Chronic radiation syndrome

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Chronic radiation syndrome (CRS), or chronic radiation enteritis, [1] [2] is a constellation of health effects of radiation that occur after months or years of chronic exposure to high amounts of radiation. Chronic radiation syndrome develops with a speed and severity proportional to the radiation dose received (i.e., it is a deterministic effect of exposure to ionizing radiation), unlike radiation-induced cancer. It is distinct from acute radiation syndrome, in that it occurs at dose rates low enough to permit natural repair mechanisms to compete with the radiation damage during the exposure period. Dose rates high enough to cause the acute form (> ~0.1 Gy/h) are fatal long before onset of the chronic form. The lower threshold for chronic radiation syndrome is between 0.7 and 1.5 Gy, at dose rates above 0.1 Gy/yr. [3] This condition is primarily known from the Kyshtym disaster, where 66 cases were diagnosed. It has received little mention in Western literature; [3] but see the ICRP’s 2012 Statement. [4]

In 2013, Alexander V. Akleyev described the chronology of the clinical course of CRS while presenting at ConRad in Munich, Germany. In his presentation, he defined the latent period as being 1–5 years, and the formation coinciding with the period of maximum radiation dose. The recovery period was described as being 3–12 months after exposure ceased. He concluded that "CRS represents a systemic response of the body as a whole to the chronic total body exposure in man." [5] In 2014, Akleyev's book "Comprehensive analysis of chronic radiation syndrome, covering epidemiology, pathogenesis, pathoanatomy, diagnosis and treatment" was published by Springer. [6]

Symptoms of chronic radiation syndrome would include, at an early stage, impaired sense of touch and smell and disturbances of the vegetative functions. At a later stage, muscle and skin atrophy and eye cataract follow, with possible fibrous formations on the skin, in case of previous radiation burns. Solid cancer or leukemia due to genetic damage may appear at any time. [7]

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Radiation therapy or radiotherapy is a treatment using ionizing radiation, generally provided as part of cancer therapy to either kill or control the growth of malignant cells. It is normally delivered by a linear particle accelerator. Radiation therapy may be curative in a number of types of cancer if they are localized to one area of the body, and have not spread to other parts. It may also be used as part of adjuvant therapy, to prevent tumor recurrence after surgery to remove a primary malignant tumor. Radiation therapy is synergistic with chemotherapy, and has been used before, during, and after chemotherapy in susceptible cancers. The subspecialty of oncology concerned with radiotherapy is called radiation oncology. A physician who practices in this subspecialty is a radiation oncologist.

<span class="mw-page-title-main">Acute radiation syndrome</span> Health problems caused by exposure to high levels of ionizing radiation

Acute radiation syndrome (ARS), also known as radiation sickness or radiation poisoning, is a collection of health effects that are caused by being exposed to high amounts of ionizing radiation in a short period of time. Symptoms can start within an hour of exposure, and can last for several months. Early symptoms are usually nausea, vomiting and loss of appetite. In the following hours or weeks, initial symptoms may appear to improve, before the development of additional symptoms, after which either recovery or death follow.

<span class="mw-page-title-main">Sievert</span> SI unit of equivalent dose of ionizing radiation

The sievert is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing radiation, which is defined as the probability of causing radiation-induced cancer and genetic damage. The sievert is important in dosimetry and radiation protection. It is named after Rolf Maximilian Sievert, a Swedish medical physicist renowned for work on radiation dose measurement and research into the biological effects of radiation.

Ionizing radiation, including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel up to 99% of the speed of light, and the electromagnetic waves are on the high-energy portion of the electromagnetic spectrum.

The gray is the unit of ionizing radiation dose in the International System of Units (SI), defined as the absorption of one joule of radiation energy per kilogram of matter.

Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. This applies both internally, due to ingested or inhaled radioactive substances, or externally due to irradiation by sources of radiation.

Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Exposure can be from a source of radiation external to the human body or due to internal irradiation caused by the ingestion of radioactive contamination.

Equivalent dose is a dose quantity H representing the stochastic health effects of low levels of ionizing radiation on the human body which represents the probability of radiation-induced cancer and genetic damage. It is derived from the physical quantity absorbed dose, but also takes into account the biological effectiveness of the radiation, which is dependent on the radiation type and energy. In the SI system of units, the unit of measure is the sievert (Sv).

The roentgen equivalent man (rem) is a CGS unit of equivalent dose, effective dose, and committed dose, which are dose measures used to estimate potential health effects of low levels of ionizing radiation on the human body.

Absorbed dose is a dose quantity which is the measure of the energy deposited in matter by ionizing radiation per unit mass. Absorbed dose is used in the calculation of dose uptake in living tissue in both radiation protection, and radiology. It is also used to directly compare the effect of radiation on inanimate matter such as in radiation hardening.

The rad is a unit of absorbed radiation dose, defined as 1 rad = 0.01 Gy = 0.01 J/kg. It was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. The material absorbing the radiation can be human tissue, air, water, or any other substance.

<span class="mw-page-title-main">Radiation burn</span> Damage to skin or biological tissue from radiation exposure

A radiation burn is a damage to the skin or other biological tissue and organs as an effect of radiation. The radiation types of greatest concern are thermal radiation, radio frequency energy, ultraviolet light and ionizing radiation.

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Radiobiology is a field of clinical and basic medical sciences that involves the study of the effects of ionizing radiation on living things, in particular health effects of radiation. Ionizing radiation is generally harmful and potentially lethal to living things but can have health benefits in radiation therapy for the treatment of cancer and thyrotoxicosis. Its most common impact is the induction of cancer with a latent period of years or decades after exposure. High doses can cause visually dramatic radiation burns, and/or rapid fatality through acute radiation syndrome. Controlled doses are used for medical imaging and radiotherapy.

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A dose rate is quantity of radiation absorbed or delivered per unit time. It is often indicated in micrograys per hour (µGy/h) or as an equivalent dose rate ḢT in rems per hour (rem/hr) or sieverts per hour (Sv/h).

Effective dose is a dose quantity in the International Commission on Radiological Protection (ICRP) system of radiological protection.

The committed dose in radiological protection is a measure of the stochastic health risk due to an intake of radioactive material into the human body. Stochastic in this context is defined as the probability of cancer induction and genetic damage, due to low levels of radiation. The SI unit of measure is the sievert.

Exposure to ionizing radiation is known to increase the future incidence of cancer, particularly leukemia. The mechanism by which this occurs is well understood, but quantitative models predicting the level of risk remain controversial. The most widely accepted model posits that the incidence of cancers due to ionizing radiation increases linearly with effective radiation dose at a rate of 5.5% per sievert; if correct, natural background radiation is the most hazardous source of radiation to general public health, followed by medical imaging as a close second. Additionally, the vast majority of non-invasive cancers are non-melanoma skin cancers caused by ultraviolet radiation. Non-ionizing radio frequency radiation from mobile phones, electric power transmission, and other similar sources have been investigated as a possible carcinogen by the WHO's International Agency for Research on Cancer, but to date, no evidence of this has been observed.

<span class="mw-page-title-main">Radiation exposure</span> Measure of ionization of air by ionizing radiation

Radiation exposure is a measure of the ionization of air due to ionizing radiation from photons. It is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air. As of 2007, "medical radiation exposure" was defined by the International Commission on Radiological Protection as exposure incurred by people as part of their own medical or dental diagnosis or treatment; by persons, other than those occupationally exposed, knowingly, while voluntarily helping in the support and comfort of patients; and by volunteers in a programme of biomedical research involving their exposure. Common medical tests and treatments involving radiation include X-rays, CT scans, mammography, lung ventilation and perfusion scans, bone scans, cardiac perfusion scan, angiography, radiation therapy, and more. Each type of test carries its own amount of radiation exposure. There are two general categories of adverse health effects caused by radiation exposure: deterministic effects and stochastic effects. Deterministic effects are due to the killing/malfunction of cells following high doses; and stochastic effects involve either cancer development in exposed individuals caused by mutation of somatic cells, or heritable disease in their offspring from mutation of reproductive (germ) cells.

References

  1. ↑ Theis, V.S.; Sripadam, R.; Ramani, V.; Lal, S. (2010). "Chronic Radiation Enteritis". Clinical Oncology. Elsevier BV. 22 (1): 70–83. doi:10.1016/j.clon.2009.10.003. ISSN   0936-6555. PMID   19897345.
  2. ↑ "Radiation Enteritis and Proctitis: Practice Essentials, Pathophysiology, Etiology". Medscape Reference. 2019-11-18. Retrieved 2019-12-27.
  3. 1 2 Gusev, Igor A.; Gusʹkova, Angelina Konstantinovna; Mettler, Fred Albert (2001-03-28). Medical Management of Radiation Accidents. CRC Press. pp. 15–29. ISBN   978-0-8493-7004-5 . Retrieved 2012-06-11.
  4. ↑ ICRP (2012). ICRP Statement on Tissue Reactions / Early and Late Effects of Radiation in Normal Tissues and Organs – Threshold Doses for Tissue Reactions in a Radiation Protection Context. Vol. ICRP Publication 118. Ann. ICRP 41(1/2). Compare the published draft (ICRP. "Early and late effects of radiation in normal tissues and organs: threshold doses for tissue reactions and other non-cancer effects of radiation in a radiation protection context" (PDF). Archived from the original (PDF) on 3 November 2014. Retrieved 11 June 2012.) and note dose thresholds.
  5. ↑ Akleyev, Alexander (2013-05-13). "Chronic Radiation Syndrome (CRS) in residents of the Techa riverside villages" (PDF). Archived from the original (PDF) on 2016-05-31.
  6. ↑ "Chronic Radiation Syndrome | Alexander V. Akleyev | Springer". www.springer.com. Retrieved 2016-04-30.
  7. ↑ Grammaticos, Philip; Giannoula, Evantia; Fountos, George P. (2013-02-27). "Acute radiation syndrome and chronic radiation syndrome" (PDF). Hellenic Journal of Nuclear Medicine. 16 (1): 56–9. PMID   23570025 . Retrieved 2019-09-09.
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