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Brachytherapy (from the Greek word βραχύς ''brachys'', meaning "short-distance"), also known as internal radiotherapy, sealed source radiotherapy, curietherapy or endocurietherapy, is a form of radiotherapy where a sealed radiation source is placed inside or next to the area requiring treatment. Brachytherapy is commonly used as an effective treatment for cervical, prostate, breast, and skin cancer and can also be used to treat tumours in many other body sites.〔 〕 Brachytherapy can be used alone or in combination with other therapies such as surgery, external beam radiotherapy (EBRT) and chemotherapy. Brachytherapy contrasts with unsealed source radiotherapy in which a therapeutic radionuclide (radioisotope) is injected into the body to chemically localize to the tissue requiring destruction. It also contrasts to EBRT, in which high-energy x-rays (or occasionally gamma-rays from a radioisotope like cobalt-60) are directed at the tumour from outside the body. Brachytherapy instead involves the precise placement of short-range radiation-sources (radioisotopes) directly at the site of the cancerous tumour. These are enclosed in a protective capsule or wire, which allows the ionizing radiation to escape to treat and kill surrounding tissue but prevents the charge of radioisotope from moving or dissolving in body fluids. The capsule may be removed later, or (with some radioisotopes) it may be allowed to remain in place.〔〔 〕 A key feature of brachytherapy is that the irradiation affects only a very localized area around the radiation sources. Exposure to radiation of healthy tissues farther away from the sources is therefore reduced. In addition, if the patient moves or if there is any movement of the tumour within the body during treatment, the radiation sources retain their correct position in relation to the tumour. These characteristics of brachytherapy provide advantages over EBRT - the tumour can be treated with very high doses of localised radiation whilst reducing the probability of unnecessary damage to surrounding healthy tissues.〔〔 A course of brachytherapy can be completed in less time than other radiotherapy techniques. This can help reduce the chance for surviving cancer cells to divide and grow in the intervals between each radiotherapy dose.〔 Patients typically have to make fewer visits to the radiotherapy clinic compared with EBRT, and the treatment is often performed on an outpatient basis. This makes treatment accessible and convenient for many patients.〔〔 〕 These features of brachytherapy mean that most patients are able to tolerate the brachytherapy procedure very well. Brachytherapy represents an effective treatment option for many types of cancer. Treatment results have demonstrated that the cancer cure rates of brachytherapy are either comparable to surgery and EBRT or are improved when used in combination with these techniques.〔 〕〔 〕〔 〕〔 〕〔 〕〔 〕〔 〕〔 〕 In addition, brachytherapy is associated with a low risk of serious adverse side effects.〔 〕〔 〕 The global market for brachytherapy reached US$680 million in 2013, of which the High-Dose Rate (HDR) and LDR segments accounted for 70%. Microspheres and electronic brachytherapy commanded the remaining 30%. The brachytherapy market is expected to reach over US$2.4 billion in 2030, growing by 8% annually, mainly driven by the microspheres market as well as electronic brachytherapy, which is gaining significant interest worldwide as a user-friendly technology.〔http://www.prlog.org/12390829-brachytherapy-market-recovery-to-reach-us-2-4-billion.html〕 ==History== Brachytherapy dates back to 1901 (shortly after the discovery of radioactivity by Henri Becquerel in 1896) when Pierre Curie suggested to Henri-Alexandre Danlos that a radioactive source could be inserted into a tumour.〔 〕〔 〕 It was found that the radiation caused the tumour to shrink.〔 Independently, Alexander Graham Bell also suggested the use of radiation in this way.〔 In the early twentieth century, techniques for the application of brachytherapy were pioneered at the Curie institute in Paris by Danlos and at St Luke's and Memorial Hospital in New York by Robert Abbe.〔〔 Interstitial radium therapy was common in the 1930s.〔 Gold seeds filled with radon were used as early as 1942 until at least 1958. Gold shells were selected by Gino Failla around 1920 to shield beta rays while passing gamma rays. Cobalt needles were also used briefly after world war II.〔 Radon and cobalt were replaced by radioactive tantalum and gold, before iridium rose in prominence.〔 First used in 1958, iridium is the most commonly used artificial source for brachytherapy today.〔 Following initial interest in brachytherapy in Europe and the US, its use declined in the middle of the twentieth century due to the problem of radiation exposure to operators from the manual application of the radioactive sources.〔〔 〕 However, the development of remote afterloading systems, which allow the radiation to be delivered from a shielded safe, and the use of new radioactive sources in the 1950s and 1960s, reduced the risk of unnecessary radiation exposure to the operator and patients.〔 This, together with more recent advancements in three-dimensional imaging modalities, computerised treatment planning systems and delivery equipment has made brachytherapy a safe and effective treatment for many types of cancer today.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「brachytherapy」の詳細全文を読む スポンサード リンク
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