to attack.
The figure shows how the electron beams, X-rays or different energy protons (expressed in MeV) penetrate human tissue. Electrons have a short distance and are therefore only interested in close to the skin (see electron therapy). Bremsstrahlung's X-rays penetrate deeper, but the doses absorbed by the tissue then exhibit a typical exponential decay with increasing thickness. For heavier protons and ions, on the other hand, doses increase as particles penetrate the tissue and lose energy continuously. Therefore the dose increases with increasing thickness to the top of Bragg that occurs near the end of the particle range. Outside of the Bragg peak, the dose drops to zero (for protons) or almost zero (for heavier ions).
The advantage of this energy deposition profile is that less energy is stored into healthy tissue around the target tissue.
Ions are first accelerated by using a cyclotron or a synchrotron. The final energy of the emerging particle beam defines the depth of penetration, and hence, the location of the maximum energy deposition. Because it is easy to bend light by means of electrons in a transverse direction, it is possible to use a raster scanning method, that is, to scan the target area quickly as the electron beam scans the TV tube. If, in addition, the light energy and hence, the penetration depth varies, the entire target volume can be covered in three dimensions, giving irradiation precisely following the shape of the tumor. This is one of the great advantages over conventional X-ray therapy.
By the end of 2008, 28 treatment facilities were operating worldwide and more than 70,000 patients had been treated by way of heavier pawns, protons and ions. Most of these therapies have been performed using protons.
By the end of 2013, 105 000 patients have been treated with proton beam, and about 13,000 patients have received carbon ion therapy.
On April 1, 2015, for proton-light therapy, there are 49 facilities in the world, including 14 in the US. with 29 other facilities under construction. For carbon ion therapy, there are eight operations centers and four are under construction. Carbon-ion therapy centers exist in Japan, Germany, Italy, and China. Two US federal agencies hope to stimulate the formation of at least one US heavy ion therapy center.
Proton therapy
> Rapid neutron therapy
Carbon ion radiotherapy
Carbon ion therapy (CIRT) uses more massive particles than protons or neutrons. Carbon-ion radiation has increasingly drawn scientific attention because the choice of technology delivery has increased and clinical studies have shown the benefits of treatment for many cancers such as prostate, head and neck, lung, and liver cancer, bone and soft tissue sarcoma, recurrent rectal cancer local, and pancreatic cancer, including advanced local disease. It also has a clear advantage for treating severe hypoxia and radio-resistant cancers as it opens the door for hypo-fractionated treatment in normal and radio-sensitive diseases.
By mid-2017, more than 15,000 patients have been treated worldwide in more than 8 operations centers. Japan has become a prominent leader in this field. There are five heavy-ion radiotherapy facilities in operation and plans are there to build some more facilities in the near future. In Germany, this type of treatment is available at the Heidelberg Ion-Ion Therapy Center (HIT) and at the Marburg Ion-Beam Therapy Center (MIT). In Italy, the National Center for Oncological Hadrontherapy (CNAO) provides this treatment. Austria will open a CIRT center by 2017, with centers in South Korea, Taiwan and China opening soon. There are no CIRT facilities operating in the United States but some are in different states.
Biological advantages of heavy-ion radiotherapy
From the point of view of radiation biology, there is sufficient reason to support the use of heavy ion beams in treating cancer patients. All protons and other heavy ionic ionic therapies show the undefined Bragg peaks in the body so they provide the maximum dose of their lethal at or near the tumor. This minimizes harmful radiation to the surrounding normal tissue. However, carbon ions are heavier than protons and thus provide higher relative biological effectiveness (RBE), which increases with depth to reach maximum at the end of the range of rays. Thus the RBE of the ionic carbon rays increases as the ion advances deeper into the lying-tumor region. CIRT provides the highest linear energy transfer (LET) of any form of clinical radiation available today. This high energy transfer to the tumor produces multiple double strand DNA solutions that are very difficult to repair by the tumor. Conventional radiation produces a single strand DNA damage that can allow many tumor cells to survive. Higher cell death rates generated by CIRT may also provide a clearer antigenic sign to stimulate the patient's immune system.
Maps Particle therapy
References
External links
- Touro University announces the first joint US particles therapy center.
Source of the article : Wikipedia
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