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Радиобиология (также известная как радиационная биология и реже - актинобиология ) - это область клинических и фундаментальных медицинских наук, которая включает изучение действия ионизирующего излучения на живые существа, особенно воздействия радиации на здоровье . Ионизирующее излучение, как правило, вредно и потенциально смертельно для живых существ, но может быть полезно для здоровья при лучевой терапии для лечения рака и тиреотоксикоза . Наиболее частым его воздействием является индукция рака с латентным периодом в годы или десятилетия после заражения. Высокие дозы могут вызвать визуально драматические лучевые ожоги.и / или быстрая смерть в результате острого лучевого синдрома . Контролируемые дозы используются для медицинской визуализации и лучевой терапии .

Воздействие на здоровье [ править ]

В общем, ионизирующее излучение вредно и потенциально смертельно для живых существ, но может быть полезно для здоровья при лучевой терапии для лечения рака и тиреотоксикоза .

Наиболее неблагоприятные последствия радиационного воздействия для здоровья можно разделить на две общие категории:

  • детерминированные эффекты (вредные тканевые реакции) в значительной степени из-за уничтожения / нарушения функции клеток после высоких доз; а также
  • стохастические эффекты, т. е. рак и наследственные эффекты, включая развитие рака у подвергшихся воздействию людей из-за мутации соматических клеток или наследственное заболевание у их потомства из-за мутации репродуктивных (зародышевых) клеток. [1]

Стохастик [ править ]

Некоторые эффекты ионизирующего излучения на здоровье человека являются стохастическими , то есть вероятность их возникновения увеличивается с дозой, а степень тяжести не зависит от дозы. [2] Радиационно-индуцированный рак , тератогенез , снижение когнитивных функций и сердечные заболевания - все это примеры стохастических эффектов.

Наиболее частым его воздействием является стохастическая индукция рака с латентным периодом в годы или десятилетия после заражения. Механизм, с помощью которого это происходит, хорошо изучен, но количественные модели, предсказывающие уровень риска, остаются противоречивыми. Наиболее широко распространенная модель утверждает, что заболеваемость раком из-за ионизирующего излучения линейно увеличивается с эффективной дозой облучения со скоростью 5,5% на зиверт . [3] Если эта линейная модель верна, то естественный фоновый радиационный фон является наиболее опасным источником радиации для здоровья населения, за которым следует медицинская визуализация. Другими стохастическими эффектами ионизирующего излучения являются тератогенез ,снижение когнитивных функций и болезни сердца .

Количественные данные о влиянии ионизирующего излучения на здоровье человека относительно ограничены по сравнению с другими медицинскими состояниями из-за небольшого числа случаев на сегодняшний день и из-за стохастической природы некоторых эффектов. Стохастические эффекты можно измерить только с помощью крупных эпидемиологических исследований, в которых было собрано достаточно данных, чтобы удалить мешающие факторы, такие как привычки к курению и другие факторы образа жизни. Самый богатый источник высококачественных данных - это исследование японских выживших после атомной бомбардировки . Информативны эксперименты in vitro и на животных, но радиорезистентность сильно различается у разных видов.

Дополнительный риск развития рака на протяжении всей жизни при однократной компьютерной томографии брюшной полости в 8 мЗв оценивается в 0,05%, или 1 случай на 2000. [4]

Детерминированный [ править ]

Детерминированные эффекты - это те эффекты, которые достоверно возникают выше пороговой дозы, и их тяжесть увеличивается с дозой. [2]

Высокая доза облучения вызывает детерминированные эффекты, которые надежно возникают выше порогового значения, и их серьезность увеличивается с дозой. Детерминированные эффекты не обязательно более или менее серьезны, чем стохастические эффекты; либо в конечном итоге может привести к временной неприятности или смертельному исходу. Примеры детерминированных эффектов:

  • Острый лучевой синдром , вызванный острым облучением всего тела
  • Радиационные ожоги , от излучения к определенной поверхности тела
  • Лучевой тиреоидит , потенциальный побочный эффект лучевой терапии гипертиреоза
  • Хронический лучевой синдром от длительного облучения.
  • Радиационно-индуцированное повреждение легких , например, от лучевой терапии легких
  • Катаракта и бесплодие. [2]

Комитет по биологическому воздействию ионизирующего излучения Национальной академии наук США «пришел к выводу, что не существует убедительных доказательств, указывающих на пороговую дозу, ниже которой риск индукции опухоли равен нулю». [5]

По типу излучения [ править ]

Когда изотопы, излучающие альфа-частицы, попадают в организм, они намного опаснее, чем можно предположить по их периоду полураспада или скорости распада. Это связано с высокой относительной биологической эффективностью альфа-излучения, вызывающего биологическое повреждение после попадания альфа-излучающих радиоизотопов в живые клетки. Попавшие внутрь радиоизотопы с альфа-излучателями, такие как трансурановые соединения или актиниды , в среднем примерно в 20 раз опаснее, а в некоторых экспериментах до 1000 раз опаснее, чем эквивалентная активность бета-излучающих или гамма-излучающих радиоизотопов. Если тип излучения неизвестен, его можно определить с помощью дифференциальных измерений в присутствии электрических полей, магнитных полей или различной степени экранирования.

Величины доз внешнего облучения, используемые в радиационной защите. См. Статью о зивертах о том, как они рассчитываются и используются.

Во время беременности [ править ]

Риск развития радиационно-индуцированного рака в какой-то момент жизни выше при облучении плода, чем взрослого, как потому, что клетки более уязвимы, когда они растут, так и потому, что после приема дозы у них намного больше времени для развития рака.

Возможные детерминированные эффекты включают облучение во время беременности, включая выкидыш , структурные врожденные дефекты , ограничение роста и умственную отсталость . [7] Детерминистические эффекты были изучены, например, у выживших после атомных бомбардировок Хиросимы и Нагасаки и случаев, когда лучевая терапия была необходима во время беременности:

The intellectual deficit has been estimated to be about 25 IQ-points per 1,000 mGy at 10 to 17 weeks of gestational age.[7]

These effects are sometimes relevant when deciding about medical imaging in pregnancy, since projectional radiography and CT scanning exposes the fetus to radiation.

Also, the risk for the mother of later acquiring radiation-induced breast cancer seems to be particularly high for radiation doses during pregnancy.[8]

Measurement[edit]

The human body cannot sense ionizing radiation except in very high doses, but the effects of ionization can be used to characterize the radiation. Parameters of interest include disintegration rate, particle flux, particle type, beam energy, kerma, dose rate, and radiation dose.

The monitoring and calculation of doses to safeguard human health is called dosimetry and is undertaken within the science of health physics. Key measurement tools are the use of dosimeters to give the external effective dose uptake and the use of bio-assay for ingested dose. The article on the sievert summarises the recommendations of the ICRU and ICRP on the use of dose quantities and includes a guide to the effects of ionizing radiation as measured in sieverts, and gives examples of approximate figures of dose uptake in certain situations.

The committed dose is a measure of the stochastic health risk due to an intake of radioactive material into the human body. The ICRP states "For internal exposure, committed effective doses are generally determined from an assessment of the intakes of radionuclides from bioassay measurements or other quantities. The radiation dose is determined from the intake using recommended dose coefficients".[9]

Absorbed, equivalent and effective dose[edit]

The Absorbed dose is a physical dose quantity D representing the mean energy imparted to matter per unit mass by ionizing radiation. In the SI system of units, the unit of measure is joules per kilogram, and its special name is gray (Gy).[10] The non-SI CGS unit rad is sometimes also used, predominantly in the USA.

To represent stochastic risk the equivalent dose H T and effective dose E are used, and appropriate dose factors and coefficients are used to calculate these from the absorbed dose.[11] Equivalent and effective dose quantities are expressed in units of the sievert or rem which implies that biological effects have been taken into account. These are usually in accordance with the recommendations of the International Committee on Radiation Protection (ICRP) and International Commission on Radiation Units and Measurements (ICRU). The coherent system of radiological protection quantities developed by them is shown in the accompanying diagram.

Organizations[edit]

The International Commission on Radiological Protection (ICRP) manages the International System of Radiological Protection, which sets recommended limits for dose uptake. Dose values may represent absorbed, equivalent, effective, or committed dose.

Other important organizations studying the topic include

  • International Commission on Radiation Units and Measurements (ICRU)
  • United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)
  • US National Council on Radiation Protection and Measurements (NCRP)
  • UK Public Health England
  • US National Academy of Sciences (NAS through the BEIR studies)
  • French Institut de radioprotection et de sûreté nucléaire (IRSN)
  • European Committee on Radiation Risk (ECRR) the stage of radiation depends on the stage the body parts are affected

Exposure pathways[edit]

External[edit]

A schematic diagram showing a rectangle being irradiated by an external source (in red) of radiation (shown in yellow).
A schematic diagram showing a rectangle being irradiated by radioactive contamination (shown in red) which is present on an external surface such as the skin; this emits radiation (shown in yellow) which can enter the animal's body

External exposure is exposure which occurs when the radioactive source (or other radiation source) is outside (and remains outside) the organism which is exposed. Examples of external exposure include:

  • A person who places a sealed radioactive source in his pocket
  • A space traveller who is irradiated by cosmic rays
  • A person who is treated for cancer by either teletherapy or brachytherapy. While in brachytherapy the source is inside the person it is still considered external exposure because it does not result in a committed dose.
  • A nuclear worker whose hands have been dirtied with radioactive dust. Assuming that his hands are cleaned before any radioactive material can be absorbed, inhaled or ingested, skin contamination is considered external exposure.

External exposure is relatively easy to estimate, and the irradiated organism does not become radioactive, except for a case where the radiation is an intense neutron beam which causes activation.

By type of medical imaging[edit]

Internal[edit]

Internal exposure occurs when the radioactive material enters the organism, and the radioactive atoms become incorporated into the organism. This can occur through inhalation, ingestion, or injection. Below are a series of examples of internal exposure.

  • The exposure caused by potassium-40 present within a normal person.
  • The exposure to the ingestion of a soluble radioactive substance, such as 89Sr in cows' milk.
  • A person who is being treated for cancer by means of a radiopharmaceutical where a radioisotope is used as a drug (usually a liquid or pill). A review of this topic was published in 1999.[15] Because the radioactive material becomes intimately mixed with the affected object it is often difficult to decontaminate the object or person in a case where internal exposure is occurring. While some very insoluble materials such as fission products within a uranium dioxide matrix might never be able to truly become part of an organism, it is normal to consider such particles in the lungs and digestive tract as a form of internal contamination which results in internal exposure.
  • Boron neutron capture therapy (BNCT) involves injecting a boron-10 tagged chemical that preferentially binds to tumor cells. Neutrons from a nuclear reactor are shaped by a neutron moderator to the neutron energy spectrum suitable for BNCT treatment. The tumor is selectively bombarded with these neutrons. The neutrons quickly slow down in the body to become low energy thermal neutrons. These thermal neutrons are captured by the injected boron-10, forming excited (boron-11) which breaks down into lithium-7 and a helium-4 alpha particle both of these produce closely spaced ionizing radiation.This concept is described as a binary system using two separate components for the therapy of cancer. Each component in itself is relatively harmless to the cells, but when combined together for treatment they produce a highly cytocidal (cytotoxic) effect which is lethal (within a limited range of 5-9 micrometers or approximately one cell diameter). Clinical trials, with promising results, are currently carried out in Finland and Japan.

When radioactive compounds enter the human body, the effects are different from those resulting from exposure to an external radiation source. Especially in the case of alpha radiation, which normally does not penetrate the skin, the exposure can be much more damaging after ingestion or inhalation. The radiation exposure is normally expressed as a committed dose.

History[edit]

Although radiation was discovered in late 19th century, the dangers of radioactivity and of radiation were not immediately recognized. Acute effects of radiation were first observed in the use of X-rays when Wilhelm Röntgen intentionally subjected his fingers to X-rays in 1895. He published his observations concerning the burns that developed, though he misattributed them to ozone, a free radical produced in air by X-rays. Other free radicals produced within the body are now understood to be more important. His injuries healed later.

As a field of medical sciences, radiobiology originated from Leopold Freund's 1896 demonstration of the therapeutic treatment of a hairy mole using a new type of electromagnetic radiation called x-rays, which was discovered 1 year previously by the German physicist, Wilhelm Röntgen. After irradiating frogs and insects with X-rays in early 1896, Ivan Romanovich Tarkhanov concluded that these newly discovered rays not only photograph, but also "affect the living function".[16] At the same time, Pierre and Marie Curie discovered the radioactive polonium and radium later used to treat cancer.

The genetic effects of radiation, including the effects on cancer risk, were recognized much later. In 1927 Hermann Joseph Muller published research showing genetic effects, and in 1946 was awarded the Nobel prize for his findings.

More generally, the 1930s saw attempts to develop a general model for radiobiology. Notable here was Douglas Lea,[17][18] whose presentation also included an exhaustive review of some 400 supporting publications.[19][page needed][20]

Before the biological effects of radiation were known, many physicians and corporations had begun marketing radioactive substances as patent medicine and radioactive quackery. Examples were radium enema treatments, and radium-containing waters to be drunk as tonics. Marie Curie spoke out against this sort of treatment, warning that the effects of radiation on the human body were not well understood. Curie later died of aplastic anemia caused by radiation poisoning. Eben Byers, a famous American socialite, died of multiple cancers (but not acute radiation syndrome) in 1932 after consuming large quantities of radium over several years; his death drew public attention to dangers of radiation. By the 1930s, after a number of cases of bone necrosis and death in enthusiasts, radium-containing medical products had nearly vanished from the market.

In the United States, the experience of the so-called Radium Girls, where thousands of radium-dial painters contracted oral cancers—[21]but no cases of acute radiation syndrome—[22]popularized the warnings of occupational health associated with radiation hazards. Robley D. Evans, at MIT, developed the first standard for permissible body burden of radium, a key step in the establishment of nuclear medicine as a field of study. With the development of nuclear reactors and nuclear weapons in the 1940s, heightened scientific attention was given to the study of all manner of radiation effects.

The atomic bombings of Hiroshima and Nagasaki resulted in a large number of incidents of radiation poisoning, allowing for greater insight into its symptoms and dangers. Red Cross Hospital surgeon Dr. Terufumi Sasaki led intensive research into the Syndrome in the weeks and months following the Hiroshima bombings. Dr Sasaki and his team were able to monitor the effects of radiation in patients of varying proximities to the blast itself, leading to the establishment of three recorded stages of the syndrome. Within 25–30 days of the explosion, the Red Cross surgeon noticed a sharp drop in white blood cell count and established this drop, along with symptoms of fever, as prognostic standards for Acute Radiation Syndrome.[23] Actress Midori Naka, who was present during the atomic bombing of Hiroshima, was the first incident of radiation poisoning to be extensively studied. Her death on August 24, 1945 was the first death ever to be officially certified as a result of radiation poisoning (or "Atomic bomb disease").

Areas of interest[edit]

The interactions between organisms and electromagnetic fields (EMF) and ionizing radiation can be studied in a number of ways:

  • Radiation physics
  • Radiation chemistry
  • molecular and cell biology
  • Molecular genetics
  • Cell death and apoptosis
  • High and low-level electromagnetic radiation and health
  • Specific absorption rates of organisms
  • Radiation poisoning
  • Radiation oncology (radiation therapy in cancer)
  • Bioelectromagnetics
  • Electric field and Magnetic field - their general nature.
  • Electrophysiology - the scientific study of the electrical properties of biological cells and tissues.
  • Biomagnetism - the magnetic properties of living systems (see, for example, the research of David Cohen using SQUID imaging) and Magnetobiology - the study of effect of magnets upon living systems. See also Electromagnetic radiation and health
  • Bioelectromagnetism - the electromagnetic properties of living systems and Bioelectromagnetics - the study of the effect of electromagnetic fields on living systems.
  • Electrotherapy
  • Radiation therapy
  • Radiogenomics
  • Electroconvulsive therapy
  • Transcranial magnetic stimulation - a powerful electric current produces a transient, spatially focussed magnetic field that can penetrate the scalp and skull of a subject and induce electrical activity in the neurons on the surface of the brain.
  • Magnetic resonance imaging - a very powerful magnetic field is used to obtain a 3D image of the density of water molecules of the brain, revealing different anatomical structures. A related technique, functional magnetic resonance imaging, reveals the pattern of blood flow in the brain and can show which parts of the brain are involved in a particular task.
  • Embryogenesis, Ontogeny and Developmental biology - a discipline that has given rise to many scientific field theories.
  • Bioenergetics - the study of energy exchange on the molecular level of living systems.
  • Biological psychiatry, Neurology, Psychoneuroimmunology
  • Bioluminescence - a marked phosphorescence found in fungi, deep-sea creatures etc., as against Biophoton - a much weaker electromagnetic radiation, thought by Alexander Gurwitsch, its discoverer, to be a form of signalling.

The activity of biological and astronomical systems inevitably generates magnetic and electrical fields, which can be measured with sensitive instruments and which have at times been suggested as a basis for "esoteric" ideas of energy.

Radiation sources for experimental radiobiology[edit]

Radiobiology experiments typically make use of a radiation source which could be:

  • An isotopic source, typically 137Cs or 60Co.
  • A particle accelerator generating high energy protons, electrons or charged ions. Biological samples can be irradiated using either a broad, uniform beam,[24] or using a microbeam, focused down to cellular or subcellular sizes.
  • A UV lamp.

See also[edit]

  • Background radiation
  • Biological effects of radiation on the epigenome
  • Cell survival curve
  • Health threat from cosmic rays
  • NASA Space Radiation Laboratory
  • Nuclear medicine
  • Radioactivity in biology
  • Radiology
  • Radiophobia
  • Radiosensitivity
  • Relative biological effectiveness

References[edit]

  1. ^ ICRP 2007, p. 49, paragraph 55.
  2. ^ a b c Christensen DM, Iddins CJ, Sugarman SL (February 2014). "Ionizing radiation injuries and illnesses". Emerg Med Clin North Am. Elsevier. 32 (1): 245–65. doi:10.1016/j.emc.2013.10.002. PMID 24275177.Note: first page available free at URL.
  3. ^ ICRP 2007, p. 55, Paragraph 83.
  4. ^ "Do CT scans cause cancer?". Harvard Health Publishing. Harvard University. March 2013. Retrieved 15 Jul 2020. Note: First paragraph provided free.
  5. ^ National Research Council (2006). Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2. National Academy of Science. p. 10. doi:10.17226/11340. ISBN 978-0-309-09156-5. Retrieved 11 Nov 2013.
  6. ^ "Radiation Exposure and Contamination - Injuries; Poisoning - Merck Manuals Professional Edition". Merck Manuals Professional Edition. Retrieved 6 Sep 2017.
  7. ^ a b c d e f g "Guidelines for Diagnostic Imaging During Pregnancy and Lactation". American Congress of Obstetricians and Gynecologists. February 2016
  8. ^ Ronckers, Cécile M; Erdmann, Christine A; Land, Charles E (23 November 2004). "Radiation and breast cancer: a review of current evidence". Breast Cancer Research (Review article.). BMC (Springer Nature). 7 (1): 21–32. doi:10.1186/bcr970. ISSN 1465-542X. PMC 1064116. PMID 15642178.
  9. ^ ICRP 2007, p. 73, paragraph 144.
  10. ^ ICRP 2007, p. 24, glossary.
  11. ^ ICRP 2007, pp. 61-62, paragraphs 104 and 105.
  12. ^ a b Unless otherwise specified in boxes, reference is:
    - "Radiation Dose in X-Ray and CT Exams". RadiologyInfo.org by Radiological Society of North America. Retrieved 23 Oct 2017.
  13. ^ Brisbane, Wayne; Bailey, Michael R.; Sorensen, Mathew D. (2016). "An overview of kidney stone imaging techniques". Nature Reviews Urology (Review article). Springer Nature. 13 (11): 654–662. doi:10.1038/nrurol.2016.154. ISSN 1759-4812. PMC 5443345.
  14. ^ Zhang, Zhuoli; Qi, Li; Meinel, Felix G.; Zhou, Chang Sheng; Zhao, Yan E.; Schoepf, U. Joseph; Zhang, Long Jiang; Lu, Guang Ming (2014). "Image Quality and Radiation Dose of Lower Extremity CT Angiography Using 70 kVp, High Pitch Acquisition and Sinogram-Affirmed Iterative Reconstruction". PLoS ONE. 9 (6): e99112. doi:10.1371/journal.pone.0099112. ISSN 1932-6203.
  15. ^ Wynn, Volkert; Hoffman, Timothy (1999). "Therapeutic Radiopharmaceuticals". Chemical Reviews (Review article). ACS Publications. 99 (9): 2269–92. doi:10.1021/cr9804386. PMID 11749482.
  16. ^ Y. B. Kudriashov. Radiation Biophysics. ISBN 9781600212802. Page xxi.
  17. ^ Hall, E J (1 May 1976). "Radiation and the single cell: the physicist's contribution to radiobiology". Physics in Medicine and Biology (Lecture). IOP. 21 (3): 347–359. doi:10.1088/0031-9155/21/3/001. PMID 819945.
  18. ^ Lea, Douglas E. "Radiobiology in the 1940s". British Institute of Radiology. Retrieved 15 Jul 2020.
  19. ^ Lea, Douglas (1955). Actions of Radiations on Living Cells (2nd ed.). Cambridge: Cambridge University Press. ISBN 9781001281377.
  20. ^ Mitchell, J. S. (2 November 1946). "Actions of Radiations on Living Cells". Nature (Book review). 158 (4018): 601–602. Bibcode:1946Natur.158..601M. doi:10.1038/158601a0. PMC 1932419.
  21. ^ Grady, Denise (6 October 1998). "A Glow in the Dark, and a Lesson in Scientific Peril". The New York Times. Retrieved 25 Nov 2009.
  22. ^ Rowland, R.E. (1994). Radium in Humans: A Review of U.S. Studies. Argonne National Laboratory. OSTI 751062. Retrieved 24 May 2012.
  23. ^ Carmichael, Ann G. (1991). Medicine: A Treasury of Art and Literature. New York: Harkavy Publishing Service. p. 376. ISBN 978-0-88363-991-7.
  24. ^ Pattison JE, Hugtenburg RP, Beddoe AH, Charles MW (2001). "Experimental Simulation of A-bomb Gamma-ray Spectra for Radiobiology Studies" (PDF). Radiation Protection Dosimetry. Oxford Academic. 95 (2): 125–136. doi:10.1093/oxfordjournals.rpd.a006532. PMID 11572640. S2CID 8711325. Archived from the original (PDF) on 16 Jul 2020.

Sources[edit]

  • ICRP, 2007. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37 (2-4).

Further reading[edit]

  • Eric Hall, Radiobiology for the Radiologist. 2006. Lippincott
  • G.Gordon Steel, "Basic Clinical Radiobiology". 2002. Hodder Arnold.
  • The Institute for Radiation Biology at the Helmholtz-Center for Environmental Health [1]